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

OpenGL 4.0 systems now have compatibility with ES2, including
support for the precision qualifiers.  If the GL_ARB_ES2_compatibility
extension is present, then we don't define highp/mediump/lowp
to the empty string.

Task-number: QTBUG-12862
Reviewed-by: Sarah Smith

1 files changed, 8 insertions, 2 deletions

diff --git a/src/opengl/qglshaderprogram.cpp b/src/opengl/qglshaderprogram.cpp
index edbb635..9bfe027 100644
--- a/src/opengl/qglshaderprogram.cpp
+++ b/src/opengl/qglshaderprogram.cpp
@@ -97,6 +97,10 @@ 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
@@ -390,8 +394,10 @@ bool QGLShader::compileSourceCode(const char *source)
             srclen.append(GLint(headerLen));
         }
 #ifdef QGL_DEFINE_QUALIFIERS
-        src.append(qualifierDefines);
-        srclen.append(GLint(sizeof(qualifierDefines) - 1));
+        if (!(QGLExtensions::glExtensions() & QGLExtensions::ES2Compatibility)) {
+            src.append(qualifierDefines);
+            srclen.append(GLint(sizeof(qualifierDefines) - 1));
+        }
 #endif
 #ifdef QGL_REDEFINE_HIGHP
         if (d->shaderType == Fragment) {