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Fix "underbars not drawing in fluid code editor (Ubuntu 24/Xwindows)" - cont'd (#1572).
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The issue occurs when drawing text with cairo+pango at some sizes (11 is one of them).
It affects both FLTK text widgets, so it's not fluid-specific.
It affects both Wayland and X11 when using Cairo+Pango.
No issue with X11+Pango-Cairo.
No issue with X11+Xft.

Thanks to @wcout for suggesting this fix.
This commit is contained in:
ManoloFLTK
2026-08-16 16:10:33 +02:00
parent d15b9d34de
commit c46c5d9051
1 changed files with 7 additions and 14 deletions
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src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
+7 -14
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@@ -1163,18 +1163,11 @@ Fl_Cairo_Font_Descriptor::Fl_Cairo_Font_Descriptor(const char* name, Fl_Fontsize
PangoFontMetrics *metrics = pango_fontset_get_metrics(fontset);
ascent = pango_font_metrics_get_ascent(metrics);
descent = pango_font_metrics_get_descent(metrics);
/*
Pango documents that function pango_font_metrics_get_height() gives
"the recommended distance between successive baselines in wrapped text".
In general pango_font_metrics_get_height() = ascent + descent,
so the recommended line height equals ascent + descent, as expected by FLTK.
However, pango_font_metrics_get_height() is sometimes < ascent + descent
(e.g., this happens when size = 11 for all FLTK standard fonts)
and that results in underscore not being reliably displayed by FLTK text widgets.
Therefore, we use ascent + descent rather than pango_font_metrics_get_height()
to compute the distance between successive lines of text (see #1572).
*/
line_height = ascent + descent;
#if PANGO_VERSION_CHECK(1,44,0)
line_height = pango_font_metrics_get_height(metrics); // 1.44
#else
line_height = ascent + descent;
#endif
pango_font_metrics_unref(metrics);
g_object_unref(fontset);
//fprintf(stderr, "[%s](%d) ascent=%d descent=%d line_height=%d\n", name, size, ascent, descent, line_height);
@@ -1308,7 +1301,7 @@ void Fl_Cairo_Graphics_Driver::draw(const char* str, int n, float x, float y) {
if (!n) return;
cairo_save(cairo_);
Fl_Cairo_Font_Descriptor *fd = (Fl_Cairo_Font_Descriptor*)font_descriptor();
cairo_translate(cairo_, x - 0.5, y - (fd->line_height - fd->descent) / float(PANGO_SCALE) - 0.5);
cairo_translate(cairo_, x - 0.5, y - fd->ascent / float(PANGO_SCALE) - 0.5);
str = clean_utf8(str, n);
pango_layout_set_text(pango_layout_, str, n);
pango_cairo_show_layout(cairo_, pango_layout_); // 1.1O
@@ -1393,7 +1386,7 @@ void Fl_Cairo_Graphics_Driver::text_extents(const char* txt, int n, int& dx, int
double f = PANGO_SCALE;
Fl_Cairo_Font_Descriptor *fd = (Fl_Cairo_Font_Descriptor*)font_descriptor();
dx = ink_rect.x / f;
dy = (ink_rect.y - fd->line_height + fd->descent) / f;
dy = (ink_rect.y - fd->ascent) / f;
w = ceil(ink_rect.width / f);
h = ceil(ink_rect.height / f);
}