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, 149 insertions, 0 deletions

diff --git a/source/blender/draw/engines/overlay/overlay_shader.c b/source/blender/draw/engines/overlay/overlay_shader.c
index e3cb052890b..4530d6e8adf 100644
--- a/source/blender/draw/engines/overlay/overlay_shader.c
+++ b/source/blender/draw/engines/overlay/overlay_shader.c
@@ -70,6 +70,15 @@ extern char datatoc_edit_mesh_analysis_vert_glsl[];
 extern char datatoc_edit_mesh_analysis_frag_glsl[];
 extern char datatoc_edit_particle_strand_vert_glsl[];
 extern char datatoc_edit_particle_point_vert_glsl[];
+extern char datatoc_edit_uv_verts_vert_glsl[];
+extern char datatoc_edit_uv_verts_frag_glsl[];
+extern char datatoc_edit_uv_edges_vert_glsl[];
+extern char datatoc_edit_uv_edges_geom_glsl[];
+extern char datatoc_edit_uv_edges_frag_glsl[];
+extern char datatoc_edit_uv_faces_vert_glsl[];
+extern char datatoc_edit_uv_face_dots_vert_glsl[];
+extern char datatoc_edit_uv_stretching_vert_glsl[];
+extern char datatoc_edit_uv_tiled_image_borders_vert_glsl[];
 extern char datatoc_extra_frag_glsl[];
 extern char datatoc_extra_vert_glsl[];
 extern char datatoc_extra_groundline_vert_glsl[];
@@ -113,6 +122,7 @@ extern char datatoc_xray_fade_frag_glsl[];
 extern char datatoc_gpu_shader_depth_only_frag_glsl[];
 extern char datatoc_gpu_shader_point_varying_color_frag_glsl[];
 extern char datatoc_gpu_shader_3D_smooth_color_frag_glsl[];
+extern char datatoc_gpu_shader_2D_smooth_color_frag_glsl[];
 extern char datatoc_gpu_shader_uniform_color_frag_glsl[];
 extern char datatoc_gpu_shader_flat_color_frag_glsl[];
 extern char datatoc_gpu_shader_point_varying_color_varying_outline_aa_frag_glsl[];
@@ -120,6 +130,7 @@ extern char datatoc_gpu_shader_common_obinfos_lib_glsl[];
 
 extern char datatoc_gpencil_common_lib_glsl[];
 
+extern char datatoc_common_overlay_lib_glsl[];
 extern char datatoc_common_colormanagement_lib_glsl[];
 extern char datatoc_common_fullscreen_vert_glsl[];
 extern char datatoc_common_fxaa_lib_glsl[];
@@ -164,6 +175,13 @@ typedef struct OVERLAY_Shaders {
   GPUShader *edit_mesh_analysis;
   GPUShader *edit_particle_strand;
   GPUShader *edit_particle_point;
+  GPUShader *edit_uv_verts;
+  GPUShader *edit_uv_faces;
+  GPUShader *edit_uv_edges;
+  GPUShader *edit_uv_face_dots;
+  GPUShader *edit_uv_stretching_angle;
+  GPUShader *edit_uv_stretching_area;
+  GPUShader *edit_uv_tiled_image_borders;
   GPUShader *extra;
   GPUShader *extra_select;
   GPUShader *extra_groundline;
@@ -175,6 +193,7 @@ typedef struct OVERLAY_Shaders {
   GPUShader *facing;
   GPUShader *gpencil_canvas;
   GPUShader *grid;
+  GPUShader *grid_image;
   GPUShader *image;
   GPUShader *motion_path_line;
   GPUShader *motion_path_vert;
@@ -203,8 +222,20 @@ typedef struct OVERLAY_Shaders {
 
 static struct {
   OVERLAY_Shaders sh_data[GPU_SHADER_CFG_LEN];
+  DRWShaderLibrary *lib;
 } e_data = {{{NULL}}};
 
+void OVERLAY_shader_library_ensure(void)
+{
+  if (e_data.lib == NULL) {
+    e_data.lib = DRW_shader_library_create();
+    /* NOTE: Theses needs to be ordered by dependencies. */
+    DRW_SHADER_LIB_ADD(e_data.lib, common_globals_lib);
+    DRW_SHADER_LIB_ADD(e_data.lib, common_overlay_lib);
+    DRW_SHADER_LIB_ADD(e_data.lib, common_view_lib);
+  }
+}
+
 GPUShader *OVERLAY_shader_antialiasing(void)
 {
   OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
@@ -1012,6 +1043,20 @@ GPUShader *OVERLAY_shader_grid(void)
   return sh_data->grid;
 }
 
