[cogl/wip/lazy-texture-allocate: 3/13] framebuffer: if size unknown; allocate for size/vp queries

[Robert Bragg <rbragg src gnome org>]

commit f71668391f72fcf83d3d1f26fd94bc76b65b0ee4
Author: Robert Bragg <robert linux intel com>
Date:   Sun Jun 30 17:01:09 2013 +0100

    framebuffer: if size unknown; allocate for size/vp queries
    
    This ensures framebuffers are implicitly allocated when querying the
    width, height or viewport width/height if the framebuffer's size is
    currently unknown. The plan is to allow texture backends to defer
    calculating the size of textures until they are allocated which in turn
    means we won't know the size of offscreen framebuffers until the texture
    has been allocated. Potentially we could be more specific about this in
    the future and only ensure the texture is allocated, but for now it will
    be simplest to just ensure the framebuffer is allocated.
    
    Note: in the case of offscreen buffers which are always initialized with
    a requested size we are careful to avoid triggering an allocation when
    this is queried otherwise we will see recursion when the winsys code
    queries the requested size during allocation.

 cogl/cogl-framebuffer.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)
---
diff --git a/cogl/cogl-framebuffer.c b/cogl/cogl-framebuffer.c
index b7a3441..ef1327a 100644
--- a/cogl/cogl-framebuffer.c
+++ b/cogl/cogl-framebuffer.c
@@ -401,15 +401,43 @@ cogl_framebuffer_clear (CoglFramebuffer *framebuffer,
                             cogl_color_get_alpha_float (color));
 }
 
+/* We will lazily allocate framebuffers if necessary when querying
+ * their size/viewport but note we need to be careful in the case of
+ * onscreen framebuffers that are instantiated with an initial request
+ * size that we don't trigger an allocation when this is queried since
+ * that would lead to a recursion when the winsys backend queries this
+ * requested size during allocation. */
+static void
+ensure_size_initialized (CoglFramebuffer *framebuffer)
+{
+  /* In the case of offscreen framebuffers backed by a texture then
+   * until that texture has been allocated we might not know the size
+   * of the framebuffer */
+  if (framebuffer->width < 0)
+    {
+      /* Currently we assume the size is always initialized for
+       * onscreen framebuffers. */
+      _COGL_RETURN_IF_FAIL (cogl_is_offscreen (framebuffer));
+
+      /* We also assume the size would have been initialized if the
+       * framebuffer were allocated. */
+      _COGL_RETURN_IF_FAIL (!framebuffer->allocated);
+
+      cogl_framebuffer_allocate (framebuffer, NULL);
+    }
+}
+
 int
 cogl_framebuffer_get_width (CoglFramebuffer *framebuffer)
 {
+  ensure_size_initialized (framebuffer);
   return framebuffer->width;
 }
 
 int
 cogl_framebuffer_get_height (CoglFramebuffer *framebuffer)
 {
+  ensure_size_initialized (framebuffer);
   return framebuffer->height;
 }
 
@@ -485,12 +513,14 @@ cogl_framebuffer_get_viewport_y (CoglFramebuffer *framebuffer)
 float
 cogl_framebuffer_get_viewport_width (CoglFramebuffer *framebuffer)
 {
+  ensure_size_initialized (framebuffer);
   return framebuffer->viewport_width;
 }
 
 float
 cogl_framebuffer_get_viewport_height (CoglFramebuffer *framebuffer)
 {
+  ensure_size_initialized (framebuffer);
   return framebuffer->viewport_height;
 }
 
@@ -498,6 +528,8 @@ void
 cogl_framebuffer_get_viewport4fv (CoglFramebuffer *framebuffer,
                                   float *viewport)
 {
+  ensure_size_initialized (framebuffer);
+
   viewport[0] = framebuffer->viewport_x;
   viewport[1] = framebuffer->viewport_y;
   viewport[2] = framebuffer->viewport_width;