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wayland: Add some useful comments explaining the cairo surface behaviour

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This commit is contained in:
Rob Bradford
2012-03-06 21:24:20 +00:00
parent ff2acecac6
commit c6b0e91e87
1 changed files with 28 additions and 0 deletions
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28
gdk/wayland/gdkwindow-wayland.c
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@ -102,8 +102,17 @@ struct _GdkWindowImplWayland
GdkWindow *transient_for;
GdkWindowTypeHint hint;
/* The surface which is being "drawn to" to */
cairo_surface_t *cairo_surface;
/* The surface that was the last surface the Wayland buffer from which was attached
* to the Wayland surface. It will be the same as cairo_surface after a call
* to gdk_wayland_window_attach_image. But after a call to
* gdk_wayland_window_update_size and then
* gdk_wayland_window_ref_cairo_surface the above pointer will be different.
*/
cairo_surface_t *server_surface;
GLuint texture;
uint32_t resize_edges;
@ -310,15 +319,25 @@ gdk_wayland_window_attach_image (GdkWindow *window)
if (GDK_WINDOW_DESTROYED (window))
return;
/* The "drawn to" Cairo surface is the same as the Cairo surface from which
* we are driving the buffer for the Wayland surface. Therefore we don't
* need to do anything here
*/
if (impl->server_surface == impl->cairo_surface)
return;
/* The wayland surface is attached to a buffer that is from the old "drawn
* to" surface. Unref the surface and restore the state.
*/
if (impl->server_surface)
{
data = cairo_surface_get_user_data (impl->server_surface,
&gdk_wayland_cairo_key);
/* Save the old dimensions used for the surface */
server_width = data->width;
server_height = data->height;
cairo_surface_destroy (impl->server_surface);
}
else
@ -327,7 +346,10 @@ gdk_wayland_window_attach_image (GdkWindow *window)
server_height = 0;
}
/* Save the current "drawn to" surface for future calls into here */
impl->server_surface = cairo_surface_reference (impl->cairo_surface);
/* Get a Wayland buffer from this new surface */
data = cairo_surface_get_user_data (impl->cairo_surface,
&gdk_wayland_cairo_key);
if (!data->buffer)
@ -344,6 +366,7 @@ gdk_wayland_window_attach_image (GdkWindow *window)
else
dy = 0;
/* Attach this new buffer to the surface */
wl_surface_attach (impl->surface, data->buffer, dx, dy);
}
@ -414,6 +437,11 @@ gdk_wayland_create_cairo_surface (GdkDisplayWayland *display,
return surface;
}
/* On this first call this creates a double reference - the first reference
* is held by the GdkWindowImplWayland struct - since unlike other backends
* the Cairo surface is not just a cheap wrapper around some other backing.
* It is the buffer itself.
*/
static cairo_surface_t *
gdk_wayland_window_ref_cairo_surface (GdkWindow *window)
{