Cleanup: Split up Window-Manager VR file (and related changes)

Splits up wm_xr.c into multiple files in their own folder:
source/blender/windowmanager/xr. So this matches how the message bus and
gizmo code have their own folder and files.

This allows better structuring and should make the code scale better.
I rather do this early on than to wait until we end up with a single,
huge file.

Also improves a bit how data is prepared and updated for drawing.

12 files changed, 884 insertions, 750 deletions

diff --git a/source/blender/windowmanager/CMakeLists.txt b/source/blender/windowmanager/CMakeLists.txt
index a1b67216f1a..90ff7bb8f85 100644
--- a/source/blender/windowmanager/CMakeLists.txt
+++ b/source/blender/windowmanager/CMakeLists.txt
@@ -191,8 +191,18 @@ endif()
 
 if(WITH_XR_OPENXR)
   add_definitions(-DWITH_XR_OPENXR)
+
+  list(APPEND INC
+    xr
+  )
+
   list(APPEND SRC
-    intern/wm_xr.c
+    xr/intern/wm_xr.c
+    xr/intern/wm_xr_draw.c
+    xr/intern/wm_xr_session.c
+
+    xr/wm_xr.h
+    xr/intern/wm_xr_intern.h
   )
 endif()
 
diff --git a/source/blender/windowmanager/intern/wm.c b/source/blender/windowmanager/intern/wm.c
index e9d2ee9c662..54e6735175d 100644
--- a/source/blender/windowmanager/intern/wm.c
+++ b/source/blender/windowmanager/intern/wm.c
@@ -55,6 +55,9 @@
 #include "wm_draw.h"
 #include "wm_event_system.h"
 #include "wm_window.h"
+#ifdef WITH_XR_OPENXR
+#  include "wm_xr.h"
+#endif
 
 #include "BKE_undo_system.h"
 #include "ED_screen.h"
diff --git a/source/blender/windowmanager/intern/wm_operators.c b/source/blender/windowmanager/intern/wm_operators.c
index f8e020b00d0..6d25874da45 100644
--- a/source/blender/windowmanager/intern/wm_operators.c
+++ b/source/blender/windowmanager/intern/wm_operators.c
@@ -106,6 +106,9 @@
 #include "wm_event_types.h"
 #include "wm_files.h"
 #include "wm_window.h"
+#ifdef WITH_XR_OPENXR
+#  include "wm_xr.h"
+#endif
 
 #define UNDOCUMENTED_OPERATOR_TIP N_("(undocumented operator)")
 
diff --git a/source/blender/windowmanager/intern/wm_window.c b/source/blender/windowmanager/intern/wm_window.c
index 699f618f956..a83432e0248 100644
--- a/source/blender/windowmanager/intern/wm_window.c
+++ b/source/blender/windowmanager/intern/wm_window.c
@@ -65,6 +65,9 @@
 #include "wm_platform_support.h"
 #include "wm_window.h"
 #include "wm_window_private.h"
+#ifdef WITH_XR_OPENXR
+#  include "wm_xr.h"
+#endif
 
 #include "ED_anim_api.h"
 #include "ED_fileselect.h"
diff --git a/source/blender/windowmanager/intern/wm_xr.c b/source/blender/windowmanager/intern/wm_xr.c
deleted file mode 100644
index be0c8b4798b..00000000000
--- a/source/blender/windowmanager/intern/wm_xr.c
+++ /dev/null
@@ -1,737 +0,0 @@
-/*
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- */
-
-/** \file
- * \ingroup wm
- *
- * \name Window-Manager XR API
- *
- * Implements Blender specific functionality for the GHOST_Xr API.
- */
-
-#include "BKE_context.h"
-#include "BKE_global.h"
-#include "BKE_idprop.h"
-#include "BKE_main.h"
-#include "BKE_object.h"
-#include "BKE_report.h"
-#include "BKE_screen.h"
-
-#include "BLI_ghash.h"
-#include "BLI_math_geom.h"
-#include "BLI_math_matrix.h"
-
-#include "CLG_log.h"
-
-#include "DNA_camera_types.h"
-#include "DNA_object_types.h"
-#include "DNA_scene_types.h"
-#include "DNA_view3d_types.h"
-#include "DNA_xr_types.h"
-
-#include "DRW_engine.h"
-
-#include "ED_view3d.h"
-#include "ED_view3d_offscreen.h"
-
-#include "GHOST_C-api.h"
-
-#include "GPU_context.h"
-#include "GPU_draw.h"
-#include "GPU_matrix.h"
-#include "GPU_viewport.h"
-
-#include "MEM_guardedalloc.h"
-
-#include "UI_interface.h"
-
-#include "WM_api.h"
-#include "WM_types.h"
-
-#include "wm.h"
-#include "wm_surface.h"
-#include "wm_window.h"
-
-struct wmXrRuntimeData *wm_xr_runtime_data_create(void);
-void wm_xr_runtime_data_free(struct wmXrRuntimeData **runtime);
-void wm_xr_draw_view(const GHOST_XrDrawViewInfo *, void *);
-void *wm_xr_session_gpu_binding_context_create(void);
-void wm_xr_session_gpu_binding_context_destroy(GHOST_ContextHandle);
-wmSurface *wm_xr_session_surface_create(void);
-void wm_xr_pose_to_viewmat(const GHOST_XrPose *pose, float r_viewmat[4][4]);
-
-/* -------------------------------------------------------------------- */
-
-typedef struct wmXrSessionState {
-  bool is_started;
-
-  /** Last known viewer pose (centroid of eyes, in world space) stored for queries. */
-  GHOST_XrPose viewer_pose;
-  /** The last known view matrix, calculated from above's viewer pose. */
-  float viewer_viewmat[4][4];
-  float focal_len;
-
-  /** Copy of XrSessionSettings.flag created on the last draw call, stored to detect changes. */
-  int prev_settings_flag;
-  /** Copy of wmXrDrawData.eye_position_ofs. */
-  float prev_eye_position_ofs[3];
-
-  bool is_view_data_set;
-} wmXrSessionState;
-
-typedef struct wmXrRuntimeData {
-  GHOST_XrContextHandle context;
-
-  /* Although this struct is internal, RNA gets a handle to this for state information queries. */
-  wmXrSessionState session_state;
-  wmXrSessionExitFn exit_fn;
-} wmXrRuntimeData;
-
-typedef struct wmXrDrawData {
-  /** The pose (location + rotation) to which eye deltas will be applied to when drawing (world
-   * space). With positional tracking enabled, it should be the same as the base pose, when
-   * disabled it also contains a location delta from the moment the option was toggled. */
-  GHOST_XrPose base_pose;
-  float eye_position_ofs[3]; /* Local/view space. */
-} wmXrDrawData;
-
-typedef struct {
-  GPUOffScreen *offscreen;
-  GPUViewport *viewport;
-} wmXrSurfaceData;
-
-typedef struct {
-  wmWindowManager *wm;
-} wmXrErrorHandlerData;
-
-/* -------------------------------------------------------------------- */
-
-static wmSurface *g_xr_surface = NULL;
-static CLG_LogRef LOG = {"wm.xr"};
-
-/* -------------------------------------------------------------------- */
-/** \name XR-Context
- *
- * All XR functionality is accessed through a #GHOST_XrContext handle.
- * The lifetime of this context also determines the lifetime of the OpenXR instance, which is the
- * representation of the OpenXR runtime connection within the application.