+GPUShader *OVERLAY_shader_grid_image(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->grid_image) {
+    sh_data->grid_image = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_tiled_image_borders_vert_glsl,
+        NULL,
+        datatoc_gpu_shader_uniform_color_frag_glsl,
+        e_data.lib,
+        "#define blender_srgb_to_framebuffer_space(a) a\n");
+  }
+  return sh_data->grid_image;
+}
+
 GPUShader *OVERLAY_shader_image(void)
 {
   const DRWContextState *draw_ctx = DRW_context_state_get();
@@ -1449,6 +1494,108 @@ GPUShader *OVERLAY_shader_xray_fade(void)
   return sh_data->xray_fade;
 }
 
+/* -------------------------------------------------------------------- */
+/** \name Edit UV shaders
+ * \{ */
+
+GPUShader *OVERLAY_shader_edit_uv_edges_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_edges) {
+    sh_data->edit_uv_edges = DRW_shader_create_with_shaderlib(datatoc_edit_uv_edges_vert_glsl,
+                                                              datatoc_edit_uv_edges_geom_glsl,
+                                                              datatoc_edit_uv_edges_frag_glsl,
+                                                              e_data.lib,
+                                                              NULL);
+  }
+  return sh_data->edit_uv_edges;
+}
+
+GPUShader *OVERLAY_shader_edit_uv_face_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_faces) {
+    sh_data->edit_uv_faces = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_faces_vert_glsl,
+        NULL,
+        datatoc_gpu_shader_flat_color_frag_glsl,
+        e_data.lib,
+        "#define blender_srgb_to_framebuffer_space(a) a\n");
+  }
+  return sh_data->edit_uv_faces;
+}
+
+GPUShader *OVERLAY_shader_edit_uv_face_dots_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_face_dots) {
+    sh_data->edit_uv_face_dots = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_face_dots_vert_glsl,
+        NULL,
+        datatoc_gpu_shader_flat_color_frag_glsl,
+        e_data.lib,
+        "#define blender_srgb_to_framebuffer_space(a) a\n");
+  }
+  return sh_data->edit_uv_face_dots;
+}
+
+GPUShader *OVERLAY_shader_edit_uv_verts_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_verts) {
+    sh_data->edit_uv_verts = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_verts_vert_glsl, NULL, datatoc_edit_uv_verts_frag_glsl, e_data.lib, NULL);
+  }
+
+  return sh_data->edit_uv_verts;
+}
+
+GPUShader *OVERLAY_shader_edit_uv_stretching_area_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_stretching_area) {
+    sh_data->edit_uv_stretching_area = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_stretching_vert_glsl,
+        NULL,
+        datatoc_gpu_shader_2D_smooth_color_frag_glsl,
+        e_data.lib,
+        "#define blender_srgb_to_framebuffer_space(a) a\n");
+  }
+
+  return sh_data->edit_uv_stretching_area;
+}
+
+GPUShader *OVERLAY_shader_edit_uv_stretching_angle_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_stretching_angle) {
+    sh_data->edit_uv_stretching_angle = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_stretching_vert_glsl,
+        NULL,
+        datatoc_gpu_shader_2D_smooth_color_frag_glsl,
+        e_data.lib,
+        "#define blender_srgb_to_framebuffer_space(a) a\n#define STRETCH_ANGLE\n");
+  }
+
+  return sh_data->edit_uv_stretching_angle;
+}
+
+GPUShader *OVERLAY_shader_edit_uv_tiled_image_borders_get(void)
+{
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[0];
+  if (!sh_data->edit_uv_tiled_image_borders) {
+    sh_data->edit_uv_tiled_image_borders = DRW_shader_create_with_shaderlib(
+        datatoc_edit_uv_tiled_image_borders_vert_glsl,
+        NULL,
+        datatoc_gpu_shader_uniform_color_frag_glsl,
+        e_data.lib,
+        "#define blender_srgb_to_framebuffer_space(a) a\n");
+  }
+  return sh_data->edit_uv_tiled_image_borders;
+}
+
+/* \} */
+
 static OVERLAY_InstanceFormats g_formats = {NULL};
 
 OVERLAY_InstanceFormats *OVERLAY_shader_instance_formats_get(void)
@@ -1521,6 +1668,8 @@ OVERLAY_InstanceFormats *OVERLAY_shader_instance_formats_get(void)
 
 void OVERLAY_shader_free(void)
 {
+  DRW_SHADER_LIB_FREE_SAFE(e_data.lib);
+
   for (int sh_data_index = 0; sh_data_index < ARRAY_SIZE(e_data.sh_data); sh_data_index++) {
     OVERLAY_Shaders *sh_data = &e_data.sh_data[sh_data_index];
     GPUShader **sh_data_as_array = (GPUShader **)sh_data;