Don't use GL_REPEAT for image-brush drawing on OpenGL ES2

Backport of commit 8dfeb1c374972f06759a92b4edc5d6a18b96ccec in QtGui
to the same class in the QtOpenGL module.

OpenGL ES2 doesn't support NPOT textures in combination with GL_REPEAT,
so for OpenGL ES2 we use a custom program that emulates repeat by taking
the fractional part of the texture coordinates.

This is not enough though, as merely setting GL_TEXTURE_WRAP_x to GL_REPEAT
with a NPOT texture is an error in some implementations, so we have to
guard the call to updateTextureFilter() in updateBrushTexture() with
a check for OpenGL ES2 and use GL_CLAMP_TO_EDGE instead.

Change-Id: Icbdd784c2c6d562849679f87da18b20d5441f389
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 2b49e4d2d1..2ec4434d57 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -223,11 +223,19 @@ void QGL2PaintEngineExPrivate::updateBrushTexture()
         if (currentBrushPixmap.width() > max_texture_size || currentBrushPixmap.height() > max_texture_size)
             currentBrushPixmap = currentBrushPixmap.scaled(max_texture_size, max_texture_size, Qt::KeepAspectRatio);
 
+        GLuint wrapMode = GL_REPEAT;
+        if (ctx->contextHandle()->isES()) {
+            // OpenGL ES does not support GL_REPEAT wrap modes for NPOT textures. So instead,
+            // we emulate GL_REPEAT by only taking the fractional part of the texture coords
+            // in the qopenglslTextureBrushSrcFragmentShader program.
+            wrapMode = GL_CLAMP_TO_EDGE;
+        }
+
         funcs.glActiveTexture(GL_TEXTURE0 + QT_BRUSH_TEXTURE_UNIT);
         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);
+        updateTextureFilter(GL_TEXTURE_2D, wrapMode, q->state()->renderHints & QPainter::SmoothPixmapTransform);
         textureInvertedY = tex->options & QGLContext::InvertedYBindOption ? -1 : 1;
     }
     brushTextureDirty = false;