Use DrawManager for Image/UV Editor

This project moves the current UV/Image editor drawing to the draw manager.
Why would we do this:

**Performance**:

Current implementation would draw each texel per time. Multiple texels could be
drawn per pixel what would overwrite the previous result. You can notice this
when working with large textures. Repeat image drawing made this visible by
drawing for a small period of time and stop drawing the rest. Now the rendering
is fast and all repeated images are drawn.

**Alpha drawing**:

Current implementation would draw directly in display space. Giving incorrect
results when displaying alpha transparent images.
This addresses {T52680}, {T74709}, {T79518}
The image editor now can show emission only colors. See {D8234} for
examples.

**Current Limitations**

Using images that are larger than supported by your GPU are resized (eg larger
than 16000x16000 are resized to 8k). This leaves some blurring artifacts. It is
a low priority to add support back of displaying individual pixels of huge
images. There is a design task {T80113} with more detail.

**Implementation overview**
Introduced an Image Engine in the draw module. this engine is responsible for
drawing the texture in the main area of the UV/Image editor. The overlay engine
has a edit_uv overlay which is responsible to draw the UV's, shadows and
overlays specifically for the UV Image editor. The background + checker pattern
is drawn by the overlay_background.

The patch will allow us to share overlays between the 3d viewport and UV/Image
editor more easily. In most cases we just need to switch the `pos` with the `u`
attribute in the vertex shader.

The project can be activated in the user preferences as experimental features.
In a later commit this will be reversed.

Reviewed By: Clément Foucault

Differential Revision: https://developer.blender.org/D8234

1 files changed, 283 insertions, 31 deletions

diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index e6d51bce54e..203f8af130d 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -78,6 +78,7 @@
 #include "RE_pipeline.h"
 
 #include "UI_resources.h"
+#include "UI_view2d.h"
 
 #include "WM_api.h"
 #include "wm_window.h"
@@ -94,6 +95,7 @@
 #include "engines/eevee/eevee_engine.h"
 #include "engines/external/external_engine.h"
 #include "engines/gpencil/gpencil_engine.h"
+#include "engines/image/image_engine.h"
 #include "engines/overlay/overlay_engine.h"
 #include "engines/select/select_engine.h"
 #include "engines/workbench/workbench_engine.h"
@@ -126,6 +128,25 @@ static void drw_state_ensure_not_reused(DRWManager *dst)
 }
 #endif
 
+static bool drw_draw_show_annotation(void)
+{
+  if (DST.draw_ctx.space_data == NULL) {
+    View3D *v3d = DST.draw_ctx.v3d;
+    return (v3d && ((v3d->flag2 & V3D_SHOW_ANNOTATION) != 0) &&
+            ((v3d->flag2 & V3D_HIDE_OVERLAYS) == 0));
+  }
+
+  switch (DST.draw_ctx.space_data->spacetype) {
+    case SPACE_IMAGE: {
+      SpaceImage *sima = (SpaceImage *)DST.draw_ctx.space_data;
+      return (sima->flag & SI_SHOW_GPENCIL) != 0;
+    }
+    default:
+      BLI_assert("");
+      return false;
+  }
+}
+
 /* -------------------------------------------------------------------- */
 /** \name Threading
  * \{ */
@@ -287,6 +308,7 @@ struct DupliObject *DRW_object_get_dupli(const Object *UNUSED(ob))
 /** \name Color Management
  * \{ */
 
+/* TODO(fclem) This should be a render engine callback to determine if we need CM or not. */
 static void drw_viewport_colormanagement_set(void)
 {
   Scene *scene = DST.draw_ctx.scene;
@@ -296,21 +318,43 @@ static void drw_viewport_colormanagement_set(void)
   ColorManagedViewSettings view_settings;
   float dither = 0.0f;
 
