backends: Adds a new Cogl based backend

This adds a new GPU accelerated backend for Cairo based on the Cogl 3D
graphics API.

This backend aims to support Cairo in a way that translates as naturally
as possible to using a GPU, it does not strive to compete with the
anti-aliasing quality of the image backend if it can't be done
efficiently using the GPU - raw performance isn't the only metric of
concern, so is power usage.

As an overview of how the backend works:
- fills are handled by tessellating paths into triangles
- the backend has an extra fill_rectangle drawing operation so we have
  a fast-path for drawing rectangles which are so common.
- strokes are also tessellated into triangles.
- stroke and fill tessellations are cached to avoid the cpu overhead
  of tessellation and cost of upload given that its common for apps to
  re-draw the same path multiple times. The tessellations can survive
  translations and rotations increasing the probability that they can be
  re-used.
- sources and masks are handled using multi-texturing.
- clipping is handled with a scissor and the stencil buffer which
  we're careful to only update when they really change.
- linear gradients are rendered to a 1d texture using a triangle
  strip + interpolating color attributes. All cairo extend modes
  are handled by corresponding texture sampler wrap modes without
  needing programmable fragment processing.
- antialiasing should be handled using Cogl's multisampling API

XXX: This is a work in progress!!
TODO:
- handle at least basic radial gradients (No need to handle full
  pdf semantics, since css, svg and canvas only allow radial gradients
  defined as one circle + a point that must lie within the first
  circle.) - currently we fall back to pixman for radial gradients.
- support glyph rendering with a decent glyph cache design. The
  current plan is a per scaled-font growable cache texture + a
  scratch cache for one-shot/short-lived glyphs.
- decide how to handle npot textures when lacking hardware support.
  Current plan is to add a transparent border to npot textures and use
  CLAMP_TO_EDGE for the default EXTEND_NONE semantics. For anything else
  we can allocate a shadow npot texture and scale the original to fit
  that so we can map extend modes to texture sampler modes.

3 files changed, 221 insertions, 0 deletions

diff --git a/boilerplate/Makefile.sources b/boilerplate/Makefile.sources
index 63ef34e4f..101e99711 100644
--- a/boilerplate/Makefile.sources
+++ b/boilerplate/Makefile.sources
@@ -38,3 +38,4 @@ cairo_boilerplate_xcb_sources = cairo-boilerplate-xcb.c
 cairo_boilerplate_xlib_headers = cairo-boilerplate-xlib.h
 cairo_boilerplate_xlib_sources = cairo-boilerplate-xlib.c
 cairo_boilerplate_vg_sources = cairo-boilerplate-vg.c
+cairo_boilerplate_cogl_sources = cairo-boilerplate-cogl.c
diff --git a/boilerplate/Makefile.win32.features b/boilerplate/Makefile.win32.features
index 8b6a67332..e60a95ba6 100644
--- a/boilerplate/Makefile.win32.features
+++ b/boilerplate/Makefile.win32.features
@@ -247,6 +247,18 @@ enabled_cairo_boilerplate_cxx_sources += $(cairo_boilerplate_glesv2_cxx_sources)
 enabled_cairo_boilerplate_sources += $(cairo_boilerplate_glesv2_sources)
 endif
 
