kicad-developers team mailing list archive

[Jon Evans <jon@xxxxxxxxxxxxx>]

Fixes background color being wrong in OpenGL canvas when AA is disabled

From a741215326bd1ff4ca5b1fca830970ad72c3028c Mon Sep 17 00:00:00 2001
From: Jon Evans <jon@xxxxxxxxxxxxx>
Date: Thu, 4 Jan 2018 23:46:50 -0500
Subject: [PATCH] OpenGL: use source alpha only for direct (no AA) rendering

Without this change, the background color was getting drawn twice and
multiplied together if AA is disabled.

Fixes: lp:1741363
* https://bugs.launchpad.net/kicad/+bug/1741363
---
 common/gal/opengl/opengl_compositor.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/common/gal/opengl/opengl_compositor.cpp b/common/gal/opengl/opengl_compositor.cpp
index 8b7e3d1a7..173cd6421 100644
--- a/common/gal/opengl/opengl_compositor.cpp
+++ b/common/gal/opengl/opengl_compositor.cpp
@@ -330,7 +330,10 @@ void OPENGL_COMPOSITOR::DrawBuffer( unsigned int aSourceHandle, unsigned int aDe
 
     // Depth test has to be disabled to make transparency working
     glDisable( GL_DEPTH_TEST );
-    glBlendFunc( GL_ONE, GL_ONE_MINUS_SRC_ALPHA );
+
+    // Use source alpha only for direct (no AA) rendering
+    GLenum sfactor = ( aDestHandle == DIRECT_RENDERING ) ? GL_SRC_ALPHA : GL_ONE;
+    glBlendFunc( sfactor, GL_ONE_MINUS_SRC_ALPHA );
 
     // Enable texturing and bind the main texture
     glEnable( GL_TEXTURE_2D );
-- 
2.14.1