onscreen: Adds support for resizable windows

This adds api to be able to request that the window system allows a
given onscreen framebuffer to be resizable, and api to add and remove
resize handlers to be called whenever the framebuffer does actually
change size.

The new functions are:
  cogl_onscreen_{get,set}_resizable()
  cogl_onscreen_{add,remove}_resize_handler()

The examples cogl-hello and cogl-x11-foreign have been updated to use
the new api. To smoke test how Cogl updates the viewport automatically
in response to window resizes the cogl-hello test doesn't explicitly
respond to resize events by setting the viewport and cogl-x11-foreign
responds by setting a viewport that is offset by a quarter of the
window's width/height and half the width and height of the window.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/examples/cogl-hello.c b/examples/cogl-hello.c
index a0b002d1..cf0e8f6d 100644
--- a/examples/cogl-hello.c
+++ b/examples/cogl-hello.c
@@ -59,6 +59,8 @@ main (int argc, char **argv)
     cogl_onscreen_show (onscreen);
     data.fb = COGL_FRAMEBUFFER (onscreen);
 
+    cogl_onscreen_set_resizable (onscreen, TRUE);
+
     data.triangle = cogl_primitive_new_p2c4 (data.ctx,
                                              COGL_VERTICES_MODE_TRIANGLES,
                                              3, triangle_vertices);