1 files changed, 19 insertions, 0 deletions
diff --git a/src/opengl/util/fast_painter.glsl b/src/opengl/util/fast_painter.glsl
new file mode 100644
index 0000000..63f5e5f
--- /dev/null
+++ b/src/opengl/util/fast_painter.glsl
@@ -0,0 +1,19 @@
+// fast painter for composition modes which can be implemented with blendfuncs
+
+uniform sampler2D mask_texture;
+uniform vec2 inv_mask_size;
+uniform vec2 mask_offset;
+uniform vec4 mask_channel;
+
+float mask()
+{
+    return dot(mask_channel, texture2D(mask_texture, (gl_FragCoord.xy + mask_offset) * inv_mask_size));
+}
+
+void main()
+{
+    // combine clip and coverage channels
+    float mask_alpha = mask();
+
+    gl_FragColor = brush() * mask_alpha;
+}