Add a simple example of stereo drawing

Add a new example that draws a triangle floating in the air in
front of the screen.

Reviewed-by: Robert Bragg <robert.bragg@intel.com>

examples/Makefile.am

@@ -33,7 +33,7 @@ cogl_info_SOURCES = cogl-info.c
 cogl_info_LDADD = $(common_ldadd)
 
 if USE_GLIB
-programs += cogl-hello cogl-msaa cogl-gles2-context cogl-point-sprites
+programs += cogl-hello cogl-msaa cogl-gles2-context cogl-point-sprites cogl-stereo
 examples_datadir = $(pkgdatadir)/examples-data
 examples_data_DATA =
 
@@ -43,6 +43,8 @@ cogl_msaa_SOURCES = cogl-msaa.c
 cogl_msaa_LDADD = $(common_ldadd)
 cogl_point_sprites_SOURCES = cogl-point-sprites.c
 cogl_point_sprites_LDADD = $(common_ldadd)
+cogl_stereo_SOURCES = cogl-stereo.c
+cogl_stereo_LDADD = $(common_ldadd)
 
 if BUILD_COGL_PANGO
 programs += cogl-crate

examples/cogl-stereo.c

@@ -0,0 +1,152 @@
+#include <cogl/cogl.h>
+#include <glib.h>
+#include <stdio.h>
+
+typedef struct _Data
+{
+    CoglContext *ctx;
+    CoglFramebuffer *fb;
+    CoglPrimitive *left_triangle;
+    CoglPrimitive *right_triangle;
+    CoglPipeline *pipeline;
+
+    unsigned int redraw_idle;
+    CoglBool is_dirty;
+    CoglBool draw_ready;
+} Data;
+
+static gboolean
+paint_cb (void *user_data)
+{
+    Data *data = user_data;
+
+    data->redraw_idle = 0;
+    data->is_dirty = FALSE;
+    data->draw_ready = FALSE;
+
+    cogl_framebuffer_set_stereo_mode (data->fb, COGL_STEREO_BOTH);
+    cogl_framebuffer_clear4f (data->fb, COGL_BUFFER_BIT_COLOR, 0, 0, 0, 1);
+
+    cogl_framebuffer_set_stereo_mode (data->fb, COGL_STEREO_LEFT);
+    cogl_primitive_draw (data->left_triangle,
+                         data->fb,
+                         data->pipeline);
+
+    if (cogl_framebuffer_get_is_stereo (data->fb))
+      {
+	cogl_framebuffer_set_stereo_mode (data->fb, COGL_STEREO_RIGHT);
+	cogl_primitive_draw (data->right_triangle,
+			     data->fb,
+			     data->pipeline);
+      }
+
+    cogl_onscreen_swap_buffers (data->fb);
+
+    return G_SOURCE_REMOVE;
+}
+
+static void
+maybe_redraw (Data *data)
+{
+    if (data->is_dirty && data->draw_ready && data->redraw_idle == 0) {
+        /* We'll draw on idle instead of drawing immediately so that
+         * if Cogl reports multiple dirty rectangles we won't
+         * redundantly draw multiple frames */
+        data->redraw_idle = g_idle_add (paint_cb, data);
+    }
+}
+
+static void
+frame_event_cb (CoglOnscreen *onscreen,
+                CoglFrameEvent event,
+                CoglFrameInfo *info,
+                void *user_data)
+{
+    Data *data = user_data;
+
+    if (event == COGL_FRAME_EVENT_SYNC) {
+        data->draw_ready = TRUE;
+        maybe_redraw (data);
+    }
+}
+
+static void
+dirty_cb (CoglOnscreen *onscreen,
+          const CoglOnscreenDirtyInfo *info,
+          void *user_data)
+{
+    Data *data = user_data;
+
+    data->is_dirty = TRUE;
+    maybe_redraw (data);
+}
+
+int
+main (int argc, char **argv)
+{
+    Data data;
+    CoglRenderer *renderer;
+    CoglOnscreenTemplate *onscreen_template;
+    CoglDisplay *display;
+    CoglOnscreen *onscreen;
+    CoglError *error = NULL;
+    CoglVertexP2C4 left_triangle_vertices[] = {
+        {0.05, 0.7, 0xff, 0x00, 0x00, 0xff},
+        {-0.65, -0.7, 0x00, 0xff, 0x00, 0xff},
+        {0.75, -0.7, 0x00, 0x00, 0xff, 0xff}
+    };
+    CoglVertexP2C4 right_triangle_vertices[] = {
+        {-0.05, 0.7, 0xff, 0x00, 0x00, 0xff},
+        {-0.75, -0.7, 0x00, 0xff, 0x00, 0xff},
+        {0.65, -0.7, 0x00, 0x00, 0xff, 0xff}
+    };
+    GSource *cogl_source;
+    GMainLoop *loop;
+
+    data.redraw_idle = 0;
+    data.is_dirty = FALSE;
+    data.draw_ready = TRUE;
+
+    renderer = cogl_renderer_new ();
+    onscreen_template = cogl_onscreen_template_new (NULL);
+    cogl_onscreen_template_set_stereo_enabled (onscreen_template, TRUE);
+    display = cogl_display_new (renderer, onscreen_template);
+
+    data.ctx = cogl_context_new (display, &error);
+    if (!data.ctx) {
+        fprintf (stderr, "Failed to create stereo context: %s\n", error->message);
+        return 1;
+    }
+
+    onscreen = cogl_onscreen_new (data.ctx, 640, 480);
+    cogl_onscreen_show (onscreen);
+    data.fb = onscreen;
+
+    cogl_onscreen_set_resizable (onscreen, TRUE);
+
+    data.left_triangle = cogl_primitive_new_p2c4 (data.ctx,
+						  COGL_VERTICES_MODE_TRIANGLES,
+						  3, left_triangle_vertices);
+    data.right_triangle = cogl_primitive_new_p2c4 (data.ctx,
+						   COGL_VERTICES_MODE_TRIANGLES,
+						   3, right_triangle_vertices);
+    data.pipeline = cogl_pipeline_new (data.ctx);
+
+    cogl_source = cogl_glib_source_new (data.ctx, G_PRIORITY_DEFAULT);
+
+    g_source_attach (cogl_source, NULL);
+
+    cogl_onscreen_add_frame_callback (data.fb,
+                                      frame_event_cb,
+                                      &data,
+                                      NULL); /* destroy notify */
+    cogl_onscreen_add_dirty_callback (data.fb,
+                                      dirty_cb,
+                                      &data,
+                                      NULL); /* destroy notify */
+
+    loop = g_main_loop_new (NULL, TRUE);
+    g_main_loop_run (loop);
+
+    return 0;
+}