config: add colors.dim-blend-towards=black|white

Before this patch, we always blended towards black when dimming
text. However, with light color themes, it usually looks better if we
dim towards white instead.

This option allows you to choose which color to blend towards.

The default is 'black' in '[colors]', and 'white' in '[colors2]'.

Closes #2187

CHANGELOG.md

@@ -71,8 +71,12 @@
 
 * Performance increased and input latency decreased on compositors
   that do not release SHM buffers immediately ([#2188][2188]).
+* `colors{,2}.dim-blend-towards=black|white` option, allowing you to
+  select towards which color to blend when dimming text. Defaults to
+  `black` in `[colors]`, and `white` in `[colors2]` ([#2187][2187]).
 
 [2188]: https://codeberg.org/dnkl/foot/issues/2188
+[2187]: https://codeberg.org/dnkl/foot/issues/2187
 
 
 ### Changed

config.c

@@ -1519,7 +1519,7 @@ parse_color_theme(struct context *ctx, struct color_theme *theme)
         return true;
     }
 
-    else if (strcmp(key, "alpha-mode") == 0) {
+    else if (streq(key, "alpha-mode")) {
         _Static_assert(sizeof(theme->alpha_mode) == sizeof(int),
         "enum is not 32-bit");
 
@@ -1529,6 +1529,16 @@ parse_color_theme(struct context *ctx, struct color_theme *theme)
             (int *)&theme->alpha_mode);
     }
 
+    else if (streq(key, "dim-blend-towards")) {
+        _Static_assert(sizeof(theme->dim_blend_towards) == sizeof(int),
+                       "enum is not 32-bit");
+
+        return value_to_enum(
+            ctx,
+            (const char *[]){"black", "white", NULL},
+            (int *)&theme->dim_blend_towards);
+    }
+
     else {
         LOG_CONTEXTUAL_ERR("not valid option");
         return false;
@@ -3428,6 +3438,7 @@ config_load(struct config *conf, const char *conf_path,
             .flash_alpha = 0x7fff,
             .alpha = 0xffff,
             .alpha_mode = ALPHA_MODE_DEFAULT,
+            .dim_blend_towards = DIM_BLEND_TOWARDS_BLACK,
             .selection_fg = 0x80000000,  /* Use default bg */
             .selection_bg = 0x80000000,  /* Use default fg */
             .cursor = {
@@ -3523,6 +3534,8 @@ config_load(struct config *conf, const char *conf_path,
     memcpy(conf->colors.table, default_color_table, sizeof(default_color_table));
     memcpy(conf->colors.sixel, default_sixel_colors, sizeof(default_sixel_colors));
     memcpy(&conf->colors2, &conf->colors, sizeof(conf->colors));
+    conf->colors2.dim_blend_towards = DIM_BLEND_TOWARDS_WHITE;
+
     parse_modifiers(XKB_MOD_NAME_SHIFT, 5, &conf->mouse.selection_override_modifiers);
 
     tokenize_cmdline(

config.h

@@ -145,6 +145,11 @@ struct color_theme {
     uint32_t dim[8];
     uint32_t sixel[16];
 
+    enum {
+        DIM_BLEND_TOWARDS_BLACK,
+        DIM_BLEND_TOWARDS_WHITE,
+    } dim_blend_towards;
+
     enum {
         ALPHA_MODE_DEFAULT,
         ALPHA_MODE_MATCHING,

doc/foot.ini.5.scd

@@ -1031,7 +1031,8 @@ dark theme (since the default theme is dark).
 	a color value, and a "dim" attribute.
 	
 	By default, foot implements this by blending the current color
-	with black. This is a generic approach that applies to both
+	with black or white, depending on what the *dim-blend-towards*
+	option is set to . This is a generic approach that applies to both
 	colors from the 256-color palette, as well as 24-bit RGB colors.
 	
 	You can change this behavior by setting the *dimN* options. When
@@ -1086,6 +1087,14 @@ dark theme (since the default theme is dark).
 	
 	Default: _default_
 
+*dim-blend-towards*
+	Which color to blend towards when "auto" dimming a color (see
+	*dim0*..*dim7* above). One of *black* or *white*. Blending towards
+	black makes the text darker, while blending towards white makes it
+	whiter (but still dimmer than normal text).
+	
+	Default: _black_ (*colors*), _white_ (*colors2*)
+
 *selection-foreground*, *selection-background*
 	Foreground (text) and background color to use in selected
 	text. Default: _inverse foreground/background_.
@@ -1124,7 +1133,8 @@ dark theme (since the default theme is dark).
 # SECTION: colors2
 
 This section defines an alternative color theme. It has the exact same
-keys as the *colors* section. The default values are the same.
+keys as the *colors* section. The default values are the same, except
+for *dim-blend-towards*, which defaults to *white* instead.
 
 Note that values are not inherited. That is, if you set a value in
 *colors*, but not in *colors2*, the value from *colors* is not

foot.ini

@@ -132,6 +132,7 @@
 # bright7=ffffff   # bright white
 
 ## dimmed colors (see foot.ini(5) man page)
+# dim-blend-towards=black
 # dim0=<not set>
 # ...
 # dim7=<not-set>
@@ -170,6 +171,8 @@
 
 [colors2]
 # Alternative color theme, see man page foot.ini(5)
+# Same builtin defaults as [color], except for:
+# dim-blend-towards=white
 
 [csd]
 # preferred=server

render.c

@@ -312,7 +312,14 @@ color_dim(const struct terminal *term, uint32_t color)
         }
     }
 
-    return color_blend_towards(color, 0x00000000, conf->dim.amount);
+    const struct color_theme *theme = term->colors.active_theme == COLOR_THEME1
+        ? &conf->colors
+        : &conf->colors2;
+
+    return color_blend_towards(
+        color,
+        theme->dim_blend_towards == DIM_BLEND_TOWARDS_BLACK ? 0x00000000 : 0x00ffffff,
+        conf->dim.amount);
 }
 
 static inline uint32_t

tests/test-config.c

@@ -753,6 +753,11 @@ test_section_colors(void)
               (int []){ALPHA_MODE_DEFAULT, ALPHA_MODE_MATCHING, ALPHA_MODE_ALL},
               (int *)&conf.colors.alpha_mode);
 
+    test_enum(&ctx, &parse_section_colors, "dim-blend-towards", 2,
+              (const char *[]){"black", "white"},
+              (int []){DIM_BLEND_TOWARDS_BLACK, DIM_BLEND_TOWARDS_WHITE},
+              (int *)&conf.colors.dim_blend_towards);
+
     for (size_t i = 0; i < 255; i++) {
         char key_name[4];
         sprintf(key_name, "%zu", i);