simple-egl: Add support for EGL_EXT_swap_buffer_with_damage

This new EGL extension lets us communicate the damage area to the compositor
by using eglSwapBuffersWithDamge() instead of the regular eglSwapBuffer().

http://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_swap_buffers_with_damage.txt

diff --git a/clients/simple-egl.c b/clients/simple-egl.c
index f4468b7..54dfe93 100644 (file)
--- a/clients/simple-egl.c
+++ b/clients/simple-egl.c
@@ -36,6 +36,12 @@
 
 #include <GLES2/gl2.h>
 #include <EGL/egl.h>
+#include <EGL/eglext.h>
+
+#ifndef EGL_EXT_swap_buffers_with_damage
+#define EGL_EXT_swap_buffers_with_damage 1
+typedef EGLBoolean (EGLAPIENTRYP PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC)(EGLDisplay dpy, EGLSurface surface, EGLint *rects, EGLint n_rects);
+#endif
 
 struct window;
 struct seat;
@@ -58,6 +64,8 @@ struct display {
                EGLConfig conf;
        } egl;
        struct window *window;
+
+       PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC swap_buffers_with_damage;
 };
 
 struct geometry {
@@ -107,6 +115,7 @@ init_egl(struct display *display, int opaque)
                EGL_CONTEXT_CLIENT_VERSION, 2,
                EGL_NONE
        };
+       const char *extensions;
 
        EGLint config_attribs[] = {
                EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
@@ -141,6 +150,18 @@ init_egl(struct display *display, int opaque)
                                            EGL_NO_CONTEXT, context_attribs);
        assert(display->egl.ctx);
 
+       display->swap_buffers_with_damage = NULL;
+       extensions = eglQueryString(display->egl.dpy, EGL_EXTENSIONS);
+       if (extensions &&
+           strstr(extensions, "EGL_EXT_swap_buffers_with_damage") &&
+           strstr(extensions, "EGL_EXT_buffer_age"))
+               display->swap_buffers_with_damage =
+                       (PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC)
+                       eglGetProcAddress("eglSwapBuffersWithDamageEXT");
+
+       if (display->swap_buffers_with_damage)
+               printf("has EGL_EXT_buffer_age and EGL_EXT_swap_buffers_with_damage\n");
+
 }
 
 static void
@@ -346,6 +367,7 @@ static void
 redraw(void *data, struct wl_callback *callback, uint32_t time)
 {
        struct window *window = data;
+       struct display *display = window->display;
        static const GLfloat verts[3][2] = {
                { -0.5, -0.5 },
                {  0.5, -0.5 },
@@ -366,6 +388,8 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
        static const int32_t speed_div = 5;
        static uint32_t start_time = 0;
        struct wl_region *region;
+       EGLint rect[4];
+       EGLint buffer_age = 0;
 
        assert(window->callback == callback);
        window->callback = NULL;
@@ -385,6 +409,10 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
        rotation[2][0] = -sin(angle);
        rotation[2][2] =  cos(angle);
 
+       if (display->swap_buffers_with_damage)
+               eglQuerySurface(display->egl.dpy, window->egl_surface,
+                               EGL_BUFFER_AGE_EXT, &buffer_age);
+
        glViewport(0, 0, window->geometry.width, window->geometry.height);
 
        glUniformMatrix4fv(window->gl.rotation_uniform, 1, GL_FALSE,
@@ -417,7 +445,17 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
        window->callback = wl_surface_frame(window->surface);
        wl_callback_add_listener(window->callback, &frame_listener, window);
 
-       eglSwapBuffers(window->display->egl.dpy, window->egl_surface);
+       if (display->swap_buffers_with_damage && buffer_age > 0) {
+               rect[0] = window->geometry.width / 4 - 1;
+               rect[1] = window->geometry.height / 4 - 1;
+               rect[2] = window->geometry.width / 2 + 2;
+               rect[3] = window->geometry.height / 2 + 2;
+               display->swap_buffers_with_damage(display->egl.dpy,
+                                                 window->egl_surface,
+                                                 rect, 1);
+       } else {
+               eglSwapBuffers(display->egl.dpy, window->egl_surface);
+       }
 }
 
 static const struct wl_callback_listener frame_listener = {