bug#51821: 29.0.50; Suggest add variable or frame parameter: line-height

["Feng Shu" <tumashu@163.com>]

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Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Tue, 16 Nov 2021 18:45:16 +0200
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: tumashu@163.com, 51821@debbugs.gnu.org
>> 
>> > From: Lars Ingebrigtsen <larsi@gnus.org>
>> > Cc: tumashu@163.com,  51821@debbugs.gnu.org
>> > Date: Tue, 16 Nov 2021 16:20:52 +0100
>> > 
>> > > That shouldn't happen, normally.  Emacs selects fonts of the same size
>> > > for a face.
>> > 
>> > No, not really.  Here's a trivial example:
>> > 
>> > 
>> > Note how the lines with jidanni are taller than the rest.
>> 
>> OK, let me see what can be done about that.
>
> Please try the patch below.  I have a very limited number of cases
> with which I can test it, so I think users of CJK scripts should say
> what they think.  Basically, set the new variable line-height-factor
> to something like 1.2 (more if you enlarge the non-ASCII font to make
> double-width characters take close to 2 columns), and see if you get
> the desired effect.
>
> If this is what people want, I will install it and document it.
>

I think the below patch has problem, maybe it relate to font
baseline, I do not know, please see attachement.


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> diff --git a/src/window.c b/src/window.c
> index e801ff8..a368b6d 100644
> --- a/src/window.c
> +++ b/src/window.c
> @@ -5246,7 +5246,10 @@ grow_mini_window (struct window *w, int delta)
>  {
>    struct frame *f = XFRAME (w->frame);
>    int old_height = window_body_height (w, true);
> -  int min_height = FRAME_LINE_HEIGHT (f);
> +  int min_height =
> +    FLOATP (Vline_height_factor)
> +    ? FRAME_LINE_HEIGHT (f) * XFLOAT_DATA (Vline_height_factor)
> +    : FRAME_LINE_HEIGHT (f);
>  
>    eassert (MINI_WINDOW_P (w));
>  
> @@ -5279,7 +5282,11 @@ grow_mini_window (struct window *w, int delta)
>  shrink_mini_window (struct window *w)
>  {
>    struct frame *f = XFRAME (w->frame);
> -  int delta = window_body_height (w, true) - FRAME_LINE_HEIGHT (f);
> +  int min_line_height =
> +    FLOATP (Vline_height_factor)
> +    ? FRAME_LINE_HEIGHT (f) * XFLOAT_DATA (Vline_height_factor)
> +    : FRAME_LINE_HEIGHT (f);
> +  int delta = window_body_height (w, true) - min_line_height;
>  
>    eassert (MINI_WINDOW_P (w));
>  
> diff --git a/src/xdisp.c b/src/xdisp.c
> index ef49297..d1f4043 100644
> --- a/src/xdisp.c
> +++ b/src/xdisp.c
> @@ -22073,6 +22073,18 @@ append_space_for_newline (struct it *it, bool default_face_p)
>  		  it->descent = it->override_descent;
>  		  boff = it->override_boff;
>  		}
> +	      else
> +		{
> +		  /* Enlarge the ascent to make the row higher by
> +		     line-height-factor if needed.  */
> +		  if (face == face->ascii_face && it->voffset == 0
> +		      && FLOATP (Vline_height_factor))
> +		    {
> +		      int enlarged_height = ((it->ascent + it->descent)
> +					     * XFLOAT_DATA (Vline_height_factor));
> +		      it->ascent = enlarged_height - it->descent;
> +		    }
> +		}
>  	      if (EQ (height, Qt))
>  		extra_line_spacing = 0;
>  	      else
> @@ -30587,9 +30599,9 @@ gui_produce_glyphs (struct it *it)
>  	  /* When no suitable font is found, display this character by
>  	     the method specified in the first extra slot of
>  	     Vglyphless_char_display.  */
> -	      Lisp_Object acronym = lookup_glyphless_char_display (-1, it);
> +	  Lisp_Object acronym = lookup_glyphless_char_display (-1, it);
>  
> -	      eassert (it->what == IT_GLYPHLESS);
> +	  eassert (it->what == IT_GLYPHLESS);
>  	  produce_glyphless_glyph (it, true,
>  				   STRINGP (acronym) ? acronym : Qnil);
>  	  goto done;
