[cogl] onscreen: Support multisample based onscreen rendering

[Robert Bragg <rbragg src gnome org>]

commit a74c81ada38d0a38ab3b4566b20ee4370a032eeb
Author: Robert Bragg <robert linux intel com>
Date:   Sun Aug 21 21:27:13 2011 +0100

    onscreen: Support multisample based onscreen rendering
    
    This adds support for multisample based rendering of onscreen windows
    whereby multiple point samples per pixel can be requested and if the
    hardware supports that it results in reduced aliasing (especially
    considering the jagged edges of polygons)
    
    Reviewed-by: Neil Roberts <neil linux intel com>

 cogl/cogl-framebuffer-private.h |    1 +
 cogl/cogl-onscreen-template.c   |   18 ++++++++++++++++++
 cogl/cogl-onscreen-template.h   |   28 ++++++++++++++++++++++++++++
 cogl/winsys/cogl-winsys-egl.c   |    8 ++++++++
 cogl/winsys/cogl-winsys-glx.c   |    9 +++++++++
 cogl/winsys/cogl-winsys-wgl.c   |    4 ++++
 6 files changed, 68 insertions(+), 0 deletions(-)
---
diff --git a/cogl/cogl-framebuffer-private.h b/cogl/cogl-framebuffer-private.h
index 8d4bbc3..fb8ddcf 100644
--- a/cogl/cogl-framebuffer-private.h
+++ b/cogl/cogl-framebuffer-private.h
@@ -51,6 +51,7 @@ typedef struct
 {
   CoglSwapChain *swap_chain;
   gboolean need_stencil;
+  int samples_per_pixel;
 } CoglFramebufferConfig;
 
 struct _CoglFramebuffer
diff --git a/cogl/cogl-onscreen-template.c b/cogl/cogl-onscreen-template.c
index b9fbd23..92caade 100644
--- a/cogl/cogl-onscreen-template.c
+++ b/cogl/cogl-onscreen-template.c
@@ -65,6 +65,24 @@ cogl_onscreen_template_new (CoglSwapChain *swap_chain)
     onscreen_template->config.swap_chain = cogl_swap_chain_new ();
 
   onscreen_template->config.need_stencil = TRUE;
+  onscreen_template->config.samples_per_pixel = 0;
+
+  user_config = getenv ("COGL_POINT_SAMPLES_PER_PIXEL");
+  if (user_config)
+    {
+      unsigned long samples_per_pixel = strtoul (user_config, NULL, 10);
+      if (samples_per_pixel != ULONG_MAX)
+        onscreen_template->config.samples_per_pixel =
+          samples_per_pixel;
+    }
 
   return _cogl_onscreen_template_object_new (onscreen_template);
 }
+
+void
+cogl_onscreen_template_set_samples_per_pixel (
+                                        CoglOnscreenTemplate *onscreen_template,
+                                        int samples_per_pixel)
+{
+  onscreen_template->config.samples_per_pixel = samples_per_pixel;
+}
diff --git a/cogl/cogl-onscreen-template.h b/cogl/cogl-onscreen-template.h
index 4769f9f..e992b7a 100644
--- a/cogl/cogl-onscreen-template.h
+++ b/cogl/cogl-onscreen-template.h
@@ -43,6 +43,34 @@ typedef struct _CoglOnscreenTemplate	      CoglOnscreenTemplate;
 CoglOnscreenTemplate *
 cogl_onscreen_template_new (CoglSwapChain *swap_chain);
 
+/**
+ * cogl_onscreen_template_set_samples_per_pixel:
+ * @onscreen: A #CoglOnscreenTemplate template framebuffer
+ * @n: The minimum number of samples per pixel
+ *
+ * Requires that any future CoglOnscreen framebuffers derived from
+ * this template must support making at least @n samples per pixel
+ * which will all contribute to the final resolved color for that
+ * pixel.
+ *
+ * By default this value is usually set to 0 and that is referred to
+ * as "single-sample" rendering. A value of 1 or greater is referred
+ * to as "multisample" rendering.
+ *
+ * <note>There are some semantic differences between single-sample
+ * rendering and multisampling with just 1 point sample such as it
+ * being redundant to use the cogl_framebuffer_resolve_samples() and
+ * cogl_framebuffer_resolve_samples_region() apis with single-sample
+ * rendering.</note>
+ *
+ * Since: 1.10
+ * Stability: unstable
+ */
+void
+cogl_onscreen_template_set_samples_per_pixel (
+                                          CoglOnscreenTemplate *onscreen_template,
+                                          int n);
+
 G_END_DECLS
 
 #endif /* __COGL_ONSCREEN_TEMPLATE_H__ */
diff --git a/cogl/winsys/cogl-winsys-egl.c b/cogl/winsys/cogl-winsys-egl.c
index 6b40fc3..5a9c937 100644
--- a/cogl/winsys/cogl-winsys-egl.c
+++ b/cogl/winsys/cogl-winsys-egl.c
@@ -644,6 +644,14 @@ egl_attributes_from_framebuffer_config (CoglDisplay *display,
   attributes[i++] = EGL_SURFACE_TYPE;
   attributes[i++] = EGL_WINDOW_BIT;
 
+  if (config->samples_per_pixel)
+    {
+       attributes[i++] = EGL_SAMPLE_BUFFERS;
+       attributes[i++] = 1;
+       attributes[i++] = EGL_SAMPLES;
+       attributes[i++] = config->samples_per_pixel;
+    }
+
   attributes[i++] = EGL_NONE;
 
   g_assert (i < MAX_EGL_CONFIG_ATTRIBS);
diff --git a/cogl/winsys/cogl-winsys-glx.c b/cogl/winsys/cogl-winsys-glx.c
index 1a42605..8b645be 100644
--- a/cogl/winsys/cogl-winsys-glx.c
+++ b/cogl/winsys/cogl-winsys-glx.c
@@ -485,6 +485,15 @@ glx_attributes_from_framebuffer_config (CoglDisplay *display,
   attributes[i++] = GLX_STENCIL_SIZE;
   attributes[i++] = config->need_stencil ? 1: GLX_DONT_CARE;
 
+  if (glx_renderer->glx_major == 1 && glx_renderer->glx_minor >= 4 &&
+      config->samples_per_pixel)
+    {
+       attributes[i++] = GLX_SAMPLE_BUFFERS;
+       attributes[i++] = 1;
+       attributes[i++] = GLX_SAMPLES;
+       attributes[i++] = config->samples_per_pixel;
+    }
+
   attributes[i++] = None;
 
   g_assert (i < MAX_GLX_CONFIG_ATTRIBS);
diff --git a/cogl/winsys/cogl-winsys-wgl.c b/cogl/winsys/cogl-winsys-wgl.c
index 8306f27..3124bcd 100644
--- a/cogl/winsys/cogl-winsys-wgl.c
+++ b/cogl/winsys/cogl-winsys-wgl.c
@@ -324,6 +324,10 @@ choose_pixel_format (CoglFramebufferConfig *config,
 
   num_formats = DescribePixelFormat (dc, 0, sizeof (best_pfd), NULL);
 
+  /* XXX: currently we don't support multisampling on windows... */
+  if (config->samples_per_pixel)
+    return best_pf;
+
   for (i = 1; i <= num_formats; i++)
     {
       memset (pfd, 0, sizeof (*pfd));