bug#54688: 29.0.50; Sliced image in margin looks bad

bug#54688: 29.0.50; Sliced image in margin looks bad

[dalanicolai]

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Passing 'left-margin' for the AREA parameter in `insert-sliced-image`
results in bad looking image. To reproduce from `emacs -q` evaluate the
following code example:

(with-current-buffer (get-buffer-create "test")
  (setq left-margin-width 5)
  (insert-sliced-image (svg-image (let* ((ph (line-pixel-height))
                                         (size (* 2 ph))
                                         (svg (svg-create size size)))
                                    (svg-circle svg ph ph ph :fill "red")
                                    svg))
                       nil
                       'left-margin
                       2)
  (switch-to-buffer (current-buffer)))

when instead of 'left-margin', nil is passed as value (i.e. the text is
inserted in the text area), then everything looks fine.

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.31,
cairo version 1.17.4)
 of 2022-01-29 built on fedora
Repository revision: 96533c18b7f9d75dce9e6bb534a16ed4ccf44ad1
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
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bug#54688: 29.0.50; Sliced image in margin looks bad

[Eli Zaretskii]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sun, 3 Apr 2022 08:50:20 +0200
> 
> Passing 'left-margin' for the AREA parameter in `insert-sliced-image`
> results in bad looking image. To reproduce from `emacs -q` evaluate the
> following code example:
> 
> (with-current-buffer (get-buffer-create "test")
>   (setq left-margin-width 5)
>   (insert-sliced-image (svg-image (let* ((ph (line-pixel-height))
>                                          (size (* 2 ph))
>                                          (svg (svg-create size size)))
>                                     (svg-circle svg ph ph ph :fill "red")
>                                     svg))
>                        nil
>                        'left-margin
>                        2)
>   (switch-to-buffer (current-buffer)))
> 
> when instead of 'left-margin', nil is passed as value (i.e. the text is
> inserted in the text area), then everything looks fine.

"Everything looks fine" until you insert some text after the 2 slices
of the image.  That is, after evaluating the form with left-margin
replaced by nil, do this:

  C-u 2 M-g c  ;; go to buffer position 2
  x            ;; insert a character
  C-n          ;; go to next line
  x            ;; insert another character

The problem is that your images are smaller than the default height of
the screen line, as determined by the 'default' face.  So slices of
the image do not produce a single circle, but two semi-circles with
empty space between them.

If this is the problem, then I see nothing wrong with this: to have
the two slices come together, you need to fit the size of the image to
the height of the default face.

bug#54688: 29.0.50; Sliced image in margin looks bad

[dalanicolai]

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Thank you for the quick reply. However, the height of the image,
(* 2 (line-pixel-height)), is equal to twice the `default-font-height`
(the 'line-pixel-height' and 'default-font-height' are equal, here both
17).

So before I add the character after the image, (line-pixel-height)
returns 17. But when I insert a character after it (with
'default-font-height' is 17), the `line-pixel-height` increases to
22. So I am not sure how to not let the line height increase.
I will try to play a little with the :ascent value.

On Sun, 3 Apr 2022 at 10:57, Eli Zaretskii <eliz@gnu.org> wrote:

> > From: dalanicolai <dalanicolai@gmail.com>
> > Date: Sun, 3 Apr 2022 08:50:20 +0200
> >
> > Passing 'left-margin' for the AREA parameter in `insert-sliced-image`
> > results in bad looking image. To reproduce from `emacs -q` evaluate the
> > following code example:
> >
> > (with-current-buffer (get-buffer-create "test")
> >   (setq left-margin-width 5)
> >   (insert-sliced-image (svg-image (let* ((ph (line-pixel-height))
> >                                          (size (* 2 ph))
> >                                          (svg (svg-create size size)))
> >                                     (svg-circle svg ph ph ph :fill "red")
> >                                     svg))
> >                        nil
> >                        'left-margin
> >                        2)
> >   (switch-to-buffer (current-buffer)))
> >
> > when instead of 'left-margin', nil is passed as value (i.e. the text is
> > inserted in the text area), then everything looks fine.
>
> "Everything looks fine" until you insert some text after the 2 slices
> of the image.  That is, after evaluating the form with left-margin
> replaced by nil, do this:
>
>   C-u 2 M-g c  ;; go to buffer position 2
>   x            ;; insert a character
>   C-n          ;; go to next line
>   x            ;; insert another character
>
> The problem is that your images are smaller than the default height of
> the screen line, as determined by the 'default' face.  So slices of
> the image do not produce a single circle, but two semi-circles with
> empty space between them.
>
> If this is the problem, then I see nothing wrong with this: to have
> the two slices come together, you need to fit the size of the image to
> the height of the default face.
>