-  /* TODO(fclem) This should be a render engine callback to determine if we need CM or not. */
-  bool use_workbench = BKE_scene_uses_blender_workbench(scene);
-
-  bool use_scene_lights = (!v3d ||
-                           ((v3d->shading.type == OB_MATERIAL) &&
-                            (v3d->shading.flag & V3D_SHADING_SCENE_LIGHTS)) ||
-                           ((v3d->shading.type == OB_RENDER) &&
-                            (v3d->shading.flag & V3D_SHADING_SCENE_LIGHTS_RENDER)));
-  bool use_scene_world =
-      (!v3d ||
-       ((v3d->shading.type == OB_MATERIAL) && (v3d->shading.flag & V3D_SHADING_SCENE_WORLD)) ||
-       ((v3d->shading.type == OB_RENDER) && (v3d->shading.flag & V3D_SHADING_SCENE_WORLD_RENDER)));
-  bool use_view_transform = v3d && (v3d->shading.type >= OB_MATERIAL);
-  bool use_render_settings = v3d && ((use_workbench && use_view_transform) || use_scene_lights ||
-                                     use_scene_world);
+  bool use_render_settings = false;
+  bool use_view_transform = false;
+
+  if (v3d) {
+    bool use_workbench = BKE_scene_uses_blender_workbench(scene);
+
+    bool use_scene_lights = (!v3d ||
+                             ((v3d->shading.type == OB_MATERIAL) &&
+                              (v3d->shading.flag & V3D_SHADING_SCENE_LIGHTS)) ||
+                             ((v3d->shading.type == OB_RENDER) &&
+                              (v3d->shading.flag & V3D_SHADING_SCENE_LIGHTS_RENDER)));
+    bool use_scene_world = (!v3d ||
+                            ((v3d->shading.type == OB_MATERIAL) &&
+                             (v3d->shading.flag & V3D_SHADING_SCENE_WORLD)) ||
+                            ((v3d->shading.type == OB_RENDER) &&
+                             (v3d->shading.flag & V3D_SHADING_SCENE_WORLD_RENDER)));
+    use_view_transform = v3d && (v3d->shading.type >= OB_MATERIAL);
+    use_render_settings = v3d && ((use_workbench && use_view_transform) || use_scene_lights ||
+                                  use_scene_world);
+  }
+  else if (DST.draw_ctx.space_data && DST.draw_ctx.space_data->spacetype == SPACE_IMAGE) {
+    SpaceImage *sima = (SpaceImage *)DST.draw_ctx.space_data;
+    Image *image = sima->image;
+
+    /* Use inverse logic as there isn't a setting for `Color And Alpha`. */
+    const eSpaceImage_Flag display_channels_mode = sima->flag;
+    const bool display_color_channel = (display_channels_mode & (SI_SHOW_ALPHA | SI_SHOW_ZBUF)) ==
+                                       0;
+    if (display_color_channel && image && (image->source != IMA_SRC_GENERATED) &&
+        ((image->flag & IMA_VIEW_AS_RENDER) != 0)) {
+      use_render_settings = true;
+    }
+  }
+  else {
+    use_render_settings = true;
+    use_view_transform = false;
+  }
 
   if (use_render_settings) {
     /* Use full render settings, for renders with scene lighting. */
@@ -495,6 +539,8 @@ static void draw_unit_state_create(void)
 static void drw_viewport_var_init(void)
 {
   RegionView3D *rv3d = DST.draw_ctx.rv3d;
+  ARegion *region = DST.draw_ctx.region;
+
   /* Refresh DST.size */
   if (DST.viewport) {
     int size[2];
@@ -585,6 +631,24 @@ static void drw_viewport_var_init(void)
     DST.view_active = DST.view_default;
     DST.view_previous = NULL;
   }
+  else if (region) {
+    View2D *v2d = &region->v2d;
+    float viewmat[4][4];
+    float winmat[4][4];
+
+    rctf region_space = {0.0f, 1.0f, 0.0f, 1.0f};
+    BLI_rctf_transform_calc_m4_pivot_min(&v2d->cur, &region_space, viewmat);
+
+    unit_m4(winmat);
+    winmat[0][0] = 2.0f;
+    winmat[1][1] = 2.0f;
+    winmat[3][0] = -1.0f;
+    winmat[3][1] = -1.0f;
+
+    DST.view_default = DRW_view_create(viewmat, winmat, NULL, NULL, NULL);
+    DST.view_active = DST.view_default;
+    DST.view_previous = NULL;
+  }
   else {
     zero_v3(DST.screenvecs[0]);
     zero_v3(DST.screenvecs[1]);
@@ -596,7 +660,7 @@ static void drw_viewport_var_init(void)
   }
 
