fix: decode the Guide button bit in decodeXInput360 (XInput-360 family)

CHANGELOG.md

@@ -7,6 +7,16 @@ computer. Those lines say "update Satellite too".
 
 ---
 
+## [Unreleased]
+
+### Fixed
+
+- The Xbox/Guide button on XInput-style wired USB controllers (Xbox 360
+  and its many licensed clones, plus the Amazon Luna Controller) now
+  works. Before this fix, pressing it did nothing.
+
+---
+
 ## [1.1.1] - 2026-08-17
 
 ### Fixed

app/src/main/cpp/usb_parsers.cpp

@@ -720,6 +720,7 @@ bool decodeXInput360(const uint8_t* buf, size_t len, DeviceState& s) {
     if (buf[2] & 0x80) b |= XUSB_THUMB_R;
     if (buf[3] & 0x01) b |= XUSB_LB;
     if (buf[3] & 0x02) b |= XUSB_RB;
+    if (buf[3] & 0x04) b |= XUSB_GUIDE;
     if (buf[3] & 0x10) b |= XUSB_A;
     if (buf[3] & 0x20) b |= XUSB_B;
     if (buf[3] & 0x40) b |= XUSB_X;

app/src/test/cpp/usb_parsers_test.cpp

@@ -418,6 +418,16 @@ TEST(Decode, Xbox360WirelessDecodesLikeWired) {
     EXPECT_EQ(wired.sLX, wireless.sLX);
 }
 
+TEST(Decode, Xbox360WiredGuideButtonSetsGuideBit) {
+    std::vector<uint8_t> r(14, 0);
+    r[0] = 0x00;
+    r[3] = 0x04; // Guide (same bit the Amazon Luna Controller's center button reports)
+    DeviceState s;
+    ParserState p;
+    ASSERT_TRUE(decodeReport(Parser::XINPUT_360, r.data(), r.size(), s, &p));
+    EXPECT_TRUE(s.wButtons & XUSB_GUIDE);
+}
+
 TEST(Rumble, Xbox360WirelessWrapsFrame) {
     uint8_t out[64];
     size_t n = buildRumbleReport(Parser::XINPUT_360_WIRELESS, 0xFF00, 0x8000, 7, out, sizeof(out));