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gtk-demo: Avoid a segfault

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The code in the fontrendering demo is a bit sloppy
and assumes that we always get a single run when
appending a sequence of 4 chars and 4 spaces.

That is not in general true, such as for Emoji.

Instead of working harder to handle Emoji here,
just give up and fall back to 'a'.

Fixes: #5166
This commit is contained in:
Matthias Clasen 2022-09-09 12:33:08 -04:00
parent d7817e6fc6
commit 54daad3878
1 changed files with 15 additions and 6 deletions
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21
demos/gtk-demo/fontrendering.c
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@ -217,30 +217,39 @@ update_image (void)
text = " ";
ch = g_utf8_get_char (text);
str = g_string_new ("");
layout = pango_layout_new (context);
retry:
for (i = 0; i < 4; i++)
{
g_string_append_unichar (str, ch);
g_string_append_unichar (str, 0x200c);
}
layout = pango_layout_new (context);
pango_layout_set_font_description (layout, desc);
pango_layout_set_text (layout, str->str, -1);
g_string_free (str, TRUE);
pango_layout_get_extents (layout, &ink, &logical);
pango_extents_to_pixels (&logical, NULL);
iter = pango_layout_get_iter (layout);
run = pango_layout_iter_get_run (iter);
if (run->glyphs->num_glyphs < 8)
{
/* not a good char to use */
g_string_truncate (str, 0);
ch = 'a';
goto retry;
}
g_string_free (str, TRUE);
surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, logical.width * 3 / 2, 4*logical.height);
cr = cairo_create (surface);
cairo_set_source_rgb (cr, 1, 1, 1);
cairo_paint (cr);
iter = pango_layout_get_iter (layout);
run = pango_layout_iter_get_run (iter);
cairo_set_source_rgb (cr, 0, 0, 0);
for (i = 0; i < 4; i++)
{