bug#38705: 26.3; set-frame-size pixelwise makes frame larger

bug#38705: 26.3; set-frame-size pixelwise makes frame larger

[ynyaaa]

set-frame-size with PIXELWISE=t makes frame larger than specified value.
(setq frame-resize-pixelwise t) makes no difference.

(progn (set-frame-size nil 500 500 t)
       (list (list (frame-outer-width)
                   (frame-pixel-width)
                   (frame-inner-width))
             (list (frame-outer-height)
                   (frame-pixel-height)
                   (frame-inner-height))))
=>((549 533 533) (595 536 536))

(progn (set-frame-size nil 1000 1000 t)
       (list (list (frame-outer-width)
                   (frame-pixel-width)
                   (frame-inner-width))
             (list (frame-outer-height)
                   (frame-pixel-height)
                   (frame-inner-height))))
=>((1049 1033 1033) (1095 1036 1036))



In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29 built on CIRROCUMULUS
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor 'Microsoft Corp.', version 6.3.9600
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bug#38705: 26.3; set-frame-size pixelwise makes frame larger

[martin rudalics]

 > set-frame-size with PIXELWISE=t makes frame larger than specified value.
 > (setq frame-resize-pixelwise t) makes no difference.
 >
 > (progn (set-frame-size nil 500 500 t)
 >         (list (list (frame-outer-width)
 >                     (frame-pixel-width)
 >                     (frame-inner-width))
 >               (list (frame-outer-height)
 >                     (frame-pixel-height)
 >                     (frame-inner-height))))
 > =>((549 533 533) (595 536 536))

Right.  But here

(progn (set-frame-size nil 500 500 t)
        (list (list (frame-outer-width)
                    (frame-pixel-width)
                    (frame-inner-width)
		   (frame-text-width))
              (list (frame-outer-height)
                    (frame-pixel-height)
                    (frame-inner-height)
		   (frame-text-height))))
=>((540 532 532 500) (583 536 536 500))

This is because 'set-frame-size' sets "the size of the text area of
FRAME" and the size of the text area is returned by 'frame-text-width'
and 'frame-text-height'.  Just another Emacs idiosyncrasy ...

martin

bug#38705: 26.3; set-frame-size pixelwise makes frame larger

[ynyaaa]

martin rudalics <rudalics@gmx.at> writes:

> Right.  But here
>
> (progn (set-frame-size nil 500 500 t)
>        (list (list (frame-outer-width)
>                    (frame-pixel-width)
>                    (frame-inner-width)
>                    (frame-text-width))
>              (list (frame-outer-height)
>                    (frame-pixel-height)
>                    (frame-inner-height)
>                    (frame-text-height))))
> =>((540 532 532 500) (583 536 536 500))
>
> This is because 'set-frame-size' sets "the size of the text area of
> FRAME" and the size of the text area is returned by 'frame-text-width'
> and 'frame-text-height'.  Just another Emacs idiosyncrasy ...
>
> martin

I tried to set up the frame outer size like below.
  ;;; sample ~/.emacs.d/init.el
  (defun test-set-frame-outer-size (frame width height)
    (set-frame-size frame width height t)
    (set-frame-size frame
                    (- width  (- (frame-outer-width  frame) width))
                    (- height (- (frame-outer-height frame) height))
                    t))
  (setq frame-inhibit-implied-resize t)
  (test-set-frame-outer-size nil 500 500)
  ;;; sample ~/.emacs.d/init.el end

But the function does not work well inside init.el.
After emacs started, the size is:
  (list (frame-outer-width) (frame-outer-height))
  =>(500 502)
When user input is allowed, evaluating
  (test-set-frame-outer-size nil 500 500)
works as expected.

About another point.
If the frame has no menu-bar, tool-bar, scroll-bar nor fringes,
frame-pixel-width and frame-pixel-height can be set by set-frame-size.
But if the frame is undecorated, the outer size is as large as the size
of non-undecorated frame regardless of the value of
frame-inhibit-implied-resize. 
The inner size is enlarged to the outer size after redisplay.
The size can not be set as expected.
  (let ((width 500) (height 500)
        (params '((undecorated . t)
                  (menu-bar-lines . 0)
                  (tool-bar-lines . 0)
                  (horizontal-scroll-bars . nil)
                  (vertical-scroll-bars . nil)
                  (left-fringe . 0)
                  (right-fringe . 0)))
        (f (lambda () (list (list (frame-outer-width)
                                  (frame-inner-width))
                            (list (frame-outer-height)
                                  (frame-inner-height))))))
    (setq frame-inhibit-implied-resize t)
    (modify-frame-parameters nil params)
    (set-frame-size nil width height t)
    (list (funcall f)
          (progn (redisplay) (funcall f))))
  =>(((516 500) (539 500)) ((516 516) (539 539)))

If the form above is evaluated twice, the frame outer size stays
516x539 pixels and the inner size shrinks to 500x500 pixels.
The inner text area is displayed at the top-left,
and there are blank areas at the right and the bottom.

bug#38705: 26.3; set-frame-size pixelwise makes frame larger

[martin rudalics]

[-- Attachment #1: Type: text/plain, Size: 4677 bytes --]

