keyboard: allow applying keyboard layout per window

Fixes #1076

It can be enabled with a config like

~/.config/labwc/rc.xml:
<keyboard layoutScope="window">

~/.config/labwc/environment:
XKB_DEFAULT_LAYOUT=de,us
XKB_DEFAULT_OPTIONS=grp:alt_shift_toggle,grp_led:scroll

With a configuration like this each window should now remember
the active keyboard layout when switching between windows.

By default, the keyboard layout keeps being a global state.

src/config/rcxml.c

@@ -735,6 +735,12 @@ entry(xmlNode *node, char *nodename, char *content)
 		rc.repeat_delay = atoi(content);
 	} else if (!strcasecmp(nodename, "numlock.keyboard")) {
 		set_bool(content, &rc.kb_numlock_enable);
+	} else if (!strcasecmp(nodename, "layoutScope.keyboard")) {
+		/*
+		 * This can be changed to an enum later on
+		 * if we decide to also support "application".
+		 */
+		rc.kb_layout_per_window = !strcasecmp(content, "window");
 	} else if (!strcasecmp(nodename, "screenEdgeStrength.resistance")) {
 		rc.screen_edge_strength = atoi(content);
 	} else if (!strcasecmp(nodename, "range.snapping")) {
@@ -953,6 +959,7 @@ rcxml_init(void)
 	rc.repeat_rate = 25;
 	rc.repeat_delay = 600;
 	rc.kb_numlock_enable = true;
+	rc.kb_layout_per_window = false;
 	rc.screen_edge_strength = 20;
 
 	rc.snap_edge_range = 1;

src/input/keyboard.c

@@ -84,6 +84,7 @@ keyboard_modifiers_notify(struct wl_listener *listener, void *data)
 			}
 		}
 	}
+	wlr_seat_set_keyboard(seat->seat, wlr_keyboard);
 	wlr_seat_keyboard_notify_modifiers(seat->seat, &wlr_keyboard->modifiers);
 }
 
@@ -485,7 +486,6 @@ keyboard_key_notify(struct wl_listener *listener, void *data)
 	struct seat *seat = keyboard->base.seat;
 	struct wlr_keyboard_key_event *event = data;
 	struct wlr_seat *wlr_seat = seat->seat;
-	struct wlr_keyboard *wlr_keyboard = keyboard->wlr_keyboard;
 	idle_manager_notify_activity(seat->seat);
 
 	/* any new press/release cancels current keybind repeat */
@@ -497,7 +497,7 @@ keyboard_key_notify(struct wl_listener *listener, void *data)
 			start_keybind_repeat(seat->server, keyboard, event);
 		}
 	} else {
-		wlr_seat_set_keyboard(wlr_seat, wlr_keyboard);
+		wlr_seat_set_keyboard(wlr_seat, keyboard->wlr_keyboard);
 		wlr_seat_keyboard_notify_key(wlr_seat, event->time_msec,
 			event->keycode, event->state);
 	}
@@ -530,6 +530,41 @@ keyboard_set_numlock(struct wlr_keyboard *keyboard)
 		keyboard->modifiers.latched, locked, keyboard->modifiers.group);
 }
 
+void
+keyboard_update_layout(struct seat *seat, xkb_layout_index_t layout)
+{
+	assert(seat);
+
+	struct input *input;
+	struct keyboard *keyboard;
+	struct wlr_keyboard *kb = NULL;
+
+	/* We are not using wlr_seat_get_keyboard() here because it might be a virtual one */
+	wl_list_for_each(input, &seat->inputs, link) {
+		if (input->wlr_input_device->type != WLR_INPUT_DEVICE_KEYBOARD) {
+			continue;
+		}
+		keyboard = (struct keyboard *)input;
+		if (keyboard->is_virtual) {
+			continue;
+		}
+		kb = keyboard->wlr_keyboard;
+		break;
+	}
+	if (!kb) {
+		wlr_log(WLR_INFO, "Restoring kb layout failed: no physical keyboard found");
+		return;
+	}
+	if (kb->modifiers.group == layout) {
+		return;
+	}
+
+	/* By updating a member of the keyboard group, all members of the group will get updated */
+	wlr_log(WLR_DEBUG, "Updating group layout to %u", layout);
+	wlr_keyboard_notify_modifiers(kb, kb->modifiers.depressed,
+		kb->modifiers.latched, kb->modifiers.locked, layout);
+}
+
 void
 keyboard_init(struct seat *seat)
 {

src/view.c

@@ -6,6 +6,7 @@
 #include "common/match.h"
 #include "common/mem.h"
 #include "common/scene-helpers.h"
+#include "input/keyboard.h"
 #include "labwc.h"
 #include "menu/menu.h"
 #include "regions.h"
@@ -266,6 +267,17 @@ view_set_activated(struct view *view, bool activated)
 		wlr_foreign_toplevel_handle_v1_set_activated(
 			view->toplevel.handle, activated);
 	}
+
+	if (rc.kb_layout_per_window) {
+		if (!activated) {
+			/* Store configured keyboard layout per view */
+			view->keyboard_layout =
+				view->server->seat.keyboard_group->keyboard.modifiers.group;
+		} else {
+			/* Switch to previously stored keyboard layout */
+			keyboard_update_layout(&view->server->seat, view->keyboard_layout);
+		}
+	}
 }
 
 void