Differentiate fused and unfused external styluses
An external stylus can be "fused" with touch data if it reports
pointer-specific data independently from the touch device. The only such
data we currently support is pressure. Thus, a fused external stylus
will reports pressure data.
If a fused stylus is connected, we withold all touches for up to 72
milliseconds to wait for pressure data from the stylus. If we get
pressure data within this time, we assume that the first pointer that
went down is actually the stylus, and fuse the pressure information from
the stylus to the pointer.
If an external stylus does not report pressure, it is an "unfused"
stylus.
When such an external stylus is connected, we don't withold any touches.
We still report button presses from these styluses through the touch
device.
DD: go/android-stylus-buttons
Bug: 246394583
Test: atest inputflinger_tests
Change-Id: I3d687a10630019756170e7e5e5f5d1902eb96e36
diff --git a/services/inputflinger/reader/mapper/TouchInputMapper.h b/services/inputflinger/reader/mapper/TouchInputMapper.h
index d2faf3f..85af1f7 100644
--- a/services/inputflinger/reader/mapper/TouchInputMapper.h
+++ b/services/inputflinger/reader/mapper/TouchInputMapper.h
@@ -795,6 +795,8 @@
[[nodiscard]] std::list<NotifyArgs> abortPointerSimple(nsecs_t when, nsecs_t readTime,
uint32_t policyFlags);
+ // Attempts to assign a pointer id to the external stylus. Returns true if the state should be
+ // withheld from further processing while waiting for data from the stylus.
bool assignExternalStylusId(const RawState& state, bool timeout);
void applyExternalStylusButtonState(nsecs_t when);
void applyExternalStylusTouchState(nsecs_t when);