Fixed text rendering with the GL2 paint engine.

When copying a glyph image into the glyph cache, garbage appeared in
the glyph cache in the lower part of the destination rectangle. This
happened whenever the glyph image's width was not a multiple of four
bytes. I suppose this is a driver bug (nVidia). As a workaround, I
converted the glyph image to ARGB32 such that the width is guaranteed
to be a multiple of four bytes.

Reviewed-by: Tom

1 files changed, 5 insertions, 2 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index bcff29b..2bfbf4a 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -252,8 +252,11 @@ void QGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph)
     if (mask.format() == QImage::Format_RGB32) {
         glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, m_height - c.y, maskWidth, maskHeight, GL_BGRA, GL_UNSIGNED_BYTE, mask.bits());
     } else {
-        mask = mask.convertToFormat(QImage::Format_Indexed8);
-        glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, GL_ALPHA, GL_UNSIGNED_BYTE, mask.bits());
+        // If the width of the uploaded data is not a multiple of four bytes, we get some garbage
+        // in the glyph cache, probably because of a driver bug.
+        // Convert to ARGB32 to get a multiple of 4 bytes per line.
+        mask = mask.convertToFormat(QImage::Format_ARGB32);
+        glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, GL_BGRA, GL_UNSIGNED_BYTE, mask.bits());
     }
 }