1 files changed, 28 insertions, 2 deletions
diff --git a/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp b/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
index 4362c0abd7..c867d60a72 100644
--- a/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
+++ b/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
@@ -339,8 +339,19 @@ void QGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph, QFixed sub
         // by converting it to a format with four bytes per pixel. Another is to copy one line at a
         // time.
 
-        for (int i = 0; i < maskHeight; ++i)
-            glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y + i, maskWidth, 1, GL_ALPHA, GL_UNSIGNED_BYTE, mask.scanLine(i));
+        if (!ctx->d_ptr->workaround_brokenAlphaTexSubImage_init) {
+            // don't know which driver versions exhibit this bug, so be conservative for now
+            const QByteArray versionString(reinterpret_cast<const char*>(glGetString(GL_VERSION)));
+            ctx->d_ptr->workaround_brokenAlphaTexSubImage = versionString.indexOf("NVIDIA") >= 0;
+            ctx->d_ptr->workaround_brokenAlphaTexSubImage_init = true;
+        }
+
+        if (ctx->d_ptr->workaround_brokenAlphaTexSubImage) {
+            for (int i = 0; i < maskHeight; ++i)
+                glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y + i, maskWidth, 1, GL_ALPHA, GL_UNSIGNED_BYTE, mask.scanLine(i));
+        } else {
+            glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, GL_ALPHA, GL_UNSIGNED_BYTE, mask.bits());
+        }
     }
 }
 
@@ -367,4 +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