plugin: require plugins to enable the frame callback for a device

The vast majority of plugins are only interested in a single or a few
devices. Require that they enable the frame callback for those devices
and don't notify them for any other frames.

Give each plugin a unique index and use that for a bitmask to check if
the plugin wants events for a particular device. If not, skip it.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1229>

src/evdev-plugin.c

@@ -128,12 +128,20 @@ evdev_device_dispatch_one(struct libinput_plugin *plugin,
 	evdev_frame_reset(frame);
 }
 
+static void
+evdev_plugin_device_added(struct libinput_plugin *plugin,
+			  struct libinput_device *device)
+
+{
+	libinput_plugin_enable_device_event_frame(plugin, device, true);
+}
+
 static const struct libinput_plugin_interface interface = {
 	.run = NULL,
 	.destroy = NULL,
 	.device_new = NULL,
 	.device_ignored = NULL,
-	.device_added = NULL,
+	.device_added = evdev_plugin_device_added,
 	.device_removed = NULL,
 	.evdev_frame = evdev_device_dispatch_one,
 };

src/libinput-plugin-system.h

@@ -44,6 +44,8 @@ struct libinput_plugin_system {
 
 	struct list plugins;
 	struct list removed_plugins;
+
+	size_t next_plugin_index; /* sequential index of all plugins */
 };
 
 void

src/libinput-plugin-tablet-double-tool.c

@@ -328,6 +328,8 @@ double_tool_plugin_device_added(struct libinput_plugin *libinput_plugin,
 	if (!libinput_device_has_capability(device, LIBINPUT_DEVICE_CAP_TABLET_TOOL))
 		return;
 
+	libinput_plugin_enable_device_event_frame(libinput_plugin, device, true);
+
 	struct plugin_data *plugin = libinput_plugin_get_user_data(libinput_plugin);
 	struct plugin_device *pd = zalloc(sizeof(*pd));
 	pd->device = libinput_device_ref(device);

src/libinput-plugin-tablet-eraser-button.c

@@ -533,6 +533,8 @@ eraser_button_plugin_device_added(struct libinput_plugin *libinput_plugin,
 	if (!libinput_device_has_capability(device, LIBINPUT_DEVICE_CAP_TABLET_TOOL))
 		return;
 
+	libinput_plugin_enable_device_event_frame(libinput_plugin, device, true);
+
 	struct plugin_data *plugin = libinput_plugin_get_user_data(libinput_plugin);
 	struct plugin_device *pd = zalloc(sizeof(*pd));
 	pd->device = libinput_device_ref(device);

src/libinput-plugin-tablet-forced-tool.c

@@ -186,6 +186,8 @@ forced_tool_plugin_device_added(struct libinput_plugin *libinput_plugin,
 	if (!libinput_device_has_capability(device, LIBINPUT_DEVICE_CAP_TABLET_TOOL))
 		return;
 
+	libinput_plugin_enable_device_event_frame(libinput_plugin, device, true);
+
 	struct plugin_data *plugin = libinput_plugin_get_user_data(libinput_plugin);
 	struct plugin_device *pd = zalloc(sizeof(*pd));
 	pd->device = libinput_device_ref(device);

src/libinput-plugin-tablet-proximity-timer.c

@@ -251,6 +251,8 @@ proximity_timer_plugin_device_added(struct libinput_plugin *libinput_plugin,
 	if (!libinput_device_has_capability(device, LIBINPUT_DEVICE_CAP_TABLET_TOOL))
 		return;
 
+	libinput_plugin_enable_device_event_frame(libinput_plugin, device, true);
+
 	struct plugin_data *plugin = libinput_plugin_get_user_data(libinput_plugin);
 	struct plugin_device *pd = zalloc(sizeof(*pd));
 	pd->device = libinput_device_ref(device);

src/libinput-plugin.c

@@ -45,6 +45,7 @@
 
 struct libinput_plugin {
 	struct libinput *libinput;
+	size_t index; /* sequential index of all plugins */
 	char *name;
 	int refcount;
 	struct list link;
@@ -98,7 +99,7 @@ libinput_plugin_new(struct libinput *libinput,
 		    void *user_data)
 {
 	struct libinput_plugin *plugin = zalloc(sizeof(*plugin));
-
+	plugin->index = libinput->plugin_system.next_plugin_index++;
 	plugin->registered = true;
 	plugin->libinput = libinput;
 	plugin->refcount = 1;
@@ -107,6 +108,10 @@ libinput_plugin_new(struct libinput *libinput,
 	plugin->name = strdup(name);
 	list_init(&plugin->timers);
 
+	if (plugin->index >= 32) {
+		log_bug_libinput(libinput, "Too many plugins, maximum is 32\n");
+	}
+
 	libinput_plugin_system_register_plugin(&libinput->plugin_system, plugin);
 
 	return plugin;
@@ -178,6 +183,18 @@ libinput_plugin_get_context(struct libinput_plugin *plugin)
 	return plugin->libinput;
 }
 
+void
+libinput_plugin_enable_device_event_frame(struct libinput_plugin *plugin,
+					  struct libinput_device *device,
+					  bool enable)
+{
+	if (enable) {
+		bitmask_set_bit(&device->plugin_frame_callbacks, plugin->index);
+	} else {
+		bitmask_clear_bit(&device->plugin_frame_callbacks, plugin->index);
+	}
+}
+
 struct plugin_queued_event {
 	struct list link;
 	struct evdev_frame *frame; /* owns a ref */
@@ -589,6 +606,12 @@ plugin_system_notify_evdev_frame(struct libinput_plugin_system *system,
 			if (evdev_frame_get_time(event->frame) == 0)
 				evdev_frame_set_time(event->frame, frame_time);
 
+			if (!bitmask_bit_is_set(device->plugin_frame_callbacks,
+					       plugin->index)) {
+				list_remove(&event->link);
+				list_append(&next_events, &event->link);
+				continue;
+			}
 #ifdef EVENT_DEBUGGING
 			_autofree_ char *prefix = strdup_printf("plugin %-25s - %s:",
 								plugin->name,

src/libinput-plugin.h

@@ -154,6 +154,11 @@ libinput_plugin_unref(struct libinput_plugin *plugin);
 DEFINE_UNREF_CLEANUP_FUNC(libinput_plugin);
 #endif
 
+void
+libinput_plugin_enable_device_event_frame(struct libinput_plugin *plugin,
+					  struct libinput_device *device,
+					  bool enable);
+
 /**
  * Inject a new event frame from the given plugin. This
  * frame is treated as if it was just sent by the kernel's

src/libinput-private.h

@@ -495,6 +495,8 @@ struct libinput_device {
 	int refcount;
 	struct libinput_device_config config;
 
+	bitmask_t plugin_frame_callbacks;
+
 	void (*inject_evdev_frame)(struct libinput_device *device,
 				   struct evdev_frame *frame);
 };