Support multiple outputs

Outputs are arranged in a horizontal layout in the order they are
created in by wlroots. Maximized xdg_shell views will span all outputs,
like the global fullscreen mode in sway.

Fixes #87

cage.c

@@ -220,6 +220,7 @@ main(int argc, char *argv[])
 	wlr_renderer_init_wl_display(renderer, server.wl_display);
 
 	wl_list_init(&server.views);
+	wl_list_init(&server.outputs);
 
 	server.output_layout = wlr_output_layout_create();
 	if (!server.output_layout) {

output.c

@@ -319,12 +319,20 @@ output_destroy(struct cg_output *output)
 	wl_list_remove(&output->transform.link);
 	wl_list_remove(&output->damage_frame.link);
 	wl_list_remove(&output->damage_destroy.link);
-	free(output);
-	server->output = NULL;
+	wl_list_remove(&output->link);
 
-	/* Since there is no use in continuing without our (single)
-	 * output, terminate. */
-	wl_display_terminate(server->wl_display);
+	wlr_output_layout_remove(server->output_layout, output->wlr_output);
+
+	struct cg_view *view;
+	wl_list_for_each(view, &output->server->views, link) {
+		view_position(view);
+	}
+
+	free(output);
+
+	if (wl_list_empty(&server->outputs)) {
+		wl_display_terminate(server->wl_display);
+	}
 }
 
 static void
@@ -354,29 +362,32 @@ handle_new_output(struct wl_listener *listener, void *data)
 		wlr_output_set_mode(wlr_output, preferred_mode);
 	}
 
-	server->output = calloc(1, sizeof(struct cg_output));
-	server->output->wlr_output = wlr_output;
-	server->output->server = server;
-	server->output->damage = wlr_output_damage_create(wlr_output);
+	struct cg_output *output = calloc(1, sizeof(struct cg_output));
+	output->wlr_output = wlr_output;
+	output->server = server;
+	output->damage = wlr_output_damage_create(wlr_output);
+	wl_list_insert(&server->outputs, &output->link);
 
-	server->output->mode.notify = handle_output_mode;
-	wl_signal_add(&wlr_output->events.mode, &server->output->mode);
-	server->output->transform.notify = handle_output_transform;
-	wl_signal_add(&wlr_output->events.transform, &server->output->transform);
-	server->output->destroy.notify = handle_output_destroy;
-	wl_signal_add(&wlr_output->events.destroy, &server->output->destroy);
-	server->output->damage_frame.notify = handle_output_damage_frame;
-	wl_signal_add(&server->output->damage->events.frame, &server->output->damage_frame);
-	server->output->damage_destroy.notify = handle_output_damage_destroy;
-	wl_signal_add(&server->output->damage->events.destroy, &server->output->damage_destroy);
+	output->mode.notify = handle_output_mode;
+	wl_signal_add(&wlr_output->events.mode, &output->mode);
+	output->transform.notify = handle_output_transform;
+	wl_signal_add(&wlr_output->events.transform, &output->transform);
+	output->destroy.notify = handle_output_destroy;
+	wl_signal_add(&wlr_output->events.destroy, &output->destroy);
+	output->damage_frame.notify = handle_output_damage_frame;
+	wl_signal_add(&output->damage->events.frame, &output->damage_frame);
+	output->damage_destroy.notify = handle_output_damage_destroy;
+	wl_signal_add(&output->damage->events.destroy, &output->damage_destroy);
+
+	struct cg_view *view;
+	wl_list_for_each(view, &output->server->views, link) {
+		view_position(view);
+	}
 
 	wlr_output_set_transform(wlr_output, server->output_transform);
 
 	wlr_output_layout_add_auto(server->output_layout, wlr_output);
 
-	/* Disconnect the signal now, because we only use one static output. */
-	wl_list_remove(&server->new_output.link);
-
 	if (wlr_xcursor_manager_load(server->seat->xcursor_manager, wlr_output->scale)) {
 		wlr_log(WLR_ERROR, "Cannot load XCursor theme for output '%s' with scale %f",
 			wlr_output->name,
@@ -385,7 +396,7 @@ handle_new_output(struct wl_listener *listener, void *data)
 
 	/* Place the cursor in the center of the screen. */
 	wlr_cursor_warp(server->seat->cursor, NULL, wlr_output->width / 2, wlr_output->height / 2);
-	wlr_output_damage_add_whole(server->output->damage);
+	wlr_output_damage_add_whole(output->damage);
 }
 
 void

output.h

@@ -19,6 +19,8 @@ struct cg_output {
 	struct wl_listener destroy;
 	struct wl_listener damage_frame;
 	struct wl_listener damage_destroy;
+
+	struct wl_list link;
 };
 
 void handle_new_output(struct wl_listener *listener, void *data);

seat.c

@@ -158,7 +158,15 @@ handle_new_touch(struct cg_seat *seat, struct wlr_input_device *device)
 	touch->destroy.notify = handle_touch_destroy;
 	wl_signal_add(&touch->device->events.destroy, &touch->destroy);
 
