Respond to changes to the size of the root window

* src/xterm.c (x_display_pixel_height, x_display_pixel_width):
Move here instead.
(handle_one_xevent): Handle ConfigureNotify for the root window.
(x_term_init): Select for structure events on the root window.

* src/xterm.h (struct x_display_info): New fields `screen_width'
and `screen_height'.
(x_display_pixel_height, x_display_pixel_width): Make
prototypes.

2 files changed, 41 insertions, 11 deletions

diff --git a/src/xterm.c b/src/xterm.c
index b5fbb474ecc..b12aa4b8438 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -14506,6 +14506,24 @@ x_dnd_update_state (struct x_display_info *dpyinfo, Time timestamp)
     }
 }
 
+int
+x_display_pixel_height (struct x_display_info *dpyinfo)
+{
+  if (dpyinfo->screen_height)
+    return dpyinfo->screen_height;
+
+  return HeightOfScreen (dpyinfo->screen);
+}
+
+int
+x_display_pixel_width (struct x_display_info *dpyinfo)
+{
+  if (dpyinfo->screen_width)
+    return dpyinfo->screen_width;
+
+  return WidthOfScreen (dpyinfo->screen);
+}
+
 /* Handles the XEvent EVENT on display DPYINFO.
 
    *FINISH is X_EVENT_GOTO_OUT if caller should stop reading events.
@@ -16514,6 +16532,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
          So if this ConfigureNotify is immediately followed by another
          for the same window, use the info from the latest update, and
          consider the events all handled.  */
+
       /* Opaque resize may be trickier; ConfigureNotify events are
          mixed with Expose events for multiple windows.  */
       configureEvent = *event;
@@ -16535,6 +16554,15 @@ handle_one_xevent (struct x_display_info *dpyinfo,
             configureEvent = next_event;
         }
 
+      /* If we get a ConfigureNotify for the root window, this means
+         the dimensions of the screen it's on changed.  */
+
+      if (configureEvent.xconfigure.window == dpyinfo->root_window)
+        {
+          dpyinfo->screen_width = configureEvent.xconfigure.width;
+          dpyinfo->screen_height = configureEvent.xconfigure.height;
+        }
+
       if (x_dnd_in_progress && x_dnd_use_toplevels
           && dpyinfo == FRAME_DISPLAY_INFO (x_dnd_frame))
         {
@@ -23870,6 +23898,11 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
     }
 #endif
 
+  /* Select for structure events on the root window, since this allows
+     us to record changes to the size of the screen.  */
+
+  XSelectInput (dpy, DefaultRootWindow (dpy), StructureNotifyMask);
+
   /* We have definitely succeeded.  Record the new connection.  */
 
   dpyinfo = xzalloc (sizeof *dpyinfo);
diff --git a/src/xterm.h b/src/xterm.h
index 3437037e674..a05bc404f69 100644
--- a/src/xterm.h
+++ b/src/xterm.h
@@ -690,6 +690,12 @@ struct x_display_info
   int n_protected_windows;
   int protected_windows_max;
 #endif
+
+  /* The current dimensions of the screen.  This is updated when a
+     ConfigureNotify is received for the root window, and is zero if
+     that didn't happen.  */
+  int screen_width;
+  int screen_height;
 };
 
 #ifdef HAVE_X_I18N
@@ -1439,17 +1445,8 @@ extern void x_dnd_do_unsupported_drop (struct x_display_info *, Lisp_Object,
                                        int, Time);
 extern void x_set_dnd_targets (Atom *, int);
 
-INLINE int
-x_display_pixel_height (struct x_display_info *dpyinfo)
-{
-  return HeightOfScreen (dpyinfo->screen);
-}
-
-INLINE int
-x_display_pixel_width (struct x_display_info *dpyinfo)
-{
-  return WidthOfScreen (dpyinfo->screen);
-}
+extern int x_display_pixel_height (struct x_display_info *);
+extern int x_display_pixel_width (struct x_display_info *);
 
 INLINE unsigned long
 x_make_truecolor_pixel (struct x_display_info *dpyinfo, int r, int g, int b)