Optimize texture glyph cache

To avoid calling the bounding box function for the same non-printable
characters in every call, we cache them as empty in the coords table
and bail out before painting them. This patch also fixes some possible
reads of uninitialized memory (reference to return value) and reference
to a default constructed object consisting of uninitialized pods.

Reviewed-by: Samuel

1 files changed, 12 insertions, 8 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index cdd785a..771d33f 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1556,7 +1556,6 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
         }
     }
 
-
     if (recreateVertexArrays) {
         vertexCoordinates->clear();
         textureCoordinates->clear();
@@ -1569,7 +1568,10 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
 
             QTextureGlyphCache::GlyphAndSubPixelPosition glyph(staticTextItem->glyphs[i], subPixelPosition);
 
-            const QTextureGlyphCache::Coord &c = cache->coords.value(glyph);
+            const QTextureGlyphCache::Coord &c = cache->coords[glyph];
+            if (c.isNull())
+                continue;
+
             int x = staticTextItem->glyphPositions[i].x.toInt() + c.baseLineX - margin;
             int y = staticTextItem->glyphPositions[i].y.toInt() - c.baseLineY - margin;
 
@@ -1580,10 +1582,12 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
         staticTextItem->userDataNeedsUpdate = false;
     }
 
-    if (elementIndices.size() < staticTextItem->numGlyphs*6) {
+    int numGlyphs = vertexCoordinates->vertexCount() / 4;
+
+    if (elementIndices.size() < numGlyphs*6) {
         Q_ASSERT(elementIndices.size() % 6 == 0);
         int j = elementIndices.size() / 6 * 4;
-        while (j < staticTextItem->numGlyphs*4) {
+        while (j < numGlyphs*4) {
             elementIndices.append(j + 0);
             elementIndices.append(j + 0);
             elementIndices.append(j + 1);
@@ -1672,9 +1676,9 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
             updateTextureFilter(GL_TEXTURE_2D, GL_REPEAT, false);
 
 #if defined(QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO)
-            glDrawElements(GL_TRIANGLE_STRIP, 6 * staticTextItem->numGlyphs, GL_UNSIGNED_SHORT, 0);
+            glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, 0);
 #else
-            glDrawElements(GL_TRIANGLE_STRIP, 6 * staticTextItem->numGlyphs, GL_UNSIGNED_SHORT, elementIndices.data());
+            glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, elementIndices.data());
 #endif
 
             shaderManager->setMaskType(QGLEngineShaderManager::SubPixelMaskPass2);
@@ -1722,10 +1726,10 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
     }
 
 #if defined(QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO)
-    glDrawElements(GL_TRIANGLE_STRIP, 6 * staticTextItem->numGlyphs, GL_UNSIGNED_SHORT, 0);
+    glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, 0);
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
 #else
-    glDrawElements(GL_TRIANGLE_STRIP, 6 * staticTextItem->numGlyphs, GL_UNSIGNED_SHORT, elementIndices.data());
+    glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, elementIndices.data());
 #endif
 }