[cogl] egl: support EGL_EXT_buffer_age

[Robert Bragg <rbragg src gnome org>]

commit 92d869764c03d0bac6b51dac833510c22669ac4a
Author: Robert Bragg <robert linux intel com>
Date:   Tue Jan 22 21:21:33 2013 +0000

    egl: support EGL_EXT_buffer_age
    
    This adds support for the EGL_EXT_buffer_age extension which is a
    counterpart to the GLX_EXT_buffer_age extension.
    
    Reviewed-by: Neil Roberts <neil linux intel com>

 cogl/winsys/cogl-winsys-egl-feature-functions.h |    6 ++++++
 cogl/winsys/cogl-winsys-egl-private.h           |    3 ++-
 cogl/winsys/cogl-winsys-egl.c                   |   23 +++++++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletions(-)
---
diff --git a/cogl/winsys/cogl-winsys-egl-feature-functions.h b/cogl/winsys/cogl-winsys-egl-feature-functions.h
index 9016f8d..5068090 100644
--- a/cogl/winsys/cogl-winsys-egl-feature-functions.h
+++ b/cogl/winsys/cogl-winsys-egl-feature-functions.h
@@ -94,4 +94,10 @@ COGL_WINSYS_FEATURE_BEGIN (create_context,
                            COGL_EGL_WINSYS_FEATURE_CREATE_CONTEXT)
 COGL_WINSYS_FEATURE_END ()
 
+COGL_WINSYS_FEATURE_BEGIN (buffer_age,
+                           "EXT\0",
+                           "buffer_age\0",
+                           COGL_EGL_WINSYS_FEATURE_BUFFER_AGE)
+COGL_WINSYS_FEATURE_END ()
+
 #endif
diff --git a/cogl/winsys/cogl-winsys-egl-private.h b/cogl/winsys/cogl-winsys-egl-private.h
index 13ce9a4..0d76065 100644
--- a/cogl/winsys/cogl-winsys-egl-private.h
+++ b/cogl/winsys/cogl-winsys-egl-private.h
@@ -69,7 +69,8 @@ typedef enum _CoglEGLWinsysFeature
   COGL_EGL_WINSYS_FEATURE_SWAP_REGION                   =1L<<0,
   COGL_EGL_WINSYS_FEATURE_EGL_IMAGE_FROM_X11_PIXMAP     =1L<<1,
   COGL_EGL_WINSYS_FEATURE_EGL_IMAGE_FROM_WAYLAND_BUFFER =1L<<2,
-  COGL_EGL_WINSYS_FEATURE_CREATE_CONTEXT                =1L<<3
+  COGL_EGL_WINSYS_FEATURE_CREATE_CONTEXT                =1L<<3,
+  COGL_EGL_WINSYS_FEATURE_BUFFER_AGE                    =1L<<4
 } CoglEGLWinsysFeature;
 
 typedef struct _CoglRendererEGL
diff --git a/cogl/winsys/cogl-winsys-egl.c b/cogl/winsys/cogl-winsys-egl.c
index cd6ae3a..a713bfb 100644
--- a/cogl/winsys/cogl-winsys-egl.c
+++ b/cogl/winsys/cogl-winsys-egl.c
@@ -689,6 +689,28 @@ _cogl_winsys_onscreen_bind (CoglOnscreen *onscreen)
   bind_onscreen (onscreen);
 }
 
+#ifndef EGL_BUFFER_AGE_EXT
+#define EGL_BUFFER_AGE_EXT 0x313D
+#endif
+
+static int
+_cogl_winsys_onscreen_get_buffer_age (CoglOnscreen *onscreen)
+{
+  CoglContext *context = COGL_FRAMEBUFFER (onscreen)->context;
+  CoglRenderer *renderer = context->display->renderer;
+  CoglRendererEGL *egl_renderer = renderer->winsys;
+  CoglOnscreenEGL *egl_onscreen = onscreen->winsys;
+  EGLSurface surface = egl_onscreen->egl_surface;
+  int age;
+
+  if (!(egl_renderer->private_features & COGL_EGL_WINSYS_FEATURE_BUFFER_AGE))
+    return 0;
+
+  eglQuerySurface (egl_renderer->edpy, surface, EGL_BUFFER_AGE_EXT, &age);
+
+  return age;
+}
+
 static void
 _cogl_winsys_onscreen_swap_region (CoglOnscreen *onscreen,
                                    const int *user_rectangles,
@@ -848,6 +870,7 @@ static CoglWinsysVtable _cogl_winsys_vtable =
     .onscreen_bind = _cogl_winsys_onscreen_bind,
     .onscreen_swap_buffers = _cogl_winsys_onscreen_swap_buffers,
     .onscreen_swap_region = _cogl_winsys_onscreen_swap_region,
+    .onscreen_get_buffer_age = _cogl_winsys_onscreen_get_buffer_age,
     .onscreen_update_swap_throttled =
       _cogl_winsys_onscreen_update_swap_throttled,