Support Alpha8 and Grayscale8 natively in the OpenGL paint engine

Adds special shaders for the Alpha8 and Grayscale8 formats so that
they do not need to rely on the support of GL_ALPHA and GL_LUMINANCE
that has been removed from core in recent OpenGL versions.

Change-Id: Ie370379b458abf2a50e252bc5099aefc1b11fb1d
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 21 insertions, 4 deletions

diff --git a/src/gui/opengl/qopengltexturecache.cpp b/src/gui/opengl/qopengltexturecache.cpp
index 5ac5eb94b6..f85a26cd6e 100644
--- a/src/gui/opengl/qopengltexturecache.cpp
+++ b/src/gui/opengl/qopengltexturecache.cpp
@@ -41,6 +41,10 @@
 
 QT_BEGIN_NAMESPACE
 
+#ifndef GL_RED
+#define GL_RED                            0x1903
+#endif
+
 #ifndef GL_RGB10_A2
 #define GL_RGB10_A2                       0x8059
 #endif
@@ -273,21 +277,34 @@ GLuint QOpenGLTextureCache::bindTexture(QOpenGLContext *context, qint64 key, con
         pixelType = GL_UNSIGNED_BYTE;
         targetFormat = image.format();
         break;
+    case QImage::Format_Indexed8:
+        if (options & UseRedFor8BitBindOption) {
+            externalFormat = internalFormat = GL_RED;
+            pixelType = GL_UNSIGNED_BYTE;
+            targetFormat = image.format();
+        }
+        break;
     case QImage::Format_Alpha8:
-        if (context->isOpenGLES() || context->format().profile() != QSurfaceFormat::CoreProfile) {
+        if (options & UseRedFor8BitBindOption) {
+            externalFormat = internalFormat = GL_RED;
+            pixelType = GL_UNSIGNED_BYTE;
+            targetFormat = image.format();
+        } else if (context->isOpenGLES() || context->format().profile() != QSurfaceFormat::CoreProfile) {
             externalFormat = internalFormat = GL_ALPHA;
             pixelType = GL_UNSIGNED_BYTE;
             targetFormat = image.format();
         }
-        // ### add support for core profiles.
         break;
     case QImage::Format_Grayscale8:
-        if (context->isOpenGLES() || context->format().profile() != QSurfaceFormat::CoreProfile) {
+        if (options & UseRedFor8BitBindOption) {
+            externalFormat = internalFormat = GL_RED;
+            pixelType = GL_UNSIGNED_BYTE;
+            targetFormat = image.format();
+        } else if (context->isOpenGLES() || context->format().profile() != QSurfaceFormat::CoreProfile) {
             externalFormat = internalFormat = GL_LUMINANCE;
             pixelType = GL_UNSIGNED_BYTE;
             targetFormat = image.format();
         }
-        // ### add support for core profiles.
         break;
     default:
         break;