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GTK: don't try to use X fonts for characters outside BMP

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X fonts are indexed by 16-bit quantities, so even Unicode-capable
fonts can only have characters in the Basic Multilingual Plane (BMP).
PuTTY, however, tried to look up all Unicode characters in X fonts,
and did so by effectively ignoring all but the low-order 16 bits of
the character code.  This meant that trying to display a non-BMP
character could get you the corresponding character from the BMP
instead, if that character was in the font.

Now, x11font_has_glyph() always returns false for glyphs outside the
BMP, which should mean that x11font_draw_text() never gets asked to
draw them.
This commit is contained in:
Ben Harris 2025-05-05 18:39:05 +01:00
parent fcadb5fed1
commit a0a92da035
1 changed files with 6 additions and 3 deletions
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9
unix/unifont.c
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@ -554,10 +554,11 @@ static bool x11font_has_glyph(unifont *font, wchar_t glyph)
if (xfont->sixteen_bit) {
/*
* This X font has 16-bit character indices, which means
* we can directly use our Unicode input value.
* we can directly use our Unicode input value as long as
* it's in the BMP.
*/
return x11_font_has_glyph(xfont->fonts[0].xfs,
glyph >> 8, glyph & 0xFF);
return glyph < 0x10000 &&
x11_font_has_glyph(xfont->fonts[0].xfs, glyph >> 8, glyph & 0xFF);
} else {
/*
* This X font has 8-bit indices, so we must convert to the
@ -790,6 +791,8 @@ static void x11font_draw_text(unifont_drawctx *ctx, unifont *font,
xcslen = len;
xcs = snewn(xcslen, XChar2b);
for (i = 0; i < xcslen; i++) {
/* We shouldn't see any character not in the font. */
assert(string[i] < 0x10000);
xcs[i].byte1 = string[i] >> 8;
xcs[i].byte2 = string[i];
}