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(1) Run `window-configuration-change-hook' if and only if at least
one window was deleted or created or shows another buffer since
last redisplay.

(2) Run `window-size-change-functions' if and only if at least
one window changed its size since last redisplay (in a few cases
`window-size-change-functions' will also run when no window
changed its size).

(3) Provide two functions `window-pixel-height-before-size-change'
and `window-pixel-width-before-size-change' that allow to easily
detect which window changed size.

* src/frame.h (struct frame): New boolean member
window_configuration_changed.
(FRAME_WINDOW_SIZES_CHANGED): Remove macro.
(FRAME_WINDOW_CONFIGURATION_CHANGED): New macro.
* src/frame.c (adjust_frame_size): Don't run
`window-configuration-change-hook'.
* src/window.h (struct window): New fields
pixel_width_before_size_change and pixel_height_before_size_change.
(WINDOW_INTERNAL_P): New macro.
* src/window.c (Fwindow_pixel_width_before_size_change)
(Fwindow_pixel_height_before_size_change): New functions.
(Fdelete_other_windows_internal, Fwindow_resize_apply)
(resize_frame_windows, Fsplit_window_internal)
(Fdelete_window_internal, grow_mini_window)
(shrink_mini_window, Fresize_mini_window_internal): Don't call
FRAME_WINDOW_SIZES_CHANGED.
(window_size_changed, window_set_before_size_change_sizes)
(run_window_size_change_functions): New functions.
(make_window): Initialize pixel_width_before_size_change and
pixel_height_before_size_change.
(Fdelete_window_internal): Don't call
run_window_configuration_change_hook.
(struct saved_window): Add pixel_height_before_size_change and
pixel_width_before_size_change.
(Fset_window_configuration): Try to identify window configuration
changes correctly so run_window_configuration_change_hook and
run_window_size_change_functions run only if configuration and size
really changed.
(save_window_save): Set the pixel_height_before_size_change and
pixel_width_before_size_change fields.
(Vwindow_size_change_functions): Move here definiton from xdisp.c.
* src/xdisp.c (prepare_menu_bars, redisplay_internal): Call
run_window_size_change_functions.
(Vwindow_size_change_functions): Move definition to window.c.
* src/xfns.c (x_set_menu_bar_lines): Don't call
run_window_configuration_change_hook.
* doc/lispref/windows.texi (Window Sizes): Document new
functions `window-pixel-height-before-size-change' and
`window-pixel-width-before-size-change'.
(Window Configurations): Mention that this may trigger
execution of `window-size-change-functions' although no window
changed size.
(Window Hooks): Update descriptions of `window-size-change-functions'
and `window-configuration-change-hook'.