cogl-slip-stack: Store clip window rect entries in Cogl coordinates

When glScissor is called it needs to pass coordinates in GL's
coordinate space where the origin is the bottom left. Previously this
conversion was done before storing the window rect in the clip
stack. However this might make it more difficult if we want to be able
to grab a handle to a clip stack and use it in different circumstances
later. This patch moves the coordinate conversion to inside the clip
state flushing code.

1 files changed, 32 insertions, 25 deletions

diff --git a/cogl/cogl-clip-stack.c b/cogl/cogl-clip-stack.c
index 204e6d53..37c9d022 100644
--- a/cogl/cogl-clip-stack.c
+++ b/cogl/cogl-clip-stack.c
@@ -128,7 +128,8 @@ struct _CoglClipStackEntryWindowRect
 {
   CoglClipStackEntry     _parent_data;
 
-  /* The window space rectangle for this clip */
+  /* The window space rectangle for this clip. This is stored in
+     Cogl's coordinate space (ie, 0,0 is the top left) */
   int                    x0;
   int                    y0;
   int                    x1;
@@ -409,7 +410,6 @@ cogl_clip_push_window_rectangle (int x_offset,
   CoglHandle framebuffer;
   CoglClipStackState *clip_state;
   CoglClipStack *stack;
-  int framebuffer_height;
   CoglClipStackEntryWindowRect *entry;
 
   _COGL_GET_CONTEXT (ctx, NO_RETVAL);
@@ -423,31 +423,14 @@ cogl_clip_push_window_rectangle (int x_offset,
 
   stack = clip_state->stacks->data;
 
-  framebuffer_height = _cogl_framebuffer_get_height (framebuffer);
-
   entry = _cogl_clip_stack_push_entry (stack,
                                        sizeof (CoglClipStackEntryWindowRect),
                                        COGL_CLIP_STACK_WINDOW_RECT);
 
-  /* We store the entry coordinates in OpenGL window coordinate space and so
-   * because Cogl defines the window origin to be top left but OpenGL defines
-   * it as bottom left we may need to convert the incoming coordinates.
-   *
-   * NB: Cogl forces all offscreen rendering to be done upside down so in this
-   * case no conversion is needed.
-   */
   entry->x0 = x_offset;
   entry->x1 = x_offset + width;
-  if (cogl_is_offscreen (framebuffer))
-    {
-      entry->y0 = y_offset;
-      entry->y1 = y_offset + height;
-    }
-  else
-    {
-      entry->y0 = framebuffer_height - y_offset - height;
-      entry->y1 = framebuffer_height - y_offset;
-    }
+  entry->y0 = y_offset;
+  entry->y1 = y_offset + height;
 
   clip_state->stack_dirty = TRUE;
 }
@@ -835,14 +818,38 @@ _cogl_flush_clip_state (CoglClipStackState *clip_state)
   if (using_clip_planes)
     enable_clip_planes ();
 
-  if (scissor_x0 >= scissor_x1 || scissor_y0 >= scissor_y1)
-    scissor_x0 = scissor_y0 = scissor_x1 = scissor_y1 = 0;
-
   if (!(scissor_x0 == 0 && scissor_y0 == 0 &&
         scissor_x1 == G_MAXINT && scissor_y1 == G_MAXINT))
     {
+      int scissor_y_start;
+
+      if (scissor_x0 >= scissor_x1 || scissor_y0 >= scissor_y1)
+        scissor_x0 = scissor_y0 = scissor_x1 = scissor_y1 = scissor_y_start = 0;
+      else
+        {
+          CoglHandle framebuffer = _cogl_get_framebuffer ();
+
+          /* We store the entry coordinates in Cogl coordinate space
+           * but OpenGL requires the window origin to be the bottom
+           * left so we may need to convert the incoming coordinates.
+           *
+           * NB: Cogl forces all offscreen rendering to be done upside
+           * down so in this case no conversion is needed.
+           */
+
+          if (cogl_is_offscreen (framebuffer))
+            scissor_y_start = scissor_y0;
+          else
+            {
+              int framebuffer_height =
+                _cogl_framebuffer_get_height (framebuffer);
+
+              scissor_y_start = framebuffer_height - scissor_y1;
+            }
+        }
+
       GE (glEnable (GL_SCISSOR_TEST));
-      GE (glScissor (scissor_x0, scissor_y0,
+      GE (glScissor (scissor_x0, scissor_y_start,
                      scissor_x1 - scissor_x0,
                      scissor_y1 - scissor_y0));
     }