Foot per-monitor scaling factor

foot-per-monitor-scale.patch

diff --git a/config.c b/config.c
index ce0e27b8..9a1ce4df 100644
--- a/config.c
+++ b/config.c
@@ -408,6 +408,73 @@ value_to_bool(struct context *ctx, bool *res)
     return false;
 }
 
+static bool
+config_monitor_scale_parse(char *pattern, struct config_monitor_scale *scale)
+{
+    char *scale_factor_str = strrchr(pattern, ':');
+    if (!scale_factor_str)
+        return false;
+
+    scale_factor_str[0] = 0;
+
+    if (pattern[0] == 0)
+        return false;
+
+    errno = 0;
+    char *end = NULL;
+    scale->scale = strtof(scale_factor_str + 1, &end);
+    if (!(errno == 0 && *end == '\0')) {
+        return false;
+    }
+
+    scale->pattern = xstrdup(pattern);
+
+    return true;
+}
+
+static struct config_monitor_scale_list NOINLINE
+value_to_monitor_scale(struct context *ctx)
+{
+    size_t count = 0;
+    size_t size = 0;
+    struct config_monitor_scale *scales = NULL;
+
+    char *copy = xstrdup(ctx->value);
+    for (char *scale = strtok(copy, ",");
+         scale != NULL;
+         scale = strtok(NULL, ","))
+    {
+        /* Trim spaces, strictly speaking not necessary, but looks nice :) */
+        while (isspace(scale[0]))
+            scale++;
+
+        if (scale[0] == '\0')
+            continue;
+
+        struct config_monitor_scale scale_data;
+        if (!config_monitor_scale_parse(scale, &scale_data)) {
+            ctx->value = scale;
+            LOG_CONTEXTUAL_ERR("invalid monitor scale specification");
+            goto err;
+        }
+
+        if (count + 1 > size) {
+            size += 4;
+            scales = xrealloc(scales, size * sizeof(scales[0]));
+        }
+
+        xassert(count + 1 <= size);
+        scales[count++] = scale_data;
+    }
+
+    free(copy);
+    return (struct config_monitor_scale_list){.arr = scales, .count = count};
+
+err:
+    free(copy);
+    free(scales);
+    return (struct config_monitor_scale_list){.arr = NULL, .count = 0};
+}
 
 static bool NOINLINE
 str_to_ulong(const char *s, int base, unsigned long *res)
@@ -939,6 +1006,16 @@ parse_section_main(struct context *ctx)
     else if (strcmp(key, "box-drawings-uses-font-glyphs") == 0)
         return value_to_bool(ctx, &conf->box_drawings_uses_font_glyphs);
 
+    else if (strcmp(key, "monitor-scale") == 0) {
+        struct config_monitor_scale_list new_list = value_to_monitor_scale(ctx);
+        if (new_list.arr == NULL)
+            return false;
+
+        config_monitor_scale_list_destroy(&conf->monitor_scale);
+        conf->monitor_scale = new_list;
+        return true;
+    }
+
     else {
         LOG_CONTEXTUAL_ERR("not a valid option: %s", key);
         return false;
@@ -2815,6 +2892,7 @@ config_load(struct config *conf, const char *conf_path,
             .osc8_underline = OSC8_UNDERLINE_URL_MODE,
         },
         .can_shape_grapheme = fcft_caps & FCFT_CAPABILITY_GRAPHEME_SHAPING,
+        .monitor_scale = {0},
         .scrollback = {
             .lines = 1000,
             .indicator = {
@@ -3293,6 +3371,15 @@ config_font_list_destroy(struct config_font_list *font_list)
     font_list->arr = NULL;
 }
 
+void
+config_monitor_scale_list_destroy(struct config_monitor_scale_list *monitor_scale_list)
+{
+    for (size_t i = 0; i < monitor_scale_list->count; i++)
+        free(monitor_scale_list->arr[i].pattern);
+    free(monitor_scale_list->arr);
+    monitor_scale_list->count = 0;
+    monitor_scale_list->arr = NULL;
+}
 
 bool
 check_if_font_is_monospaced(const char *pattern,
diff --git a/config.h b/config.h
index de5d8a7b..41771b13 100644
--- a/config.h
+++ b/config.h
@@ -33,6 +33,12 @@ struct config_font {
 };
 DEFINE_LIST(struct config_font);
 
+struct config_monitor_scale {
+    char *pattern;
+    float scale;
+};
+DEFINE_LIST(struct config_monitor_scale);
+
 struct config_key_modifiers {
     bool shift;
     bool alt;
@@ -154,6 +160,8 @@ struct config {
     bool box_drawings_uses_font_glyphs;
     bool can_shape_grapheme;
 
+    struct config_monitor_scale_list monitor_scale;
+
     struct {
         bool urgent;
         bool notify;
@@ -343,6 +351,7 @@ struct config *config_clone(const struct config *old);
 
 bool config_font_parse(const char *pattern, struct config_font *font);
 void config_font_list_destroy(struct config_font_list *font_list);
+void config_monitor_scale_list_destroy(struct config_monitor_scale_list *monitor_scale_list);
 
 struct seat;
 xkb_mod_mask_t
diff --git a/foot.ini b/foot.ini
index 10eb56e8..8ff75ab8 100644
--- a/foot.ini
+++ b/foot.ini
@@ -33,6 +33,8 @@
 # selection-target=primary
 # workers=<number of logical CPUs>
 
+# monitor-scale=eDPI-1:1 HDMI-A-1:1.8
+
 [environment]
 # name=value
 
diff --git a/terminal.c b/terminal.c
index dd84b8cf..f05471a8 100644
--- a/terminal.c
+++ b/terminal.c
@@ -727,6 +727,20 @@ term_set_fonts(struct terminal *term, struct fcft_font *fonts[static 4])
     return true;
 }
 
+static float get_monitor_scaled_dpi(const struct terminal *term, const struct monitor *mon)
+{
+    float dpi = mon->dpi;
+    /* Try to match a monitor from the config, and multiply the dpi by that */
+    for (size_t i = 0; i < term->conf->monitor_scale.count; ++i) {
+        const struct config_monitor_scale *scale = &term->conf->monitor_scale.arr[i];
+        if (strstr(mon->description, scale->pattern) != NULL) {
+            dpi *= scale->scale;
+            break;
+        }
+    }
+    return dpi;
+}
+
 static float
 get_font_dpi(const struct terminal *term)
 {
@@ -755,14 +769,15 @@ get_font_dpi(const struct terminal *term)
     double dpi = 0.0;
     xassert(term->window != NULL);
     tll_foreach(term->window->on_outputs, it) {
-        if (it->item->dpi > dpi)
-            dpi = it->item->dpi;
+        float monitor_dpi = get_monitor_scaled_dpi(term, it->item);
+        if (monitor_dpi > dpi)
+            dpi = monitor_dpi;
     }
 
     /* If we're not mapped, use DPI from first monitor. Hopefully this is where we'll get mapped later... */
     if (dpi == 0.) {
         tll_foreach(term->wl->monitors, it) {
-            dpi = it->item.dpi;
+            dpi = get_monitor_scaled_dpi(term, &it->item);
             break;
         }
     }