+unsupported_cairo_boilerplate_headers += $(cairo_boilerplate_cogl_headers)
+all_cairo_boilerplate_headers += $(cairo_boilerplate_cogl_headers)
+all_cairo_boilerplate_private += $(cairo_boilerplate_cogl_private)
+all_cairo_boilerplate_cxx_sources += $(cairo_boilerplate_cogl_cxx_sources)
+all_cairo_boilerplate_sources += $(cairo_boilerplate_cogl_sources)
+ifeq ($(CAIRO_HAS_COGL_SURFACE),1)
+enabled_cairo_boilerplate_headers += $(cairo_boilerplate_cogl_headers)
+enabled_cairo_boilerplate_private += $(cairo_boilerplate_cogl_private)
+enabled_cairo_boilerplate_cxx_sources += $(cairo_boilerplate_cogl_cxx_sources)
+enabled_cairo_boilerplate_sources += $(cairo_boilerplate_cogl_sources)
+endif
+
 unsupported_cairo_boilerplate_headers += $(cairo_boilerplate_directfb_headers)
 all_cairo_boilerplate_headers += $(cairo_boilerplate_directfb_headers)
 all_cairo_boilerplate_private += $(cairo_boilerplate_directfb_private)
diff --git a/boilerplate/cairo-boilerplate-cogl.c b/boilerplate/cairo-boilerplate-cogl.c
new file mode 100644
index 000000000..8dda31727
--- /dev/null
+++ b/boilerplate/cairo-boilerplate-cogl.c
@@ -0,0 +1,208 @@
+/* Cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2009 Chris Wilson
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is Chris Wilson.
+ */
+
+#include "cairo-boilerplate-private.h"
+
+#include <cairo-cogl.h>
+#include <cogl/cogl2-experimental.h>
+
+typedef struct _cogl_closure {
+    cairo_device_t *device;
+    CoglFramebuffer *fb;
+    cairo_surface_t *surface;
+} cogl_closure_t;
+
+static const cairo_user_data_key_t cogl_closure_key;
+
+static CoglContext *context = NULL;
+
+static void
+_cairo_boilerplate_cogl_cleanup (void *abstract_closure)
+{
+    cogl_closure_t *closure = abstract_closure;
+
+    cogl_object_unref (closure->fb);
+
+    cairo_device_finish (closure->device);
+    cairo_device_destroy (closure->device);
+
+    free (closure);
+}
+
+static cairo_surface_t *
+_cairo_boilerplate_cogl_create_offscreen_color_surface (const char		*name,
+							cairo_content_t		 content,
+							double			 width,
+							double			 height,
+							double			 max_width,
+							double			 max_height,
+							cairo_boilerplate_mode_t mode,
+							int			 id,
+							void		       **abstract_closure)
+{
+    cairo_device_t *device;
+    CoglTexture *tex;
+    CoglHandle offscreen;
+    CoglFramebuffer *fb;
+    cogl_closure_t *closure;
+    cairo_status_t status;
+
+    if (!context)
+	context = cogl_context_new (NULL, NULL);
+
+    device = cairo_cogl_device_create (context);
+    tex = cogl_texture_new_with_size (width, height,
+				      COGL_TEXTURE_NO_SLICING,
+				      COGL_PIXEL_FORMAT_BGRA_8888_PRE);
+    offscreen = cogl_offscreen_new_to_texture (tex);
+    fb = COGL_FRAMEBUFFER (offscreen);
+
+    cogl_framebuffer_allocate (fb, NULL);
+    cogl_push_framebuffer (fb);
+    cogl_ortho (0, cogl_framebuffer_get_width (fb),
+                cogl_framebuffer_get_height (fb), 0,
+                -1, 100);
+    cogl_pop_framebuffer ();
+
+    closure = malloc (sizeof (cogl_closure_t));
+    *abstract_closure = closure;
+    closure->device = device;
+    closure->fb = fb;
+    closure->surface = cairo_cogl_surface_create (device, fb);
+
+    status = cairo_surface_set_user_data (closure->surface,
+					  &cogl_closure_key, closure, NULL);
+    if (status == CAIRO_STATUS_SUCCESS)
+	return closure->surface;
+
+    _cairo_boilerplate_cogl_cleanup (closure);
+    return cairo_boilerplate_surface_create_in_error (status);
+}
+
+static cairo_surface_t *
+_cairo_boilerplate_cogl_create_onscreen_color_surface (const char	       *name,
+						       cairo_content_t		content,
+						       double			width,
+						       double			height,
+						       double			max_width,
+						       double			max_height,
+						       cairo_boilerplate_mode_t mode,
+						       int			id,
+						       void		      **abstract_closure)
+{
+    cairo_device_t *device;
+    CoglOnscreen *onscreen;
+    CoglFramebuffer *fb;
+    cogl_closure_t *closure;
+    cairo_status_t status;
+
+    if (!context)
+	context = cogl_context_new (NULL, NULL);
+
+    device = cairo_cogl_device_create (context);
+    onscreen = cogl_onscreen_new (context, width, height);
+    fb = COGL_FRAMEBUFFER (onscreen);
+
+    cogl_onscreen_show (onscreen);
+
+    cogl_push_framebuffer (fb);
+    cogl_ortho (0, cogl_framebuffer_get_width (fb),
+                cogl_framebuffer_get_height (fb), 0,
+                -1, 100);
+    cogl_pop_framebuffer ();
+
+    closure = malloc (sizeof (cogl_closure_t));
+    *abstract_closure = closure;
+    closure->device = device;
+    closure->fb = fb;
+    closure->surface = cairo_cogl_surface_create (device, fb);
+
+    status = cairo_surface_set_user_data (closure->surface,
+					  &cogl_closure_key, closure, NULL);
+    if (status == CAIRO_STATUS_SUCCESS)
+	return closure->surface;
+
+    _cairo_boilerplate_cogl_cleanup (closure);
+    return cairo_boilerplate_surface_create_in_error (status);
+}
+
+static cairo_status_t
+_cairo_boilerplate_cogl_finish_onscreen (cairo_surface_t *surface)
+{
+    cogl_closure_t *closure = cairo_surface_get_user_data (surface, &cogl_closure_key);
+
+    cairo_cogl_surface_end_frame (surface);
+
+    cogl_framebuffer_swap_buffers (closure->fb);
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+static void
+_cairo_boilerplate_cogl_synchronize (void *abstract_closure)
+{
+    cogl_closure_t *closure = abstract_closure;
+    cogl_framebuffer_finish (closure->fb);
+}
+
+static const cairo_boilerplate_target_t targets[] = {
+    {
+	"cogl-offscreen-color", "cogl", NULL, NULL,
+	CAIRO_SURFACE_TYPE_COGL, CAIRO_CONTENT_COLOR_ALPHA, 1,
+	"cairo_cogl_device_create",
+	_cairo_boilerplate_cogl_create_offscreen_color_surface,
+	cairo_surface_create_similar,
+	NULL, NULL,
+	_cairo_boilerplate_get_image_surface,
+	cairo_surface_write_to_png,
+	_cairo_boilerplate_cogl_cleanup,
+	_cairo_boilerplate_cogl_synchronize,
+        NULL,
+	TRUE, FALSE, FALSE
+    },
+    {
+	"cogl-onscreen-color", "cogl", NULL, NULL,
+	CAIRO_SURFACE_TYPE_COGL, CAIRO_CONTENT_COLOR_ALPHA, 1,
+	"cairo_cogl_device_create",
+	_cairo_boilerplate_cogl_create_onscreen_color_surface,
+	cairo_surface_create_similar,
+	NULL,
+	_cairo_boilerplate_cogl_finish_onscreen,
+	_cairo_boilerplate_get_image_surface,
+	cairo_surface_write_to_png,
+	_cairo_boilerplate_cogl_cleanup,
+	_cairo_boilerplate_cogl_synchronize,
+        NULL,
+	TRUE, FALSE, FALSE
+    }
+};
+CAIRO_BOILERPLATE (cogl, targets)