framebuffer: Move clear code to cogl-framebuffer.c

This moves the implementation of cogl_clear into cogl-framebuffer.c as
two new internal functions _cogl_framebuffer_clear and
_cogl_framebuffer_clear4f. It's not clear if this is what the API will
look like as we make more of the CoglFramebuffer API public due to the
limitations of using flags to identify buffers when framebuffers may
contain any number of ancillary buffers but conceptually it makes some
sense to tie the operation of clearing a color buffer to a framebuffer.

The short term intention is to enable tracking the current clear color
as a property of the framebuffer as part of an optimization for reading
back single pixels when the geometry is simple enough that we can
compute the result quickly on the CPU. (If the point doesn't intersect
any geometry we'll need to return the last clear color.)

cogl/cogl-framebuffer-private.h

@@ -87,6 +87,26 @@ typedef struct _CoglOnscreen
 void
 _cogl_framebuffer_state_init (void);
 
+void
+_cogl_clear4f (unsigned long buffers,
+               float red,
+               float green,
+               float blue,
+               float alpha);
+
+void
+_cogl_framebuffer_clear (CoglFramebuffer *framebuffer,
+                         unsigned long buffers,
+                         const CoglColor *color);
+
+void
+_cogl_framebuffer_clear4f (CoglFramebuffer *framebuffer,
+                           unsigned long buffers,
+                           float red,
+                           float green,
+                           float blue,
+                           float alpha);
+
 int
 _cogl_framebuffer_get_width (CoglFramebuffer *framebuffer);
 

cogl/cogl-framebuffer.c

@@ -169,6 +169,109 @@ _cogl_framebuffer_free (CoglFramebuffer *framebuffer)
   framebuffer->projection_stack = NULL;
 }
 
+/* This version of cogl_clear can be used internally as an alternative
+ * to avoid flushing the journal or the framebuffer state. This is
+ * needed when doing operations that may be called whiling flushing
+ * the journal */
+void
+_cogl_clear4f (unsigned long buffers,
+               float red,
+               float green,
+               float blue,
+               float alpha)
+{
+  GLbitfield gl_buffers = 0;
+
+  if (buffers & COGL_BUFFER_BIT_COLOR)
+    {
+      GE( glClearColor (red, green, blue, alpha) );
+      gl_buffers |= GL_COLOR_BUFFER_BIT;
+    }
+
+  if (buffers & COGL_BUFFER_BIT_DEPTH)
+    gl_buffers |= GL_DEPTH_BUFFER_BIT;
+
+  if (buffers & COGL_BUFFER_BIT_STENCIL)
+    gl_buffers |= GL_STENCIL_BUFFER_BIT;
+
+  if (!gl_buffers)
+    {
+      static gboolean shown = FALSE;
+
+      if (!shown)
+        {
+	  g_warning ("You should specify at least one auxiliary buffer "
+                     "when calling cogl_clear");
+        }
+
+      return;
+    }
+
+  GE (glClear (gl_buffers));
+}
+
+void
+_cogl_framebuffer_clear4f (CoglFramebuffer *framebuffer,
+                           unsigned long buffers,
+                           float red,
+                           float green,
+                           float blue,
+                           float alpha)
+{
+  COGL_NOTE (DRAW, "Clear begin");
+
+  _cogl_journal_flush ();
+
+  /* NB: _cogl_framebuffer_flush_state may disrupt various state (such
+   * as the pipeline state) when flushing the clip stack, so should
+   * always be done first when preparing to draw. */
+  _cogl_framebuffer_flush_state (framebuffer, 0);
+
+  _cogl_clear4f (buffers, red, green, blue, alpha);;
+
+  /* This is a debugging variable used to visually display the quad
+   * batches from the journal. It is reset here to increase the
+   * chances of getting the same colours for each frame during an
+   * animation */
+  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_RECTANGLES) &&
+      buffers & COGL_BUFFER_BIT_COLOR)
+    {
+      _COGL_GET_CONTEXT (ctxt, NO_RETVAL);
+      ctxt->journal_rectangles_color = 1;
+    }
+
+  COGL_NOTE (DRAW, "Clear end");
+}
+
+/* XXX: We'll need to consider if this API is a good approach for the
+ * planned, public, CoglFramebuffer API. A framebuffer may have
+ * multiple color buffers associated with it and the user may want to
+ * only clear a subset of those buffers. Flags aren't a great
+ * mechanism for handling this, but I don't think it would be very
+ * convenient if you had to explicitly enumerate the individual
+ * ancillary buffers to clear them.
+ *
+ * My current expectation is that we'll keep this flag based API but
+ * also add a way to enumerate the individual color buffers for
+ * clearing individually.
+ *
+ * Note: the 'buffers' and 'color' arguments were switched around on
+ * purpose compared to the original cogl_clear API since it was odd
+ * that you would be expected to specify a color before even
+ * necessarily choosing to clear the color buffer.
+ */
+void
+_cogl_framebuffer_clear (CoglFramebuffer *framebuffer,
+                         unsigned long buffers,
+                         const CoglColor *color)
+{
+  _cogl_framebuffer_clear4f (framebuffer, buffers,
+                             cogl_color_get_red_float (color),
+                             cogl_color_get_green_float (color),
+                             cogl_color_get_blue_float (color),
+                             cogl_color_get_alpha_float (color));
+}
+
 int
 _cogl_framebuffer_get_width (CoglFramebuffer *framebuffer)
 {

