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, 13 insertions, 18 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_2D_area_borders_vert.glsl b/source/blender/gpu/shaders/gpu_shader_2D_area_borders_vert.glsl
index 5326076e269..816e12342a1 100644
--- a/source/blender/gpu/shaders/gpu_shader_2D_area_borders_vert.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_2D_area_borders_vert.glsl
@@ -7,35 +7,30 @@ uniform float scale;
 
 in vec2 pos;
 
-const vec2 jitter_ofs[8] = vec2[8](
-	vec2( 0.468813, -0.481430), vec2(-0.155755, -0.352820),
-	vec2( 0.219306, -0.238501), vec2(-0.393286, -0.110949),
-	vec2(-0.024699,  0.013908), vec2( 0.343805,  0.147431),
-	vec2(-0.272855,  0.269918), vec2( 0.095909,  0.388710)
-);
+out vec2 uv;
+
 
 void main()
 {
 	int corner_id = (gl_VertexID / cornerLen) % 4;
-	int jitter_id = gl_VertexID / (cornerLen * 4) % 8;
 
 	vec2 final_pos = pos * scale;
 
-	if (corner_id == 0)
+	if (corner_id == 0) {
+		uv = pos + vec2(1.0, 1.0);
 		final_pos += rect.yw;  /* top right */
-	else if (corner_id == 1)
+	}
+	else if (corner_id == 1) {
+		uv = pos + vec2(-1.0, 1.0);
 		final_pos += rect.xw;  /* top left */
-	else if (corner_id == 2)
+	}
+	else if (corner_id == 2) {
+		uv = pos + vec2(-1.0, -1.0);
 		final_pos += rect.xz;  /* bottom left */
-	else
+	}
+	else {
+		uv = pos + vec2(1.0, -1.0);
 		final_pos += rect.yz;  /* bottom right */
-
-	/* Only jitter verts inside the corner (not the one shared with the edges). */
-	if ((gl_VertexID % cornerLen) % (cornerLen - 2) != 0) {
-		/* Only jitter intern verts not boundaries. */
-		if ((gl_VertexID % 2) == 0) {
-			final_pos += jitter_ofs[jitter_id];
-		}
 	}
 
 	gl_Position = (ModelViewProjectionMatrix * vec4(final_pos, 0.0, 1.0));