From fb6937565be558e7ff8ba3dd815a427721783cba Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Mon, 9 Feb 2009 15:30:21 -0800
Subject: [PATCH] [gl] Add interface for creating surfaces from window
 backbuffers.

---
 src/cairo-gl-surface.c | 85 ++++++++++++++++++++++++++++++++++++++++--
 src/cairo-gl.h         |  9 ++---
 2 files changed, 85 insertions(+), 9 deletions(-)

diff --git a/src/cairo-gl-surface.c b/src/cairo-gl-surface.c
index c24e0590a..47745c5c5 100644
--- a/src/cairo-gl-surface.c
+++ b/src/cairo-gl-surface.c
@@ -54,6 +54,7 @@ typedef struct _cairo_gl_surface {
     cairo_content_t content;
     int width, height;
 
+    Window win; /* window if not rendering to FBO */
     GLuint tex; /* GL texture object containing our data. */
     GLuint fb; /* GL framebuffer object wrapping our data. */
 } cairo_gl_surface_t;
@@ -75,6 +76,11 @@ const cairo_gl_context_t _nil_context = {
     CAIRO_STATUS_NO_MEMORY
 };
 
+static cairo_bool_t _cairo_surface_is_gl (cairo_surface_t *surface)
+{
+    return surface->backend == &_cairo_gl_surface_backend;
+}
+
 static cairo_gl_context_t *
 _cairo_gl_context_create_in_error (cairo_status_t status)
 {
@@ -155,15 +161,26 @@ _cairo_gl_context_release (cairo_gl_context_t *ctx)
 static void
 _cairo_gl_set_destination (cairo_gl_surface_t *surface)
 {
-    glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, surface->fb);
-    glDrawBuffer (GL_COLOR_ATTACHMENT0_EXT);
-    glReadBuffer (GL_COLOR_ATTACHMENT0_EXT);
+    if (surface->fb) {
+	glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, surface->fb);
+	glDrawBuffer (GL_COLOR_ATTACHMENT0_EXT);
+	glReadBuffer (GL_COLOR_ATTACHMENT0_EXT);
+    } else {
+	/* Set the window as the target of our context. */
+	glXMakeCurrent (surface->ctx->dpy, surface->win, surface->ctx->gl_ctx);
+	glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, 0);
+	glDrawBuffer (GL_BACK_LEFT);
+	glReadBuffer (GL_BACK_LEFT);
+    }
 
     glViewport (0, 0, surface->width, surface->height);
 
     glMatrixMode (GL_PROJECTION);
     glLoadIdentity();
-    glOrtho(0, surface->width, 0, surface->height, -1.0, 1.0);
+    if (surface->fb)
+	glOrtho(0, surface->width, 0, surface->height, -1.0, 1.0);
+    else
+	glOrtho(0, surface->width, surface->height, 0, -1.0, 1.0);
 
     glMatrixMode (GL_MODELVIEW);
     glLoadIdentity();
@@ -328,6 +345,66 @@ cairo_gl_surface_create (cairo_gl_context_t   *ctx,
     return &surface->base;
 }
 
+
+cairo_surface_t *
+cairo_gl_surface_create_for_window (cairo_gl_context_t   *ctx,
+				    Window                win,
+				    int                   width,
+				    int                   height)
+{
+    cairo_gl_surface_t *surface;
+    cairo_content_t content = CAIRO_CONTENT_COLOR_ALPHA;
+
+    surface = calloc (1, sizeof (cairo_gl_surface_t));
+    if (unlikely (surface == NULL))
+	return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
+
+    _cairo_surface_init (&surface->base,
+			 &_cairo_gl_surface_backend,
+			 content);
+
+    surface->ctx = cairo_gl_context_reference (ctx);
+    surface->content = content;
+    surface->width = width;
+    surface->height = height;
+    surface->win = win;
+
+    return &surface->base;
+}
+
+void
+cairo_gl_surface_set_size (cairo_surface_t *abstract_surface,
+			   int              width,
+			   int              height)
+{
+    cairo_gl_surface_t *surface = (cairo_gl_surface_t *) abstract_surface;
+    cairo_status_t status;
+
+    if (! _cairo_surface_is_gl (abstract_surface) || surface->fb) {
+	status = _cairo_surface_set_error (abstract_surface,
+		                           CAIRO_STATUS_SURFACE_TYPE_MISMATCH);
+	return;
+    }
+
+    surface->width = width;
+    surface->height = height;
+}
+
+void
+cairo_gl_surface_swapbuffers (cairo_surface_t *abstract_surface)
+{
+    cairo_gl_surface_t *surface = (cairo_gl_surface_t *) abstract_surface;
+    cairo_status_t status;
+
+    if (! _cairo_surface_is_gl (abstract_surface) || surface->fb) {
+	status = _cairo_surface_set_error (abstract_surface,
+		                           CAIRO_STATUS_SURFACE_TYPE_MISMATCH);
+	return;
+    }
+
+    glXSwapBuffers(surface->ctx->dpy, surface->win);
+}
+
 static cairo_surface_t *
 _cairo_gl_surface_create_similar (void		 *abstract_surface,
 				  cairo_content_t  content,
diff --git a/src/cairo-gl.h b/src/cairo-gl.h
index ffe5879b7..eb9897733 100644
--- a/src/cairo-gl.h
+++ b/src/cairo-gl.h
@@ -64,17 +64,16 @@ cairo_gl_surface_create (cairo_gl_context_t *ctx,
 cairo_public cairo_surface_t *
 cairo_gl_surface_create_for_window (cairo_gl_context_t *ctx,
 				    Window win,
-				    cairo_content_t content,
 				    int width, int height);
 
 cairo_public cairo_gl_context_t *
 cairo_gl_surface_get_context (cairo_surface_t *abstract_surface);
 
-cairo_public int
-cairo_gl_surface_get_width (cairo_surface_t *surface);
+cairo_public void
+cairo_gl_surface_set_size (cairo_surface_t *surface, int width, int height);
 
-cairo_public int
-cairo_gl_surface_get_height (cairo_surface_t *surface);
+cairo_public void
+cairo_gl_surface_swapbuffers (cairo_surface_t *surface);
 
 cairo_public cairo_status_t
 cairo_gl_surface_glfinish (cairo_surface_t *surface);