Add support for notifying clients about pointer movements

This change adds support for the VMware Mouse Position
pseudo-encoding[1], which is used to notify VNC clients when X11 clients
call `XWarpPointer()`[2]. This function is called by SDL (and other
similar libraries)  when they detect that the server does not support
native relative motion, like some RFB clients.

With this, RFB clients can choose to adjust the local cursor position
under certain circumstances to match what the server has set. For
instance, if pointer lock has been enabled on the client's machine and
the cursor is not being drawn locally, the local position of the cursor
is irrelevant, so the RFB client can use what the server sends as the
canonical absolute position of the cursor. This ultimately enables the
possibility of games (especially FPS games) to behave how users expect
(if the clients implement the corresponding change).

Part of: TigerVNC#619

1: https://github.com/rfbproto/rfbproto/blob/master/rfbproto.rst#vmware-cursor-position-pseudo-encoding
2: https://tronche.com/gui/x/xlib/input/XWarpPointer.html
3: https://hg.libsdl.org/SDL/file/28e3b60e2131/src/events/SDL_mouse.c#l804

common/rfb/ClientParams.cxx

@@ -30,7 +30,7 @@ ClientParams::ClientParams()
     compressLevel(2), qualityLevel(-1), fineQualityLevel(-1),
     subsampling(subsampleUndefined),
     width_(0), height_(0), name_(0),
-    ledState_(ledUnknown)
+    cursorPos_(0, 0), ledState_(ledUnknown)
 {
   setName("");
 
@@ -85,6 +85,11 @@ void ClientParams::setCursor(const Cursor& other)
   cursor_ = new Cursor(other);
 }
 
+void ClientParams::setCursorPos(const Point& pos)
+{
+  cursorPos_ = pos;
+}
+
 bool ClientParams::supportsEncoding(rdr::S32 encoding) const
 {
   return encodings_.count(encoding) != 0;
@@ -182,6 +187,13 @@ bool ClientParams::supportsLocalCursor() const
   return false;
 }
 
+bool ClientParams::supportsCursorPosition() const
+{
+  if (supportsEncoding(pseudoEncodingVMwareCursorPosition))
+    return true;
+  return false;
+}
+
 bool ClientParams::supportsDesktopSize() const
 {
   if (supportsEncoding(pseudoEncodingExtendedDesktopSize))

common/rfb/ClientParams.h

@@ -77,6 +77,9 @@ namespace rfb {
     const Cursor& cursor() const { return *cursor_; }
     void setCursor(const Cursor& cursor);
 
+    const Point& cursorPos() const { return cursorPos_; }
+    void setCursorPos(const Point& pos);
+
     bool supportsEncoding(rdr::S32 encoding) const;
 
     void setEncodings(int nEncodings, const rdr::S32* encodings);
@@ -91,6 +94,7 @@ namespace rfb {
     // Wrappers to check for functionality rather than specific
     // encodings
     bool supportsLocalCursor() const;
+    bool supportsCursorPosition() const;
     bool supportsDesktopSize() const;
     bool supportsLEDState() const;
     bool supportsFence() const;
@@ -110,6 +114,7 @@ namespace rfb {
     PixelFormat pf_;
     char* name_;
     Cursor* cursor_;
+    Point cursorPos_;
     std::set<rdr::S32> encodings_;
     unsigned int ledState_;
     rdr::U32 clipFlags;

common/rfb/SMsgWriter.cxx

@@ -42,7 +42,8 @@ SMsgWriter::SMsgWriter(ClientParams* client_, rdr::OutStream* os_)
   : client(client_), os(os_),
     nRectsInUpdate(0), nRectsInHeader(0),
     needSetDesktopName(false), needCursor(false),
-    needLEDState(false), needQEMUKeyEvent(false)
+    needCursorPos(false), needLEDState(false),
+    needQEMUKeyEvent(false)
 {
 }
 
@@ -269,6 +270,14 @@ void SMsgWriter::writeCursor()
   needCursor = true;
 }
 
+void SMsgWriter::writeCursorPos()
+{
+  if (!client->supportsEncoding(pseudoEncodingVMwareCursorPosition))
+    throw Exception("Client does not support cursor position");
+
+  needCursorPos = true;
+}
+
 void SMsgWriter::writeLEDState()
 {
   if (!client->supportsEncoding(pseudoEncodingLEDState) &&
@@ -294,6 +303,8 @@ bool SMsgWriter::needFakeUpdate()
     return true;
   if (needCursor)
     return true;
+  if (needCursorPos)
+    return true;
   if (needLEDState)
     return true;
   if (needQEMUKeyEvent)
@@ -340,6 +351,8 @@ void SMsgWriter::writeFramebufferUpdateStart(int nRects)
       nRects++;
     if (needCursor)
       nRects++;
+    if (needCursorPos)
+      nRects++;
     if (needLEDState)
       nRects++;
     if (needQEMUKeyEvent)
@@ -455,6 +468,18 @@ void SMsgWriter::writePseudoRects()
     needCursor = false;
   }
 