   /* fclem: Is this still needed ? */
-  if (DST.draw_ctx.object_edit) {
+  if (DST.draw_ctx.object_edit && rv3d) {
     ED_view3d_init_mats_rv3d(DST.draw_ctx.object_edit, rv3d);
   }
 
@@ -1163,6 +1227,19 @@ static void drw_engines_enable_basic(void)
   use_drw_engine(&draw_engine_basic_type);
 }
 
+static void drw_engines_enable_editors(void)
+{
+  SpaceLink *space_data = DST.draw_ctx.space_data;
+  if (!space_data) {
+    return;
+  }
+
+  if (space_data->spacetype == SPACE_IMAGE) {
+    use_drw_engine(&draw_engine_image_type);
+    use_drw_engine(&draw_engine_overlay_type);
+  }
+}
+
 static void drw_engines_enable(ViewLayer *UNUSED(view_layer),
                                RenderEngineType *engine_type,
                                bool gpencil_engine_needed)
@@ -1299,8 +1376,7 @@ void DRW_draw_callbacks_post_scene(void)
   View3D *v3d = DST.draw_ctx.v3d;
   Depsgraph *depsgraph = DST.draw_ctx.depsgraph;
 
-  const bool do_annotations = (v3d && ((v3d->flag2 & V3D_SHOW_ANNOTATION) != 0) &&
-                               ((v3d->flag2 & V3D_HIDE_OVERLAYS) == 0));
+  const bool do_annotations = drw_draw_show_annotation();
 
   if (DST.draw_ctx.evil_C) {
     DefaultFramebufferList *dfbl = DRW_viewport_framebuffer_list_get();
@@ -1387,21 +1463,30 @@ struct DRWTextStore *DRW_text_cache_ensure(void)
  * for each relevant engine / mode engine. */
 void DRW_draw_view(const bContext *C)
 {
-  Depsgraph *depsgraph = CTX_data_expect_evaluated_depsgraph(C);
-  ARegion *region = CTX_wm_region(C);
   View3D *v3d = CTX_wm_view3d(C);
-  Scene *scene = DEG_get_evaluated_scene(depsgraph);
-  RenderEngineType *engine_type = ED_view3d_engine_type(scene, v3d->shading.type);
-  GPUViewport *viewport = WM_draw_region_get_bound_viewport(region);
+  if (v3d) {
+    Depsgraph *depsgraph = CTX_data_expect_evaluated_depsgraph(C);
+    ARegion *region = CTX_wm_region(C);
+    Scene *scene = DEG_get_evaluated_scene(depsgraph);
+    RenderEngineType *engine_type = ED_view3d_engine_type(scene, v3d->shading.type);
+    GPUViewport *viewport = WM_draw_region_get_bound_viewport(region);
 
