From 2570e9ec61a00461520aa6434ca4371e442434b5 Mon Sep 17 00:00:00 2001
From: "Pierre-Loup A. Griffais" <pgriffais@nvidia.com>
Date: Sun, 16 Oct 2011 01:09:16 -0700
Subject: [PATCH] kwin-gles: add support for EGL_NV_post_sub_buffer

The EGL path had no support for presenting sub-regions of the screen, we can
leverage EGL_NV_post_sub_buffer for that. This wouldn't be a win if we didn't
have to opt-out of flipping.

REVIEW: 102889
---
 libkwineffects/kwinglutils_funcs.cpp |  7 +++++++
 libkwineffects/kwinglutils_funcs.h   |  2 ++
 scene_opengl_egl.cpp                 | 10 +++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/libkwineffects/kwinglutils_funcs.cpp b/libkwineffects/kwinglutils_funcs.cpp
index 33c8c7c9dd..0c66dc148e 100644
--- a/libkwineffects/kwinglutils_funcs.cpp
+++ b/libkwineffects/kwinglutils_funcs.cpp
@@ -296,6 +296,7 @@ namespace KWin
 // EGL
 eglCreateImageKHR_func eglCreateImageKHR;
 eglDestroyImageKHR_func eglDestroyImageKHR;
+eglPostSubBufferNV_func eglPostSubBufferNV;
 // GLES
 glEGLImageTargetTexture2DOES_func glEGLImageTargetTexture2DOES;
 
@@ -310,6 +311,12 @@ void eglResolveFunctions()
         eglCreateImageKHR = NULL;
         eglDestroyImageKHR = NULL;
     }
+
+    if (hasGLExtension("EGL_NV_post_sub_buffer")) {
+        eglPostSubBufferNV = (eglPostSubBufferNV_func)eglGetProcAddress("eglPostSubBufferNV");
+    } else {
+        eglPostSubBufferNV = NULL;
+    }
 }
 
 void glResolveFunctions()
diff --git a/libkwineffects/kwinglutils_funcs.h b/libkwineffects/kwinglutils_funcs.h
index 2f5829c09d..cbd40fc1dd 100644
--- a/libkwineffects/kwinglutils_funcs.h
+++ b/libkwineffects/kwinglutils_funcs.h
@@ -358,8 +358,10 @@ void KWIN_EXPORT glResolveFunctions();
 // EGL
 typedef EGLImageKHR(*eglCreateImageKHR_func)(EGLDisplay, EGLContext, EGLenum, EGLClientBuffer, const EGLint*);
 typedef EGLBoolean(*eglDestroyImageKHR_func)(EGLDisplay, EGLImageKHR);
+typedef EGLBoolean (*eglPostSubBufferNV_func)(EGLDisplay dpy, EGLSurface surface, EGLint x, EGLint y, EGLint width, EGLint height);
 extern KWIN_EXPORT eglCreateImageKHR_func eglCreateImageKHR;
 extern KWIN_EXPORT eglDestroyImageKHR_func eglDestroyImageKHR;
+extern KWIN_EXPORT eglPostSubBufferNV_func eglPostSubBufferNV;
 
 // GLES
 typedef GLvoid(*glEGLImageTargetTexture2DOES_func)(GLenum, GLeglImageOES);
diff --git a/scene_opengl_egl.cpp b/scene_opengl_egl.cpp
index c3fa845491..09a6feded9 100644
--- a/scene_opengl_egl.cpp
+++ b/scene_opengl_egl.cpp
@@ -26,6 +26,7 @@ EGLDisplay dpy;
 EGLConfig config;
 EGLSurface surface;
 EGLContext ctx;
+int surfaceHasSubPost;
 
 SceneOpenGL::SceneOpenGL(Workspace* ws)
     : Scene(ws)
@@ -108,6 +109,8 @@ bool SceneOpenGL::initRenderingContext()
 
     eglSurfaceAttrib(dpy, surface, EGL_SWAP_BEHAVIOR, EGL_BUFFER_PRESERVED);
 
+    eglQuerySurface(dpy, surface, EGL_POST_SUB_BUFFER_SUPPORTED_NV, &surfaceHasSubPost);
+
     const EGLint context_attribs[] = {
         EGL_CONTEXT_CLIENT_VERSION, 2,
         EGL_NONE
@@ -200,9 +203,10 @@ void SceneOpenGL::flushBuffer(int mask, QRegion damage)
 {
     Q_UNUSED(damage)
     glFlush();
-    if (mask & PAINT_SCREEN_REGION) {
-        // TODO: implement me properly
-        eglSwapBuffers(dpy, surface);
+    if (mask & PAINT_SCREEN_REGION && surfaceHasSubPost && eglPostSubBufferNV) {
+        QRect damageRect = damage.boundingRect();
+
+        eglPostSubBufferNV(dpy, surface, damageRect.left(), displayHeight() - damageRect.bottom() - 1, damageRect.width(), damageRect.height());
     } else {
         eglSwapBuffers(dpy, surface);
     }