+  if (needCursorPos) {
+    const Point& cursorPos = client->cursorPos();
+
+    if (client->supportsEncoding(pseudoEncodingVMwareCursorPosition)) {
+      writeSetVMwareCursorPositionRect(cursorPos.x, cursorPos.y);
+    } else {
+      throw Exception("Client does not support cursor position");
+    }
+
+    needCursorPos = false;
+  }
+
   if (needSetDesktopName) {
     writeSetDesktopNameRect(client->name());
     needSetDesktopName = false;
@@ -650,6 +675,20 @@ void SMsgWriter::writeSetVMwareCursorRect(int width, int height,
   os->writeBytes(data, width*height*4);
 }
 
+void SMsgWriter::writeSetVMwareCursorPositionRect(int hotspotX, int hotspotY)
+{
+  if (!client->supportsEncoding(pseudoEncodingVMwareCursorPosition))
+    throw Exception("Client does not support cursor position");
+  if (++nRectsInUpdate > nRectsInHeader && nRectsInHeader)
+    throw Exception("SMsgWriter::writeSetVMwareCursorRect: nRects out of sync");
+
+  os->writeS16(hotspotX);
+  os->writeS16(hotspotY);
+  os->writeU16(0);
+  os->writeU16(0);
+  os->writeU32(pseudoEncodingVMwareCursorPosition);
+}
+
 void SMsgWriter::writeLEDStateRect(rdr::U8 state)
 {
   if (!client->supportsEncoding(pseudoEncodingLEDState) &&

common/rfb/SMsgWriter.h

@@ -83,6 +83,9 @@ namespace rfb {
     // immediately. 
     void writeCursor();
 
+    // Notifies the client that the cursor pointer was moved by the server.
+    void writeCursorPos();
+
     // Same for LED state message
     void writeLEDState();
 
@@ -141,6 +144,7 @@ namespace rfb {
     void writeSetVMwareCursorRect(int width, int height,
                                   int hotspotX, int hotspotY,
                                   const rdr::U8* data);
+    void writeSetVMwareCursorPositionRect(int hotspotX, int hotspotY);
     void writeLEDStateRect(rdr::U8 state);
     void writeQEMUKeyEventRect();
 
@@ -152,6 +156,7 @@ namespace rfb {
 
     bool needSetDesktopName;
     bool needCursor;
+    bool needCursorPos;
     bool needLEDState;
     bool needQEMUKeyEvent;
 

common/rfb/VNCSConnectionST.cxx

@@ -370,6 +370,15 @@ void VNCSConnectionST::renderedCursorChange()
   }
 }
 
+// cursorPositionChange() is called whenever the cursor has changed position by
+// the server.  If the client supports being informed about these changes then
+// it will arrange for the new cursor position to be sent to the client.
+
+void VNCSConnectionST::cursorPositionChange()
+{
+  setCursorPos();
+}
+
 // needRenderedCursor() returns true if this client needs the server-side
 // rendered cursor.  This may be because it does not support local cursor or
 // because the current cursor position has not been set by this client.
@@ -1123,6 +1132,21 @@ void VNCSConnectionST::setCursor()
     writer()->writeCursor();
 }
 
+// setCursorPos() is called whenever the cursor has changed position by the
+// server.  If the client supports being informed about these changes then it
+// will arrange for the new cursor position to be sent to the client.
+
+void VNCSConnectionST::setCursorPos()
+{
+  if (state() != RFBSTATE_NORMAL)
+    return;
+
+  if (client.supportsCursorPosition()) {
+    client.setCursorPos(server->getCursorPos());
+    writer()->writeCursorPos();
+  }
+}
+
 void VNCSConnectionST::setDesktopName(const char *name)
 {
   client.setName(name);

common/rfb/VNCSConnectionST.h

@@ -93,6 +93,11 @@ namespace rfb {
     // cursor.
     void renderedCursorChange();
 
