windows: Use EGL extensions as they ought to be used

We take some shortcuts still because we know that with ANGLE the header
with the extension constants is always available. A proper implementation
would not rely on the constants being available and would dynamically
check for the extension and would take care of defining the constants if
not available. However, just getting the extension list to check if the
functions needed to get the display are available is already a chicken-egg
problem so we won't go there.

Using eglGetProcAddress properly solves the issues with static builds too
since this always works.

Task-number: QTBUG-46284
Change-Id: Iff23669ebacaffa0c5f76fd2c928af689307874f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Gunnar Roth
Reviewed-by: Andrew Knight <andrew.knight@intopalo.com>

1 files changed, 11 insertions, 5 deletions

diff --git a/src/plugins/platforms/windows/qwindowseglcontext.cpp b/src/plugins/platforms/windows/qwindowseglcontext.cpp
index 0184877fdd..06c9985cac 100644
--- a/src/plugins/platforms/windows/qwindowseglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowseglcontext.cpp
@@ -39,7 +39,6 @@
 #include <QtGui/QOpenGLContext>
 
 #if defined(QT_OPENGL_ES_2_ANGLE) || defined(QT_OPENGL_DYNAMIC)
-#  define EGL_EGLEXT_PROTOTYPES
 #  include <QtANGLE/EGL/eglext.h>
 #endif
 
@@ -137,7 +136,6 @@ bool QWindowsLibEGL::init()
 
     eglGetError = RESOLVE((EGLint (EGLAPIENTRY *)(void)), eglGetError);
     eglGetDisplay = RESOLVE((EGLDisplay (EGLAPIENTRY *)(EGLNativeDisplayType)), eglGetDisplay);
-    eglGetPlatformDisplayEXT = RESOLVE((EGLDisplay (EGLAPIENTRY *)(EGLenum platform, void *native_display, const EGLint *attrib_list)), eglGetPlatformDisplayEXT);
     eglInitialize = RESOLVE((EGLBoolean (EGLAPIENTRY *)(EGLDisplay, EGLint *, EGLint *)), eglInitialize);
     eglTerminate = RESOLVE((EGLBoolean (EGLAPIENTRY *)(EGLDisplay)), eglTerminate);
     eglChooseConfig = RESOLVE((EGLBoolean (EGLAPIENTRY *)(EGLDisplay, const EGLint *, EGLConfig *, EGLint, EGLint *)), eglChooseConfig);
@@ -156,7 +154,15 @@ bool QWindowsLibEGL::init()
     eglSwapBuffers = RESOLVE((EGLBoolean (EGLAPIENTRY *)(EGLDisplay , EGLSurface)), eglSwapBuffers);
     eglGetProcAddress = RESOLVE((__eglMustCastToProperFunctionPointerType (EGLAPIENTRY * )(const char *)), eglGetProcAddress);
 
-    return eglGetError && eglGetDisplay && eglInitialize;
+    if (!eglGetError || !eglGetDisplay || !eglInitialize || !eglGetProcAddress)
+        return false;
+
+    eglGetPlatformDisplayEXT = 0;
+#ifdef EGL_ANGLE_platform_angle
+    eglGetPlatformDisplayEXT = reinterpret_cast<EGLDisplay (EGLAPIENTRY *)(EGLenum, void *, const EGLint *)>(eglGetProcAddress("eglGetPlatformDisplayEXT"));
+#endif
+
+    return true;
 }
 
 #if !defined(QT_STATIC) || defined(QT_OPENGL_DYNAMIC)
@@ -360,7 +366,7 @@ QWindowsEGLStaticContext *QWindowsEGLStaticContext::create(QWindowsOpenGLTester:
     EGLDisplay display = EGL_NO_DISPLAY;
     EGLint major = 0;
     EGLint minor = 0;
-#ifdef EGL_ANGLE_platform_angle_opengl
+#ifdef EGL_ANGLE_platform_angle
     if (libEGL.eglGetPlatformDisplayEXT
         && (preferredType & QWindowsOpenGLTester::AngleBackendMask)) {
         const EGLint anglePlatformAttributes[][5] = {
@@ -384,7 +390,7 @@ QWindowsEGLStaticContext *QWindowsEGLStaticContext::create(QWindowsOpenGLTester:
             }
         }
     }
-#else // EGL_ANGLE_platform_angle_opengl
+#else // EGL_ANGLE_platform_angle
     Q_UNUSED(preferredType)
 #endif
     if (display == EGL_NO_DISPLAY)