XR: Add runtime window area for XR events

This adds an offscreen View3D window area for the VR view in order to
execute XR events/operators in the proper context. The area is created
as runtime data before XR events are dispatched and set as the active
area during XR event handling.

Since the area is runtime-only, it will not be saved in files and since
the area is offscreen, it will not interfere with regular window areas.
The area is removed with the rest of the XR runtime data on exit, file
read, or when stopping the VR session.

Note: This also adds internal types (EVT_DATA_XR, EVT_XR_ACTION) and
structs (wmXrActionData) for XR events.

Reviewed By: Severin

Differential Revision: https://developer.blender.org/D12472

1 files changed, 92 insertions, 0 deletions

diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index cc0a13e96af..c92208c4818 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -3461,6 +3461,70 @@ static void wm_event_free_and_remove_from_queue_if_valid(wmEvent *event)
  * Handle events for all windows, run from the #WM_main event loop.
  * \{ */
 
+#ifdef WITH_XR_OPENXR
+/**
+ * Special handling for XR events.
+ *
+ * Although XR events are added to regular window queues, they are handled in an "offscreen area"
+ * context that is owned entirely by XR runtime data and not tied to a window.
+ */
+static void wm_event_handle_xrevent(bContext *C,
+                                    wmWindowManager *wm,
+                                    wmWindow *win,
+                                    wmEvent *event)
+{
+  ScrArea *area = WM_xr_session_area_get(&wm->xr);
+  if (!area) {
+    return;
+  }
+  BLI_assert(area->spacetype == SPACE_VIEW3D && area->spacedata.first);
+
+  /* Find a valid region for XR operator execution and modal handling. */
+  ARegion *region = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
+  if (!region) {
+    return;
+  }
+  BLI_assert(WM_region_use_viewport(area, region)); /* For operators using GPU-based selection. */
+
+  CTX_wm_area_set(C, area);
+  CTX_wm_region_set(C, region);
+
+  int action = wm_handlers_do(C, event, &win->modalhandlers);
+
+  if ((action & WM_HANDLER_BREAK) == 0) {
+    wmXrActionData *actiondata = event->customdata;
+    if (actiondata->ot->modal && event->val == KM_RELEASE) {
+      /* Don't execute modal operators on release. */
+    }
+    else {
+      PointerRNA properties = {.type = actiondata->ot->srna, .data = actiondata->op_properties};
+      if (actiondata->ot->invoke) {
+        /* Invoke operator, either executing operator or transferring responsibility to window
+         * modal handlers. */
+        wm_operator_invoke(C,
+                           actiondata->ot,
+                           event,
+                           actiondata->op_properties ? &properties : NULL,
+                           NULL,
+                           false,
+                           false);
+      }
+      else {
+        /* Execute operator. */
+        wmOperator *op = wm_operator_create(
+            wm, actiondata->ot, actiondata->op_properties ? &properties : NULL, NULL);
+        if ((WM_operator_call(C, op) & OPERATOR_HANDLED) == 0) {
+          WM_operator_free(op);
+        }
+      }
+    }
+  }
+
+  CTX_wm_region_set(C, NULL);
+  CTX_wm_area_set(C, NULL);
+}
+#endif /* WITH_XR_OPENXR */
+
 /* Called in main loop. */
 /* Goes over entire hierarchy:  events -> window -> screen -> area -> region. */
 void wm_event_do_handlers(bContext *C)
@@ -3558,6 +3622,16 @@ void wm_event_do_handlers(bContext *C)
 
       CTX_wm_window_set(C, win);
 
+#ifdef WITH_XR_OPENXR
+      if (event->type == EVT_XR_ACTION) {
+        wm_event_handle_xrevent(C, wm, win, event);
+        BLI_remlink(&win->event_queue, event);
+        wm_event_free(event);
+        /* Skip mouse event handling below, which is unnecessary for XR events. */
+        continue;
+      }
+#endif
+
       /* Clear tool-tip on mouse move. */
       if (screen->tool_tip && screen->tool_tip->exit_on_event) {
         if (ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE)) {
@@ -5110,6 +5184,24 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, int type, void
 #endif
 }
 
+#ifdef WITH_XR_OPENXR
+void wm_event_add_xrevent(wmWindow *win, wmXrActionData *actiondata, short val)
+{
+  BLI_assert(val == KM_PRESS || val == KM_RELEASE);
+
+  wmEvent event = {
+      .type = EVT_XR_ACTION,
+      .val = val,
+      .is_repeat = false,
+      .custom = EVT_DATA_XR,
+      .customdata = actiondata,
+      .customdatafree = 1,
+  };
+
+  wm_event_add(win, &event);
+}
+#endif /* WITH_XR_OPENXR */
+
 /** \} */
 
 /* -------------------------------------------------------------------- */