- *
- * \{ */
-
-static void wm_xr_error_handler(const GHOST_XrError *error)
-{
-  wmXrErrorHandlerData *handler_data = error->customdata;
-  wmWindowManager *wm = handler_data->wm;
-
-  BKE_reports_clear(&wm->reports);
-  WM_report(RPT_ERROR, error->user_message);
-  WM_report_banner_show();
-
-  if (wm->xr.runtime) {
-    /* Just play safe and destroy the entire runtime data, including context. */
-    wm_xr_runtime_data_free(&wm->xr.runtime);
-  }
-}
-
-bool wm_xr_init(wmWindowManager *wm)
-{
-  if (wm->xr.runtime && wm->xr.runtime->context) {
-    return true;
-  }
-  static wmXrErrorHandlerData error_customdata;
-
-  /* Set up error handling */
-  error_customdata.wm = wm;
-  GHOST_XrErrorHandler(wm_xr_error_handler, &error_customdata);
-
-  {
-    const GHOST_TXrGraphicsBinding gpu_bindings_candidates[] = {
-        GHOST_kXrGraphicsOpenGL,
-#ifdef WIN32
-        GHOST_kXrGraphicsD3D11,
-#endif
-    };
-    GHOST_XrContextCreateInfo create_info = {
-        .gpu_binding_candidates = gpu_bindings_candidates,
-        .gpu_binding_candidates_count = ARRAY_SIZE(gpu_bindings_candidates),
-    };
-    GHOST_XrContextHandle context;
-
-    if (G.debug & G_DEBUG_XR) {
-      create_info.context_flag |= GHOST_kXrContextDebug;
-    }
-    if (G.debug & G_DEBUG_XR_TIME) {
-      create_info.context_flag |= GHOST_kXrContextDebugTime;
-    }
-
-    if (!(context = GHOST_XrContextCreate(&create_info))) {
-      return false;
-    }
-
-    /* Set up context callbacks */
-    GHOST_XrGraphicsContextBindFuncs(context,
-                                     wm_xr_session_gpu_binding_context_create,
-                                     wm_xr_session_gpu_binding_context_destroy);
-    GHOST_XrDrawViewFunc(context, wm_xr_draw_view);
-
-    if (!wm->xr.runtime) {
-      wm->xr.runtime = wm_xr_runtime_data_create();
-      wm->xr.runtime->context = context;
-    }
-  }
-  BLI_assert(wm->xr.runtime && wm->xr.runtime->context);
-
-  return true;
-}
-
-void wm_xr_exit(wmWindowManager *wm)
-{
-  if (wm->xr.runtime != NULL) {
-    wm_xr_runtime_data_free(&wm->xr.runtime);
-  }
-  if (wm->xr.session_settings.shading.prop) {
-    IDP_FreeProperty(wm->xr.session_settings.shading.prop);
-    wm->xr.session_settings.shading.prop = NULL;
-  }
-}
-
-bool wm_xr_events_handle(wmWindowManager *wm)
-{
-  if (wm->xr.runtime && wm->xr.runtime->context) {
-    return GHOST_XrEventsHandle(wm->xr.runtime->context);
-  }
-  return false;
-}
-
-/** \} */ /* XR-Context */
-
-/* -------------------------------------------------------------------- */
-/** \name XR Runtime Data
- *
- * \{ */
-
-wmXrRuntimeData *wm_xr_runtime_data_create(void)
-{
-  wmXrRuntimeData *runtime = MEM_callocN(sizeof(*runtime), __func__);
-  return runtime;
-}
-
-void wm_xr_runtime_data_free(wmXrRuntimeData **runtime)
-{
-  /* Note that this function may be called twice, because of an indirect recursion: If a session is
-   * running while WM-XR calls this function, calling GHOST_XrContextDestroy() will call this
-   * again, because it's also set as the session exit callback. So NULL-check and NULL everything
-   * that is freed here. */
-
-  /* We free all runtime XR data here, so if the context is still alive, destroy it. */
-  if ((*runtime)->context != NULL) {
-    GHOST_XrContextHandle context = (*runtime)->context;
-    /* Prevent recursive GHOST_XrContextDestroy() call by NULL'ing the context pointer before the
-     * first call, see comment above. */
-    (*runtime)->context = NULL;
-    GHOST_XrContextDestroy(context);
-  }
-  MEM_SAFE_FREE(*runtime);
-}
-
-static void wm_xr_base_pose_calc(const Scene *scene,
-                                 const XrSessionSettings *settings,
-                                 GHOST_XrPose *r_base_pose)
-{
-  const Object *base_pose_object = ((settings->base_pose_type == XR_BASE_POSE_OBJECT) &&
-                                    settings->base_pose_object) ?
-                                       settings->base_pose_object :
-                                       scene->camera;
-
-  if (settings->base_pose_type == XR_BASE_POSE_CUSTOM) {
-    float tmp_quatx[4], tmp_quatz[4];
-
-    copy_v3_v3(r_base_pose->position, settings->base_pose_location);
-    axis_angle_to_quat_single(tmp_quatx, 'X', M_PI_2);
-    axis_angle_to_quat_single(tmp_quatz, 'Z', settings->base_pose_angle);
-    mul_qt_qtqt(r_base_pose->orientation_quat, tmp_quatz, tmp_quatx);
-  }
-  else if (base_pose_object) {
-    float tmp_quat[4];
-    float tmp_eul[3];
-
-    mat4_to_loc_quat(r_base_pose->position, tmp_quat, base_pose_object->obmat);
-
-    /* Only use rotation around Z-axis to align view with floor. */
-    quat_to_eul(tmp_eul, tmp_quat);
-    tmp_eul[0] = M_PI_2;
-    tmp_eul[1] = 0;
-    eul_to_quat(r_base_pose->orientation_quat, tmp_eul);
-  }
-  else {
-    copy_v3_fl(r_base_pose->position, 0.0f);
-    axis_angle_to_quat_single(r_base_pose->orientation_quat, 'X', M_PI_2);
-  }
-}
-
-static void wm_xr_draw_data_populate(const wmXrSessionState *state,
-                                     const GHOST_XrDrawViewInfo *draw_view,
-                                     const XrSessionSettings *settings,
-                                     const Scene *scene,
-                                     wmXrDrawData *r_draw_data)
-{
-  const bool position_tracking_toggled = ((state->prev_settings_flag &
-                                           XR_SESSION_USE_POSITION_TRACKING) !=
-                                          (settings->flag & XR_SESSION_USE_POSITION_TRACKING));
-  const bool use_position_tracking = settings->flag & XR_SESSION_USE_POSITION_TRACKING;
-
-  memset(r_draw_data, 0, sizeof(*r_draw_data));
-
-  wm_xr_base_pose_calc(scene, settings, &r_draw_data->base_pose);
-
-  /* Set the eye position offset, it's used to offset the base pose when changing positional
-   * tracking. */
-  if (!state->is_view_data_set) {
-    /* Always use the exact base pose with no offset when starting the session. */
-    copy_v3_fl(r_draw_data->eye_position_ofs, 0.0f);
-  }
-  else if (position_tracking_toggled) {
-    if (use_position_tracking) {
-      copy_v3_fl(r_draw_data->eye_position_ofs, 0.0f);
-    }
-    else {
-      /* Store the current local offset (local pose) so that we can apply that to the eyes. This
-       * way the eyes stay exactly where they are when disabling positional tracking. */
-      copy_v3_v3(r_draw_data->eye_position_ofs, draw_view->local_pose.position);
-    }
-  }
-  else if (!use_position_tracking) {
-    /* Keep previous offset when positional tracking is disabled. */
-    copy_v3_v3(r_draw_data->eye_position_ofs, state->prev_eye_position_ofs);
-  }
-}
-
-/**
- * Update information that is only stored for external state queries. E.g. for Python API to
- * request the current (as in, last known) viewer pose.
