desktop-shell: add option to avoid creating the panel

This option is so we can disable showing any panel at all. The default
is to continue showing the panel and no example is added to weston.ini
because it's an uncommon request.

Tested-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

clients/desktop-shell.c

@@ -1130,7 +1130,8 @@ static void
 output_destroy(struct output *output)
 {
 	background_destroy(output->background);
-	panel_destroy(output->panel);
+	if (output->panel)
+		panel_destroy(output->panel);
 	wl_output_destroy(output->output);
 	wl_list_remove(&output->link);
 
@@ -1160,7 +1161,8 @@ output_handle_geometry(void *data,
 {
 	struct output *output = data;
 
-	window_set_buffer_transform(output->panel->window, transform);
+	if (output->panel)
+		window_set_buffer_transform(output->panel->window, transform);
 	window_set_buffer_transform(output->background->window, transform);
 }
 
@@ -1187,7 +1189,8 @@ output_handle_scale(void *data,
 {
 	struct output *output = data;
 
-	window_set_buffer_scale(output->panel->window, scale);
+	if (output->panel)
+		window_set_buffer_scale(output->panel->window, scale);
 	window_set_buffer_scale(output->background->window, scale);
 }
 
@@ -1198,15 +1201,36 @@ static const struct wl_output_listener output_listener = {
 	output_handle_scale
 };
 
+static int
+want_panel(struct desktop *desktop)
+{
+	struct weston_config_section *s;
+	char *location = NULL;
+	int ret = 1;
+
+	s = weston_config_get_section(desktop->config, "shell", NULL, NULL);
+	weston_config_section_get_string(s, "panel-location",
+					 &location, "top");
+
+	if (strcmp(location, "top") != 0)
+		ret = 0;
+
+	free(location);
+
+	return ret;
+}
+
 static void
 output_init(struct output *output, struct desktop *desktop)
 {
 	struct wl_surface *surface;
 
-	output->panel = panel_create(desktop);
+	if (want_panel(desktop)) {
-	surface = window_get_wl_surface(output->panel->window);
+		output->panel = panel_create(desktop);
-	desktop_shell_set_panel(desktop->shell,
+		surface = window_get_wl_surface(output->panel->window);
-				output->output, surface);
+		desktop_shell_set_panel(desktop->shell,
+					output->output, surface);
+	}
 
 	output->background = background_create(desktop);
 	surface = window_get_wl_surface(output->background->window);

man/weston.ini.man

@@ -186,6 +186,11 @@ digit pairs are in order transparency, red, green, and blue. Examples:
 .fi
 .RE
 .TP 7
+.BI "panel-location=" top
+sets the location of the panel (string). Can be
+.B top,
+.B none.
+.TP 7
 .BI "locking=" true
 enables screen locking (boolean).
 .TP 7