Implement Texture-From-Pixmap using EGLImage extensions on X11/EGL

There's lots of EGLImage extensions, split between EGL and client
rendering APIs like OpenGL ES & OpenVG. To implement texture-from-
pixmap using EGLImage, both EGL extensions and OpenGL ES extensions
are needed. This patch resolves the EGL extension function pointers
after the display is initialized in QEgl::display(). These are then
exported from QtGui so they can be used in QtOpenGL. The OpenGL ES
extension function pointers are resolved using the usual
qglextensions.cpp mechanism.

Using EGLImage seems to remove a fixed ~10 millisecond overhead per
pixmap bind when compared to using EGLSurface. Exact results per bind
for 100 QPixmaps are:

   8x8   Pixmap: 12   -> 1.71 msecs (EGLSurface -> EGLImage)
  64x64  Pixmap: 11.6 -> 1.83 msecs (EGLSurface -> EGLImage)
 128x128 Pixmap: 12.8 -> 2.74 msecs (EGLSurface -> EGLImage)
 256x256 Pixmap: 16   -> 6.20 msecs (EGLSurface -> EGLImage)

Reviewed-By: Trond

2 files changed, 31 insertions, 2 deletions

diff --git a/src/gui/egl/qegl.cpp b/src/gui/egl/qegl.cpp
index b870523..507fab3 100644
--- a/src/gui/egl/qegl.cpp
+++ b/src/gui/egl/qegl.cpp
@@ -528,6 +528,9 @@ QEglProperties QEglContext::configProperties() const
     return QEglProperties(config());
 }
 
+_eglCreateImageKHR eglCreateImageKHR = 0;
+_eglDestroyImageKHR eglDestroyImageKHR = 0;
+
 EGLDisplay QEgl::display()
 {
     static EGLDisplay dpy = EGL_NO_DISPLAY;
@@ -549,6 +552,12 @@ EGLDisplay QEgl::display()
             qWarning() << "QEgl::display(): Cannot initialize EGL display:" << QEgl::errorString();
             return EGL_NO_DISPLAY;
         }
+
+        // Resolve the egl extension function pointers:
+        if (QEgl::hasExtension("EGL_KHR_image") || QEgl::hasExtension("EGL_KHR_image_base")) {
+            eglCreateImageKHR = (_eglCreateImageKHR) eglGetProcAddress("eglCreateImageKHR");
+            eglDestroyImageKHR = (_eglDestroyImageKHR) eglGetProcAddress("eglDestroyImageKHR");
+        }
     }
 
     return dpy;
diff --git a/src/gui/egl/qegl_p.h b/src/gui/egl/qegl_p.h
index 7dad9fe..b570329 100644
--- a/src/gui/egl/qegl_p.h
+++ b/src/gui/egl/qegl_p.h
@@ -100,13 +100,34 @@ typedef NativeDisplayType EGLNativeDisplayType;
 QT_END_INCLUDE_NAMESPACE
 
 #include <QtGui/qpaintdevice.h>
-
 #include <QFlags>
 
 QT_BEGIN_NAMESPACE
 
 #define QEGL_NO_CONFIG ((EGLConfig)-1)
 
+#ifndef EGLAPIENTRY
+#define EGLAPIENTRY
+#endif
+
+#if !defined(EGL_KHR_image) || !defined(EGL_KHR_image_base)
+
+typedef void *EGLImageKHR;
+#define EGL_NO_IMAGE_KHR            ((EGLImageKHR)0)
+#define EGL_IMAGE_PRESERVED_KHR     0x30D2
+
+typedef EGLImageKHR (EGLAPIENTRY *_eglCreateImageKHR)(EGLDisplay, EGLContext, EGLenum, EGLClientBuffer, EGLint*);
+typedef EGLBoolean (EGLAPIENTRY *_eglDestroyImageKHR)(EGLDisplay, EGLImageKHR);
+
+// Defined in qegl.cpp:
+extern Q_GUI_EXPORT _eglCreateImageKHR eglCreateImageKHR;
+extern Q_GUI_EXPORT _eglDestroyImageKHR eglDestroyImageKHR;
+
+#endif // !defined(EGL_KHR_image) || !defined(EGL_KHR_image_base)
+
+#if !defined(EGL_KHR_image) || !defined(EGL_KHR_image_pixmap)
+#define EGL_NATIVE_PIXMAP_KHR       0x30B0
+#endif
 
 
 class QEglProperties;
@@ -132,7 +153,6 @@ namespace QEgl {
     };
     Q_DECLARE_FLAGS(ConfigOptions, ConfigOption);
 
-
     // Most of the time we use the same config for things like widgets & pixmaps, so rather than
     // go through the eglChooseConfig loop every time, we use defaultConfig, which will return
     // the config for a particular device/api/option combo. This function assumes that once a