From aeac5ad6f1cfcf462c8a8babf0066c6d58e7c956 Mon Sep 17 00:00:00 2001
From: David Rosca <nowrep@gmail.com>
Date: Wed, 21 Jul 2021 09:17:43 +0200
Subject: [PATCH] Add option to enable subpixel font rendering with transparent
 background

---
 config.c           | 4 ++++
 config.h           | 2 ++
 doc/foot.ini.5.scd | 4 ++++
 foot.ini           | 1 +
 terminal.c         | 4 ++--
 5 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/config.c b/config.c
index a9acb58e..f17f1367 100644
--- a/config.c
+++ b/config.c
@@ -961,6 +961,9 @@ 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 if (strcmp(key, "subpixel-with-alpha") == 0)
+        conf->subpixel_with_alpha = str_to_bool(value);
+
     else {
         LOG_AND_NOTIFY_ERR("%s:%u: [default]: %s: invalid key", path, lineno, key);
         return false;
@@ -2740,6 +2743,7 @@ 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,
+        .subpixel_with_alpha = false,
         .dpi_aware = DPI_AWARE_AUTO, /* DPI-aware when scaling-factor == 1 */
         .bell = {
             .urgent = false,
diff --git a/config.h b/config.h
index 729eba3e..8a998187 100644
--- a/config.h
+++ b/config.h
@@ -114,6 +114,8 @@ struct config {
     bool box_drawings_uses_font_glyphs;
     bool can_shape_grapheme;
 
+    bool subpixel_with_alpha;
+
     struct {
         bool urgent;
         bool notify;
diff --git a/doc/foot.ini.5.scd b/doc/foot.ini.5.scd
index 8b2f1dc8..640fc831 100644
--- a/doc/foot.ini.5.scd
+++ b/doc/foot.ini.5.scd
@@ -145,6 +145,10 @@ in this order:
 	
 	Default: _no_.
 
+	*subpixel-with-alpha*
+	Boolean. When enabled, subpixel font rendering will be used also
+	with transparent background. 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
diff --git a/foot.ini b/foot.ini
index 31167cd5..55677d7d 100644
--- a/foot.ini
+++ b/foot.ini
@@ -19,6 +19,7 @@
 # underline-offset=<font metrics>
 # box-drawings-uses-font-glyphs=no
 # dpi-aware=yes
+# subpixel-with-alpha=no
 
 # initial-window-size-pixels=700x500  # Or,
 # initial-window-size-chars=<COLSxROWS>
diff --git a/terminal.c b/terminal.c
index 46e7fc01..2fe452fd 100644
--- a/terminal.c
+++ b/terminal.c
@@ -760,7 +760,7 @@ get_font_dpi(const struct terminal *term)
 static enum fcft_subpixel
 get_font_subpixel(const struct terminal *term)
 {
-    if (term->colors.alpha != 0xffff) {
+    if (!term->conf->subpixel_with_alpha && term->colors.alpha != 0xffff) {
         /* Can't do subpixel rendering on transparent background */
         return FCFT_SUBPIXEL_NONE;
     }
@@ -1086,7 +1086,7 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
             xmalloc(sizeof(term->font_sizes[3][0]) * conf->fonts[3].count),
         },
         .font_dpi = 0.,
-        .font_subpixel = (conf->colors.alpha == 0xffff  /* Can't do subpixel rendering on transparent background */
+        .font_subpixel = ((conf->subpixel_with_alpha || conf->colors.alpha == 0xffff)  /* Can't do subpixel rendering on transparent background */
                           ? FCFT_SUBPIXEL_DEFAULT
                           : FCFT_SUBPIXEL_NONE),
         .cursor_keys_mode = CURSOR_KEYS_NORMAL,