-  /* Reset before using it. */
-  drw_state_prepare_clean_for_draw(&DST);
-  DST.options.draw_text = ((v3d->flag2 & V3D_HIDE_OVERLAYS) == 0 &&
-                           (v3d->overlay.flag & V3D_OVERLAY_HIDE_TEXT) != 0);
-  DST.options.draw_background = (scene->r.alphamode == R_ADDSKY) ||
-                                (v3d->shading.type != OB_RENDER);
-  DST.options.do_color_management = true;
-  DRW_draw_render_loop_ex(depsgraph, engine_type, region, v3d, viewport, C);
+    /* Reset before using it. */
+    drw_state_prepare_clean_for_draw(&DST);
+    DST.options.draw_text = ((v3d->flag2 & V3D_HIDE_OVERLAYS) == 0 &&
+                             (v3d->overlay.flag & V3D_OVERLAY_HIDE_TEXT) != 0);
+    DST.options.draw_background = (scene->r.alphamode == R_ADDSKY) ||
+                                  (v3d->shading.type != OB_RENDER);
+    DST.options.do_color_management = true;
+    DRW_draw_render_loop_ex(depsgraph, engine_type, region, v3d, viewport, C);
+  }
+  else {
+    Depsgraph *depsgraph = CTX_data_expect_evaluated_depsgraph(C);
+    ARegion *ar = CTX_wm_region(C);
+    GPUViewport *viewport = WM_draw_region_get_bound_viewport(ar);
+    drw_state_prepare_clean_for_draw(&DST);
+    DRW_draw_render_loop_2d_ex(depsgraph, ar, viewport, C);
+  }
 }
 
 /**
@@ -1909,6 +1994,171 @@ void DRW_cache_restart(void)
   copy_v2_v2(DST.inv_size, inv_size);
 }
 
