From: Alex Gramiak <agrambot@gmail.com>
To: Andy Moreton <andrewjmoreton@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Replace XChar2b with unsigned in all font backends
Date: Mon, 20 May 2019 13:34:58 -0600 [thread overview]
Message-ID: <87imu4vs0t.fsf@gmail.com> (raw)
In-Reply-To: <vz17eal0yk1.fsf@gmail.com> (Andy Moreton's message of "Mon, 20 May 2019 19:29:34 +0100")
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Andy Moreton <andrewjmoreton@gmail.com> writes:
> On Mon 20 May 2019, Alex Gramiak wrote:
>
>> Andy Moreton <andrewjmoreton@gmail.com> writes:
>>
>>> Confirmed. This patch replaces use of XChar2b (a 16bit type) with
>>> unsigned (usually 32bit) which seems wrong.
>>>
>>> AndyM
>>
>> I originally used unsigned short for this patch, but Eli[1] nudged me
>> towards unsigned. Unsigned fits better with other parts of the font
>> system, e.g., *encode_char returns unsigned, and *text_extents takes a
>> pointer to unsigned.
>>
>> [1] https://lists.gnu.org/archive/html/emacs-devel/2019-05/msg00457.html
>
> Yes, but Eli was concerned with efficiency, but correctness comes first.
> If you are calling APIs that expect a pointer to an array of 16bit
> values, then an array of 32bit values will not suffice.
Right, at least not without converting the array; the xfont backend does
this when the API expects an array of 8bit values.
> Many of the comments around this code talk of 2-byte values, so
> changing the code to use 4-byte values is surprising to the reader.
I agree, but at least the char2b name signifies that it's a 2-byte
value.
> The changes also removed the explicit packing/unpacking of 16bit values,
> which may give rise to endianness issues on some systems.
I haven't dealt with endianness issues before, but from a quick search
[1][2] it doesn't appear that it's an issue:
[1] https://developer.ibm.com/articles/au-endianc/
[2] https://stackoverflow.com/a/7184905
> Please revert this patch to fix the build on master, and then revisit
> these changes after that.
I think that the solution is just to do a conversion on the w32font_draw
side. Can you confirm if the following diff fixes the build for you?
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diff --git a/src/w32font.c b/src/w32font.c
index bd68e22cc9..d3ec2916a5 100644
--- a/src/w32font.c
+++ b/src/w32font.c
@@ -704,11 +704,20 @@ w32font_draw (struct glyph_string *s, int from, int to,
int i;
for (i = 0; i < len; i++)
- ExtTextOutW (s->hdc, x + i, y, options, NULL,
- s->char2b + from + i, 1, NULL);
+ {
+ const wchar_t ch = s->char2b[from + i];
+ ExtTextOutW (s->hdc, x + i, y, options, NULL, &ch, 1, NULL);
+ }
}
else
- ExtTextOutW (s->hdc, x, y, options, NULL, s->char2b + from, len, NULL);
+ {
+ USE_SAFE_ALLOCA;
+ wchar_t *str = SAFE_ALLOCA (len * (sizeof (*str)));
+ for (int i = 0; i < len; ++i)
+ str[i] = s->char2b[from + i];
+ ExtTextOutW (s->hdc, x, y, options, NULL, str, len, NULL);
+ SAFE_FREE ();
+ }
/* Restore clip region. */
if (s->num_clips > 0)
next prev parent reply other threads:[~2019-05-20 19:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-20 8:26 Replace XChar2b with unsigned in all font backends martin rudalics
2019-05-20 12:05 ` Andy Moreton
2019-05-20 18:14 ` Alex Gramiak
2019-05-20 18:29 ` Andy Moreton
2019-05-20 19:20 ` Eli Zaretskii
2019-05-20 22:52 ` Andy Moreton
2019-05-21 8:00 ` Eli Zaretskii
2019-05-21 11:50 ` Andy Moreton
2019-05-21 12:38 ` Eli Zaretskii
2019-05-20 19:34 ` Alex Gramiak [this message]
2019-05-20 18:07 ` Alex Gramiak
2019-05-21 7:33 ` martin rudalics
2019-05-21 21:32 ` Alex Gramiak
2019-05-21 23:04 ` Andy Moreton
2019-05-22 8:30 ` martin rudalics
2019-05-21 11:47 ` Andy Moreton
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