controller: merge stick and sensor events into the newest unread pad sample

src/libs/controller.cpp

@@ -519,7 +519,20 @@ void GameController::SetDevices(int active_id) {
 	m_trigger_state      = {};
 }
 
+// Input that changes no button or touch contact updates the newest unread sample, so a burst of
+// stick or sensor events between two reads cannot push unread button or touch changes out.
 void GameController::AddState() {
+	if (m_states_num != 0) {
+		const auto newest = (m_first_state + m_states_num - 1) % STATES_MAX;
+		auto&      last   = m_states[newest];
+		if (!m_obtained[newest] && last.buttons == m_state.buttons &&
+		    last.touch[0].down == m_state.touch[0].down &&
+		    last.touch[1].down == m_state.touch[1].down) {
+			last = m_state;
+			return;
+		}
+	}
+
 	if (m_states_num >= STATES_MAX) {
 		m_states_num  = STATES_MAX - 1;
 		m_first_state = (m_first_state + 1) % STATES_MAX;

tests/ControllerSettingsTests.cpp

@@ -689,6 +689,27 @@ void TestTriggerEffectState() {
 	check_state(0, 0, "switching controllers retained effect states");
 }
 
+void TestUnreadPressSurvivesStickBurst() {
+	Controller              controller;
+	std::array<PadData, 64> data {};
+	SetButton(1, PAD_BUTTON_CROSS, true);
+	for (int value = 0; value < 100; value++) {
+		SetAxis(1, Axis::LeftX, value);
+	}
+	SetButton(1, PAD_BUTTON_CROSS, false);
+	for (int value = 100; value < 200; value++) {
+		SetAxis(1, Axis::LeftX, value);
+	}
+	Check(PadRead(1, data.data(), 64) == 2 && data[0].buttons == PAD_BUTTON_CROSS &&
+	          data[0].left_stick_x == 99 && data[1].buttons == 0 && data[1].left_stick_x == 199,
+	      "a stick burst pushed an unread press out of the pad history");
+	SetAxis(1, Axis::LeftX, 50);
+	SetButton(1, PAD_BUTTON_CROSS, true);
+	Check(PadRead(1, data.data(), 64) == 2 && data[0].buttons == 0 &&
+	          data[0].left_stick_x == 50 && data[1].buttons == PAD_BUTTON_CROSS,
+	      "a stick move after a read did not add a sample");
+}
+
 } // namespace
 
 int main() {
@@ -702,6 +723,7 @@ int main() {
 	TestMaskedTriggersAndValidation();
 	TestIndependentOutputsAndPadSwitch();
 	TestTriggerEffectState();
+	TestUnreadPressSurvivesStickBurst();
 	TestMultiplayerRouting();
 	TestDedicatedKeyboardOutputs();
 	Config::Shutdown();