Call 'window-size-change-functions' for mini-windows

* src/window.c (grow_mini_window, shrink_mini_window): Set the
frame's 'window_sizes_changed' flag.
* src/xdisp.c (redisplay_internal): Call the hooks on
'window-size-change-functions' if the call to 'echo_area_display'
sets the frame's 'window_sizes_changed' flag.
(syms_of_xdisp) <window-size-change-functions>:
Update doc string to indicate the mini-window resizes trigger a
call to the hooks, and don't promise that will happen "before
redisplay".  (Bug#19576, Bug#21333)

* doc/lispref/windows.texi (Window Hooks): Update the description
of 'window-size-change-functions'.

2 files changed, 34 insertions, 4 deletions

diff --git a/src/window.c b/src/window.c
index 0ac76d41861..753c4ab8123 100644
--- a/src/window.c
+++ b/src/window.c
@@ -4555,6 +4555,7 @@ grow_mini_window (struct window *w, int delta, bool pixelwise)
           /* Enforce full redisplay of the frame.  */
           /* FIXME: Shouldn't window--resize-root-window-vertically do it?  */
           fset_redisplay (f);
+          FRAME_WINDOW_SIZES_CHANGED (f) = true;
           adjust_frame_glyphs (f);
           unblock_input ();
         }
@@ -4594,6 +4595,7 @@ shrink_mini_window (struct window *w, bool pixelwise)
           /* Enforce full redisplay of the frame.  */
           /* FIXME: Shouldn't window--resize-root-window-vertically do it?  */
           fset_redisplay (f);
+          FRAME_WINDOW_SIZES_CHANGED (f) = true;
           adjust_frame_glyphs (f);
           unblock_input ();
         }
diff --git a/src/xdisp.c b/src/xdisp.c
index 30dfac55601..85d356e9ba5 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -13536,6 +13536,32 @@ redisplay_internal (void)
     {
       echo_area_display (false);
 
+      /* If echo_area_display resizes the mini-window, the redisplay and
+         window_sizes_changed flags of the selected frame are set, but
+         it's too late for the hooks in window-size-change-functions,
+         which have been examined already in prepare_menu_bars.  So in
+         that case we call the hooks here only for the selected frame.  */
+      if (sf->redisplay && FRAME_WINDOW_SIZES_CHANGED (sf))
+        {
+          Lisp_Object functions;
+          ptrdiff_t count1 = SPECPDL_INDEX ();
+
+          record_unwind_save_match_data ();
+
+          /* Clear flag first in case we get an error below.  */
+          FRAME_WINDOW_SIZES_CHANGED (sf) = false;
+          functions = Vwindow_size_change_functions;
+
+          while (CONSP (functions))
+            {
+              if (!EQ (XCAR (functions), Qt))
+                call1 (XCAR (functions), selected_frame);
+              functions = XCDR (functions);
+            }
+
+          unbind_to (count1, Qnil);
+        }
+
       if (message_cleared_p)
         update_miniwindow_p = true;
 
@@ -31132,11 +31158,13 @@ the buffer when it becomes large.  */);
   Vmessage_log_max = make_number (1000);
 
   DEFVAR_LISP ("window-size-change-functions", Vwindow_size_change_functions,
-    doc: /* Functions called before redisplay, if window sizes have changed.
+    doc: /* Functions called during redisplay, if window sizes have changed.
 The value should be a list of functions that take one argument.
-Just before redisplay, for each frame, if any of its windows have changed
-size since the last redisplay, or have been split or deleted,
-all the functions in the list are called, with the frame as argument.  */);
+During the first part of redisplay, for each frame, if any of its windows
+have changed size since the last redisplay, or have been split or deleted,
+all the functions in the list are called, with the frame as argument.
+If redisplay decides to resize the minibuffer window, it calls these
+functions on behalf of that as well.  */);
   Vwindow_size_change_functions = Qnil;
 
   DEFVAR_LISP ("window-scroll-functions", Vwindow_scroll_functions,