[tests] Adds test-cogl-offscreen to validate offscreen draw buffer

This adds a basic test to check that rendering a few colored rectangles
offscreen works and that the modelview gets restored when switching back to
the previous buffer.

tests/conform/Makefile.am

@@ -37,6 +37,7 @@ test_conformance_SOURCES = 		\
 	test-actor-size.c		\
 	test-texture-fbo.c		\
 	test-cogl-viewport.c		\
+	test-cogl-offscreen.c		\
         $(NULL)
 
 # For convenience, this provides a way to easily run individual unit tests:

tests/conform/test-cogl-offscreen.c

@@ -0,0 +1,169 @@
+
+#include <clutter/clutter.h>
+#include <cogl/cogl.h>
+
+#include "test-conform-common.h"
+
+#define RED 0
+#define GREEN 1
+#define BLUE 2
+
+#define DRAW_BUFFER_WIDTH  640
+#define DRAW_BUFFER_HEIGHT 480
+
+static const ClutterColor stage_color = { 0x0, 0x0, 0x0, 0xff };
+
+
+static void
+on_paint (ClutterActor *actor, void *state)
+{
+  float saved_viewport[4];
+  CoglMatrix saved_projection;
+  CoglMatrix projection;
+  CoglMatrix modelview;
+  guchar *data;
+  CoglHandle tex;
+  CoglHandle offscreen;
+  guint8 pixel[4];
+
+  /* Save the Clutter viewport/matrices and load identity matrices */
+
+  cogl_get_viewport (saved_viewport);
+  cogl_get_projection_matrix (&saved_projection);
+  cogl_push_matrix ();
+
+  cogl_matrix_init_identity (&projection);
+  cogl_matrix_init_identity (&modelview);
+
+  cogl_set_projection_matrix (&projection);
+  cogl_set_modelview_matrix (&modelview);
+
+  data = g_malloc (DRAW_BUFFER_WIDTH * 4 * DRAW_BUFFER_HEIGHT);
+  tex = cogl_texture_new_from_data (DRAW_BUFFER_WIDTH, DRAW_BUFFER_HEIGHT,
+                                    COGL_TEXTURE_NO_SLICING,
+                                    COGL_PIXEL_FORMAT_RGBA_8888, /* data fmt */
+                                    COGL_PIXEL_FORMAT_ANY, /* internal fmt */
+                                    DRAW_BUFFER_WIDTH * 4, /* rowstride */
+                                    data);
+  g_free (data);
+  offscreen = cogl_offscreen_new_to_texture (tex);
+
+  /* Set a scale and translate transform on the window draw buffer before
+   * switching to the offscreen draw buffer so we can verify it gets restored
+   * when we switch back
+   *
+   * The test is going to draw a grid of 4 colors to a texture which we
+   * subsequently draw to the window with a fullscreen rectangle. This
+   * transform will flip the texture left to right, scale it to a quater of the
+   * window size and slide it to the top right of the window.
+   */
+  cogl_translate (0.5, 0.5, 0);
+  cogl_scale (-0.5, 0.5, 1);
+
+  cogl_push_draw_buffer ();
+  cogl_set_draw_buffer (0 /* unused */, offscreen);
+
+  /* Cogl should release the last reference when we call cogl_pop_draw_buffer()
+   */
+  cogl_handle_unref (offscreen);
+
+  /* Setup something other than the identity matrix for the modelview so we can
+   * verify it gets restored when we call cogl_pop_draw_buffer () */
+  cogl_scale (2, 2, 1);
+
+  /* red, top left */
+  cogl_set_source_color4ub (0xff, 0x00, 0x00, 0xff);
+  cogl_rectangle (-0.5, 0.5, 0, 0);
+  /* green, top right */
+  cogl_set_source_color4ub (0x00, 0xff, 0x00, 0xff);
+  cogl_rectangle (0, 0.5, 0.5, 0);
+  /* blue, bottom left */