+    // cursorPositionChange() is called whenever the cursor has changed position by
+    // the server.  If the client supports being informed about these changes then
+    // it will arrange for the new cursor position to be sent to the client.
+    void cursorPositionChange();
+
     // needRenderedCursor() returns true if this client needs the server-side
     // rendered cursor.  This may be because it does not support local cursor
     // or because the current cursor position has not been set by this client.
@@ -155,6 +160,7 @@ namespace rfb {
 
     void screenLayoutChange(rdr::U16 reason);
     void setCursor();
+    void setCursorPos();
     void setDesktopName(const char *name);
     void setLEDState(unsigned int state);
 

common/rfb/VNCServer.h

@@ -97,8 +97,10 @@ namespace rfb {
     virtual void setCursor(int width, int height, const Point& hotspot,
                            const rdr::U8* cursorData) = 0;
 
-    // setCursorPos() tells the server the current position of the cursor.
-    virtual void setCursorPos(const Point& p) = 0;
+    // setCursorPos() tells the server the current position of the cursor, and
+    // whether the server initiated that change (e.g. through another X11
+    // client calling XWarpPointer()).
+    virtual void setCursorPos(const Point& p, bool warped) = 0;
 
     // setName() tells the server what desktop title to supply to clients
     virtual void setName(const char* name) = 0;

common/rfb/VNCServerST.cxx

@@ -429,14 +429,17 @@ void VNCServerST::setCursor(int width, int height, const Point& newHotspot,
   }
 }
 
-void VNCServerST::setCursorPos(const Point& pos)
+void VNCServerST::setCursorPos(const Point& pos, bool warped)
 {
   if (!cursorPos.equals(pos)) {
     cursorPos = pos;
     renderedCursorInvalid = true;
     std::list<VNCSConnectionST*>::iterator ci;
-    for (ci = clients.begin(); ci != clients.end(); ci++)
+    for (ci = clients.begin(); ci != clients.end(); ci++) {
       (*ci)->renderedCursorChange();
+      if (warped)
+        (*ci)->cursorPositionChange();
+    }
   }
 }
 

common/rfb/VNCServerST.h

@@ -99,7 +99,7 @@ namespace rfb {
     virtual void add_copied(const Region &dest, const Point &delta);
     virtual void setCursor(int width, int height, const Point& hotspot,
                            const rdr::U8* data);
-    virtual void setCursorPos(const Point& p);
+    virtual void setCursorPos(const Point& p, bool warped);
     virtual void setName(const char* name_);
     virtual void setLEDState(unsigned state);
 

common/rfb/encodings.h

@@ -61,6 +61,7 @@ namespace rfb {
 
   // VMware-specific
   const int pseudoEncodingVMwareCursor = 0x574d5664;
+  const int pseudoEncodingVMwareCursorPosition = 0x574d5666;
   const int pseudoEncodingVMwareLEDState = 0x574d5668;
 
   // UltraVNC-specific

unix/x0vncserver/XDesktop.cxx

@@ -217,7 +217,7 @@ void XDesktop::poll() {
                   &x, &y, &wx, &wy, &mask);
     x -= geometry->offsetLeft();
     y -= geometry->offsetTop();
-    server->setCursorPos(rfb::Point(x, y));
+    server->setCursorPos(rfb::Point(x, y), false);
   }
 }
 

unix/xserver/hw/vnc/XserverDesktop.cc

@@ -261,6 +261,15 @@ void XserverDesktop::setCursor(int width, int height, int hotX, int hotY,
   delete [] cursorData;
 }
 
+void XserverDesktop::setCursorPos(int x, int y, bool warped)
+{
+  try {
+    server->setCursorPos(Point(x, y), warped);
+  } catch (rdr::Exception& e) {
+    vlog.error("XserverDesktop::setCursorPos: %s",e.str());
+  }
+}
+
 void XserverDesktop::add_changed(const rfb::Region &region)
 {
   try {
@@ -377,7 +386,7 @@ void XserverDesktop::blockHandler(int* timeout)
     if (oldCursorPos.x != cursorX || oldCursorPos.y != cursorY) {
       oldCursorPos.x = cursorX;
       oldCursorPos.y = cursorY;
-      server->setCursorPos(oldCursorPos);
+      server->setCursorPos(oldCursorPos, false);
     }
 