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bug#54688: 29.0.50; Sliced image in margin looks bad

[Eli Zaretskii]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sun, 3 Apr 2022 12:33:01 +0200
> Cc: 54688@debbugs.gnu.org
> 
> Thank you for the quick reply. However, the height of the image,
> (* 2 (line-pixel-height)), is equal to twice the `default-font-height`
> (the 'line-pixel-height' and 'default-font-height' are equal, here both
> 17).
> 
> So before I add the character after the image, (line-pixel-height)
> returns 17. But when I insert a character after it (with
> 'default-font-height' is 17), the `line-pixel-height` increases to
> 22. So I am not sure how to not let the line height increase.
> I will try to play a little with the :ascent value.

Images can also have margins:

  int
  image_ascent (struct image *img, struct face *face, struct glyph_slice *slice)
  {
    int height;
    int ascent;

    if (slice->height == img->height)
      height = img->height + img->vmargin;
    else if (slice->y == 0)
      height = slice->height + img->vmargin;
    else
      height = slice->height;

Maybe those make the difference?

In any case, once I add a character, the line height grows, which
tells us some vertical dimension somewhere is unaccounted for.

bug#54688: 29.0.50; Sliced image in margin looks bad

[dalanicolai]

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(Once more using reply-all)

Playing around with :ascent, makes possible to keep the line-pixel-height
fixed.

So in the following I simply use `insert-image`. Without the :ascent, the
'line-pixel-height' increases when inserting another character. With the
:ascent it is possible to reduce this 'increase'. For me the increase is 0
when I use an ascent value of 80.
(below the used code)

(with-current-buffer (get-buffer-create "test")
  (setq left-margin-width 5)
  (insert-image (svg-image (let* ((ph (line-pixel-height))
                                  (size ph)
                                  (svg (svg-create size size)))
                             (svg-circle svg ph ph ph :fill "red")
                             svg)
                           :ascent 80))
  (switch-to-buffer (current-buffer)))

On Sun, 3 Apr 2022 at 12:54, Eli Zaretskii <eliz@gnu.org> wrote:

> > From: dalanicolai <dalanicolai@gmail.com>
> > Date: Sun, 3 Apr 2022 12:33:01 +0200
> > Cc: 54688@debbugs.gnu.org
> >
> > Thank you for the quick reply. However, the height of the image,
> > (* 2 (line-pixel-height)), is equal to twice the `default-font-height`
> > (the 'line-pixel-height' and 'default-font-height' are equal, here both
> > 17).
> >
> > So before I add the character after the image, (line-pixel-height)
> > returns 17. But when I insert a character after it (with
> > 'default-font-height' is 17), the `line-pixel-height` increases to
> > 22. So I am not sure how to not let the line height increase.
> > I will try to play a little with the :ascent value.
>
> Images can also have margins:
>
>   int
>   image_ascent (struct image *img, struct face *face, struct glyph_slice
> *slice)
>   {
>     int height;
>     int ascent;
>
>     if (slice->height == img->height)
>       height = img->height + img->vmargin;
>     else if (slice->y == 0)
>       height = slice->height + img->vmargin;
>     else
>       height = slice->height;
>
> Maybe those make the difference?
>
> In any case, once I add a character, the line height grows, which
> tells us some vertical dimension somewhere is unaccounted for.
>

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bug#54688: 29.0.50; Sliced image in margin looks bad

[dalanicolai]

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I would think that this :ascent of 80, behaves how :ascent 50 (the default)
is supposed to behave?

