From 62fcd7e86e428197752cd50b53d874ed437daef2 Mon Sep 17 00:00:00 2001
From: Alistair Buxton <a.j.buxton@gmail.com>
Date: Fri, 17 Jan 2014 00:21:17 +0000
Subject: [PATCH] Improve the tasklist multimonitor handling.

The tasklist widget has an option to only show windows from the
current monitor. This previously worked by calculating the centre
pixel of the window, and then testing that against the monitor.
However, it is possible to position a window such that the centre
pixel does not appear on any monitor.

Instead, find the monitor which has the largest intersection with
the window and display the window button there.
---
 plugins/tasklist/tasklist-widget.c | 57 +++++++++++++++++++++++++-------------
 1 file changed, 38 insertions(+), 19 deletions(-)

diff --git a/plugins/tasklist/tasklist-widget.c b/plugins/tasklist/tasklist-widget.c
index 9d35d85..923466c 100644
--- a/plugins/tasklist/tasklist-widget.c
+++ b/plugins/tasklist/tasklist-widget.c
@@ -71,13 +71,8 @@
 #define xfce_tasklist_horizontal(tasklist) ((tasklist)->mode == XFCE_PANEL_PLUGIN_MODE_HORIZONTAL)
 #define xfce_tasklist_vertical(tasklist) ((tasklist)->mode == XFCE_PANEL_PLUGIN_MODE_VERTICAL)
 #define xfce_tasklist_deskbar(tasklist) ((tasklist)->mode == XFCE_PANEL_PLUGIN_MODE_DESKBAR)
-#define xfce_tasklist_filter_monitors(tasklist) (!(tasklist)->all_monitors && (tasklist)->monitor_geometry.width != -1)
-#define xfce_tasklist_geometry_set_invalid(tasklist) ((tasklist)->monitor_geometry.width = -1)
-#define xfce_tasklist_geometry_has_point(tasklist, x, y) ( \
-  (x) >= ((tasklist)->monitor_geometry.x) \
-  && (x) < ((tasklist)->monitor_geometry.x + (tasklist)->monitor_geometry.width) \
-  && (y) >= ((tasklist)->monitor_geometry.y) \
-  && (y) < ((tasklist)->monitor_geometry.y + (tasklist)->monitor_geometry.height))
+#define xfce_tasklist_filter_monitors(tasklist) (!(tasklist)->all_monitors && (tasklist)->n_monitors > 1)
+#define xfce_tasklist_geometry_set_invalid(tasklist) ((tasklist)->n_monitors = 0)
 
 
 
@@ -167,7 +162,9 @@ struct _XfceTasklist
   /* whether we only show windows that are in the geometry of
    * the monitor the tasklist is on */
   guint                 all_monitors : 1;
-  GdkRectangle          monitor_geometry;
+  guint                 n_monitors;
+  guint                 my_monitor;
+  GdkRectangle *        all_monitors_geometry;
 
   /* whether we show wireframes when hovering a button in
    * the tasklist */
@@ -560,6 +557,8 @@ xfce_tasklist_init (XfceTasklist *tasklist)
   tasklist->show_wireframes = FALSE;
   tasklist->show_handle = TRUE;
   tasklist->all_monitors = TRUE;
+  tasklist->n_monitors = 0;
+  tasklist->all_monitors_geometry = NULL;
   tasklist->window_scrolling = TRUE;
   tasklist->all_blinking = TRUE;
   tasklist->middle_click = XFCE_TASKLIST_MIDDLE_CLICK_DEFAULT;
@@ -1904,6 +1903,7 @@ xfce_tasklist_update_monitor_geometry_idle (gpointer data)
   GdkScreen    *screen;
   gboolean      geometry_set = FALSE;
   GdkWindow    *window;
+  guint         tmp;
 
   panel_return_val_if_fail (XFCE_IS_TASKLIST (tasklist), FALSE);
 
@@ -1916,12 +1916,25 @@ xfce_tasklist_update_monitor_geometry_idle (gpointer data)
 
       if (G_LIKELY (screen != NULL
           && window != NULL
-          && gdk_screen_get_n_monitors (screen) > 1))
+          && (tasklist->n_monitors = gdk_screen_get_n_monitors (screen)) > 1))
         {
           /* set the monitor geometry */
-          gdk_screen_get_monitor_geometry (screen,
-              gdk_screen_get_monitor_at_window (screen, window),
-              &tasklist->monitor_geometry);
+          tasklist->my_monitor = gdk_screen_get_monitor_at_window (screen, window);
+
+          if (tasklist->all_monitors_geometry)
+          {
+              tasklist->all_monitors_geometry = g_renew (GdkRectangle, tasklist->all_monitors_geometry, tasklist->n_monitors);
+          }
+          else
+          {
+              tasklist->all_monitors_geometry = g_new (GdkRectangle, tasklist->n_monitors);
+          }
+
+          for(tmp=0;tmp<tasklist->n_monitors;tmp++)
+          {
+              gdk_screen_get_monitor_geometry (screen, tmp,
+                  &tasklist->all_monitors_geometry[tmp]);
+          }
 
           geometry_set = TRUE;
         }
@@ -2242,7 +2255,8 @@ xfce_tasklist_button_visible (XfceTasklistChild *child,
                               WnckWorkspace     *active_ws)
 {
   XfceTasklist *tasklist = XFCE_TASKLIST (child->tasklist);
-  gint          x, y, w, h;
+  GdkRectangle  window, intersection;
+  guint         best_size=0, best_monitor=0, size, tmp;
 
   panel_return_val_if_fail (active_ws == NULL || WNCK_IS_WORKSPACE (active_ws), FALSE);
   panel_return_val_if_fail (XFCE_IS_TASKLIST (tasklist), FALSE);
@@ -2251,12 +2265,17 @@ xfce_tasklist_button_visible (XfceTasklistChild *child,
   if (xfce_tasklist_filter_monitors (tasklist))
     {
       /* center of the window must be on this screen */
-      wnck_window_get_geometry (child->window, &x, &y, &w, &h);
-      x += w / 2;
-      y += h / 2;
-
-      if (!xfce_tasklist_geometry_has_point (tasklist, x, y))
-        return FALSE;
+      wnck_window_get_geometry (child->window, &window.x, &window.y, &window.width, &window.height);
+
+      for(tmp=0;tmp<tasklist->n_monitors;tmp++) {
+          gdk_rectangle_intersect(&tasklist->all_monitors_geometry[tmp], &window, &intersection);
+          size = intersection.width * intersection.height;
+          if(size > best_size) {
+              best_size = size;
+              best_monitor = tmp;
+          }
+      }
+      if (best_monitor != tasklist->my_monitor) return FALSE;
     }
 
   if (tasklist->all_workspaces
-- 
1.8.3.2