From 65755f9a68947e774c640ce92c022d677acdcc4a Mon Sep 17 00:00:00 2001
From: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>
Date: Tue, 6 Nov 2012 12:22:39 +0100
Subject: [PATCH] Fix native RGB text on OpenGL ES 2 without BGRA extension
MIME-Version: 1.0
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Angle, for instance, which is now the default on Windows,
does not support the GL_BGRA_EXT format as input for
glTexSubImage2D(). In the case where it's not detected, we
therefore need to flip the bytes in the input.

Change-Id: Ibe78d0223e3c2c39cb1943cdcf67103044d00aa7
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>
---
 src/gui/opengl/qopenglfunctions.cpp         |  4 ++++
 src/gui/opengl/qopengltextureglyphcache.cpp | 18 +++++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/gui/opengl/qopenglfunctions.cpp b/src/gui/opengl/qopenglfunctions.cpp
index e2191d6f3a..4d6a0e437d 100644
--- a/src/gui/opengl/qopenglfunctions.cpp
+++ b/src/gui/opengl/qopenglfunctions.cpp
@@ -344,6 +344,10 @@ static int qt_gl_resolve_extensions()
         extensions |= QOpenGLExtensions::ElementIndexUint;
     if (extensionMatcher.match("GL_OES_depth24"))
         extensions |= QOpenGLExtensions::Depth24;
+
+    if (extensionMatcher.match("GL_EXT_bgra"))
+        extensions |= QOpenGLExtensions::BGRATextureFormat;
+
 #else
     extensions |= QOpenGLExtensions::ElementIndexUint | QOpenGLExtensions::MapBuffer;
 
diff --git a/src/gui/opengl/qopengltextureglyphcache.cpp b/src/gui/opengl/qopengltextureglyphcache.cpp
index 4538961359..4e20f6aad2 100644
--- a/src/gui/opengl/qopengltextureglyphcache.cpp
+++ b/src/gui/opengl/qopengltextureglyphcache.cpp
@@ -42,6 +42,7 @@
 #include "qopengltextureglyphcache_p.h"
 #include "qopenglpaintengine_p.h"
 #include "private/qopenglengineshadersource_p.h"
+#include "qopenglextensions_p.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -301,6 +302,11 @@ void QOpenGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph, QFixed
     const int maskWidth = mask.width();
     const int maskHeight = mask.height();
 
+#if defined(QT_OPENGL_ES_2)
+    QOpenGLExtensions extensions(ctx);
+    bool hasBGRA = extensions.hasOpenGLExtension(QOpenGLExtensions::BGRATextureFormat);
+#endif
+
     if (mask.format() == QImage::Format_Mono) {
         mask = mask.convertToFormat(QImage::Format_Indexed8);
         for (int y = 0; y < maskHeight; ++y) {
@@ -318,7 +324,14 @@ void QOpenGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph, QFixed
                 uchar g = src[x] >> 8;
                 uchar b = src[x];
                 quint32 avg = (quint32(r) + quint32(g) + quint32(b) + 1) / 3; // "+1" for rounding.
-                src[x] = (src[x] & 0x00ffffff) | (avg << 24);
+
+#if defined(QT_OPENGL_ES_2)
+                if (!hasBGRA) {
+                    // Reverse bytes to match GL_RGBA
+                    src[x] = (avg << 24) | (quint32(r) << 0) | (quint32(g) << 8) | (quint32(b) << 16);
+                } else
+#endif
+                    src[x] = (src[x] & 0x00ffffff) | (avg << 24);
             }
         }
     }
@@ -326,8 +339,7 @@ void QOpenGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph, QFixed
     glBindTexture(GL_TEXTURE_2D, m_textureResource->m_texture);
     if (mask.format() == QImage::Format_RGB32) {
 #if defined(QT_OPENGL_ES_2)
-        // ###TODO Ensure extension is actually present on ES2
-        glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, GL_BGRA_EXT, GL_UNSIGNED_BYTE, mask.bits());
+        glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, hasBGRA ? GL_BGRA_EXT : GL_RGBA, GL_UNSIGNED_BYTE, mask.bits());
 #else
         glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, GL_BGRA, GL_UNSIGNED_BYTE, mask.bits());
 #endif