+  cogl_set_source_color4ub (0x00, 0x00, 0xff, 0xff);
+  cogl_rectangle (-0.5, 0, 0, -0.5);
+  /* white, bottom right */
+  cogl_set_source_color4ub (0xff, 0xff, 0xff, 0xff);
+  cogl_rectangle (0, 0, 0.5, -0.5);
+
+  cogl_pop_draw_buffer ();
+
+  cogl_set_source_texture (tex);
+  cogl_rectangle (-1, 1, 1, -1);
+
+  cogl_handle_unref (tex);
+
+  /* NB: The texture is drawn flipped horizontally and scaled to fit in the
+   * top right corner of the window. */
+
+  /* red, top right */
+  cogl_read_pixels (DRAW_BUFFER_WIDTH - 1, 0, 1, 1,
+                    COGL_READ_PIXELS_COLOR_BUFFER,
+                    COGL_PIXEL_FORMAT_RGBA_8888,
+                    pixel);
+  g_assert (pixel[RED] == 0xff && pixel[GREEN] == 0x00 && pixel[BLUE] == 0x00);
+
+  /* green, top left */
+  cogl_read_pixels ((DRAW_BUFFER_WIDTH/2), 0, 1, 1,
+                    COGL_READ_PIXELS_COLOR_BUFFER,
+                    COGL_PIXEL_FORMAT_RGBA_8888,
+                    pixel);
+  g_assert (pixel[RED] == 0x00 && pixel[GREEN] == 0xff && pixel[BLUE] == 0x00);
+
+  /* blue, bottom right */
+  cogl_read_pixels (DRAW_BUFFER_WIDTH - 1, (DRAW_BUFFER_HEIGHT/2) - 1, 1, 1,
+                    COGL_READ_PIXELS_COLOR_BUFFER,
+                    COGL_PIXEL_FORMAT_RGBA_8888,
+                    pixel);
+  g_assert (pixel[RED] == 0x00 && pixel[GREEN] == 0x00 && pixel[BLUE] == 0xff);
+
+  /* white, bottom left */
+  cogl_read_pixels ((DRAW_BUFFER_WIDTH/2), (DRAW_BUFFER_HEIGHT/2) - 1, 1, 1,
+                    COGL_READ_PIXELS_COLOR_BUFFER,
+                    COGL_PIXEL_FORMAT_RGBA_8888,
+                    pixel);
+  g_assert (pixel[RED] == 0xff && pixel[GREEN] == 0xff && pixel[BLUE] == 0xff);
+
+  /* Comment this out if you want visual feedback of what this test
+   * paints.
+   */
+  clutter_main_quit ();
+}
+
+static gboolean
+queue_redraw (gpointer stage)
+{
+  clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
+
+  return TRUE;
+}
+
+void
+test_cogl_offscreen (TestConformSimpleFixture *fixture,
+                     gconstpointer data)
+{
+  guint idle_source;
+  ClutterActor *stage;
+
+  stage = clutter_stage_get_default ();
+  clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
+  clutter_actor_set_size (stage, DRAW_BUFFER_WIDTH, DRAW_BUFFER_HEIGHT);
+
+  /* We force continuous redrawing of the stage, since we need to skip
+   * the first few frames, and we wont be doing anything else that
+   * will trigger redrawing. */
+  idle_source = g_idle_add (queue_redraw, stage);
+  g_signal_connect_after (stage, "paint", G_CALLBACK (on_paint), NULL);
+
+  clutter_actor_show (stage);
+  clutter_main ();
+
+  g_source_remove (idle_source);
+
+  /* Remove all of the actors from the stage */
+  clutter_container_foreach (CLUTTER_CONTAINER (stage),
+                             (ClutterCallback) clutter_actor_destroy,
+                             NULL);
+
+  if (g_test_verbose ())
+    g_print ("OK\n");
+}
+

tests/conform/test-conform-main.c

@@ -176,6 +176,7 @@ main (int argc, char **argv)
   TEST_CONFORM_SIMPLE ("/sizing", test_preferred_size);
 
   TEST_CONFORM_SIMPLE ("/cogl", test_cogl_viewport);
+  TEST_CONFORM_SIMPLE ("/cogl", test_cogl_offscreen);
 
   return g_test_run ();
 }