 > I tried to set up the frame outer size like below.
 >    ;;; sample ~/.emacs.d/init.el
 >    (defun test-set-frame-outer-size (frame width height)
 >      (set-frame-size frame width height t)
 >      (set-frame-size frame
 >                      (- width  (- (frame-outer-width  frame) width))
 >                      (- height (- (frame-outer-height frame) height))
 >                      t))
 >    (setq frame-inhibit-implied-resize t)
 >    (test-set-frame-outer-size nil 500 500)
 >    ;;; sample ~/.emacs.d/init.el end
 >
 > But the function does not work well inside init.el.
 > After emacs started, the size is:
 >    (list (frame-outer-width) (frame-outer-height))
 >    =>(500 502)
 > When user input is allowed, evaluating
 >    (test-set-frame-outer-size nil 500 500)
 > works as expected.

Look up the function 'frame-geometry'.  If its return value for
something like the 'external-border-size' differs for a frame before
and after "user input is allowed" then it's because that something has
not been specified before the frame was "mapped" and so Emacs won't
know it.

If you are sure that your decorations won't change from one emacs
session to the next, you can try to remember them from the last
session and apply them manually.  However, in general, calling
'frame-outer-width/-height' from init.el is not a good idea.

 > About another point.
 > If the frame has no menu-bar, tool-bar, scroll-bar nor fringes,
 > frame-pixel-width and frame-pixel-height can be set by set-frame-size.
 > But if the frame is undecorated, the outer size is as large as the size
 > of non-undecorated frame regardless of the value of
 > frame-inhibit-implied-resize.
 > The inner size is enlarged to the outer size after redisplay.
 > The size can not be set as expected.
 >    (let ((width 500) (height 500)
 >          (params '((undecorated . t)
 >                    (menu-bar-lines . 0)
 >                    (tool-bar-lines . 0)
 >                    (horizontal-scroll-bars . nil)
 >                    (vertical-scroll-bars . nil)
 >                    (left-fringe . 0)
 >                    (right-fringe . 0)))
 >          (f (lambda () (list (list (frame-outer-width)
 >                                    (frame-inner-width))
 >                              (list (frame-outer-height)
 >                                    (frame-inner-height))))))
 >      (setq frame-inhibit-implied-resize t)
 >      (modify-frame-parameters nil params)
 >      (set-frame-size nil width height t)
 >      (list (funcall f)
 >            (progn (redisplay) (funcall f))))
 >    =>(((516 500) (539 500)) ((516 516) (539 539)))
 >
 > If the form above is evaluated twice, the frame outer size stays
 > 516x539 pixels and the inner size shrinks to 500x500 pixels.

Please note again that the values you pass to 'set-frame-size' are the
values later reported by 'frame-text-width' and 'frame-text-height'.
These are fictive values and neither inner, nor outer or native sizes
might match these.

 > The inner text area is displayed at the top-left,
 > and there are blank areas at the right and the bottom.

This is the result of a bug that made frame resizing incorrect for
undecorated frames on Windows ever since.  To explain why this bug
usually goes unnoticed note that 'set-frame-size' causes three things
to happen: (1) it asks the window manager to resize the frame's
(window system) window.  (2) it "prematurely" resizes the frame's
windows because in their code some users want to know the new window
sizes right away.

Now if (1) eventually results in a frame size different from the one
expected in (2), the corresponding message from the window manager
will cause Emacs to (3) re-resize the frame's windows if they don't
match and everything should go well.  Usually, the sizes returned by
the window manager match those expected by (2) and in (3) no such
re-resizing is needed.

But in your scenario the first

(set-frame-size nil 500 500 t)

call will, due to the bug, pass incorrect values to the window
manager, which makes the values eventually returned by the window
manager differ from those calculated in (2).  (3) will fix this.  But
the subsequent calls will cause the window manager do nothing in (1)
because it is supplied the old values again and thus will decide that
no resizing is needed.  Yet Emacs will perform (2) with the values it
expects and these values will never be corrected because (3) will
never happen.

Please try the attached patch.  I will install it on Emacs-27 as soon
as I have upgraded my working environment, something which may happen
in a couple of days only.

Many thanks again for reporting these obscure behaviors, martin

[-- Attachment #2: w32fns.c.diffs --]
[-- Type: text/plain, Size: 388 bytes --]

diff --git a/src/w32fns.c b/src/w32fns.c
index bf2a7a3e54..8145b82416 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -2146,6 +2146,9 @@ w32_set_undecorated (struct frame *f, Lisp_Object new_value, Lisp_Object old_val
 		    | SWP_FRAMECHANGED);
       FRAME_UNDECORATED (f) = false;
     }
+
+  f->output_data.w32->dwStyle = GetWindowLong (hwnd, GWL_STYLE);
+
   unblock_input ();
 }
 

bug#38705: 26.3; set-frame-size pixelwise makes frame larger

[martin rudalics]

tags 38705 fixed
close 38705 27.1
quit

 > Please try the attached patch.  I will install it on Emacs-27 as soon
 > as I have upgraded my working environment, something which may happen
 > in a couple of days only.

Installed.  Closing this bug.

Thanks again for the report, martin