Don't use GL_REPEAT for NPOT textures in GLES2.

We already handle NPOT textures correctly by calling fract() on the
texture coordinates in the fragment shader, but we also need to make
sure not to set GL_REPEAT as the wrap mode, because the GLES2 spec says
that the driver should return (0, 0, 0, 1) if an NPOT texture has wrap
mode different from GL_CLAMP_TO_EDGE. Previous GLES2-implementations
we've tested on have thus not been GLES2-compliant (or supported
GL_OES_texture_npot).

Partial back-port / modification of
c5a377e944f9a87c372ff8371c66b03d861803a6 in 4.8.

Reviewed-by: Kim

1 files changed, 12 insertions, 1 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 803f949..047d589 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -90,6 +90,11 @@
 
 QT_BEGIN_NAMESPACE
 
+inline static bool isPowerOfTwo(uint x)
+{
+    return x && !(x & (x - 1));
+}
+
 #if defined(Q_WS_WIN)
 extern Q_GUI_EXPORT bool qt_cleartype_enabled;
 #endif
@@ -229,7 +234,13 @@ void QGL2PaintEngineExPrivate::updateBrushTexture()
         QGLTexture *tex = ctx->d_func()->bindTexture(currentBrushPixmap, GL_TEXTURE_2D, GL_RGBA,
                                                      QGLContext::InternalBindOption |
                                                      QGLContext::CanFlipNativePixmapBindOption);
-        updateTextureFilter(GL_TEXTURE_2D, GL_REPEAT, q->state()->renderHints & QPainter::SmoothPixmapTransform);
+        GLenum wrapMode = GL_REPEAT;
+#ifdef QT_OPENGL_ES_2
+        // should check for GL_OES_texture_npot or GL_IMG_texture_npot extension
+        if (!isPowerOfTwo(currentBrushPixmap.width()) || !isPowerOfTwo(currentBrushPixmap.height()))
+            wrapMode = GL_CLAMP_TO_EDGE;
+#endif
+        updateTextureFilter(GL_TEXTURE_2D, wrapMode, q->state()->renderHints & QPainter::SmoothPixmapTransform);
         textureInvertedY = tex->options & QGLContext::InvertedYBindOption ? -1 : 1;
     }
     brushTextureDirty = false;