UI: Simplify the area border drawing

Instead of doing a lot of alpha blended drawing with jittering, use the
fragment shader to do the masking using a circle mask.

This is much simpler and requires much less resources.

Hopefully this may solve the issue we have with the Intels UHD Graphics 620
on linux.

1 files changed, 16 insertions, 0 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_2D_area_borders_frag.glsl b/source/blender/gpu/shaders/gpu_shader_2D_area_borders_frag.glsl
new file mode 100644
index 00000000000..620568db500
--- /dev/null
+++ b/source/blender/gpu/shaders/gpu_shader_2D_area_borders_frag.glsl
@@ -0,0 +1,16 @@
+
+uniform vec4 color;
+uniform float scale;
+
+in vec2 uv;
+
+out vec4 fragColor;
+
+void main()
+{
+	/* Should be 0.8 but minimize the AA on the edges. */
+	float dist = (length(uv) - 0.78) * scale;
+
+	fragColor = color;
+	fragColor.a *= smoothstep(-0.09, 1.09, dist);
+}