examples: Adds a simple 4x msaa example

This adds a very basic test of onscreen and offscreen multisample
rendering with 4 samples per pixel. The test simply draws two triangles;
the one on the left is rendered directly to the onscreen framebuffer and
the other is first rendered offscreen before copying it onscreen.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

examples/Makefile.am

@@ -18,12 +18,14 @@ common_ldadd = \
 	$(COGL_DEP_LIBS) \
 	$(top_builddir)/cogl/libcogl.la
 
-programs = cogl-hello
+programs = cogl-hello cogl-msaa
 examples_datadir = $(pkgdatadir)/examples-data
 examples_data_DATA =
 
 cogl_hello_SOURCES = cogl-hello.c
 cogl_hello_LDADD = $(common_ldadd)
+cogl_msaa_SOURCES = cogl-msaa.c
+cogl_msaa_LDADD = $(common_ldadd)
 
 if BUILD_COGL_PANGO
 programs += cogl-crate

examples/cogl-msaa.c

@@ -0,0 +1,112 @@
+#include <cogl/cogl.h>
+#include <glib.h>
+#include <stdio.h>
+
+CoglColor black;
+
+int
+main (int argc, char **argv)
+{
+    CoglOnscreenTemplate *onscreen_template;
+    CoglDisplay *display;
+    CoglContext *ctx;
+    CoglOnscreen *onscreen;
+    CoglFramebuffer *fb;
+    GError *error = NULL;
+    CoglVertexP2C4 triangle_vertices[] = {
+        {0, 0.7, 0xff, 0x00, 0x00, 0x80},
+        {-0.7, -0.7, 0x00, 0xff, 0x00, 0xff},
+        {0.7, -0.7, 0x00, 0x00, 0xff, 0xff}
+    };
+    CoglPrimitive *triangle;
+    CoglHandle tex;
+    CoglHandle offscreen;
+    CoglFramebuffer *offscreen_fb;
+    CoglPipeline *pipeline;
+
+    onscreen_template = cogl_onscreen_template_new (NULL);
+    cogl_onscreen_template_set_samples_per_pixel (onscreen_template, 4);
+    display = cogl_display_new (NULL, onscreen_template);
+
+    if (!cogl_display_setup (display, &error))
+      {
+        fprintf (stderr, "Platform doesn't support onscreen 4x msaa rendering: %s\n",
+                 error->message);
+        return 1;
+      }
+
+    ctx = cogl_context_new (display, &error);
+    if (!ctx)
+      {
+        fprintf (stderr, "Failed to create context: %s\n", error->message);
+        return 1;
+      }
+
+    onscreen = cogl_onscreen_new (ctx, 640, 480);
+    /* Eventually there will be an implicit allocate on first use so this
+     * will become optional... */
+    fb = COGL_FRAMEBUFFER (onscreen);
+
+    cogl_framebuffer_set_samples_per_pixel (fb, 4);
+
+    if (!cogl_framebuffer_allocate (fb, &error))
+      {
+        g_error_free (error);
+        fprintf (stderr, "Failed to allocate 4x msaa offscreen framebuffer, "
+                 "disabling msaa for onscreen rendering\n");
+        cogl_framebuffer_set_samples_per_pixel (fb, 0);
+
+        error = NULL;
+        if (!cogl_framebuffer_allocate (fb, &error))
+          {
+            fprintf (stderr, "Failed to allocate framebuffer: %s\n", error->message);
+            return 1;
+          }
+      }
+
+    cogl_onscreen_show (onscreen);
+
+    tex = cogl_texture_new_with_size (320, 480,
+                                      COGL_TEXTURE_NO_SLICING,
+                                      COGL_PIXEL_FORMAT_ANY);
+    offscreen = cogl_offscreen_new_to_texture (tex);
+    offscreen_fb = COGL_FRAMEBUFFER (offscreen);
+    cogl_framebuffer_set_samples_per_pixel (offscreen_fb, 4);
+    if (!cogl_framebuffer_allocate (offscreen_fb, &error))
+      {
+        g_error_free (error);
+        error = NULL;
+        fprintf (stderr, "Failed to allocate 4x msaa offscreen framebuffer, "
+                 "disabling msaa for offscreen rendering");
+        cogl_framebuffer_set_samples_per_pixel (offscreen_fb, 0);
+      }
+
+    cogl_push_framebuffer (fb);
+
+    triangle = cogl_primitive_new_p2c4 (COGL_VERTICES_MODE_TRIANGLES,
+                                        3, triangle_vertices);
+    pipeline = cogl_pipeline_new ();
+
+    for (;;) {
+        cogl_clear (&black, COGL_BUFFER_BIT_COLOR);
+
+        cogl_push_matrix ();
+        cogl_scale (0.5, 1, 1);
+        cogl_translate (-1, 0, 0);
+        cogl_set_source (pipeline);
+        cogl_primitive_draw (triangle);
+        cogl_pop_matrix ();
+
+        cogl_push_framebuffer (offscreen_fb);
+        cogl_primitive_draw (triangle);
+        cogl_framebuffer_resolve_samples (offscreen_fb);
+        cogl_pop_framebuffer ();
+
+        cogl_set_source_texture (tex);
+        cogl_rectangle (0, 1, 1, -1);
+
+        cogl_framebuffer_swap_buffers (fb);
+    }
+
+    return 0;
+}