From 70cfcf11fb26a1e3954e72550e4c24e0fa43a8b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Thu, 7 Jan 2021 11:46:18 +0100
Subject: [PATCH] config: letter-spacing: make this a relative value

0, the default, means no additional spacing; the cell width is defined
by the font metrics.

A positive value *adds* to the width from the font metrics, while a
negative value *subtracts*.
---
 config.c   | 17 +++++++++++++++--
 foot.ini   |  2 +-
 terminal.c |  9 +++++----
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/config.c b/config.c
index 6af8803b..8f0b334f 100644
--- a/config.c
+++ b/config.c
@@ -360,6 +360,19 @@ str_to_bool(const char *s)
         strtoul(s, NULL, 0) > 0;
 }
 
+static bool
+str_to_long(const char *s, int base, long *res)
+{
+    if (s == NULL)
+        return false;
+
+    errno = 0;
+    char *end = NULL;
+
+    *res = strtol(s, &end, base);
+    return errno == 0 && *end == '\0';
+}
+
 static bool
 str_to_ulong(const char *s, int base, unsigned long *res)
 {
@@ -567,8 +580,8 @@ parse_section_main(const char *key, const char *value, struct config *conf,
     }
 
     else if (strcmp(key, "letter-spacing") == 0) {
-        unsigned long spacing;
-        if (!str_to_ulong(value, 10, &spacing)) {
+        long spacing;
+        if (!str_to_long(value, 10, &spacing)) {
             LOG_AND_NOTIFY_ERR(
                 "%s:%d: [default]: letter-spacing: expected an integer, got '%s'",
                 path, lineno, value);
diff --git a/foot.ini b/foot.ini
index ed9e5a72..f13d8e63 100644
--- a/foot.ini
+++ b/foot.ini
@@ -9,7 +9,7 @@
 # font-italic=<italic variant of regular font>
 # font-bold-italic=<bold+italic variant of regular font>
 # line-height=<font metrics>
-# letter-spacing=<font metrics>
+# letter-spacing=0
 # horizontal-letter-offset=0
 # vertical-letter-offset=0
 # dpi-aware=yes
diff --git a/terminal.c b/terminal.c
index c7383ae2..c23450fb 100644
--- a/terminal.c
+++ b/terminal.c
@@ -629,10 +629,11 @@ term_set_fonts(struct terminal *term, struct fcft_font *fonts[static 4])
     const int old_cell_width = term->cell_width;
     const int old_cell_height = term->cell_height;
 
-    term->cell_width = term->conf->letter_spacing >= 0
-        ? term->conf->letter_spacing
-        : (term->fonts[0]->space_advance.x > 0
-           ? term->fonts[0]->space_advance.x : term->fonts[0]->max_advance.x);
+    term->cell_width = (term->fonts[0]->space_advance.x > 0
+                        ? term->fonts[0]->space_advance.x
+                        : term->fonts[0]->max_advance.x)
+        + term->conf->letter_spacing;
+
     term->cell_height = term->conf->line_height >= 0
         ? term->conf->line_height
         : max(term->fonts[0]->height,