It took me a little while to figure out how struts & workareas are updated

2005-11-21  Elijah Newren  <newren@gmail.com>

	* doc/strut-and-related-updating.txt: It took me a little while to
	figure out how struts & workareas are updated and to learn what
	all the related functions were used for so I thought I'd clean up
	my notes and make them available.  This will probably be more
	useful now since regions and edges are also computed and stored at
	the some time as the workareas.

ChangeLog

@@ -1,3 +1,12 @@
+2005-11-21  Elijah Newren  <newren@gmail.com>
+
+	* doc/strut-and-related-updating.txt: It took me a little while to
+	figure out how struts & workareas are updated and to learn what
+	all the related functions were used for so I thought I'd clean up
+	my notes and make them available.  This will probably be more
+	useful now since regions and edges are also computed and stored at
+	the some time as the workareas.
+
 2005-11-20  Elijah Newren  <newren@gmail.com>
 
 	* src/constraints.c (place_window_if_needed): compute the frame

doc/strut-and-related-updating.txt

@@ -0,0 +1,53 @@
+How updates happen for struts, workareas, and screen/xinerama regions/edges
+  One of three things causes meta_window_update_struts to be called
+    (a) initial window map (window.c:meta_window_new_with_attrs())
+    (b) update of _net_wm_strut* properties (window.c:process_property_notify())
+    (c) screen.c (meta_screen_resize_func())
+  meta_window_update_struts (MetaWindow *window)
+    - Gets new list of struts from window properties
+    - Makes sure window doesn't single-handedly fill the screen
+    - records new struts if different and calls invalidate_work_areas()
+  invalidate_work_areas ()
+    - Calls meta_workspace_invalidate_work_area() for each workspace it's on
+  meta_workspace_invalidate_work_area()
+    - Cleans out all strut lists
+    - queues all windows for resizing
+    - Calls meta_screen_queue_workarea_recalc (workspace->screen);
+  meta_screen_queue_workarea_recalc ()
+    - Adds set_work_area_idle_func() as an idle handler
+
+  set_work_area_idle_func()
+    - Calls set_work_area_hint()
+  set_work_area_hint()
+    - Calls meta_workspace_get_work_area_all_xineramas()
+    - Sets _NET_WORKAREA property
+  meta_workspace_get_work_area_all_xineramas()
+    - Calls ensure_work_areas_validated()
+  ensure_work_areas_validated()
+    - Loops over xineramas
+      - Loops over windows, then struts:
+        - Adds struts to list first time through xinerama loop
+        - Find the amount of the strut on the given xinerama for <dir>_strut
+        - Just max the amount of the strut with the all_<dir>_strut
+      - Makes sure there's a non-empty xinerama workarea
+      - Record the xinerama workarea
+    - Make sure there's a non-empty screen workarea
+    - Record the screen workarea
+    - Cache the spanning rects for the screen and xinerama regions
+
+  Alternatively to all the above, if the idle function for the screen
+  has not yet fired, constraints.c:setup_constraint_info() can call
+  either workspace.c:meta_workspace_get_onscreen_region() or
+  workspace.c:meta_workspace_get_onxinerama_region() which in turn
+  call workspace.c:ensure_work_areas_validated().
+
+Meaning of related functions that might be difficult to tell apart:
+  screen.c:meta_screen_get_current_xinerama ()
+    - Finds out which xinerama the mouse is on with an XQueryPointer
+  window.c:meta_window_get_work_area_current_xinerama()
+  window.c:meta_window_get_work_area_for_xinerama()
+  window.c:meta_window_get_work_area_all_xineramas ()
+    - All three are for finding the intersection of workareas across
+      multiple workspaces so that placement of windows can be
+      determined in such a way that they remain in the workarea for
+      all workspaces that they are on.