tablet: if a serial comes in late, discard it

If a tool starts reporting with serial 0 and later updates to a real serial,
discard that serial and keep reporting as serial 0. We cannot really change
the tool after proximity in as we don't know when callers query for the serial
(well, we could know but any well-written caller will ask for the serial on
the proximity in event, so what's the point).

Thus if we do get a serial in and the matching tool, check if we have a tool
with the serial 0 already. If so, re-use that. This means we lose correct tool
tracking on such tablets but so far these seem to only be on devices where the
use of multiple tools is unlikely.

https://bugs.freedesktop.org/show_bug.cgi?id=97526

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>

2 files changed, 106 insertions, 7 deletions

diff --git a/src/evdev-tablet.c b/src/evdev-tablet.c
index 3ddb543..254d669 100644
--- a/src/evdev-tablet.c
+++ b/src/evdev-tablet.c
@@ -900,13 +900,12 @@ tablet_get_tool(struct tablet_dispatch *tablet,
 		uint32_t tool_id,
 		uint32_t serial)
 {
+	struct libinput *libinput = tablet_libinput_context(tablet);
 	struct libinput_tablet_tool *tool = NULL, *t;
 	struct list *tool_list;
 
 	if (serial) {
-		struct libinput *libinput = tablet_libinput_context(tablet);
 		tool_list = &libinput->tool_list;
-
 		/* Check if we already have the tool in our list of tools */
 		list_for_each(t, tool_list, link) {
 			if (type == t->type && serial == t->serial) {
@@ -914,20 +913,32 @@ tablet_get_tool(struct tablet_dispatch *tablet,
 				break;
 			}
 		}
-	} else {
+	}
+
+	/* If we get a tool with a delayed serial number, we already created
+	 * a 0-serial number tool for it earlier. Re-use that, even though
+	 * it means we can't distinguish this tool from others.
+	 * https://bugs.freedesktop.org/show_bug.cgi?id=97526
+	 */
+	if (!tool) {
+		tool_list = &tablet->tool_list;
 		/* We can't guarantee that tools without serial numbers are
 		 * unique, so we keep them local to the tablet that they come
 		 * into proximity of instead of storing them in the global tool
-		 * list */
-		tool_list = &tablet->tool_list;
-
-		/* Same as above, but don't bother checking the serial number */
+		 * list
+		 * Same as above, but don't bother checking the serial number
+		 */
 		list_for_each(t, tool_list, link) {
 			if (type == t->type) {
 				tool = t;
 				break;
 			}
 		}
+
+		/* Didn't find the tool but we have a serial. Switch
+		 * tool_list back so we create in the correct list */
+		if (!tool && serial)
+			tool_list = &libinput->tool_list;
 	}
 
 	/* If we didn't already have the new_tool in our list of tools,
diff --git a/test/tablet.c b/test/tablet.c
index 8575669..30588a4 100644
--- a/test/tablet.c
+++ b/test/tablet.c
@@ -2153,6 +2153,93 @@ START_TEST(tools_without_serials)
 }
 END_TEST
 
