SOURCE_STYLUS
The input source is a stylus pointing device.
Note that this bit merely indicates that an input device is capable of obtaining input from a stylus. To determine whether a given touch event was produced by a stylus, examine the tool type returned by getToolType for each individual pointer.
A single touch event may multiple pointers with different tool types, such as an event that has one pointer with tool type TOOL_TYPE_FINGER and another pointer with tool type TOOL_TYPE_STYLUS. So it is important to examine the tool type of each pointer, regardless of the source reported by getSource.