- */
-static void wm_xr_session_state_update(wmXrSessionState *state,
-                                       const GHOST_XrDrawViewInfo *draw_view,
-                                       const XrSessionSettings *settings,
-                                       const wmXrDrawData *draw_data)
-{
-  GHOST_XrPose viewer_pose;
-  const bool use_position_tracking = settings->flag & XR_SESSION_USE_POSITION_TRACKING;
-
-  mul_qt_qtqt(viewer_pose.orientation_quat,
-              draw_data->base_pose.orientation_quat,
-              draw_view->local_pose.orientation_quat);
-  copy_v3_v3(viewer_pose.position, draw_data->base_pose.position);
-  /* The local pose and the eye pose (which is copied from an earlier local pose) both are view
-   * space, so Y-up. In this case we need them in regular Z-up. */
-  viewer_pose.position[0] += draw_data->eye_position_ofs[0];
-  viewer_pose.position[1] -= draw_data->eye_position_ofs[2];
-  viewer_pose.position[2] += draw_data->eye_position_ofs[1];
-  if (use_position_tracking) {
-    viewer_pose.position[0] += draw_view->local_pose.position[0];
-    viewer_pose.position[1] -= draw_view->local_pose.position[2];
-    viewer_pose.position[2] += draw_view->local_pose.position[1];
-  }
-
-  copy_v3_v3(state->viewer_pose.position, viewer_pose.position);
-  copy_qt_qt(state->viewer_pose.orientation_quat, viewer_pose.orientation_quat);
-  wm_xr_pose_to_viewmat(&viewer_pose, state->viewer_viewmat);
-  /* No idea why, but multiplying by two seems to make it match the VR view more. */
-  state->focal_len = 2.0f *
-                     fov_to_focallength(draw_view->fov.angle_right - draw_view->fov.angle_left,
-                                        DEFAULT_SENSOR_WIDTH);
-
-  copy_v3_v3(state->prev_eye_position_ofs, draw_data->eye_position_ofs);
-  state->prev_settings_flag = settings->flag;
-  state->is_view_data_set = true;
-}
-
-wmXrSessionState *WM_xr_session_state_handle_get(const wmXrData *xr)
-{
-  return xr->runtime ? &xr->runtime->session_state : NULL;
-}
-
-bool WM_xr_session_state_viewer_pose_location_get(const wmXrData *xr, float r_location[3])
-{
-  if (!WM_xr_session_is_ready(xr) || !xr->runtime->session_state.is_view_data_set) {
-    zero_v3(r_location);
-    return false;
-  }
-
-  copy_v3_v3(r_location, xr->runtime->session_state.viewer_pose.position);
-  return true;
-}
-
-bool WM_xr_session_state_viewer_pose_rotation_get(const wmXrData *xr, float r_rotation[4])
-{
-  if (!WM_xr_session_is_ready(xr) || !xr->runtime->session_state.is_view_data_set) {
-    unit_qt(r_rotation);
-    return false;
-  }
-
-  copy_v4_v4(r_rotation, xr->runtime->session_state.viewer_pose.orientation_quat);
-  return true;
-}
-
-bool WM_xr_session_state_viewer_pose_matrix_info_get(const wmXrData *xr,
-                                                     float r_viewmat[4][4],
-                                                     float *r_focal_len)
-{
-  if (!WM_xr_session_is_ready(xr) || !xr->runtime->session_state.is_view_data_set) {
-    unit_m4(r_viewmat);
-    *r_focal_len = 0.0f;
-    return false;
-  }
-
-  copy_m4_m4(r_viewmat, xr->runtime->session_state.viewer_viewmat);
-  *r_focal_len = xr->runtime->session_state.focal_len;
-
-  return true;
-}
-
-/** \} */ /* XR Runtime Data */
-
-/* -------------------------------------------------------------------- */
-/** \name XR-Session
- *
- * \{ */
-
-void *wm_xr_session_gpu_binding_context_create(void)
-{
-  wmSurface *surface = wm_xr_session_surface_create();
-
-  wm_surface_add(surface);
-
-  /* Some regions may need to redraw with updated session state after the session is entirely up
-   * and running. */
-  WM_main_add_notifier(NC_WM | ND_XR_DATA_CHANGED, NULL);
-
-  return surface->ghost_ctx;
-}
-
-void wm_xr_session_gpu_binding_context_destroy(GHOST_ContextHandle UNUSED(context))
-{
-  if (g_xr_surface) { /* Might have been freed already */
-    wm_surface_remove(g_xr_surface);
-  }
-
-  wm_window_reset_drawable();
-
-  /* Some regions may need to redraw with updated session state after the session is entirely
-   * stopped. */
-  WM_main_add_notifier(NC_WM | ND_XR_DATA_CHANGED, NULL);
-}
-
-static void wm_xr_session_exit_cb(void *customdata)
-{
-  wmXrData *xr_data = customdata;
-
-  xr_data->runtime->session_state.is_started = false;
-  if (xr_data->runtime->exit_fn) {
-    xr_data->runtime->exit_fn(xr_data);
-  }
-
-  /* Free the entire runtime data (including session state and context), to play safe. */
-  wm_xr_runtime_data_free(&xr_data->runtime);
-}
-
-static void wm_xr_session_begin_info_create(wmXrData *xr_data,
-                                            GHOST_XrSessionBeginInfo *r_begin_info)
-{
-  /* WM-XR exit function, does some own stuff and calls callback passed to wm_xr_session_toggle(),
-   * to allow external code to execute its own session-exit logic. */
-  r_begin_info->exit_fn = wm_xr_session_exit_cb;
-  r_begin_info->exit_customdata = xr_data;
-}
-
-void wm_xr_session_toggle(wmWindowManager *wm, wmXrSessionExitFn session_exit_fn)
-{
-  wmXrData *xr_data = &wm->xr;
-
-  if (WM_xr_session_exists(xr_data)) {
-    GHOST_XrSessionEnd(xr_data->runtime->context);
-  }
-  else {
-    GHOST_XrSessionBeginInfo begin_info;
-
-    xr_data->runtime->session_state.is_started = true;
-    xr_data->runtime->exit_fn = session_exit_fn;
-
-    wm_xr_session_begin_info_create(xr_data, &begin_info);
-    GHOST_XrSessionStart(xr_data->runtime->context, &begin_info);
-  }
-}
-
-/**
- * Check if the XR-Session was triggered.
- * If an error happened while trying to start a session, this returns false too.
- */
-bool WM_xr_session_exists(const wmXrData *xr)
-{
-  return xr->runtime && xr->runtime->context && xr->runtime->session_state.is_started;
-}
-
-/**
- * Check if the session is running, according to the OpenXR definition.
- */
-bool WM_xr_session_is_ready(const wmXrData *xr)
-{
-  return WM_xr_session_exists(xr) && GHOST_XrSessionIsRunning(xr->runtime->context);
-}
-
-/** \} */ /* XR-Session */
-
-/* -------------------------------------------------------------------- */
-/** \name XR-Session Surface
- *
- * A wmSurface is used to manage drawing of the VR viewport. It's created and destroyed with the
- * session.
- *
- * \{ */
-
-/**
- * \brief Call Ghost-XR to draw a frame
- *
- * Draw callback for the XR-session surface. It's expected to be called on each main loop iteration
- * and tells Ghost-XR to submit a new frame by drawing its views. Note that for drawing each view,
- * #wm_xr_draw_view() will be called through Ghost-XR (see GHOST_XrDrawViewFunc()).
