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Work around Pango fonts with fractional width.

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By retrieving characters' widths using get_extents and not
get_pixel_extents, we can spot when they're not actually an exact
multiple of a pixel, and avoid getting confused by the overall width
of a long string being off by up to a pixel per character.
This commit is contained in:
Simon Tatham 2015-08-31 16:37:05 +01:00
parent 7658b291db
commit ad994bab57
1 changed files with 8 additions and 7 deletions
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15
unix/gtkfont.c
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@ -1338,10 +1338,10 @@ static int pangofont_char_width(PangoLayout *layout, struct pangofont *pfont,
/* /*
* Here we check whether a character has the same width as the * Here we check whether a character has the same width as the
* character cell it'll be drawn in. Because profiling showed that * character cell it'll be drawn in. Because profiling showed that
* pango_layout_get_pixel_extents() was a huge bottleneck when we * asking Pango for text sizes was a huge bottleneck when we were
* were calling it every time we needed to know this, we instead * calling it every time we needed to know this, we instead call
* call it only on characters we don't already know about, and * it only on characters we don't already know about, and cache
* cache the results. * the results.
*/ */
if ((unsigned)uchr >= pfont->nwidthcache) { if ((unsigned)uchr >= pfont->nwidthcache) {
@ -1354,7 +1354,7 @@ static int pangofont_char_width(PangoLayout *layout, struct pangofont *pfont,
if (pfont->widthcache[uchr] < 0) { if (pfont->widthcache[uchr] < 0) {
PangoRectangle rect; PangoRectangle rect;
pango_layout_set_text(layout, utfchr, utflen); pango_layout_set_text(layout, utfchr, utflen);
pango_layout_get_pixel_extents(layout, NULL, &rect); pango_layout_get_extents(layout, NULL, &rect);
pfont->widthcache[uchr] = rect.width; pfont->widthcache[uchr] = rect.width;
} }
@ -1437,6 +1437,7 @@ static void pangofont_draw_text(unifont_drawctx *ctx, unifont *font,
utfptr = utfstring; utfptr = utfstring;
while (utflen > 0) { while (utflen > 0) {
int clen, n; int clen, n;
int desired = cellwidth * PANGO_SCALE;
/* /*
* We want to display every character from this string in * We want to display every character from this string in
@ -1475,7 +1476,7 @@ static void pangofont_draw_text(unifont_drawctx *ctx, unifont *font,
if (is_rtl(string[0]) || if (is_rtl(string[0]) ||
pangofont_char_width(layout, pfont, string[n-1], pangofont_char_width(layout, pfont, string[n-1],
utfptr, clen) != cellwidth) { utfptr, clen) != desired) {
/* /*
* If this character is a right-to-left one, or has an * If this character is a right-to-left one, or has an
* unusual width, then we must display it on its own. * unusual width, then we must display it on its own.
@ -1497,7 +1498,7 @@ static void pangofont_draw_text(unifont_drawctx *ctx, unifont *font,
n++; n++;
if (pangofont_char_width(layout, pfont, if (pangofont_char_width(layout, pfont,
string[n-1], utfptr + oldclen, string[n-1], utfptr + oldclen,
clen - oldclen) != cellwidth) { clen - oldclen) != desired) {
clen = oldclen; clen = oldclen;
n--; n--;
break; break;