Refactor|GL|libgui: Use Qt 5.4 OpenGL APIs, renamed GLTarget/GLFrameb…

…uffer

Qt 5 comes with new OpenGL classes (prefix "QOpenGL") and a portable
way to access OpenGL and extension functions. This commit takes these
into use and removes the old custom "glentrypoints".

The functionality of the GL code was not changed, and the OpenGL
version is kept at 2.1 (for now). Bumping to OpenGL 3/4 will require
larger revisions in the world renderer.

Multisampling is temporarily disabled pending a better implementation.

`GLTarget` was renamed to `GLFramebuffer` to more clearly indicate that
this is a wrapper around an FBO.

(The old) `GLFramebuffer` was renamed to `GLTextureFramebuffer` and is
now a subclass of (the new) `GLFramebuffer`, to indicate that this is
a specialized FBO that owns the buffer textures.

doomsday/sdk/libcore/include/de/libcore.h

@@ -72,9 +72,10 @@
 
 #if defined(__cplusplus) && !defined(DENG2_C_API_ONLY)
 #  define DENG2_USE_QT
+#  include <cstddef> // size_t
+#  include <cstring> // memset
 #  include <typeinfo>
 #  include <memory>  // unique_ptr, shared_ptr
-#  include <cstring> // memset
 #endif
 
 #if defined(__x86_64__) || defined(__x86_64) || defined(_LP64) || defined(DENG_64BIT_HOST)

doomsday/sdk/libgui/CMakeLists.txt

@@ -51,6 +51,12 @@ set (CMAKE_C_FLAGS ${oldCFlags})
 # Apply Doomsday's configuration.
 include (../../cmake/Config.cmake)
 
+# libgui uses Qt 5.4 OpenGL APIs.
+qmake_query (QT_VERSION "QT_VERSION")
+if (QT_VERSION VERSION_LESS 5.4)
+    message (FATAL_ERROR "libgui requires Qt 5.4 or newer! You can disable all GUI features with DENG_ENABLE_GUI=OFF.")
+endif ()
+
 if (APPLE)
     # Don't change display modes on OS X. We'll instead resize the
     # frame buffer and scale up.
@@ -65,8 +71,6 @@ option (DENG_ENABLE_DISPLAYMODE "Enable/disable changing the display mode"
 # Dependencies.
 find_package (DengCore)
 find_package (Assimp REQUIRED)
-include (OpenGL)
-
 if (DENG_X11)
     find_package (X11 REQUIRED)
 endif ()
@@ -97,9 +101,9 @@ deng_add_library (libgui ${SOURCES} ${HEADERS})
 
 target_link_libraries (libgui
     PUBLIC Deng::libcore
-    PRIVATE opengl libassimp
+    PRIVATE libassimp
 )
-deng_target_link_qt (libgui PUBLIC Gui OpenGL)
+deng_target_link_qt (libgui PUBLIC Gui OpenGLExtensions Widgets)
 
 if (UNIX AND NOT APPLE)
     # The assimp target may be linked to some system libraries that

doomsday/sdk/libgui/include/de/GLTextureFramebuffer

@@ -0,0 +1 @@
+#include "graphics/gltextureframebuffer.h"

doomsday/sdk/libgui/include/de/graphics/drawable.h

@@ -13,7 +13,7 @@
  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
  * General Public License for more details. You should have received a copy of
  * the GNU Lesser General Public License along with this program; if not, see:
- * http://www.gnu.org/licenses</small> 
+ * http://www.gnu.org/licenses</small>
  */
 
 #ifndef LIBGUI_DRAWABLE_H
@@ -35,7 +35,7 @@ namespace de {
 /**
  * Drawable object with buffers, programs and states.
  *
- * This is the higher level, flexible, user-friendly combination of the lower
+ * This is the higher level, flexible and user-friendly combination of the lower
  * level GL classes. It is not mandatory to use this class for drawing; one can
  * always use the lower level classes directly.
  *