On Sun, 3 Apr 2022 at 13:03, dalanicolai <dalanicolai@gmail.com> wrote:

> (Once more using reply-all)
>
> Playing around with :ascent, makes possible to keep the line-pixel-height
> fixed.
>
> So in the following I simply use `insert-image`. Without the :ascent, the
> 'line-pixel-height' increases when inserting another character. With the
> :ascent it is possible to reduce this 'increase'. For me the increase is 0
> when I use an ascent value of 80.
> (below the used code)
>
> (with-current-buffer (get-buffer-create "test")
>   (setq left-margin-width 5)
>   (insert-image (svg-image (let* ((ph (line-pixel-height))
>                                   (size ph)
>                                   (svg (svg-create size size)))
>                              (svg-circle svg ph ph ph :fill "red")
>                              svg)
>                            :ascent 80))
>   (switch-to-buffer (current-buffer)))
>
> On Sun, 3 Apr 2022 at 12:54, Eli Zaretskii <eliz@gnu.org> wrote:
>
>> > From: dalanicolai <dalanicolai@gmail.com>
>> > Date: Sun, 3 Apr 2022 12:33:01 +0200
>> > Cc: 54688@debbugs.gnu.org
>> >
>> > Thank you for the quick reply. However, the height of the image,
>> > (* 2 (line-pixel-height)), is equal to twice the `default-font-height`
>> > (the 'line-pixel-height' and 'default-font-height' are equal, here both
>> > 17).
>> >
>> > So before I add the character after the image, (line-pixel-height)
>> > returns 17. But when I insert a character after it (with
>> > 'default-font-height' is 17), the `line-pixel-height` increases to
>> > 22. So I am not sure how to not let the line height increase.
>> > I will try to play a little with the :ascent value.
>>
>> Images can also have margins:
>>
>>   int
>>   image_ascent (struct image *img, struct face *face, struct glyph_slice
>> *slice)
>>   {
>>     int height;
>>     int ascent;
>>
>>     if (slice->height == img->height)
>>       height = img->height + img->vmargin;
>>     else if (slice->y == 0)
>>       height = slice->height + img->vmargin;
>>     else
>>       height = slice->height;
>>
>> Maybe those make the difference?
>>
>> In any case, once I add a character, the line height grows, which
>> tells us some vertical dimension somewhere is unaccounted for.
>>
>

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bug#54688: 29.0.50; Sliced image in margin looks bad

[Eli Zaretskii]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sun, 3 Apr 2022 13:04:55 +0200
> Cc: 54688@debbugs.gnu.org
> 
> I would think that this :ascent of 80, behaves how :ascent 50 (the default)
> is supposed to behave?

I don't think I understand the question.

(Is it still relevant, given your followup?)

bug#54688: 29.0.50; Sliced image in margin looks bad

[Eli Zaretskii]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sun, 3 Apr 2022 13:03:27 +0200
> Cc: 54688@debbugs.gnu.org
> 
> Playing around with :ascent, makes possible to keep the line-pixel-height fixed.
> 
> So in the following I simply use `insert-image`. Without the :ascent, the
> 'line-pixel-height' increases when inserting another character. With the
> :ascent it is possible to reduce this 'increase'. For me the increase is 0
> when I use an ascent value of 80.
> (below the used code)
> 
> (with-current-buffer (get-buffer-create "test")
>   (setq left-margin-width 5)
>   (insert-image (svg-image (let* ((ph (line-pixel-height))
>                                   (size ph)
>                                   (svg (svg-create size size)))
>                              (svg-circle svg ph ph ph :fill "red")
>                              svg)
>                            :ascent 80))
>   (switch-to-buffer (current-buffer)))

Does this mean the problem is solved, and we can close this bug?

bug#54688: 29.0.50; Sliced image in margin looks bad

[dalanicolai]

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>
> Does this mean the problem is solved, and we can close this bug?


I am not sure. It depends on what is the intended behavior. I would say it
is desirable
if inserting text after an image, of height equal to the text height, would
not increase
the `line-pixel-height`. The elisp manual
<https://www.gnu.org/software/emacs/manual/html_node/elisp/Image-Descriptors.html>
mentions that the default value for :ascent is
50, in which case the `line-pixel-height` is larger than the both the
'image height' and
the 'text height'. So maybe the default value of :ascent should be 80, in
which case
the 'line-pixel-height' 'remains' equal to the image height and text height.

However, there might be various arguments for the current default value of
50 (and its
behavior of increasing the 'line-pixel'height' when combining images with
text on a
single line).

> I would think that this :ascent of 80, behaves how :ascent 50 (the
> default)
> > is supposed to behave?
>
> I don't think I understand the question.
>

I mean that I would expect the default behavior to be that, when combining
images and
text of equal height on a single line, the 'line-pixel-height' would also
be/stay of equal
height.
But as mentioned before, there might be various arguments for the current
behavior,
however (as a layman) I am not aware of any.