-	wlr_cursor_map_input_to_output(seat->cursor, device, seat->server->output->wlr_output);
+	if (device->output_name != NULL) {
+		struct cg_output *output;
+		wl_list_for_each(output, &seat->server->outputs, link) {
+			if (strcmp(device->output_name, output->wlr_output->name) == 0) {
+				wlr_cursor_map_input_to_output(seat->cursor, device, output->wlr_output);
+				break;
+			}
+		}
+	}
 }
 
 static void
@@ -192,7 +200,15 @@ handle_new_pointer(struct cg_seat *seat, struct wlr_input_device *device)
 	pointer->destroy.notify = handle_pointer_destroy;
 	wl_signal_add(&device->events.destroy, &pointer->destroy);
 
-	wlr_cursor_map_input_to_output(seat->cursor, device, seat->server->output->wlr_output);
+	if (device->output_name != NULL) {
+		struct cg_output *output;
+		wl_list_for_each(output, &seat->server->outputs, link) {
+			if (strcmp(device->output_name, output->wlr_output->name) == 0) {
+				wlr_cursor_map_input_to_output(seat->cursor, device, output->wlr_output);
+				break;
+			}
+		}
+	}
 }
 
 static void
@@ -568,7 +584,10 @@ handle_cursor_motion(struct wl_listener *listener, void *data)
 static void
 drag_icon_damage(struct cg_drag_icon *drag_icon)
 {
-	output_damage_drag_icon(drag_icon->seat->server->output, drag_icon);
+	struct cg_output *output;
+	wl_list_for_each(output, &drag_icon->seat->server->outputs, link) {
+		output_damage_drag_icon(output, drag_icon);
+	}
 }
 
 static void
@@ -835,7 +854,10 @@ seat_set_focus(struct cg_seat *seat, struct cg_view *view)
 
 	view_activate(view, true);
 	char *title = view_get_title(view);
-	output_set_window_title(server->output, title);
+	struct cg_output *output;
+	wl_list_for_each(output, &server->outputs, link) {
+		output_set_window_title(output, title);
+	}
 	free(title);
 
 	struct wlr_keyboard *keyboard = wlr_seat_get_keyboard(wlr_seat);

server.h

@@ -29,7 +29,7 @@ struct cg_server {
 	struct wl_list inhibitors;
 
 	struct wlr_output_layout *output_layout;
-	struct cg_output *output;
+	struct wl_list outputs;
 	struct wl_listener new_output;
 
 	struct wl_listener xdg_toplevel_decoration;

view.c

@@ -138,13 +138,19 @@ view_is_transient_for(struct cg_view *child, struct cg_view *parent) {
 void
 view_damage_surface(struct cg_view *view)
 {
-	output_damage_view_surface(view->server->output, view);
+	struct cg_output *output;
+	wl_list_for_each(output, &view->server->outputs, link) {
+		output_damage_view_surface(output, view);
+	}
 }
 
 void
 view_damage_whole(struct cg_view *view)
 {
-	output_damage_view_whole(view->server->output, view);
+	struct cg_output *output;
+	wl_list_for_each(output, &view->server->outputs, link) {
+		output_damage_view_whole(output, view);
+	}
 }
 
 void
@@ -153,23 +159,35 @@ view_activate(struct cg_view *view, bool activate)
 	view->impl->activate(view, activate);
 }
 
+static void
+get_view_output_dimensions(struct cg_view *view, int *output_width, int *output_height)
+{
+	*output_width = 0;
+	*output_height = 0;
+	struct cg_output *output;
+	wl_list_for_each(output, &view->server->outputs, link) {
+		int h, w;
+		wlr_output_transformed_resolution(output->wlr_output, &w, &h);
+		*output_width += w;
+		if (h > *output_height) {
+			*output_height = h;
+		}
+	}
+}
+
 static void
 view_maximize(struct cg_view *view)
 {
-	struct cg_output *output = view->server->output;
 	int output_width, output_height;
-
-	wlr_output_transformed_resolution(output->wlr_output, &output_width, &output_height);
+	get_view_output_dimensions(view, &output_width, &output_height);
 	view->impl->maximize(view, output_width, output_height);
 }
 
 static void
 view_center(struct cg_view *view)
 {
-	struct wlr_output *output = view->server->output->wlr_output;
-
 	int output_width, output_height;
-	wlr_output_transformed_resolution(output, &output_width, &output_height);
+	get_view_output_dimensions(view, &output_width, &output_height);
 
 	int width, height;
 	view->impl->get_geometry(view, &width, &height);

xdg_shell.c

@@ -93,10 +93,12 @@ static void
 popup_unconstrain(struct cg_xdg_popup *popup)
 {
 	struct cg_view *view = popup->view_child.view;
-	struct wlr_output *output = view->server->output->wlr_output;
-	struct wlr_output_layout *output_layout = view->server->output_layout;
+	struct cg_server *server = view->server;
+	struct wlr_box *popup_box = &popup->wlr_popup->geometry;
 
-	struct wlr_box *output_box = wlr_output_layout_get_box(output_layout, output);
+	struct wlr_output_layout *output_layout = server->output_layout;
+	struct wlr_output *wlr_output = wlr_output_layout_output_at(output_layout, view->x + popup_box->x, view->y + popup_box->y);
+	struct wlr_box *output_box = wlr_output_layout_get_box(output_layout, wlr_output);
 
 	struct wlr_box output_toplevel_box = {
 		.x = output_box->x - view->x,