Optimization for text drawing on OpenGL

Only call glBindTexture() if the glyph cache texture is not already
bound. This can potentially give performance improvement of around 30%.

Reviewed-by: Gunnar

2 files changed, 8 insertions, 2 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 74ec97b..fe6d15c 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1596,7 +1596,10 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
     //### TODO: Gamma correction
 
     glActiveTexture(GL_TEXTURE0 + QT_MASK_TEXTURE_UNIT);
-    glBindTexture(GL_TEXTURE_2D, cache->texture());
+    if (lastMaskTextureUsed != cache->texture()) {
+        glBindTexture(GL_TEXTURE_2D, cache->texture());
+        lastMaskTextureUsed = cache->texture();
+    }
     updateTextureFilter(GL_TEXTURE_2D, GL_REPEAT, false);
 
     shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::MaskTexture), QT_MASK_TEXTURE_UNIT);
@@ -1861,6 +1864,7 @@ void QGL2PaintEngineEx::ensureActive()
         d->transferMode(BrushDrawingMode);
         glViewport(0, 0, d->width, d->height);
         d->needsSync = false;
+        d->lastMaskTextureUsed = 0;
         d->shaderManager->setDirty();
         d->ctx->d_func()->syncGlState();
         for (int i = 0; i < 3; ++i)
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index c60eac1..7108741 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -176,7 +176,8 @@ public:
             useSystemClip(true),
             snapToPixelGrid(false),
             addOffset(false),
-            inverseScale(1)
+            inverseScale(1),
+            lastMaskTextureUsed(0)
     { }
 
     ~QGL2PaintEngineExPrivate();
@@ -278,6 +279,7 @@ public:
     GLfloat inverseScale;
 
     GLuint lastTextureUsed;
+    GLuint lastMaskTextureUsed;
 
     bool needsSync;
     bool multisamplingAlwaysEnabled;