+START_TEST(tool_delayed_serial)
+{
+	struct litest_device *dev = litest_current_device();
+	struct libinput *li = dev->libinput;
+	struct libinput_event *event;
+	struct libinput_event_tablet_tool *tev;
+	struct libinput_tablet_tool *tool;
+	unsigned int serial;
+
+	litest_drain_events(li);
+
+	litest_event(dev, EV_ABS, ABS_X, 4500);
+	litest_event(dev, EV_ABS, ABS_Y, 2000);
+	litest_event(dev, EV_MSC, MSC_SERIAL, 0);
+	litest_event(dev, EV_KEY, BTN_TOOL_PEN, 1);
+	litest_event(dev, EV_SYN, SYN_REPORT, 0);
+	libinput_dispatch(li);
+
+	event = libinput_get_event(li);
+	tev = litest_is_tablet_event(event,
+				     LIBINPUT_EVENT_TABLET_TOOL_PROXIMITY);
+	tool = libinput_event_tablet_tool_get_tool(tev);
+	serial = libinput_tablet_tool_get_serial(tool);
+	ck_assert_int_eq(serial, 0);
+	libinput_event_destroy(event);
+
+	for (int x = 4500; x < 8000; x += 1000) {
+		litest_event(dev, EV_ABS, ABS_X, x);
+		litest_event(dev, EV_ABS, ABS_Y, 2000);
+		litest_event(dev, EV_MSC, MSC_SERIAL, 0);
+		litest_event(dev, EV_SYN, SYN_REPORT, 0);
+		libinput_dispatch(li);
+	}
+	litest_drain_events(li);
+
+	/* Now send the serial */
+	litest_event(dev, EV_ABS, ABS_X, 4500);
+	litest_event(dev, EV_ABS, ABS_Y, 2000);
+	litest_event(dev, EV_MSC, MSC_SERIAL, 1234566);
+	litest_event(dev, EV_SYN, SYN_REPORT, 0);
+	libinput_dispatch(li);
+
+	event = libinput_get_event(li);
+	tev = litest_is_tablet_event(event,
+				     LIBINPUT_EVENT_TABLET_TOOL_AXIS);
+	tool = libinput_event_tablet_tool_get_tool(tev);
+	serial = libinput_tablet_tool_get_serial(tool);
+	ck_assert_int_eq(serial, 0);
+	libinput_event_destroy(event);
+
+	for (int x = 4500; x < 8000; x += 500) {
+		litest_event(dev, EV_ABS, ABS_X, x);
+		litest_event(dev, EV_ABS, ABS_Y, 2000);
+		litest_event(dev, EV_MSC, MSC_SERIAL, 1234566);
+		litest_event(dev, EV_SYN, SYN_REPORT, 0);
+		libinput_dispatch(li);
+	}
+
+	event = libinput_get_event(li);
+	do {
+		tev = litest_is_tablet_event(event,
+					     LIBINPUT_EVENT_TABLET_TOOL_AXIS);
+		tool = libinput_event_tablet_tool_get_tool(tev);
+		serial = libinput_tablet_tool_get_serial(tool);
+		ck_assert_int_eq(serial, 0);
+		libinput_event_destroy(event);
+		event = libinput_get_event(li);
+	} while (event != NULL);
+
+	/* Quirk: tool out event is a serial of 0 */
+	litest_event(dev, EV_ABS, ABS_X, 4500);
+	litest_event(dev, EV_ABS, ABS_Y, 2000);
+	litest_event(dev, EV_MSC, MSC_SERIAL, 0);
+	litest_event(dev, EV_KEY, BTN_TOOL_PEN, 0);
+	litest_event(dev, EV_SYN, SYN_REPORT, 0);
+	libinput_dispatch(li);
+
+	event = libinput_get_event(li);
+	tev = litest_is_tablet_event(event,
+				     LIBINPUT_EVENT_TABLET_TOOL_PROXIMITY);
+	tool = libinput_event_tablet_tool_get_tool(tev);
+	serial = libinput_tablet_tool_get_serial(tool);
+	ck_assert_int_eq(serial, 0);
+	libinput_event_destroy(event);
+}
+END_TEST
+
 START_TEST(tool_capabilities)
 {
 	struct libinput *li = litest_create_context();
@@ -3692,6 +3779,7 @@ litest_setup_tests_tablet(void)
 	litest_add("tablet:tool_serial", invalid_serials, LITEST_TABLET | LITEST_TOOL_SERIAL, LITEST_ANY);
 	litest_add_no_device("tablet:tool_serial", tools_with_serials);
 	litest_add_no_device("tablet:tool_serial", tools_without_serials);
+	litest_add_for_device("tablet:tool_serial", tool_delayed_serial, LITEST_WACOM_HID4800_PEN);
 	litest_add("tablet:proximity", proximity_out_clear_buttons, LITEST_TABLET, LITEST_ANY);
 	litest_add("tablet:proximity", proximity_in_out, LITEST_TABLET, LITEST_ANY);
 	litest_add("tablet:proximity", proximity_in_button_down, LITEST_TABLET, LITEST_ANY);