Viewer: Send horizontal scroll wheel events

On macOS and Windows, these are communicated to applications as vertical
scroll wheel events with the Shift key held down.  (The operating system
acts as if the Shift key is held down, but no Shift key press/release
events are actually fired.)  We use RFB Buttons 6 and 7 for,
respectively, left and right scroll wheel events, since X11 Buttons 6
and 7 are used for the same purpose.  (Thus, implementing this feature
in the TurboVNC Server simply required incrementing the loop limit in
PtrAddEvent().)  Java doesn't need to use Java Buttons 4 and 5 for
vertical scroll wheel events, since those events have a separate
subclass.  Thus, X11 Buttons 6 and 7 map to Java Buttons 4 and 5, and we
simply map Java Buttons 4 and 5 to RFB Buttons 6 and 7 in order to
implement horizontal scrolling for X11 clients.

Server and macOS/Windows viewer implementation based on:
rsparlin@77e266d

Closes #416

ChangeLog.md

@@ -12,6 +12,10 @@ if all viewer connections originate from the loopback IP address.)  The
 TurboVNC Server now also logs the total number of simultaneously connected
 viewers.
 
+2. The TurboVNC Viewer now sends horizontal scroll wheel events to the VNC
+server.  (These events can be generated with horizontal scroll gestures on a
+trackpad or, with certain mice, by side-clicking the scroll wheel.)
+
 
 3.1.1
 =====

java/com/turbovnc/rfb/RFB.java

@@ -337,6 +337,8 @@ public static String encodingName(int num) {
   public static final int BUTTON3_MASK = 4;
   public static final int BUTTON4_MASK = 8;
   public static final int BUTTON5_MASK = 16;
+  public static final int BUTTON6_MASK = 32;
+  public static final int BUTTON7_MASK = 64;
 
   //***************************************************************************
   // GII

java/com/turbovnc/vncviewer/CConn.java

@@ -2825,11 +2825,20 @@ public void writePointerEvent(MouseEvent ev) {
             buttonMask |= RFB.BUTTON2_MASK;  break;
           case 3:
             buttonMask |= RFB.BUTTON3_MASK;  break;
+          case 4:
+            // X11 uses Buttons 6 and 7 for (respectively) left and right
+            // scroll wheel events, but Java/X11 uses Buttons 4 and 5.
+            if (!Utils.isX11()) return;
+            buttonMask |= RFB.BUTTON6_MASK;  break;
+          case 5:
+            if (!Utils.isX11()) return;
+            buttonMask |= RFB.BUTTON7_MASK;  break;
           default:
             return;
         }
-        vlog.debug("mouse PRESS, button " + ev.getButton() +
-                   ", coords " + ev.getX() + "," + ev.getY());
+        if (ev.getButton() <= 3)
+          vlog.debug("mouse PRESS, button " + ev.getButton() +
+                     ", coords " + ev.getX() + "," + ev.getY());
         break;
       case MouseEvent.MOUSE_RELEASED:
         switch (ev.getButton()) {
@@ -2839,11 +2848,18 @@ public void writePointerEvent(MouseEvent ev) {
             buttonMask &= ~RFB.BUTTON2_MASK;  break;
           case 3:
             buttonMask &= ~RFB.BUTTON3_MASK;  break;
+          case 4:
+            if (!Utils.isX11()) return;
+            buttonMask &= ~RFB.BUTTON6_MASK;  break;
+          case 5:
+            if (!Utils.isX11()) return;
+            buttonMask &= ~RFB.BUTTON7_MASK;  break;
           default:
             return;
         }
-        vlog.debug("mouse release, button " + ev.getButton() +
-                   ", coords " + ev.getX() + "," + ev.getY());
+        if (ev.getButton() <= 3)
+          vlog.debug("mouse release, button " + ev.getButton() +
+                     ", coords " + ev.getX() + "," + ev.getY());
         break;
     }
 
@@ -2881,10 +2897,20 @@ public void writeWheelEvent(MouseWheelEvent ev) {
     if (params.reverseScroll.get()) {
       clicks = -clicks;
     }
+    // On macOS and Windows, horizontal scroll wheel events are simply vertical
+    // scroll wheel events with the Shift key held down.  (The operating system
+    // acts as if the Shift key is held down, but no Shift key press/release
+    // events are actually fired.)
+    boolean isHorizontal =
+      (Utils.isMac() || Utils.isWindows()) && ev.isShiftDown();
+    // X11 uses Buttons 4, 5, 6, and 7 for (respectively) up, down, left, and
+    // right scroll wheel events.
     if (clicks < 0) {
-      wheelMask = buttonMask | RFB.BUTTON4_MASK;
+      wheelMask = buttonMask |
+                  (isHorizontal ? RFB.BUTTON6_MASK : RFB.BUTTON4_MASK);
     } else {
-      wheelMask = buttonMask | RFB.BUTTON5_MASK;
+      wheelMask = buttonMask |
+                  (isHorizontal ? RFB.BUTTON7_MASK : RFB.BUTTON5_MASK);
     }
 
     if (cp.width != desktop.scaledWidth ||

unix/Xvnc/programs/Xserver/hw/vnc/kbdptr.c

@@ -529,7 +529,7 @@ void PtrAddEvent(int buttonMask, int x, int y, rfbClientPtr cl)
     cursorPosY = y;
   }
 
-  for (i = 0; i < 5; i++) {
+  for (i = 0; i < 7; i++) {
     if ((buttonMask ^ oldButtonMask) & (1 << i)) {
       if (buttonMask & (1 << i)) {
         valuator_mask_set_range(&mask, 0, 0, NULL);