Fix T57650 UVEdit: selection not visible if behind unselected UVs

Use depth buffer to order the uv edges correctly to always draw selected
edges on top.
We still use the double drawing workaround for points to keep the smooth
antialiased display.

3 files changed, 9 insertions, 2 deletions

diff --git a/source/blender/gpu/GPU_framebuffer.h b/source/blender/gpu/GPU_framebuffer.h
index 3cc972fabfb..b919a3dd8f3 100644
--- a/source/blender/gpu/GPU_framebuffer.h
+++ b/source/blender/gpu/GPU_framebuffer.h
@@ -209,6 +209,7 @@ void GPU_offscreen_viewport_data_get(GPUOffScreen *ofs,
                                      struct GPUTexture **r_depth);
 
 void GPU_clear_color(float red, float green, float blue, float alpha);
+void GPU_clear_depth(float depth);
 void GPU_clear(eGPUFrameBufferBits flags);
 
 #ifdef __cplusplus
diff --git a/source/blender/gpu/intern/gpu_framebuffer.c b/source/blender/gpu/intern/gpu_framebuffer.c
index 5950027a103..27a088fa922 100644
--- a/source/blender/gpu/intern/gpu_framebuffer.c
+++ b/source/blender/gpu/intern/gpu_framebuffer.c
@@ -1041,6 +1041,11 @@ void GPU_clear_color(float red, float green, float blue, float alpha)
   glClearColor(red, green, blue, alpha);
 }
 
+void GPU_clear_depth(float depth)
+{
+  glClearDepth(depth);
+}
+
 void GPU_clear(eGPUFrameBufferBits flags)
 {
   glClear(convert_buffer_bits_to_gl(flags));
diff --git a/source/blender/gpu/shaders/gpu_shader_2D_edituvs_edges_vert.glsl b/source/blender/gpu/shaders/gpu_shader_2D_edituvs_edges_vert.glsl
index 5c6b8f0a1a1..02bbe545436 100644
--- a/source/blender/gpu/shaders/gpu_shader_2D_edituvs_edges_vert.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_2D_edituvs_edges_vert.glsl
@@ -19,13 +19,14 @@ flat out vec4 finalColor;
 
 void main()
 {
-  gl_Position = ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0);
-
 #ifdef SMOOTH_COLOR
   bool is_select = (flag & VERT_UV_SELECT) != 0;
 #else
   bool is_select = (flag & EDGE_UV_SELECT) != 0;
 #endif
 
+  gl_Position = ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0);
+  gl_Position.z = float(!is_select);
+
   finalColor = (is_select) ? selectColor : edgeColor;
 }