- */
-static void wm_xr_session_surface_draw(bContext *C)
-{
-  wmXrSurfaceData *surface_data = g_xr_surface->customdata;
-  wmWindowManager *wm = CTX_wm_manager(C);
-
-  if (!GHOST_XrSessionIsRunning(wm->xr.runtime->context)) {
-    return;
-  }
-  DRW_xr_drawing_begin();
-  GHOST_XrSessionDrawViews(wm->xr.runtime->context, C);
-  GPU_offscreen_unbind(surface_data->offscreen, false);
-  DRW_xr_drawing_end();
-}
-
-static void wm_xr_session_free_data(wmSurface *surface)
-{
-  wmXrSurfaceData *data = surface->customdata;
-
-  if (data->viewport) {
-    GPU_viewport_free(data->viewport);
-  }
-  if (data->offscreen) {
-    GPU_offscreen_free(data->offscreen);
-  }
-
-  MEM_freeN(surface->customdata);
-
-  g_xr_surface = NULL;
-}
-
-static bool wm_xr_session_surface_offscreen_ensure(const GHOST_XrDrawViewInfo *draw_view)
-{
-  wmXrSurfaceData *surface_data = g_xr_surface->customdata;
-  const bool size_changed = surface_data->offscreen &&
-                            (GPU_offscreen_width(surface_data->offscreen) != draw_view->width) &&
-                            (GPU_offscreen_height(surface_data->offscreen) != draw_view->height);
-  char err_out[256] = "unknown";
-  bool failure = false;
-
-  if (surface_data->offscreen) {
-    BLI_assert(surface_data->viewport);
-
-    if (!size_changed) {
-      return true;
-    }
-    GPU_viewport_free(surface_data->viewport);
-    GPU_offscreen_free(surface_data->offscreen);
-  }
-
-  if (!(surface_data->offscreen = GPU_offscreen_create(
-            draw_view->width, draw_view->height, 0, true, false, err_out))) {
-    failure = true;
-  }
-
-  if (failure) {
-    /* Pass. */
-  }
-  else if (!(surface_data->viewport = GPU_viewport_create())) {
-    GPU_offscreen_free(surface_data->offscreen);
-    failure = true;
-  }
-
-  if (failure) {
-    CLOG_ERROR(&LOG, "Failed to get buffer, %s\n", err_out);
-    return false;
-  }
-
-  return true;
-}
-
-wmSurface *wm_xr_session_surface_create(void)
-{
-  if (g_xr_surface) {
-    BLI_assert(false);
-    return g_xr_surface;
-  }
-
-  wmSurface *surface = MEM_callocN(sizeof(*surface), __func__);
-  wmXrSurfaceData *data = MEM_callocN(sizeof(*data), "XrSurfaceData");
-
-  surface->draw = wm_xr_session_surface_draw;
-  surface->free_data = wm_xr_session_free_data;
-  surface->ghost_ctx = DRW_xr_opengl_context_get();
-  surface->gpu_ctx = DRW_xr_gpu_context_get();
-
-  surface->customdata = data;
-
-  g_xr_surface = surface;
-
-  return surface;
-}
-
-/** \} */ /* XR-Session Surface */
-
-/* -------------------------------------------------------------------- */
-/** \name XR Drawing
- *
- * \{ */
-
-void wm_xr_pose_to_viewmat(const GHOST_XrPose *pose, float r_viewmat[4][4])
-{
-  float iquat[4];
-  invert_qt_qt_normalized(iquat, pose->orientation_quat);
-  quat_to_mat4(r_viewmat, iquat);
-  translate_m4(r_viewmat, -pose->position[0], -pose->position[1], -pose->position[2]);
-}
-
-static void wm_xr_draw_matrices_create(const wmXrDrawData *draw_data,
-                                       const GHOST_XrDrawViewInfo *draw_view,
-                                       const XrSessionSettings *session_settings,
-                                       float r_view_mat[4][4],
-                                       float r_proj_mat[4][4])
-{
-  GHOST_XrPose eye_pose;
-
-  copy_qt_qt(eye_pose.orientation_quat, draw_view->eye_pose.orientation_quat);
-  copy_v3_v3(eye_pose.position, draw_view->eye_pose.position);
-  add_v3_v3(eye_pose.position, draw_data->eye_position_ofs);
-  if ((session_settings->flag & XR_SESSION_USE_POSITION_TRACKING) == 0) {
-    sub_v3_v3(eye_pose.position, draw_view->local_pose.position);
-  }
-
-  perspective_m4_fov(r_proj_mat,
-                     draw_view->fov.angle_left,
-                     draw_view->fov.angle_right,
-                     draw_view->fov.angle_up,
-                     draw_view->fov.angle_down,
-                     session_settings->clip_start,
-                     session_settings->clip_end);
-
-  float eye_mat[4][4];
-  float base_mat[4][4];
-
-  wm_xr_pose_to_viewmat(&eye_pose, eye_mat);
-  /* Calculate the base pose matrix (in world space!). */
-  wm_xr_pose_to_viewmat(&draw_data->base_pose, base_mat);
-
-  mul_m4_m4m4(r_view_mat, eye_mat, base_mat);
-}
-
-static void wm_xr_draw_viewport_buffers_to_active_framebuffer(
-    const wmXrRuntimeData *runtime_data,
-    const wmXrSurfaceData *surface_data,
-    const GHOST_XrDrawViewInfo *draw_view)
-{
-  const bool is_upside_down = GHOST_XrSessionNeedsUpsideDownDrawing(runtime_data->context);
-  rcti rect = {.xmin = 0, .ymin = 0, .xmax = draw_view->width - 1, .ymax = draw_view->height - 1};
-
-  wmViewport(&rect);
-
-  /* For upside down contexts, draw with inverted y-values. */
-  if (is_upside_down) {
-    SWAP(int, rect.ymin, rect.ymax);
-  }
-  GPU_viewport_draw_to_screen_ex(surface_data->viewport, 0, &rect, draw_view->expects_srgb_buffer);
-}
-
-/**
- * \brief Draw a viewport for a single eye.
- *
- * This is the main viewport drawing function for VR sessions. It's assigned to Ghost-XR as a
- * callback (see GHOST_XrDrawViewFunc()) and executed for each view (read: eye).
- */
-void wm_xr_draw_view(const GHOST_XrDrawViewInfo *draw_view, void *customdata)
-{
-  bContext *C = customdata;
-  wmWindowManager *wm = CTX_wm_manager(C);
-  wmXrSurfaceData *surface_data = g_xr_surface->customdata;
-  wmXrSessionState *session_state = &wm->xr.runtime->session_state;
-  XrSessionSettings *settings = &wm->xr.session_settings;
-  wmXrDrawData draw_data;
-  Scene *scene = CTX_data_scene(C);
-
-  const int display_flags = V3D_OFSDRAW_OVERRIDE_SCENE_SETTINGS | settings->draw_flags;
-
-  float viewmat[4][4], winmat[4][4];
-
-  BLI_assert(WM_xr_session_is_ready(&wm->xr));
-
-  wm_xr_draw_data_populate(session_state, draw_view, settings, scene, &draw_data);
-  wm_xr_draw_matrices_create(&draw_data, draw_view, settings, viewmat, winmat);
-  wm_xr_session_state_update(session_state, draw_view, settings, &draw_data);
-
-  if (!wm_xr_session_surface_offscreen_ensure(draw_view)) {
-    return;
-  }
-
-  /* In case a framebuffer is still bound from drawing the last eye. */
-  GPU_framebuffer_restore();
-  /* Some systems have drawing glitches without this. */
-  GPU_clear(GPU_DEPTH_BIT);
-
-  /* Draws the view into the surface_data->viewport's framebuffers */
-  ED_view3d_draw_offscreen_simple(CTX_data_ensure_evaluated_depsgraph(C),
-                                  scene,
-                                  &wm->xr.session_settings.shading,
-                                  wm->xr.session_settings.shading.type,
-                                  draw_view->width,
-                                  draw_view->height,
-                                  display_flags,
-                                  viewmat,
-                                  winmat,
-                                  settings->clip_start,
-                                  settings->clip_end,
-                                  false,
-                                  true,
-                                  true,
-                                  NULL,
-                                  false,
-                                  surface_data->offscreen,
-                                  surface_data->viewport);
-
-  /* The draw-manager uses both GPUOffscreen and GPUViewport to manage frame and texture buffers. A
-   * call to GPU_viewport_draw_to_screen() is still needed to get the final result from the
-   * viewport buffers composited together and potentially color managed for display on screen.
-   * It needs a bound frame-buffer to draw into, for which we simply reuse the GPUOffscreen one.
