config: add setting for underline thickness

This adds an "underline-thickness" setting to the "main" section,
similar to the existing "underline-offset" setting. This setting is used
to specify a custom height for regular (= non-cursor) underlines.

Fixes #1136

CHANGELOG.md

@@ -42,6 +42,12 @@
 
 ## Unreleased
 ### Added
+
+* Support for adjusting the thickness of regular underlines ([#1136][1136]).
+
+[1136]: https://codeberg.org/dnkl/foot/issues/1136
+
+
 ### Changed
 
 * Window is now dimmed while in Unicode input mode.

config.c

@@ -904,6 +904,9 @@ parse_section_main(struct context *ctx)
         return true;
     }
 
+    else if (strcmp(key, "underline-thickness") == 0)
+        return value_to_pt_or_px(ctx, &conf->underline_thickness);
+
     else if (strcmp(key, "dpi-aware") == 0) {
         if (strcmp(value, "auto") == 0)
             conf->dpi_aware = DPI_AWARE_AUTO;
@@ -2833,6 +2836,7 @@ config_load(struct config *conf, const char *conf_path,
         .vertical_letter_offset = {.pt = 0, .px = 0},
         .use_custom_underline_offset = false,
         .box_drawings_uses_font_glyphs = false,
+        .underline_thickness = {.pt = 0., .px = -1},
         .dpi_aware = DPI_AWARE_AUTO, /* DPI-aware when scaling-factor == 1 */
         .bell = {
             .urgent = false,

config.h

@@ -150,6 +150,7 @@ struct config {
 
     bool use_custom_underline_offset;
     struct pt_or_px underline_offset;
+    struct pt_or_px underline_thickness;
 
     bool box_drawings_uses_font_glyphs;
     bool can_shape_grapheme;

doc/foot.ini.5.scd

@@ -132,6 +132,18 @@ commented out will usually be installed to */etc/xdg/foot/foot.ini*.
 	
 	Default: _unset_.
 
+*underline-thickness*
+	Use a custom thickness (height) for underlines. The thickness is, by
+	default, in _points_.
+
+	To specify a thickness in _pixels_, append *px*:
+	*underline-thickness=1px*.
+
+	If left unset (the default), the thickness specified in the font is
+	used.
+
+	Default: _unset_
+
 *box-drawings-uses-font-glyphs* Boolean. When disabled, foot generates
 	box/line drawing characters itself. The are several advantages to
 	doing this instead of using font glyphs:

foot.ini

@@ -17,6 +17,7 @@
 # horizontal-letter-offset=0
 # vertical-letter-offset=0
 # underline-offset=<font metrics>
+# underline-thickness=<font underline thickness>
 # box-drawings-uses-font-glyphs=no
 # dpi-aware=auto
 

render.c

@@ -372,7 +372,10 @@ draw_underline(const struct terminal *term, pixman_image_t *pix,
                const struct fcft_font *font,
                const pixman_color_t *color, int x, int y, int cols)
 {
-    const int thickness = font->underline.thickness;
+    const int thickness = term->conf->underline_thickness.px >= 0
+        ? term_pt_or_px_as_pixels(
+            term, &term->conf->underline_thickness)
+        : font->underline.thickness;
 
     /* Make sure the line isn't positioned below the cell */
     const int y_ofs = min(underline_offset(term, font),

tests/test-config.c

@@ -470,6 +470,7 @@ test_section_main(void)
     test_pt_or_px(&ctx, &parse_section_main, "letter-spacing", &conf.letter_spacing);
     test_pt_or_px(&ctx, &parse_section_main, "horizontal-letter-offset", &conf.horizontal_letter_offset);
     test_pt_or_px(&ctx, &parse_section_main, "vertical-letter-offset", &conf.vertical_letter_offset);
+    test_pt_or_px(&ctx, &parse_section_main, "underline-thickness", &conf.underline_thickness);
 
     test_uint16(&ctx, &parse_section_main, "resize-delay-ms", &conf.resize_delay_ms);
     test_uint16(&ctx, &parse_section_main, "workers", &conf.render_worker_count);