gl: Only allocate a framebuffer if we need one

This way, we don't clobber the current target when creating textures for
image surfaces.

3 files changed, 29 insertions, 19 deletions

diff --git a/src/cairo-gl-device.c b/src/cairo-gl-device.c
index 1741ac07..2e6bfb94 100644
--- a/src/cairo-gl-device.c
+++ b/src/cairo-gl-device.c
@@ -221,6 +221,31 @@ _cairo_gl_context_init (cairo_gl_context_t *ctx)
     return CAIRO_STATUS_SUCCESS;
 }
 
+static void
+_cairo_gl_ensure_framebuffer (cairo_gl_context_t *ctx,
+                              cairo_gl_surface_t *surface)
+{
+    GLenum status;
+
+    if (likely (surface->fb))
+        return;
+
+    /* Create a framebuffer object wrapping the texture so that we can render
+     * to it.
+     */
+    glGenFramebuffersEXT (1, &surface->fb);
+    glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, surface->fb);
+    glFramebufferTexture2DEXT (GL_FRAMEBUFFER_EXT,
+			       GL_COLOR_ATTACHMENT0_EXT,
+			       ctx->tex_target,
+			       surface->tex,
+			       0);
+
+    status = glCheckFramebufferStatusEXT (GL_FRAMEBUFFER_EXT);
+    if (status != GL_FRAMEBUFFER_COMPLETE_EXT)
+	fprintf (stderr, "destination is framebuffer incomplete\n");
+}
+
 void
 _cairo_gl_context_set_destination (cairo_gl_context_t *ctx,
                                    cairo_gl_surface_t *surface)
@@ -233,6 +258,7 @@ _cairo_gl_context_set_destination (cairo_gl_context_t *ctx,
     ctx->current_target = surface;
 
     if (_cairo_gl_surface_is_texture (surface)) {
+        _cairo_gl_ensure_framebuffer (ctx, surface);
         glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, surface->fb);
         glDrawBuffer (GL_COLOR_ATTACHMENT0_EXT);
         glReadBuffer (GL_COLOR_ATTACHMENT0_EXT);
diff --git a/src/cairo-gl-private.h b/src/cairo-gl-private.h
index fe5be0c3..eaf11434 100644
--- a/src/cairo-gl-private.h
+++ b/src/cairo-gl-private.h
@@ -235,7 +235,7 @@ _cairo_gl_surface_init (cairo_device_t *device,
 static cairo_always_inline cairo_bool_t cairo_warn
 _cairo_gl_surface_is_texture (cairo_gl_surface_t *surface)
 {
-    return surface->fb != 0;
+    return surface->tex != 0;
 }
 
 cairo_private cairo_status_t
diff --git a/src/cairo-gl-surface.c b/src/cairo-gl-surface.c
index 1d264133..9a75e28d 100644
--- a/src/cairo-gl-surface.c
+++ b/src/cairo-gl-surface.c
@@ -242,7 +242,6 @@ _cairo_gl_surface_create_scratch (cairo_gl_context_t   *ctx,
 {
     cairo_gl_surface_t *surface;
     GLenum format;
-    cairo_status_t status;
 
     assert (width <= ctx->max_framebuffer_size && height <= ctx->max_framebuffer_size);
 
@@ -289,22 +288,6 @@ _cairo_gl_surface_create_scratch (cairo_gl_context_t   *ctx,
     glTexImage2D (ctx->tex_target, 0, format, width, height, 0,
 		  format, GL_UNSIGNED_BYTE, NULL);
 
-    /* Create a framebuffer object wrapping the texture so that we can render
-     * to it.
-     */
-    glGenFramebuffersEXT (1, &surface->fb);
-    glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, surface->fb);
-    glFramebufferTexture2DEXT (GL_FRAMEBUFFER_EXT,
-			       GL_COLOR_ATTACHMENT0_EXT,
-			       ctx->tex_target,
-			       surface->tex,
-			       0);
-    ctx->current_target = NULL;
-
-    status = glCheckFramebufferStatusEXT (GL_FRAMEBUFFER_EXT);
-    if (status != GL_FRAMEBUFFER_COMPLETE_EXT)
-	fprintf (stderr, "destination is framebuffer incomplete\n");
-
     return &surface->base;
 }
 
@@ -707,7 +690,8 @@ _cairo_gl_surface_finish (void *abstract_surface)
     if (ctx->current_target == surface)
 	ctx->current_target = NULL;
 
-    glDeleteFramebuffersEXT (1, &surface->fb);
+    if (surface->fb)
+        glDeleteFramebuffersEXT (1, &surface->fb);
     glDeleteTextures (1, &surface->tex);
 
     _cairo_gl_context_release (ctx);