-   *
-   * In a next step, Ghost-XR will use the currently bound frame-buffer to retrieve the image
-   * to be submitted to the OpenXR swap-chain. So do not un-bind the off-screen yet! */
-
-  GPU_offscreen_bind(surface_data->offscreen, false);
-
-  wm_xr_draw_viewport_buffers_to_active_framebuffer(wm->xr.runtime, surface_data, draw_view);
-}
-
-/** \} */ /* XR Drawing */
diff --git a/source/blender/windowmanager/wm.h b/source/blender/windowmanager/wm.h
index 97403a0315a..e5df4a44bd4 100644
--- a/source/blender/windowmanager/wm.h
+++ b/source/blender/windowmanager/wm.h
@@ -96,14 +96,4 @@ void wm_stereo3d_set_cancel(bContext *C, wmOperator *op);
 void wm_open_init_load_ui(wmOperator *op, bool use_prefs);
 void wm_open_init_use_scripts(wmOperator *op, bool use_prefs);
 
-#ifdef WITH_XR_OPENXR
-typedef void (*wmXrSessionExitFn)(const wmXrData *xr_data);
-
-/* wm_xr.c */
-bool wm_xr_init(wmWindowManager *wm);
-void wm_xr_exit(wmWindowManager *wm);
-void wm_xr_session_toggle(wmWindowManager *wm, wmXrSessionExitFn session_exit_fn);
-bool wm_xr_events_handle(wmWindowManager *wm);
-#endif
-
-#endif /* __WM_H__ */
+#endif
\ No newline at end of file
diff --git a/source/blender/windowmanager/wm_surface.h b/source/blender/windowmanager/wm_surface.h
index 98d67c55619..e1b00ae1ade 100644
--- a/source/blender/windowmanager/wm_surface.h
+++ b/source/blender/windowmanager/wm_surface.h
@@ -46,7 +46,7 @@ void wm_surface_remove(wmSurface *surface);
 void wm_surfaces_free(void);
 
 /* Utils */
-void wm_surfaces_iter(struct bContext *C, void (*cb)(bContext *, wmSurface *));
+void wm_surfaces_iter(struct bContext *C, void (*cb)(struct bContext *, wmSurface *));
 
 /* Drawing */
 void wm_surface_make_drawable(wmSurface *surface);
diff --git a/source/blender/windowmanager/xr/intern/wm_xr.c b/source/blender/windowmanager/xr/intern/wm_xr.c
new file mode 100644
index 00000000000..69c9034d51f
--- /dev/null
+++ b/source/blender/windowmanager/xr/intern/wm_xr.c
@@ -0,0 +1,163 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup wm
+ *
+ * All XR functionality is accessed through a #GHOST_XrContext handle.
+ * The lifetime of this context also determines the lifetime of the OpenXR instance, which is the
+ * representation of the OpenXR runtime connection within the application.
+ */
+
+#include "BKE_global.h"
+#include "BKE_idprop.h"
+#include "BKE_report.h"
+
+#include "DNA_scene_types.h"
+#include "DNA_windowmanager_types.h"
+
+#include "DEG_depsgraph.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "GHOST_C-api.h"
+
+#include "WM_api.h"
+
+#include "wm_surface.h"
+#include "wm_xr_intern.h"
+
+typedef struct {
+  wmWindowManager *wm;
+} wmXrErrorHandlerData;
+
+/* -------------------------------------------------------------------- */
+
+static void wm_xr_error_handler(const GHOST_XrError *error)
+{
+  wmXrErrorHandlerData *handler_data = error->customdata;
+  wmWindowManager *wm = handler_data->wm;
+
+  BKE_reports_clear(&wm->reports);
+  WM_report(RPT_ERROR, error->user_message);
+  WM_report_banner_show();
+
+  if (wm->xr.runtime) {
+    /* Just play safe and destroy the entire runtime data, including context. */
+    wm_xr_runtime_data_free(&wm->xr.runtime);
+  }
+}
+
+bool wm_xr_init(wmWindowManager *wm)
+{
+  if (wm->xr.runtime && wm->xr.runtime->context) {
+    return true;
+  }
+  static wmXrErrorHandlerData error_customdata;
+
+  /* Set up error handling */
+  error_customdata.wm = wm;
+  GHOST_XrErrorHandler(wm_xr_error_handler, &error_customdata);
+
+  {
+    const GHOST_TXrGraphicsBinding gpu_bindings_candidates[] = {
+        GHOST_kXrGraphicsOpenGL,
+#ifdef WIN32
+        GHOST_kXrGraphicsD3D11,
+#endif
+    };
+    GHOST_XrContextCreateInfo create_info = {
+        .gpu_binding_candidates = gpu_bindings_candidates,
+        .gpu_binding_candidates_count = ARRAY_SIZE(gpu_bindings_candidates),
+    };
+    GHOST_XrContextHandle context;
+
+    if (G.debug & G_DEBUG_XR) {
+      create_info.context_flag |= GHOST_kXrContextDebug;
+    }
+    if (G.debug & G_DEBUG_XR_TIME) {
+      create_info.context_flag |= GHOST_kXrContextDebugTime;
+    }
+
+    if (!(context = GHOST_XrContextCreate(&create_info))) {
+      return false;
+    }
+
+    /* Set up context callbacks */
+    GHOST_XrGraphicsContextBindFuncs(context,
+                                     wm_xr_session_gpu_binding_context_create,
+                                     wm_xr_session_gpu_binding_context_destroy);
+    GHOST_XrDrawViewFunc(context, wm_xr_draw_view);
+
+    if (!wm->xr.runtime) {
+      wm->xr.runtime = wm_xr_runtime_data_create();
+      wm->xr.runtime->context = context;
+    }
+  }
+  BLI_assert(wm->xr.runtime && wm->xr.runtime->context);
+
+  return true;
+}
+
+void wm_xr_exit(wmWindowManager *wm)
+{
+  if (wm->xr.runtime != NULL) {
+    wm_xr_runtime_data_free(&wm->xr.runtime);
+  }
+  if (wm->xr.session_settings.shading.prop) {
+    IDP_FreeProperty(wm->xr.session_settings.shading.prop);
+    wm->xr.session_settings.shading.prop = NULL;
+  }
+}
+
+bool wm_xr_events_handle(wmWindowManager *wm)
+{
+  if (wm->xr.runtime && wm->xr.runtime->context) {
+    return GHOST_XrEventsHandle(wm->xr.runtime->context);
+  }
+  return false;
+}
+
+/* -------------------------------------------------------------------- */
+/** \name XR Runtime Data
+ *
+ * \{ */
+
+wmXrRuntimeData *wm_xr_runtime_data_create(void)
+{
+  wmXrRuntimeData *runtime = MEM_callocN(sizeof(*runtime), __func__);
+  return runtime;
+}
+
+void wm_xr_runtime_data_free(wmXrRuntimeData **runtime)
+{
+  /* Note that this function may be called twice, because of an indirect recursion: If a session is
+   * running while WM-XR calls this function, calling GHOST_XrContextDestroy() will call this
+   * again, because it's also set as the session exit callback. So NULL-check and NULL everything
+   * that is freed here. */
+
+  /* We free all runtime XR data here, so if the context is still alive, destroy it. */
+  if ((*runtime)->context != NULL) {
+    GHOST_XrContextHandle context = (*runtime)->context;
+    /* Prevent recursive GHOST_XrContextDestroy() call by NULL'ing the context pointer before the
+     * first call, see comment above. */
+    (*runtime)->context = NULL;
+    GHOST_XrContextDestroy(context);
+  }
+  MEM_SAFE_FREE(*runtime);
+}
+
+/** \} */ /* XR Runtime Data */
diff --git a/source/blender/windowmanager/xr/intern/wm_xr_draw.c b/source/blender/windowmanager/xr/intern/wm_xr_draw.c
new file mode 100644
index 00000000000..684e59eb8b2
--- /dev/null
+++ b/source/blender/windowmanager/xr/intern/wm_xr_draw.c
@@ -0,0 +1,162 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup wm
+ *
+ * \name Window-Manager XR Drawing
+ *
+ * Implements Blender specific drawing functionality for use with the Ghost-XR API.
