Fixed uploading of glyphs to the glyph cache in the GL2 engine.

Upload the glyph one scanline at a time to work around what probably is
a driver bug. This replaces a previous fix
6d0290b2202d4fc084595ba678c2a2d984392e72.

Reviewed-by: Tom

1 files changed, 15 insertions, 5 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index a3475c7..3f14fdf 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -261,11 +261,21 @@ 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 {
-        // 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());
+#ifdef QT_OPENGL_ES2
+        glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, GL_ALPHA, GL_UNSIGNED_BYTE, mask.bits());
+#else
+        // glTexSubImage2D() might cause some garbage to appear in the texture if the mask width is
+        // not a multiple of four bytes. The bug appeared on a computer with 32-bit Windows Vista
+        // and nVidia GeForce 8500GT. GL_UNPACK_ALIGNMENT is set to four bytes, 'mask' has a
+        // multiple of four bytes per line, and most of the glyph shows up correctly in the
+        // texture, which makes me think that this is a driver bug.
+        // One workaround is to make sure the mask width is a multiple of four bytes, for instance
+        // by converting it to a format with four bytes per pixel. Another is to copy one line at a
+        // time.
+
+        for (uint 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));
+#endif
     }
 }