OpenGL examples: Add error message about ANGLE on Windows

These OpenGL examples require a Desktop OpenGL and will
not build with OpenGL ES 2.0. This means those examples
do not build on Windows with the default configuration
using ANGLE.
ANGLE is wrapping OpenGL ES 2.0 to DirectX and does not support
the full Desktop OpenGL feature set.

Since this is confusing for Windows users that do not know about ANGLE
this patch adds an explicit error message describing the solution.
(configuring Qt with -opengl desktop)

Task-number: QTBUG-28590

Change-Id: I782e6830b9e282ddcc8a2ee0a47faf3579d36aab
Reviewed-by: hjk <qthjk@ovi.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
(cherry picked from commit 63693430c7)
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>

examples/opengl/framebufferobject2/framebufferobject2.pro

@@ -10,3 +10,9 @@ INSTALLS += target
 
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}

examples/opengl/grabber/grabber.pro

@@ -11,3 +11,9 @@ INSTALLS += target
 
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}

examples/opengl/hellogl/hellogl.pro

@@ -16,3 +16,9 @@ INSTALLS += target
 
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}

examples/opengl/overpainting/overpainting.pro

@@ -15,3 +15,9 @@ target.path = $$[QT_INSTALL_EXAMPLES]/opengl/overpainting
 INSTALLS += target
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}

examples/opengl/pbuffers/pbuffers.pro

@@ -11,3 +11,9 @@ target.path = $$[QT_INSTALL_EXAMPLES]/opengl/pbuffers
 INSTALLS += target
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}

examples/opengl/pbuffers2/pbuffers2.pro

@@ -9,3 +9,9 @@ target.path = $$[QT_INSTALL_EXAMPLES]/opengl/pbuffers2
 INSTALLS += target
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}

examples/opengl/samplebuffers/samplebuffers.pro

@@ -9,3 +9,9 @@ INSTALLS += target
 
 
 simulator: warning(This example might not fully work on Simulator platform)
+
+contains(QT_CONFIG, opengles.) {
+    contains(QT_CONFIG, angle): \
+        warning("Qt was built with ANGLE, which provides only OpenGL ES 2.0 on top of DirectX 9.0c")
+    error("This example requires Qt to be configured with -opengl desktop")
+}