+ */
+
+#include <string.h>
+
+#include "BLI_math.h"
+
+#include "ED_view3d_offscreen.h"
+
+#include "GHOST_C-api.h"
+
+#include "GPU_viewport.h"
+
+#include "WM_api.h"
+
+#include "wm_surface.h"
+#include "wm_xr_intern.h"
+
+void wm_xr_pose_to_viewmat(const GHOST_XrPose *pose, float r_viewmat[4][4])
+{
+  float iquat[4];
+  invert_qt_qt_normalized(iquat, pose->orientation_quat);
+  quat_to_mat4(r_viewmat, iquat);
+  translate_m4(r_viewmat, -pose->position[0], -pose->position[1], -pose->position[2]);
+}
+
+static void wm_xr_draw_matrices_create(const wmXrDrawData *draw_data,
+                                       const GHOST_XrDrawViewInfo *draw_view,
+                                       const XrSessionSettings *session_settings,
+                                       float r_view_mat[4][4],
+                                       float r_proj_mat[4][4])
+{
+  GHOST_XrPose eye_pose;
+
+  copy_qt_qt(eye_pose.orientation_quat, draw_view->eye_pose.orientation_quat);
+  copy_v3_v3(eye_pose.position, draw_view->eye_pose.position);
+  add_v3_v3(eye_pose.position, draw_data->eye_position_ofs);
+  if ((session_settings->flag & XR_SESSION_USE_POSITION_TRACKING) == 0) {
+    sub_v3_v3(eye_pose.position, draw_view->local_pose.position);
+  }
+
+  perspective_m4_fov(r_proj_mat,
+                     draw_view->fov.angle_left,
+                     draw_view->fov.angle_right,
+                     draw_view->fov.angle_up,
+                     draw_view->fov.angle_down,
+                     session_settings->clip_start,
+                     session_settings->clip_end);
+
+  float eye_mat[4][4];
+  float base_mat[4][4];
+
+  wm_xr_pose_to_viewmat(&eye_pose, eye_mat);
+  /* Calculate the base pose matrix (in world space!). */
+  wm_xr_pose_to_viewmat(&draw_data->base_pose, base_mat);
+
+  mul_m4_m4m4(r_view_mat, eye_mat, base_mat);
+}
+
+static void wm_xr_draw_viewport_buffers_to_active_framebuffer(
+    const wmXrRuntimeData *runtime_data,
+    const wmXrSurfaceData *surface_data,
+    const GHOST_XrDrawViewInfo *draw_view)
+{
+  const bool is_upside_down = GHOST_XrSessionNeedsUpsideDownDrawing(runtime_data->context);
+  rcti rect = {.xmin = 0, .ymin = 0, .xmax = draw_view->width - 1, .ymax = draw_view->height - 1};
+
+  wmViewport(&rect);
+
+  /* For upside down contexts, draw with inverted y-values. */
+  if (is_upside_down) {
+    SWAP(int, rect.ymin, rect.ymax);
+  }
+  GPU_viewport_draw_to_screen_ex(surface_data->viewport, 0, &rect, draw_view->expects_srgb_buffer);
+}
+
+/**
+ * \brief Draw a viewport for a single eye.
+ *
+ * This is the main viewport drawing function for VR sessions. It's assigned to Ghost-XR as a
+ * callback (see GHOST_XrDrawViewFunc()) and executed for each view (read: eye).
+ */
+void wm_xr_draw_view(const GHOST_XrDrawViewInfo *draw_view, void *customdata)
+{
+  wmXrDrawData *draw_data = customdata;
+  wmXrData *xr_data = draw_data->xr_data;
+  wmXrSurfaceData *surface_data = draw_data->surface_data;
+  wmXrSessionState *session_state = &xr_data->runtime->session_state;
+  XrSessionSettings *settings = &xr_data->session_settings;
+
+  const int display_flags = V3D_OFSDRAW_OVERRIDE_SCENE_SETTINGS | settings->draw_flags;
+
+  float viewmat[4][4], winmat[4][4];
+
+  BLI_assert(WM_xr_session_is_ready(xr_data));
+
+  wm_xr_session_draw_data_update(session_state, settings, draw_view, draw_data);
+  wm_xr_draw_matrices_create(draw_data, draw_view, settings, viewmat, winmat);
+  wm_xr_session_state_update(settings, draw_data, draw_view, session_state);
+
+  if (!wm_xr_session_surface_offscreen_ensure(surface_data, draw_view)) {
+    return;
+  }
+
+  /* In case a framebuffer is still bound from drawing the last eye. */
+  GPU_framebuffer_restore();
+  /* Some systems have drawing glitches without this. */
+  GPU_clear(GPU_DEPTH_BIT);
+
+  /* Draws the view into the surface_data->viewport's framebuffers */
+  ED_view3d_draw_offscreen_simple(draw_data->depsgraph,
+                                  draw_data->scene,
+                                  &settings->shading,
+                                  settings->shading.type,
+                                  draw_view->width,
+                                  draw_view->height,
+                                  display_flags,
+                                  viewmat,
+                                  winmat,
+                                  settings->clip_start,
+                                  settings->clip_end,
+                                  false,
+                                  true,
+                                  true,
+                                  NULL,
+                                  false,
+                                  surface_data->offscreen,
+                                  surface_data->viewport);
+
+  /* The draw-manager uses both GPUOffscreen and GPUViewport to manage frame and texture buffers. A
+   * call to GPU_viewport_draw_to_screen() is still needed to get the final result from the
+   * viewport buffers composited together and potentially color managed for display on screen.
+   * It needs a bound frame-buffer to draw into, for which we simply reuse the GPUOffscreen one.
+   *
+   * In a next step, Ghost-XR will use the currently bound frame-buffer to retrieve the image
+   * to be submitted to the OpenXR swap-chain. So do not un-bind the off-screen yet! */
+
+  GPU_offscreen_bind(surface_data->offscreen, false);
+
+  wm_xr_draw_viewport_buffers_to_active_framebuffer(xr_data->runtime, surface_data, draw_view);
+}
diff --git a/source/blender/windowmanager/xr/intern/wm_xr_intern.h b/source/blender/windowmanager/xr/intern/wm_xr_intern.h
new file mode 100644
index 00000000000..b53ae45a29f
--- /dev/null
+++ b/source/blender/windowmanager/xr/intern/wm_xr_intern.h
@@ -0,0 +1,91 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup wm
+ */
+
+#ifndef __WM_XR_INTERN_H__
+#define __WM_XR_INTERN_H__
+
+#include "CLG_log.h"
+
+#include "wm_xr.h"
+
+typedef struct wmXrSessionState {
+  bool is_started;
+
+  /** Last known viewer pose (centroid of eyes, in world space) stored for queries. */
+  GHOST_XrPose viewer_pose;
+  /** The last known view matrix, calculated from above's viewer pose. */
+  float viewer_viewmat[4][4];
+  float focal_len;
+
+  /** Copy of XrSessionSettings.flag created on the last draw call, stored to detect changes. */
+  int prev_settings_flag;
+  /** Copy of wmXrDrawData.eye_position_ofs. */
+  float prev_eye_position_ofs[3];
+
+  bool is_view_data_set;
+} wmXrSessionState;
+
+typedef struct wmXrRuntimeData {
+  GHOST_XrContextHandle context;
+
+  /* Although this struct is internal, RNA gets a handle to this for state information queries. */
+  wmXrSessionState session_state;
+  wmXrSessionExitFn exit_fn;
+} wmXrRuntimeData;
+
+typedef struct {
+  struct GPUOffScreen *offscreen;
+  struct GPUViewport *viewport;
+} wmXrSurfaceData;
+
+typedef struct wmXrDrawData {
+  struct Scene *scene;
+  struct Depsgraph *depsgraph;
+
+  wmXrData *xr_data;
+  wmXrSurfaceData *surface_data;
+
+  /** The pose (location + rotation) to which eye deltas will be applied to when drawing (world
+   * space). With positional tracking enabled, it should be the same as the base pose, when
+   * disabled it also contains a location delta from the moment the option was toggled. */
+  GHOST_XrPose base_pose;
+  float eye_position_ofs[3]; /* Local/view space. */
+} wmXrDrawData;
+
+wmXrRuntimeData *wm_xr_runtime_data_create(void);
+void wm_xr_runtime_data_free(wmXrRuntimeData **runtime);
+
+void wm_xr_session_draw_data_update(const wmXrSessionState *state,
+                                    const XrSessionSettings *settings,
+                                    const GHOST_XrDrawViewInfo *draw_view,
+                                    wmXrDrawData *draw_data);
+void wm_xr_session_state_update(const XrSessionSettings *settings,
+                                const wmXrDrawData *draw_data,
+                                const GHOST_XrDrawViewInfo *draw_view,
+                                wmXrSessionState *state);
+bool wm_xr_session_surface_offscreen_ensure(wmXrSurfaceData *surface_data,
+                                            const GHOST_XrDrawViewInfo *draw_view);
+void *wm_xr_session_gpu_binding_context_create(void);
+void wm_xr_session_gpu_binding_context_destroy(GHOST_ContextHandle context);
+
+void wm_xr_pose_to_viewmat(const GHOST_XrPose *pose, float r_viewmat[4][4]);
+void wm_xr_draw_view(const GHOST_XrDrawViewInfo *draw_view, void *customdata);
+
+#endif
diff --git a/source/blender/windowmanager/xr/intern/wm_xr_session.c b/source/blender/windowmanager/xr/intern/wm_xr_session.c
new file mode 100644
index 00000000000..dc228d1b18b
--- /dev/null
+++ b/source/blender/windowmanager/xr/intern/wm_xr_session.c
@@ -0,0 +1,411 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup wm
+ */
+
+#include "BKE_context.h"
+
+#include "BLI_math.h"
+
+#include "DEG_depsgraph.h"
+
+#include "DNA_camera_types.h"
+
+#include "DRW_engine.h"
+
+#include "GHOST_C-api.h"
+
+#include "GPU_viewport.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+#include "wm_surface.h"
+#include "wm_window.h"
+#include "wm_xr_intern.h"
+
+wmSurface *g_xr_surface = NULL;
+CLG_LogRef LOG = {"wm.xr"};
+
+/* -------------------------------------------------------------------- */
+
+static void wm_xr_session_exit_cb(void *customdata)
+{
+  wmXrData *xr_data = customdata;
+
+  xr_data->runtime->session_state.is_started = false;
+  if (xr_data->runtime->exit_fn) {
+    xr_data->runtime->exit_fn(xr_data);
+  }
+
+  /* Free the entire runtime data (including session state and context), to play safe. */
+  wm_xr_runtime_data_free(&xr_data->runtime);
+}
+
+static void wm_xr_session_begin_info_create(wmXrData *xr_data,
+                                            GHOST_XrSessionBeginInfo *r_begin_info)
+{
+  /* WM-XR exit function, does some own stuff and calls callback passed to wm_xr_session_toggle(),
+   * to allow external code to execute its own session-exit logic. */
+  r_begin_info->exit_fn = wm_xr_session_exit_cb;
+  r_begin_info->exit_customdata = xr_data;
+}
+
+void wm_xr_session_toggle(wmWindowManager *wm, wmXrSessionExitFn session_exit_fn)
+{
+  wmXrData *xr_data = &wm->xr;
+
+  if (WM_xr_session_exists(xr_data)) {
+    GHOST_XrSessionEnd(xr_data->runtime->context);
+  }
+  else {
+    GHOST_XrSessionBeginInfo begin_info;
+
+    xr_data->runtime->session_state.is_started = true;
+    xr_data->runtime->exit_fn = session_exit_fn;
+
+    wm_xr_session_begin_info_create(xr_data, &begin_info);
+    GHOST_XrSessionStart(xr_data->runtime->context, &begin_info);
+  }
+}
+
+/**
+ * Check if the XR-Session was triggered.
