In article <tl7vd77z591....@m17n.org>, Kenichi Handa <ha...@m17n.org> writes:
> I'd like to extend the elements of a display table.
> Currently only a glyph vector or nil is allowed. It seems
> good to extend it so that it can completely control the
> displaying of a character (like by face and display text
> properties).
> At least, for (2), I want to specify a space width (relative
> or absolute), and for (4) I want to specify a special form
> (list?) containing a mnemonic label.
I've just committed a basic infrastructure for displaying
non-graphic and no-font characters. For that, instead of
extending the current display table, I implemented a new
char table glyphless-char-display.
------------------------------------------------------------
Char-table to control displaying of glyphless characters.
Each element, if non-nil, is an ASCII acronym string (displayed in a box)
or one of these symbols:
hexa-code: display with hexadecimal character code in a box
empty-box: display with an empty box
thin-space: display with 1-pixel width space
zero-width: don't display
It has one extra slot to control the display of a character for which
no font is found. The value of the slot is `hexa-code' or `empty-box'.
The default is `empty-box'.
------------------------------------------------------------
It is easy to merge such functionality to a display table
later if we decide to do so.
But, there left these works.
(1) As it is not convenient for a user to specify each
element of glyphless-char-display, I made variables
char-acronym-table and glyphless-char-control. The
former is a simple char-table that contains acronym
strings. The latter is as this:
------------------------------------------------------------
glyphless-char-control is a variable defined in `characters.el'.
Its value is
((format-control . thin-space)
(no-font . hexa-code))
Documentation:
List of directives to control displaying of glyphless characters.
Each element has the form (TARGET . METHOD), where TARGET is a
symbol specifying the target character group to control, and
METHOD is a symbol specifying the method of displaying them.
TARGET must be one of these symbols:
`c0-control': U+0000..U+001F.
`c1-control': U+0080..U+009F.
`format-control': Characters of Unicode General Category `Cf'.
Ex: U+200C (ZWNJ), U+200E (LRM)), but don't include characters
that have graphic image such as U+00AD (SHY).
`no-font': characters for which no suitable font is found.
METHOD must be one of these symbols:
`zero-width': don't display.
`thin-space': display a thin space (1-pixel width).
`empty-box': display an empty box.
`acronym': display an acronum string in a box.
`hexa-code': display a hexadecimal character code in a box.
Just setting this variable does not take effect. Call the
function `update-glyphless-char-display' (which see) after
setting this variable.
------------------------------------------------------------
When acronum is specified, the function
update-glyphless-char-display sets elements in
glyphless-char-display to acronyms stored in
char-acronym-table.
Actually, glyphless-char-control should be a customizable
variable with proper set: function. But, I don't know how
to write the correct 'defcustom' form. Could someone DTRT?
(2) For Windows port:
I wrote x_draw_glyphless_glyph_string_foreground (in
w32term.c) by referring to x_draw_glyph_string_foreground in
the same file. But, it doesn't draw acronym nor hexa-code.
I couldn't figure out what is wrong. Please someone who
knows Windows code fix it.
(3) For mac port:
As I have no idea how to write a code for mac, the 'case
GLYPHLESS_GLYPH:' part in ns_draw_glyph_string (in nsterm.m)
is not finished. Please fill in the correct code by
referring to x_draw_glyph_string_foreground in xterm.c.
---
Kenichi Handa
ha...@m17n.org
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