+void DRW_draw_render_loop_2d_ex(struct Depsgraph *depsgraph,
+                                ARegion *region,
+                                GPUViewport *viewport,
+                                const bContext *evil_C)
+{
+  Scene *scene = DEG_get_evaluated_scene(depsgraph);
+  ViewLayer *view_layer = DEG_get_evaluated_view_layer(depsgraph);
+
+  DST.draw_ctx.evil_C = evil_C;
+  DST.viewport = viewport;
+
+  /* Setup viewport */
+  DST.draw_ctx = (DRWContextState){
+      .region = region,
+      .scene = scene,
+      .view_layer = view_layer,
+      .obact = OBACT(view_layer),
+      .depsgraph = depsgraph,
+      .space_data = CTX_wm_space_data(evil_C),
+
+      /* reuse if caller sets */
+      .evil_C = DST.draw_ctx.evil_C,
+  };
+
+  drw_context_state_init();
+  drw_viewport_var_init();
+  drw_viewport_colormanagement_set();
+
+  /* TODO(jbakker): Only populate when editor needs to draw object.
+   * for the image editor this is when showing UV's.*/
+  const bool do_populate_loop = true;
+  const bool do_annotations = drw_draw_show_annotation();
+
+  /* Get list of enabled engines */
+  drw_engines_enable_editors();
+  drw_engines_data_validate();
+
+  /* Update ubos */
+  DRW_globals_update();
+
+  drw_debug_init();
+
+  /* No framebuffer allowed before drawing. */
+  BLI_assert(GPU_framebuffer_active_get() == GPU_framebuffer_back_get());
+  GPU_framebuffer_bind(DST.default_framebuffer);
+  GPU_framebuffer_clear_depth_stencil(DST.default_framebuffer, 1.0f, 0xFF);
+
+  /* Init engines */
+  drw_engines_init();
+  drw_task_graph_init();
+
+  /* Cache filling */
+  {
+    PROFILE_START(stime);
+    drw_engines_cache_init();
+
+    /* Only iterate over objects when overlay uses object data. */
+    if (do_populate_loop) {
+      DEG_OBJECT_ITER_FOR_RENDER_ENGINE_BEGIN (depsgraph, ob) {
+        drw_engines_cache_populate(ob);
+      }
+      DEG_OBJECT_ITER_FOR_RENDER_ENGINE_END;
+    }
+
+    drw_engines_cache_finish();
+
+    DRW_render_instance_buffer_finish();
+
+#ifdef USE_PROFILE
+    double *cache_time = GPU_viewport_cache_time_get(DST.viewport);
+    PROFILE_END_UPDATE(*cache_time, stime);
+#endif
+  }
+  drw_task_graph_deinit();
+
+  DRW_stats_begin();
+
+  GPU_framebuffer_bind(DST.default_framebuffer);
+
+  /* Start Drawing */
+  DRW_state_reset();
+
+  if (DST.draw_ctx.evil_C) {
+    ED_region_draw_cb_draw(DST.draw_ctx.evil_C, DST.draw_ctx.region, REGION_DRAW_PRE_VIEW);
+  }
+
+  drw_engines_draw_scene();
+
+  /* Fix 3D view being "laggy" on macos and win+nvidia. (See T56996, T61474) */
+  GPU_flush();
+
+  if (DST.draw_ctx.evil_C) {
+    DefaultFramebufferList *dfbl = DRW_viewport_framebuffer_list_get();
+    DRW_state_reset();
+
+    GPU_framebuffer_bind(dfbl->overlay_fb);
+
+    if (do_annotations) {
+      GPU_depth_test(false);
+      GPU_matrix_push_projection();
+      wmOrtho2(
+          region->v2d.cur.xmin, region->v2d.cur.xmax, region->v2d.cur.ymin, region->v2d.cur.ymax);
+      ED_annotation_draw_view2d(DST.draw_ctx.evil_C, true);
+      GPU_matrix_pop_projection();
+
+      GPU_depth_test(true);
+    }
+
+    GPU_depth_test(false);
+    ED_region_draw_cb_draw(DST.draw_ctx.evil_C, DST.draw_ctx.region, REGION_DRAW_POST_VIEW);
+    GPU_depth_test(true);
+    /* Callback can be nasty and do whatever they want with the state.
+     * Don't trust them! */
+    DRW_state_reset();
+
+    GPU_depth_test(false);
+    drw_engines_draw_text();
+    GPU_depth_test(true);
+
+    if (do_annotations) {
+      GPU_depth_test(false);
+      ED_annotation_draw_view2d(DST.draw_ctx.evil_C, false);
+      GPU_depth_test(true);
+    }
+  }
+
+  DRW_draw_cursor_2d();
+  ED_region_pixelspace(DST.draw_ctx.region);
+
+  {
+    GPU_depth_test(false);
+    DRW_draw_gizmo_2d();
+    GPU_depth_test(true);
+  }
+
+  DRW_stats_reset();
+
+  if (G.debug_value > 20 && G.debug_value < 30) {
+    GPU_depth_test(false);
+    /* local coordinate visible rect inside region, to accommodate overlapping ui */
+    const rcti *rect = ED_region_visible_rect(DST.draw_ctx.region);
+    DRW_stats_draw(rect);
+    GPU_depth_test(true);
+  }
+
+  if (WM_draw_region_get_bound_viewport(region)) {
+    /* Don't unbind the framebuffer yet in this case and let
+     * GPU_viewport_unbind do it, so that we can still do further
+     * drawing of action zones on top. */
+  }
+  else {
+    GPU_framebuffer_restore();
+  }
+
+  DRW_state_reset();
+  drw_engines_disable();
+
+  drw_viewport_cache_resize();
+
+#ifdef DEBUG
+  /* Avoid accidental reuse. */
+  drw_state_ensure_not_reused(&DST);
+#endif
+}
+
 static struct DRWSelectBuffer {
   struct GPUFrameBuffer *framebuffer_depth_only;
   struct GPUTexture *texture_depth;
@@ -2637,6 +2887,8 @@ void DRW_engines_register(void)
   DRW_engine_register(&draw_engine_select_type);
   DRW_engine_register(&draw_engine_basic_type);
 
+  DRW_engine_register(&draw_engine_image_type);
+
   /* setup callbacks */
   {
     BKE_mball_batch_cache_dirty_tag_cb = DRW_mball_batch_cache_dirty_tag;