+ * If an error happened while trying to start a session, this returns false too.
+ */
+bool WM_xr_session_exists(const wmXrData *xr)
+{
+  return xr->runtime && xr->runtime->context && xr->runtime->session_state.is_started;
+}
+
+/**
+ * Check if the session is running, according to the OpenXR definition.
+ */
+bool WM_xr_session_is_ready(const wmXrData *xr)
+{
+  return WM_xr_session_exists(xr) && GHOST_XrSessionIsRunning(xr->runtime->context);
+}
+
+static void wm_xr_session_base_pose_calc(const Scene *scene,
+                                         const XrSessionSettings *settings,
+                                         GHOST_XrPose *r_base_pose)
+{
+  const Object *base_pose_object = ((settings->base_pose_type == XR_BASE_POSE_OBJECT) &&
+                                    settings->base_pose_object) ?
+                                       settings->base_pose_object :
+                                       scene->camera;
+
+  if (settings->base_pose_type == XR_BASE_POSE_CUSTOM) {
+    float tmp_quatx[4], tmp_quatz[4];
+
+    copy_v3_v3(r_base_pose->position, settings->base_pose_location);
+    axis_angle_to_quat_single(tmp_quatx, 'X', M_PI_2);
+    axis_angle_to_quat_single(tmp_quatz, 'Z', settings->base_pose_angle);
+    mul_qt_qtqt(r_base_pose->orientation_quat, tmp_quatz, tmp_quatx);
+  }
+  else if (base_pose_object) {
+    float tmp_quat[4];
+    float tmp_eul[3];
+
+    mat4_to_loc_quat(r_base_pose->position, tmp_quat, base_pose_object->obmat);
+
+    /* Only use rotation around Z-axis to align view with floor. */
+    quat_to_eul(tmp_eul, tmp_quat);
+    tmp_eul[0] = M_PI_2;
+    tmp_eul[1] = 0;
+    eul_to_quat(r_base_pose->orientation_quat, tmp_eul);
+  }
+  else {
+    copy_v3_fl(r_base_pose->position, 0.0f);
+    axis_angle_to_quat_single(r_base_pose->orientation_quat, 'X', M_PI_2);
+  }
+}
+
+static void wm_xr_session_draw_data_populate(wmXrData *xr_data,
+                                             Scene *scene,
+                                             Depsgraph *depsgraph,
+                                             wmXrDrawData *r_draw_data)
+{
+  const XrSessionSettings *settings = &xr_data->session_settings;
+
+  memset(r_draw_data, 0, sizeof(*r_draw_data));
+  r_draw_data->scene = scene;
+  r_draw_data->depsgraph = depsgraph;
+  r_draw_data->xr_data = xr_data;
+  r_draw_data->surface_data = g_xr_surface->customdata;
+
+  wm_xr_session_base_pose_calc(r_draw_data->scene, settings, &r_draw_data->base_pose);
+}
+
+void wm_xr_session_draw_data_update(const wmXrSessionState *state,
+                                    const XrSessionSettings *settings,
+                                    const GHOST_XrDrawViewInfo *draw_view,
+                                    wmXrDrawData *draw_data)
+{
+  const bool position_tracking_toggled = ((state->prev_settings_flag &
+                                           XR_SESSION_USE_POSITION_TRACKING) !=
+                                          (settings->flag & XR_SESSION_USE_POSITION_TRACKING));
+  const bool use_position_tracking = settings->flag & XR_SESSION_USE_POSITION_TRACKING;
+
+  /* Set the eye position offset, it's used to offset the base pose when changing positional
+   * tracking. */
+  if (!state->is_view_data_set) {
+    /* Always use the exact base pose with no offset when starting the session. */
+    copy_v3_fl(draw_data->eye_position_ofs, 0.0f);
+  }
+  else if (position_tracking_toggled) {
+    if (use_position_tracking) {
+      copy_v3_fl(draw_data->eye_position_ofs, 0.0f);
+    }
+    else {
+      /* Store the current local offset (local pose) so that we can apply that to the eyes. This
+       * way the eyes stay exactly where they are when disabling positional tracking. */
+      copy_v3_v3(draw_data->eye_position_ofs, draw_view->local_pose.position);
+    }
+  }
+  else if (!use_position_tracking) {
+    /* Keep previous offset when positional tracking is disabled. */
+    copy_v3_v3(draw_data->eye_position_ofs, state->prev_eye_position_ofs);
+  }
+}
+
+/**
+ * Update information that is only stored for external state queries. E.g. for Python API to
+ * request the current (as in, last known) viewer pose.
