Reset GL glyph cache when texture limit is reached

This is a port of 72f161739b270b01807f97cd853030440f0fd430 which was
reverted in integration to master, since it was incompatible with
the refactored glyph cache.

When the GL glyph cache reached its texture limit, we have to reset it
and start over. Added a new cleanup() function in
QGLContextGroupResourceBase which deletes the resource for a given
context and removes itself from that context group.

Task-number: QTBUG-13784
Reviewed-by: Samuel

3 files changed, 24 insertions, 2 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index a134078..1fa02e1 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1581,8 +1581,13 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
     // cache so this text is performed before we test if the cache size has changed.
     if (recreateVertexArrays) {
         cache->setPaintEnginePrivate(this);
-        cache->populate(staticTextItem->fontEngine(), staticTextItem->numGlyphs,
-                        staticTextItem->glyphs, staticTextItem->glyphPositions);
+        if (!cache->populate(staticTextItem->fontEngine(), staticTextItem->numGlyphs,
+                             staticTextItem->glyphs, staticTextItem->glyphPositions)) {
+            // No space for glyphs in cache. We need to reset it and try again.
+            cache->clear();
+            cache->populate(staticTextItem->fontEngine(), staticTextItem->numGlyphs,
+                            staticTextItem->glyphs, staticTextItem->glyphPositions);
+        }
         cache->fillInPendingGlyphs();
     }
 
diff --git a/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp b/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
index 9e8e828..c867d60 100644
--- a/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
+++ b/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
@@ -378,4 +378,19 @@ int QGLTextureGlyphCache::maxTextureHeight() const
     else
         return ctx->d_ptr->maxTextureSize();
 }
+
+void QGLTextureGlyphCache::clear()
+{
+    if (ctx != 0) {
+        m_textureResource.cleanup(ctx);
+
+        m_w = 0;
+        m_h = 0;
+        m_cx = 0;
+        m_cy = 0;
+        m_currentRowHeight = 0;
+        coords.clear();
+    }
+}
+
 QT_END_NAMESPACE
diff --git a/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h b/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h
index cc6de28..133289e 100644
--- a/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h
+++ b/src/opengl/gl2paintengineex/qtextureglyphcache_gl_p.h
@@ -142,6 +142,8 @@ public:
     FilterMode filterMode() const { return m_filterMode; }
     void setFilterMode(FilterMode m) { m_filterMode = m; }
 
+    void clear();
+
     void freeResource(void *) { ctx = 0; }
 
 private: