Implement horizontal scrolling protocol extension for Sunshine

src/Input.h

@@ -110,4 +110,10 @@ typedef struct _NV_SCROLL_PACKET {
     short zero3;
 } NV_SCROLL_PACKET, *PNV_SCROLL_PACKET;
 
+#define SS_HSCROLL_MAGIC 0x55000001
+typedef struct _SS_HSCROLL_PACKET {
+    NV_INPUT_HEADER header;
+    short scrollAmount;
+} SS_HSCROLL_PACKET, *PSS_HSCROLL_EVENT;
+
 #pragma pack(pop)

src/InputStream.c

@@ -44,6 +44,7 @@ typedef struct _PACKET_HOLDER {
         NV_CONTROLLER_PACKET controller;
         NV_MULTI_CONTROLLER_PACKET multiController;
         NV_SCROLL_PACKET scroll;
+        SS_HSCROLL_PACKET hscroll;
         NV_HAPTICS_PACKET haptics;
         NV_UNICODE_PACKET unicode;
     } packet;
@@ -949,3 +950,42 @@ int LiSendHighResScrollEvent(short scrollAmount) {
 int LiSendScrollEvent(signed char scrollClicks) {
     return LiSendHighResScrollEvent(scrollClicks * LI_WHEEL_DELTA);
 }
+
+// Send a high resolution horizontal scroll event
+int LiSendHighResHScrollEvent(short scrollAmount) {
+    PPACKET_HOLDER holder;
+    int err;
+
+    if (!initialized) {
+        return -2;
+    }
+
+    // This is a protocol extension only supported with Sunshine
+    if (!IS_SUNSHINE()) {
+        return -3;
+    }
+
+    if (scrollAmount == 0) {
+        return 0;
+    }
+
+    holder = allocatePacketHolder(0);
+    if (holder == NULL) {
+        return -1;
+    }
+
+    holder->packet.hscroll.header.size = BE32(sizeof(SS_HSCROLL_PACKET) - sizeof(uint32_t));
+    holder->packet.hscroll.header.magic = LE32(SS_HSCROLL_MAGIC);
+    holder->packet.hscroll.scrollAmount = BE16(scrollAmount);
+
+    err = LbqOfferQueueItem(&packetQueue, holder, &holder->entry);
+    if (err != LBQ_SUCCESS) {
+        LC_ASSERT(err == LBQ_BOUND_EXCEEDED);
+        Limelog("Input queue reached maximum size limit\n");
+        freePacketHolder(holder);
+    }
+}
+
+int LiSendHScrollEvent(signed char scrollClicks) {
+    return LiSendHighResHScrollEvent(scrollClicks * LI_WHEEL_DELTA);
+}

src/Limelight-internal.h

@@ -55,6 +55,8 @@ extern uint16_t VideoPortNumber;
      (AppVersionQuad[0] == (a) && AppVersionQuad[1] > (b)) ||                               \
      (AppVersionQuad[0] == (a) && AppVersionQuad[1] == (b) && AppVersionQuad[2] >= (c)))
 
+#define IS_SUNSHINE() (AppVersionQuad[3] == -1)
+
 #define UDP_RECV_POLL_TIMEOUT_MS 100
 
 // At this value or above, we will request high quality audio unless CAPABILITY_SLOW_OPUS_DECODER

src/Limelight.h

@@ -599,6 +599,12 @@ int LiSendScrollEvent(signed char scrollClicks);
 // scrolling (Apple Trackpads, Microsoft Precision Touchpads, etc.).
 int LiSendHighResScrollEvent(short scrollAmount);
 
+// These functions send horizontal scroll events to the host which are
+// analogous to LiSendScrollEvent() and LiSendHighResScrollEvent().
+// This is a Sunshine protocol extension.
+int LiSendHScrollEvent(signed char scrollClicks);
+int LiSendHighResHScrollEvent(short scrollAmount);
+
 // This function returns a time in milliseconds with an implementation-defined epoch.
 uint64_t LiGetMillis(void);