config: add box-drawings-uses-font-glyphs=no|yes option

When disabled, we render box drawing characters ourselves. This is the
default.

When enabled, we instead use font glyphs. I.e. no special treatment.

Closes #430

CHANGELOG.md

@@ -32,6 +32,8 @@
   (https://codeberg.org/dnkl/foot/issues/436).
 * OSC 17/117/19/119 - change/reset selection background/foreground
   color.
+* `box-drawings-uses-font-glyphs=yes|no` option to `foot.ini`
+  (https://codeberg.org/dnkl/foot/issues/430).
 
 
 ### Changed

config.c

@@ -770,6 +770,9 @@ parse_section_main(const char *key, const char *value, struct config *conf,
         }
     }
 
+    else if (strcmp(key, "box-drawings-uses-font-glyphs") == 0)
+        conf->box_drawings_uses_font_glyphs = str_to_bool(value);
+
     else {
         LOG_AND_NOTIFY_ERR("%s:%u: [default]: %s: invalid key", path, lineno, key);
         return false;
@@ -2198,6 +2201,7 @@ config_load(struct config *conf, const char *conf_path,
         .letter_spacing = { .pt = 0, .px = 0, },
         .horizontal_letter_offset = {.pt = 0, .px = 0, },
         .vertical_letter_offset = {.pt = 0, .px = 0, },
+        .box_drawings_uses_font_glyphs = false,
         .dpi_aware = DPI_AWARE_AUTO, /* DPI-aware when scaling-factor == 1 */
         .scrollback = {
             .lines = 1000,

config.h

@@ -99,6 +99,8 @@ struct config {
     struct pt_or_px horizontal_letter_offset;
     struct pt_or_px vertical_letter_offset;
 
+    bool box_drawings_uses_font_glyphs;
+
     struct {
         int lines;
 

doc/foot.ini.5.scd

@@ -96,6 +96,24 @@ in this order:
 	
 	Default: _0_.
 
+*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:
+	
+		- No antaliasing effects where e.g. line endpoints appear dimmer.
+		- Line- and box characters are guaranteed to span the entire cell,
+		  resulting in a gap-less appearance.
+		- No alignment issues, i.e. lines are centered when they should be.
+		- Many fonts lack some, or all, of the line- and box drawing
+		  characters, causing fallback fonts to be used, which results
+		  in out-of-place (for example, badly sized) looking glyphs.
+	
+	When enabled, box/line drawing characters are rendered using font
+	glyphs. This may result in a more uniform look, in some use cases.
+	
+	Default: _no_.
+
 *dpi-aware*
 	*auto*, *yes*, or *no*. When set to *yes*, fonts are sized using
 	the monitor's DPI, making a font of a given size have the same

foot.ini

@@ -12,6 +12,7 @@
 # letter-spacing=0
 # horizontal-letter-offset=0
 # vertical-letter-offset=0
+# box-drawings-uses-font-glyphs=no
 # dpi-aware=yes
 
 # initial-window-size-pixels=700x500  # Or,

render.c

@@ -466,7 +466,9 @@ render_cell(struct terminal *term, pixman_image_t *pix,
         }
 
         if (unlikely((base >= 0x2500 && base <= 0x259f) ||
-                     (base >= 0x1fb00 && base <= 0x1fb3b))) {
+                     (base >= 0x1fb00 && base <= 0x1fb3b)) &&
+            likely(!term->conf->box_drawings_uses_font_glyphs))
+        {
             /* Box drawing characters */
             size_t idx = base >= 0x1fb00 ? base - 0x1fb00 + 160 : base - 0x2500;
             xassert(idx < ALEN(term->box_drawing));