+ */
+void wm_xr_session_state_update(const XrSessionSettings *settings,
+                                const wmXrDrawData *draw_data,
+                                const GHOST_XrDrawViewInfo *draw_view,
+                                wmXrSessionState *state)
+{
+  GHOST_XrPose viewer_pose;
+  const bool use_position_tracking = settings->flag & XR_SESSION_USE_POSITION_TRACKING;
+
+  mul_qt_qtqt(viewer_pose.orientation_quat,
+              draw_data->base_pose.orientation_quat,
+              draw_view->local_pose.orientation_quat);
+  copy_v3_v3(viewer_pose.position, draw_data->base_pose.position);
+  /* The local pose and the eye pose (which is copied from an earlier local pose) both are view
+   * space, so Y-up. In this case we need them in regular Z-up. */
+  viewer_pose.position[0] += draw_data->eye_position_ofs[0];
+  viewer_pose.position[1] -= draw_data->eye_position_ofs[2];
+  viewer_pose.position[2] += draw_data->eye_position_ofs[1];
+  if (use_position_tracking) {
+    viewer_pose.position[0] += draw_view->local_pose.position[0];
+    viewer_pose.position[1] -= draw_view->local_pose.position[2];
+    viewer_pose.position[2] += draw_view->local_pose.position[1];
+  }
+
+  copy_v3_v3(state->viewer_pose.position, viewer_pose.position);
+  copy_qt_qt(state->viewer_pose.orientation_quat, viewer_pose.orientation_quat);
+  wm_xr_pose_to_viewmat(&viewer_pose, state->viewer_viewmat);
+  /* No idea why, but multiplying by two seems to make it match the VR view more. */
+  state->focal_len = 2.0f *
+                     fov_to_focallength(draw_view->fov.angle_right - draw_view->fov.angle_left,
+                                        DEFAULT_SENSOR_WIDTH);
+
+  copy_v3_v3(state->prev_eye_position_ofs, draw_data->eye_position_ofs);
+  state->prev_settings_flag = settings->flag;
+  state->is_view_data_set = true;
+}
+
+wmXrSessionState *WM_xr_session_state_handle_get(const wmXrData *xr)
+{
+  return xr->runtime ? &xr->runtime->session_state : NULL;
+}
+
+bool WM_xr_session_state_viewer_pose_location_get(const wmXrData *xr, float r_location[3])
+{
+  if (!WM_xr_session_is_ready(xr) || !xr->runtime->session_state.is_view_data_set) {
+    zero_v3(r_location);
+    return false;
+  }
+
+  copy_v3_v3(r_location, xr->runtime->session_state.viewer_pose.position);
+  return true;
+}
+
+bool WM_xr_session_state_viewer_pose_rotation_get(const wmXrData *xr, float r_rotation[4])
+{
+  if (!WM_xr_session_is_ready(xr) || !xr->runtime->session_state.is_view_data_set) {
+    unit_qt(r_rotation);
+    return false;
+  }
+
+  copy_v4_v4(r_rotation, xr->runtime->session_state.viewer_pose.orientation_quat);
+  return true;
+}
+
+bool WM_xr_session_state_viewer_pose_matrix_info_get(const wmXrData *xr,
+                                                     float r_viewmat[4][4],
+                                                     float *r_focal_len)
+{
+  if (!WM_xr_session_is_ready(xr) || !xr->runtime->session_state.is_view_data_set) {
+    unit_m4(r_viewmat);
+    *r_focal_len = 0.0f;
+    return false;
+  }
+
+  copy_m4_m4(r_viewmat, xr->runtime->session_state.viewer_viewmat);
+  *r_focal_len = xr->runtime->session_state.focal_len;
+
+  return true;
+}
+
+/* -------------------------------------------------------------------- */
+/** \name XR-Session Surface
+ *
+ * A wmSurface is used to manage drawing of the VR viewport. It's created and destroyed with the
+ * session.
+ *
+ * \{ */
+
+/**
+ * \brief Call Ghost-XR to draw a frame
+ *
+ * Draw callback for the XR-session surface. It's expected to be called on each main loop iteration
+ * and tells Ghost-XR to submit a new frame by drawing its views. Note that for drawing each view,
+ * #wm_xr_draw_view() will be called through Ghost-XR (see GHOST_XrDrawViewFunc()).
+ */
+static void wm_xr_session_surface_draw(bContext *C)
+{
+  wmXrSurfaceData *surface_data = g_xr_surface->customdata;
+  wmWindowManager *wm = CTX_wm_manager(C);
+  wmXrDrawData draw_data;
+
+  if (!GHOST_XrSessionIsRunning(wm->xr.runtime->context)) {
+    return;
+  }
+  wm_xr_session_draw_data_populate(
+      &wm->xr, CTX_data_scene(C), CTX_data_ensure_evaluated_depsgraph(C), &draw_data);
+
+  DRW_xr_drawing_begin();
+
+  GHOST_XrSessionDrawViews(wm->xr.runtime->context, &draw_data);
+
+  GPU_offscreen_unbind(surface_data->offscreen, false);
+  DRW_xr_drawing_end();
+}
+
+bool wm_xr_session_surface_offscreen_ensure(wmXrSurfaceData *surface_data,
+                                            const GHOST_XrDrawViewInfo *draw_view)
+{
+  const bool size_changed = surface_data->offscreen &&
+                            (GPU_offscreen_width(surface_data->offscreen) != draw_view->width) &&
+                            (GPU_offscreen_height(surface_data->offscreen) != draw_view->height);
+  char err_out[256] = "unknown";
+  bool failure = false;
+
+  if (surface_data->offscreen) {
+    BLI_assert(surface_data->viewport);
+
+    if (!size_changed) {
+      return true;
+    }
+    GPU_viewport_free(surface_data->viewport);
+    GPU_offscreen_free(surface_data->offscreen);
+  }
+
+  if (!(surface_data->offscreen = GPU_offscreen_create(
+            draw_view->width, draw_view->height, 0, true, false, err_out))) {
+    failure = true;
+  }
+
+  if (failure) {
+    /* Pass. */
+  }
+  else if (!(surface_data->viewport = GPU_viewport_create())) {
+    GPU_offscreen_free(surface_data->offscreen);
+    failure = true;
+  }
+
+  if (failure) {
+    CLOG_ERROR(&LOG, "Failed to get buffer, %s\n", err_out);
+    return false;
+  }
+
+  return true;
+}
+
+static void wm_xr_session_surface_free_data(wmSurface *surface)
+{
+  wmXrSurfaceData *data = surface->customdata;
+
+  if (data->viewport) {
+    GPU_viewport_free(data->viewport);
+  }
+  if (data->offscreen) {
+    GPU_offscreen_free(data->offscreen);
+  }
+
+  MEM_freeN(surface->customdata);
+
+  g_xr_surface = NULL;
+}
+
+static wmSurface *wm_xr_session_surface_create(void)
+{
+  if (g_xr_surface) {
+    BLI_assert(false);
+    return g_xr_surface;
+  }
+
+  wmSurface *surface = MEM_callocN(sizeof(*surface), __func__);
+  wmXrSurfaceData *data = MEM_callocN(sizeof(*data), "XrSurfaceData");
+
+  surface->draw = wm_xr_session_surface_draw;
+  surface->free_data = wm_xr_session_surface_free_data;
+  surface->ghost_ctx = DRW_xr_opengl_context_get();
+  surface->gpu_ctx = DRW_xr_gpu_context_get();
+
+  surface->customdata = data;
+
+  g_xr_surface = surface;
+
+  return surface;
+}
+
+void *wm_xr_session_gpu_binding_context_create(void)
+{
+  wmSurface *surface = wm_xr_session_surface_create();
+
+  wm_surface_add(surface);
+
+  /* Some regions may need to redraw with updated session state after the session is entirely up
+   * and running. */
+  WM_main_add_notifier(NC_WM | ND_XR_DATA_CHANGED, NULL);
+
+  return surface->ghost_ctx;
+}
+
+void wm_xr_session_gpu_binding_context_destroy(GHOST_ContextHandle UNUSED(context))
+{
+  if (g_xr_surface) { /* Might have been freed already */
+    wm_surface_remove(g_xr_surface);
+  }
+
+  wm_window_reset_drawable();
+
+  /* Some regions may need to redraw with updated session state after the session is entirely
+   * stopped. */
+  WM_main_add_notifier(NC_WM | ND_XR_DATA_CHANGED, NULL);
+}
+
+/** \} */ /* XR-Session Surface */
diff --git a/source/blender/windowmanager/xr/wm_xr.h b/source/blender/windowmanager/xr/wm_xr.h
new file mode 100644
index 00000000000..33f79bc75b2
--- /dev/null
+++ b/source/blender/windowmanager/xr/wm_xr.h
@@ -0,0 +1,35 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup wm
+ */
+
+#ifndef __WM_XR_H__
+#define __WM_XR_H__
+
+struct wmWindowManager;
+struct wmXrData;
+
+typedef void (*wmXrSessionExitFn)(const wmXrData *xr_data);
+
+/* wm_xr.c */
+bool wm_xr_init(wmWindowManager *wm);
+void wm_xr_exit(wmWindowManager *wm);
+void wm_xr_session_toggle(wmWindowManager *wm, wmXrSessionExitFn session_exit_fn);
+bool wm_xr_events_handle(wmWindowManager *wm);
+
+#endif