Commit cffddd2a authored by Kristian Rietveld's avatar Kristian Rietveld

Document how Cocoa coordinate and monitor layout transforms to GDK work

parent 087348a5
......@@ -25,6 +25,40 @@
#include "gdkprivate-quartz.h"
/* A couple of notes about this file are in order. In GDK, a
* GdkScreen can contain multiple monitors. A GdkScreen has an
* associated root window, in which the monitors are placed. The
* root window "spans" all monitors. The origin is at the top-left
* corner of the root window.
*
* Cocoa works differently. The system has a "screen" (NSScreen) for
* each monitor that is connected (note the conflicting definitions
* of screen). The screen containing the menu bar is screen 0 and the
* bottom-left corner of this screen is the origin of the "monitor
* coordinate space". All other screens are positioned according to this
* origin. If the menu bar is on a secondary screen (for example on
* a monitor hooked up to a laptop), then this screen is screen 0 and
* other monitors will be positioned according to the "secondary screen".
* The main screen is the monitor that shows the window that is currently
* active (has focus), the position of the menu bar does not have influence
* on this!
*
* Upon start up and changes in the layout of screens, we calculate the
* size of the GdkScreen root window that is needed to be able to place
* all monitors in the root window. Once that size is known, we iterate
* over the monitors and translate their Cocoa position to a position
* in the root window of the GdkScreen. This happens below in the
* function gdk_screen_quartz_calculate_layout().
*
* A Cocoa coordinate is always relative to the origin of the monitor
* coordinate space. Such coordinates are mapped to their respective
* position in the GdkScreen root window (_gdk_quartz_window_xy_to_gdk_xy)
* and vice versa (_gdk_quartz_window_gdk_xy_to_xy). Both functions can
* be found in gdkwindow-quartz.c. Note that Cocoa coordinates can have
* negative values (in case a monitor is located left or below of screen 0),
* but GDK coordinates can *not*!
*/
static void gdk_screen_quartz_dispose (GObject *object);
static void gdk_screen_quartz_finalize (GObject *object);
static void gdk_screen_quartz_calculate_layout (GdkScreenQuartz *screen);
......
......@@ -653,6 +653,7 @@ _gdk_quartz_window_is_ancestor (GdkWindow *ancestor,
}
/* See notes on top of gdkscreen-quartz.c */
void
_gdk_quartz_window_gdk_xy_to_xy (gint gdk_x,
gint gdk_y,
......
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