Add libinput_device_has_button function

In some cases the compositor will want to know which buttons a device has.

E.g. for scrolling we want the compositor to be able to set a button to change
a relative device (e.g. a trackball) into scroll mode, so that it sends
scroll-axis events instead of pointer motion events.

In order for the compositor to be able to present a sane UI for this, it needs
to know which buttons a device has.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/evdev.c

@@ -1491,6 +1491,15 @@ evdev_device_get_size(struct evdev_device *device,
 	return 0;
 }
 
+int
+evdev_device_has_button(struct evdev_device *device, uint32_t code)
+{
+	if (!(device->seat_caps & EVDEV_DEVICE_POINTER))
+		return -1;
+
+	return libevdev_has_event_code(device->evdev, EV_KEY, code);
+}
+
 static inline bool
 evdev_is_scrolling(const struct evdev_device *device,
 		   enum libinput_pointer_axis axis)

src/evdev.h

@@ -239,6 +239,9 @@ evdev_device_get_size(struct evdev_device *device,
 		      double *w,
 		      double *h);
 
+int
+evdev_device_has_button(struct evdev_device *device, uint32_t code);
+
 double
 evdev_device_transform_x(struct evdev_device *device,
 			 double x,

src/libinput.c

@@ -1254,6 +1254,12 @@ libinput_device_get_size(struct libinput_device *device,
 				     height);
 }
 
+LIBINPUT_EXPORT int
+libinput_device_has_button(struct libinput_device *device, uint32_t code)
+{
+	return evdev_device_has_button((struct evdev_device *)device, code);
+}
+
 LIBINPUT_EXPORT struct libinput_event *
 libinput_event_device_notify_get_base_event(struct libinput_event_device_notify *event)
 {

src/libinput.h

@@ -1440,6 +1440,20 @@ libinput_device_get_size(struct libinput_device *device,
 			 double *width,
 			 double *height);
 
+/**
+ * @ingroup device
+ *
+ * Check if a @ref LIBINPUT_DEVICE_CAP_POINTER device has a button with the
+ * passed in code (see linux/input.h).
+ *
+ * @param device A current input device
+ * @param code button code to check for
+ *
+ * @return 1 if the device supports this button code, 0 if it does not, -1
+ * on error.
+ */
+int
+libinput_device_has_button(struct libinput_device *device, uint32_t code);
 
 /**
  * @defgroup config Device configuration