> @@ -30613,6 +30625,15 @@ gui_produce_glyphs (struct it *it)
>   	    {
>   	      it->ascent = FONT_BASE (font) + boff;
>   	      it->descent = FONT_DESCENT (font) - boff;
> +	      /* If this glyph uses the ASCII face, enlarge the ascent
> +		 to make the row higher by line-height-factor.  */
> +	      if (face == face->ascii_face && it->voffset == 0
> +		  && FLOATP (Vline_height_factor))
> +		{
> +		  int enlarged_height = ((it->ascent + it->descent)
> +					 * XFLOAT_DATA (Vline_height_factor));
> +		  it->ascent = enlarged_height - it->descent;
> +		}
>   	    }
>  
>  	  if (get_char_glyph_code (it->char_to_display, font, &char2b))
> @@ -30763,6 +30784,13 @@ gui_produce_glyphs (struct it *it)
>  		{
>  		  it->ascent = FONT_BASE (font) + boff;
>  		  it->descent = FONT_DESCENT (font) - boff;
> +		  if (face == face->ascii_face && it->voffset == 0
> +		      && FLOATP (Vline_height_factor))
> +		    {
> +		      int enlarged_height = ((it->ascent + it->descent)
> +					     * XFLOAT_DATA (Vline_height_factor));
> +		      it->ascent = enlarged_height - it->descent;
> +		    }
>  		}
>  	    }
>  
> @@ -30886,6 +30914,13 @@ gui_produce_glyphs (struct it *it)
>  		{
>  		  it->ascent = FONT_BASE (font) + boff;
>  		  it->descent = FONT_DESCENT (font) - boff;
> +		  if (face == face->ascii_face && it->voffset == 0
> +		      && FLOATP (Vline_height_factor))
> +		    {
> +		      int enlarged_height = ((it->ascent + it->descent)
> +					     * XFLOAT_DATA (Vline_height_factor));
> +		      it->ascent = enlarged_height - it->descent;
> +		    }
>  		}
>  	      it->phys_ascent = it->ascent;
>  	      it->phys_descent = it->descent;
> @@ -31243,6 +31278,24 @@ gui_produce_glyphs (struct it *it)
>  	  if (it->glyph_row
>  	      && (metrics.lbearing < 0 || metrics.rbearing > metrics.width))
>  	    it->glyph_row->contains_overlapping_glyphs_p = true;
> +	  if (it->voffset == 0 && FLOATP (Vline_height_factor))
> +	    {
> +	      Lisp_Object font_object = LGSTRING_FONT (gstring);
> +	      struct font *gstring_font = XFONT_OBJECT (font_object);
> +
> +	      /* This is for when the grapheme cluster displays some
> +		 ligature using ASCII font: if the height is smaller
> +		 than line-height-factor says, enlarge the ascent.  */
> +	      if (face == face->ascii_face
> +		  && face->ascii_face->font == gstring_font)
> +		{
> +		  int enlarged_height =
> +		    ((FONT_BASE (gstring_font) + FONT_DESCENT (gstring_font))
> +		     * XFLOAT_DATA (Vline_height_factor));
> +		  if (metrics.ascent + metrics.descent < enlarged_height)
> +		    metrics.ascent = enlarged_height - metrics.descent;
> +		}
> +	    }
>  	  it->ascent = it->phys_ascent = metrics.ascent;
>  	  it->descent = it->phys_descent = metrics.descent;
>  	}
> @@ -35581,6 +35634,16 @@ syms_of_xdisp (void)
>  mini-window frame's default font's height.  */);
>    Vmax_mini_window_height = make_float (0.25);
>  
> +  DEFVAR_LISP ("line-height-factor", Vline_height_factor,
> +    doc: /* Factor for enlarging the height of lines that use the default font.
> +The value should be a float number greater than 1.  It determines how
> +much will Emacs enlarge the height of a screen line that shows only
> +characters displayed with the default face's font for ASCII characters.
> +This is to avoid differences in height between lines that use the
> +ASCII font and those which use non-ASCII (for example, Chinese)
> +font, which is typically higher than the ASCII one.  */);
> +  Vline_height_factor = Qnil;
> +
>    DEFVAR_LISP ("resize-mini-windows", Vresize_mini_windows,
>      doc: /* How to resize mini-windows (the minibuffer and the echo area).
>  A value of nil means don't automatically resize mini-windows.

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