Revert "Don't define highp/mediump/lowp if desktop GL has them"

This reverts commit 6155050.
The GL_ARB_ES2_compatibility extension does not mention the lowp,
mediump or highp keywords.

Task-number: QTBUG-14384
Reviewed-by: Samuel
Reviewed-by: Prasanth

Author: Trond Kjernåsen

dist/changes-4.6.4

@@ -66,8 +66,6 @@ QtOpenGL
  - QGLShaderProgram
     * [QTBUG-12478] Don't resolve GLSL extensions if no shaders.
     * [QTBUG-12591] setUniformValue(QSize) was setting (w,w) not (w,h).
-    * [QTBUG-12862] Don't #define highp/mediump/lowp if the desktop OpenGL
-      implementation has the GL_ARB_ES2_compatibility extension.
     * [QTBUG-12554] Wrong OpenGLVersionFlags on OpenGL 4.0 systems.
 
 QtScript
@@ -109,7 +107,7 @@ Third party components
 Qt for Unix (X11 and Mac OS X)
 ------------------------------
 
- - 
+ -
 
 Qt for Linux/X11
 ----------------

src/opengl/qgl.cpp

@@ -4933,8 +4933,6 @@ QGLExtensions::Extensions QGLExtensions::currentContextExtensions()
         glExtensions |= FragmentShader;
     if (extensions.match("GL_ARB_shader_objects"))
         glExtensions |= FragmentShader;
-    if (extensions.match("GL_ARB_ES2_compatibility"))
-        glExtensions |= ES2Compatibility;
     if (extensions.match("GL_ARB_texture_mirrored_repeat"))
         glExtensions |= MirroredRepeat;
     if (extensions.match("GL_EXT_framebuffer_object"))
@@ -4953,7 +4951,6 @@ QGLExtensions::Extensions QGLExtensions::currentContextExtensions()
     glExtensions |= FramebufferObject;
     glExtensions |= GenerateMipmap;
     glExtensions |= FragmentShader;
-    glExtensions |= ES2Compatibility;
 #endif
 #if defined(QT_OPENGL_ES_1) || defined(QT_OPENGL_ES_1_CL)
     if (extensions.match("GL_OES_framebuffer_object"))

src/opengl/qgl_p.h

@@ -291,8 +291,7 @@ class QGLExtensions {
         DDSTextureCompression   = 0x00008000,
         ETC1TextureCompression  = 0x00010000,
         PVRTCTextureCompression = 0x00020000,
-        FragmentShader          = 0x00040000,
-        ES2Compatibility        = 0x00080000
+        FragmentShader          = 0x00040000
     };
     Q_DECLARE_FLAGS(Extensions, Extension)
 

src/opengl/qglshaderprogram.cpp

@@ -97,10 +97,6 @@ QT_BEGIN_NAMESPACE
     to just features that are present in GLSL/ES, and avoid
     standard variable names that only work on the desktop.
 
-    If the \c{GL_ARB_ES2_compatibility} extension is present,
-    then the above prefix is not added because the desktop OpenGL
-    implementation supports precision qualifiers.
-
     \section1 Simple shader example
 
     \snippet doc/src/snippets/code/src_opengl_qglshaderprogram.cpp 1
@@ -394,10 +390,8 @@ bool QGLShader::compileSourceCode(const char *source)
             srclen.append(GLint(headerLen));
         }
 #ifdef QGL_DEFINE_QUALIFIERS
-        if (!(QGLExtensions::glExtensions() & QGLExtensions::ES2Compatibility)) {
-            src.append(qualifierDefines);
-            srclen.append(GLint(sizeof(qualifierDefines) - 1));
-        }
+        src.append(qualifierDefines);
+        srclen.append(GLint(sizeof(qualifierDefines) - 1));
 #endif
 #ifdef QGL_REDEFINE_HIGHP
         if (d->shaderType == Fragment) {