cogl/cogl.c

@@ -46,6 +46,7 @@
 #include "cogl-texture-private.h"
 #include "cogl-texture-driver.h"
 #include "cogl-vertex-attribute-private.h"
+#include "cogl-framebuffer-private.h"
 
 #ifdef HAVE_COGL_GL
 #define glClientActiveTexture ctx->drv.pf_glClientActiveTexture
@@ -145,71 +146,12 @@ cogl_check_extension (const char *name, const char *ext)
   return _cogl_check_extension (name, ext);
 }
 
-/* This version of cogl_clear can be used internally as an alternative
+/* XXX: it's expected that we'll deprecated this with
-   to avoid flushing the journal or the framebuffer state. This is
+ * cogl_framebuffer_clear at some point. */
-   needed when doing operations that may be called whiling flushing
-   the journal */
-void
-_cogl_clear (const CoglColor *color, unsigned long buffers)
-{
-  GLbitfield gl_buffers = 0;
-
-  if (buffers & COGL_BUFFER_BIT_COLOR)
-    {
-      GE( glClearColor (cogl_color_get_red_float (color),
-			cogl_color_get_green_float (color),
-			cogl_color_get_blue_float (color),
-			cogl_color_get_alpha_float (color)) );
-      gl_buffers |= GL_COLOR_BUFFER_BIT;
-    }
-
-  if (buffers & COGL_BUFFER_BIT_DEPTH)
-    gl_buffers |= GL_DEPTH_BUFFER_BIT;
-
-  if (buffers & COGL_BUFFER_BIT_STENCIL)
-    gl_buffers |= GL_STENCIL_BUFFER_BIT;
-
-  if (!gl_buffers)
-    {
-      static gboolean shown = FALSE;
-
-      if (!shown)
-        {
-	  g_warning ("You should specify at least one auxiliary buffer "
-                     "when calling cogl_clear");
-        }
-
-      return;
-    }
-
-  GE (glClear (gl_buffers));
-
-  /* This is a debugging variable used to visually display the quad
-     batches from the journal. It is reset here to increase the
-     chances of getting the same colours for each frame during an
-     animation */
-  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_RECTANGLES))
-    {
-      _COGL_GET_CONTEXT (ctxt, NO_RETVAL);
-      ctxt->journal_rectangles_color = 1;
-    }
-}
-
 void
 cogl_clear (const CoglColor *color, unsigned long buffers)
 {
-  COGL_NOTE (DRAW, "Clear begin");
+  _cogl_framebuffer_clear (_cogl_get_framebuffer (), buffers, color);
-
-  _cogl_journal_flush ();
-
-  /* NB: _cogl_framebuffer_flush_state may disrupt various state (such
-   * as the pipeline state) when flushing the clip stack, so should
-   * always be done first when preparing to draw. */
-  _cogl_framebuffer_flush_state (_cogl_get_framebuffer (), 0);
-
-  _cogl_clear (color, buffers);;
-
-  COGL_NOTE (DRAW, "Clear end");
 }
 
 static gboolean

cogl/cogl2-path.c

@@ -396,9 +396,9 @@ _cogl_add_path_to_stencil_buffer (CoglPath *path,
            will have set up a scissor for the minimum bounding box of
            all of the clips. That box will likely mean that this
            _cogl_clear won't need to clear the entire
-           buffer. _cogl_clear is used instead of cogl_clear because
+           buffer. _cogl_clear4f is used instead of cogl_clear because
            it won't try to flush the journal */
-        _cogl_clear (NULL, COGL_BUFFER_BIT_STENCIL);
+        _cogl_clear4f (COGL_BUFFER_BIT_STENCIL, 0, 0, 0, 0);
       else
         {
           /* Just clear the bounding box */