config: add [csd].hide-when-maximized=yes|no

When enabled, the CSD titlebar will be hidden when the window is
maximized.

Closes #1019

config.c

@@ -1361,6 +1361,9 @@ parse_section_csd(struct context *ctx)
     else if (strcmp(key, "border-width") == 0)
         return value_to_uint16(ctx, 10, &conf->csd.border_width_visible);
 
+    else if (strcmp(key, "hide-when-maximized") == 0)
+        return value_to_bool(ctx, &conf->csd.hide_when_maximized);
+
     else {
         LOG_CONTEXTUAL_ERR("not a valid action: %s", key);
         return false;
@@ -2835,6 +2838,7 @@ config_load(struct config *conf, const char *conf_path,
         .csd = {
             .preferred = CONF_CSD_PREFER_SERVER,
             .font = {0},
+            .hide_when_maximized = false,
             .title_height = 26,
             .border_width = 5,
             .border_width_visible = 0,

config.h

@@ -262,6 +262,8 @@ struct config {
         uint16_t border_width_visible;
         uint16_t button_width;
 
+        bool hide_when_maximized;
+
         struct {
             bool title_set:1;
             bool buttons_set:1;

doc/foot.ini.5.scd

@@ -592,7 +592,9 @@ Examples:
 
 *size*
 	Height, in pixels (subject to output scaling), of the
-	titlebar. Default: _26_.
+	titlebar. Setting it to 0 will hide the titlebar, while still
+	showing the border (if *border-width* is set to a non-zero
+	value). Default: _26_.
 
 *color*
 	Titlebar color. Default: use the default _foreground_ color.
@@ -603,6 +605,11 @@ Examples:
 	title bar size. That is, all *:size* and *:pixelsize* attributes
 	will be ignored. Default: _primary font_.
 
+*hide-when-maximized*
+	Boolean. When enabled, the CSD titlebar is hidden when the window
+	is maximized. The completely disable the titlebar, set *size* to 0
+	instead. Default: _no_.
+
 *border-width*
 	Width of the border, in pixels (subject to output scaling). Note
 	that the border encompasses the entire window, including the title

foot.ini

@@ -110,6 +110,7 @@
 # size=26
 # font=<primary font>
 # color=<foreground color>
+# hide-when-typing=no
 # border-width=0
 # border-color=<csd.color>
 # button-width=26

tests/test-config.c

@@ -666,6 +666,8 @@ test_section_csd(void)
                &conf.csd.color.maximize);
     test_color(&ctx, &parse_section_csd, "button-close-color", true,
                &conf.csd.color.quit);
+    test_boolean(&ctx, &parse_section_csd, "hide-when-maximized",
+                 &conf.csd.hide_when_maximized);
 
     /* TODO: verify the ‘set’ bit is actually set for colors */
     /* TODO: font */

wayland.c

@@ -1768,7 +1768,8 @@ bool
 wayl_win_csd_titlebar_visible(const struct wl_window *win)
 {
     return win->csd_mode == CSD_YES &&
-        !win->is_fullscreen;
+        !win->is_fullscreen &&
+        !(win->is_maximized && win->term->conf->csd.hide_when_maximized);
 }
 
 bool