If the current behavior is the desired behavior, then indeed this issue can
be closed.

On Sun, 3 Apr 2022 at 14:03, Eli Zaretskii <eliz@gnu.org> wrote:

> > From: dalanicolai <dalanicolai@gmail.com>
> > Date: Sun, 3 Apr 2022 13:03:27 +0200
> > Cc: 54688@debbugs.gnu.org
> >
> > Playing around with :ascent, makes possible to keep the
> line-pixel-height fixed.
> >
> > So in the following I simply use `insert-image`. Without the :ascent, the
> > 'line-pixel-height' increases when inserting another character. With the
> > :ascent it is possible to reduce this 'increase'. For me the increase is
> 0
> > when I use an ascent value of 80.
> > (below the used code)
> >
> > (with-current-buffer (get-buffer-create "test")
> >   (setq left-margin-width 5)
> >   (insert-image (svg-image (let* ((ph (line-pixel-height))
> >                                   (size ph)
> >                                   (svg (svg-create size size)))
> >                              (svg-circle svg ph ph ph :fill "red")
> >                              svg)
> >                            :ascent 80))
> >   (switch-to-buffer (current-buffer)))
>
> Does this mean the problem is solved, and we can close this bug?
>

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bug#54688: 29.0.50; Sliced image in margin looks bad

[dalanicolai]

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In the first sentence, I mean text of the same height as the image height.
When I say 'current behavior' I mean that the 'line-pixel-height' when
combining
images and text of equal height on a single line, is larger than the
text/image height.

On Sun, 3 Apr 2022 at 15:05, dalanicolai <dalanicolai@gmail.com> wrote:

> Does this mean the problem is solved, and we can close this bug?
>
>
> I am not sure. It depends on what is the intended behavior. I would say it
> is desirable
> if inserting text after an image, of height equal to the text height,
> would not increase
> the `line-pixel-height`. The elisp manual
> <https://www.gnu.org/software/emacs/manual/html_node/elisp/Image-Descriptors.html>
> mentions that the default value for :ascent is
> 50, in which case the `line-pixel-height` is larger than the both the
> 'image height' and
> the 'text height'. So maybe the default value of :ascent should be 80, in
> which case
> the 'line-pixel-height' 'remains' equal to the image height and text
> height.
>
> However, there might be various arguments for the current default value of
> 50 (and its
> behavior of increasing the 'line-pixel'height' when combining images with
> text on a
> single line).
>
> > I would think that this :ascent of 80, behaves how :ascent 50 (the
>> default)
>> > is supposed to behave?
>>
>> I don't think I understand the question.
>>
>
> I mean that I would expect the default behavior to be that, when combining
> images and
> text of equal height on a single line, the 'line-pixel-height' would also
> be/stay of equal
> height.
> But as mentioned before, there might be various arguments for the current
> behavior,
> however (as a layman) I am not aware of any.
>
> If the current behavior is the desired behavior, then indeed this issue
> can be closed.
>
> On Sun, 3 Apr 2022 at 14:03, Eli Zaretskii <eliz@gnu.org> wrote:
>
>> > From: dalanicolai <dalanicolai@gmail.com>
>> > Date: Sun, 3 Apr 2022 13:03:27 +0200
>> > Cc: 54688@debbugs.gnu.org
>> >
>> > Playing around with :ascent, makes possible to keep the
>> line-pixel-height fixed.
>> >
>> > So in the following I simply use `insert-image`. Without the :ascent,
>> the
>> > 'line-pixel-height' increases when inserting another character. With the
>> > :ascent it is possible to reduce this 'increase'. For me the increase
>> is 0
>> > when I use an ascent value of 80.
>> > (below the used code)
>> >
>> > (with-current-buffer (get-buffer-create "test")
>> >   (setq left-margin-width 5)
>> >   (insert-image (svg-image (let* ((ph (line-pixel-height))
>> >                                   (size ph)
>> >                                   (svg (svg-create size size)))
>> >                              (svg-circle svg ph ph ph :fill "red")
>> >                              svg)
>> >                            :ascent 80))
>> >   (switch-to-buffer (current-buffer)))
>>
>> Does this mean the problem is solved, and we can close this bug?
>>
>

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