OpenGL: Use official glext.h and gl2ext.h headers

The Khronos group makes the glext.h (Desktop OpenGL) and gl2ext.h
(OpenGL ES2) headers officially available nowadays. Most (all?)
Linux systems ship this by default. On Windows platforms the
glext.h file needs to be downloaded from

http://www.opengl.org/registry/api/glext.h

and placed alongside the system OpenGL header.

Making use of the official header reduces the maintenance
overhead for OpenGL support in Qt by removing the need to copy
and paste definitions into the Qt sources.

As the Khronos-provided headers are standardised and backwards and
forwards compatible we can utilise these for all platforms rather
than just for Windows. This means that all definitions required
by Qt will be present even if the system ships out-dated
equivalents.

Mac OS X needs special handling in that we should always use the
system-provided headers there. This is because Apple controls the
OpenGL driver and the headers that go along with it. As such there
is no possibility that the driver exposes additional functionality
compared with the system-provided OpenGL headers. Apple has also
decided to make different decisions about some OpenGL typedefs
compared to other implementations. For example, Apple typdefs
GLhandleARB to void* whereas other platforms use unsigned int.

The alternative, which is to use the system provided glext.h (or
gl2ext.h) header means that Qt code would need to check for the
availability of such definitions wherever it is not guaranteed
to be provided by core OpenGL/ES just to compile.

The proposed approach means that Qt can compile regardless of
the system's OpenGL extension support. We just need to be
rigourous in runtime checking of support for extensions but
that is already a requirement (and is missing in a few places,
see TODO's added in this commit).

The official Khronos headers are added to Qt as

qopenglext.h - Desktop OpenGL
qopengles2ext.h - OpenGL ES2

They need to be public but not part of QtGui module include, hence
the headers have been modified by adding

 #if 0
 #pragma qt_no_master_include
 #endif

to them.

This has been tested on:

Gentoo Linux with GCC 4.6.3
Windows 7 with MSVC 2010
Mac OSX 10.8 with Apple clang 4.0 (based on LLVM 3.1svn)
QNX with qcc (based on GCC 4.4)

A small change is needed to QtDeclarative when building for OpenGL
ES 2 after applying this commit. See
https://codereview.qt-project.org/#change,31794

Change-Id: I4b3d2b1680baf4c78be9a87b4d8de076d23e8f82
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

1 files changed, 26 insertions, 3 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index c55be6189c..2bd10de389 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -1760,11 +1760,22 @@ struct DDSFormat {
 #define FOURCC_DXT4  0x34545844
 #define FOURCC_DXT5  0x35545844
 
+// ####TODO Properly #ifdef this class to use #define symbols actually defined
+// by system GL includes
 #ifndef GL_COMPRESSED_RGB_S3TC_DXT1_EXT
 #define GL_COMPRESSED_RGB_S3TC_DXT1_EXT   0x83F0
+#endif
+
+#ifndef GL_COMPRESSED_RGBA_S3TC_DXT1_EXT
 #define GL_COMPRESSED_RGBA_S3TC_DXT1_EXT  0x83F1
-#define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT  0x83F2
-#define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT  0x83F3
+#endif
+
+#ifndef GL_COMPRESSED_RGBA_S3TC_DXT3_EXT
+#define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
+#endif
+
+#ifndef GL_COMPRESSED_RGBA_S3TC_DXT5_EXT
+#define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 #endif
 
 #ifndef GL_GENERATE_MIPMAP_SGIS
@@ -2146,6 +2157,12 @@ QGLTexture *QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
 
 // #define QGL_BIND_TEXTURE_DEBUG
 
+// ####TODO Properly #ifdef this file to use #define symbols actually defined
+// by OpenGL/ES includes
+#ifndef GL_UNSIGNED_INT_8_8_8_8_REV
+#define GL_UNSIGNED_INT_8_8_8_8_REV 0x8367
+#endif
+
 // map from Qt's ARGB endianness-dependent format to GL's big-endian RGBA layout
 static inline void qgl_byteSwapImage(QImage &img, GLenum pixel_type)
 {
@@ -4729,6 +4746,12 @@ void QGLExtensionMatcher::init(const char *str)
     }
 }
 
+// ####TODO Properly #ifdef this class to use #define symbols actually defined
+// by OpenGL/ES includes
+#ifndef GL_FRAMEBUFFER_SRGB_CAPABLE_EXT
+#define GL_FRAMEBUFFER_SRGB_CAPABLE_EXT 0x8DBA
+#endif
+
 /*
     Returns the GL extensions for the current context.
 */
@@ -4805,7 +4828,7 @@ QGLExtensions::Extensions QGLExtensions::currentContextExtensions()
 
     {
         GLboolean srgbCapableFramebuffers;
-        glGetBooleanv(FRAMEBUFFER_SRGB_CAPABLE_EXT, &srgbCapableFramebuffers);
+        glGetBooleanv(GL_FRAMEBUFFER_SRGB_CAPABLE_EXT, &srgbCapableFramebuffers);
         if (srgbCapableFramebuffers)
             glExtensions |= SRGBFrameBuffer;
     }