     // Trigger timers and check when the next will expire

unix/xserver/hw/vnc/XserverDesktop.h

@@ -67,6 +67,7 @@ class XserverDesktop : public rfb::SDesktop, public rfb::FullFramePixelBuffer,
   void setDesktopName(const char* name);
   void setCursor(int width, int height, int hotX, int hotY,
                  const unsigned char *rgbaData);
+  void setCursorPos(int x, int y, bool warped);
   void add_changed(const rfb::Region &region);
   void add_copied(const rfb::Region &dest, const rfb::Point &delta);
   void handleSocketEvent(int fd, bool read, bool write);

unix/xserver/hw/vnc/vncExtInit.cc

@@ -394,6 +394,11 @@ void vncSetCursor(int width, int height, int hotX, int hotY,
     desktop[scr]->setCursor(width, height, hotX, hotY, rgbaData);
 }
 
+void vncSetCursorPos(int scrIdx, int x, int y)
+{
+  desktop[scrIdx]->setCursorPos(x, y, true);
+}
+
 void vncPreScreenResize(int scrIdx)
 {
   // We need to prevent the RFB core from accessing the framebuffer

unix/xserver/hw/vnc/vncExtInit.h

@@ -81,6 +81,7 @@ void vncAddCopied(int scrIdx, int nRects,
 
 void vncSetCursor(int width, int height, int hotX, int hotY,
                   const unsigned char *rgbaData);
+void vncSetCursorPos(int scrIdx, int x, int y);
 
 void vncPreScreenResize(int scrIdx);
 void vncPostScreenResize(int scrIdx, int success, int width, int height);

unix/xserver/hw/vnc/vncHooks.c

@@ -62,6 +62,7 @@ typedef struct _vncHooksScreenRec {
   CopyWindowProcPtr            CopyWindow;
   ClearToBackgroundProcPtr     ClearToBackground;
   DisplayCursorProcPtr         DisplayCursor;
+  CursorWarpedToProcPtr        CursorWarpedTo;
   ScreenBlockHandlerProcPtr    BlockHandler;
 #ifdef RENDER
   CompositeProcPtr             Composite;
@@ -113,6 +114,10 @@ static void vncHooksClearToBackground(WindowPtr pWin, int x, int y, int w,
                                       int h, Bool generateExposures);
 static Bool vncHooksDisplayCursor(DeviceIntPtr pDev,
                                   ScreenPtr pScreen, CursorPtr cursor);
+static void vncHooksCursorWarpedTo(DeviceIntPtr pDev,
+                                   ScreenPtr pScreen_, ClientPtr pClient,
+                                   WindowPtr pWindow, SpritePtr pSprite,
+                                   int x, int y);
 #if XORG <= 118
 static void vncHooksBlockHandler(ScreenPtr pScreen, void * pTimeout,
                                  void * pReadmask);
@@ -271,6 +276,7 @@ int vncHooksInit(int scrIdx)
   wrap(vncHooksScreen, pScreen, CopyWindow, vncHooksCopyWindow);
   wrap(vncHooksScreen, pScreen, ClearToBackground, vncHooksClearToBackground);
   wrap(vncHooksScreen, pScreen, DisplayCursor, vncHooksDisplayCursor);
+  wrap(vncHooksScreen, pScreen, CursorWarpedTo, vncHooksCursorWarpedTo);
   wrap(vncHooksScreen, pScreen, BlockHandler, vncHooksBlockHandler);
 #ifdef RENDER
   ps = GetPictureScreenIfSet(pScreen);
@@ -631,6 +637,18 @@ static Bool vncHooksDisplayCursor(DeviceIntPtr pDev,
   return ret;
 }
 
+// CursorWarpedTo - notify that the cursor was warped
+
+static void vncHooksCursorWarpedTo(DeviceIntPtr pDev,
+                                   ScreenPtr pScreen_, ClientPtr pClient,
+                                   WindowPtr pWindow, SpritePtr pSprite,
+                                   int x, int y)
+{
+  SCREEN_PROLOGUE(pScreen_, CursorWarpedTo);
+  vncSetCursorPos(pScreen->myNum, x, y);
+  SCREEN_EPILOGUE(CursorWarpedTo);
+}
+
 // BlockHandler - ignore any changes during the block handler - it's likely
 // these are just drawing the cursor.
 

win/rfb_win32/SDisplay.cxx

@@ -417,7 +417,7 @@ SDisplay::processEvent(HANDLE event) {
         // Update the cursor position
         // NB: First translate from Screen coordinates to Desktop
         Point desktopPos = info.position.translate(screenRect.tl.negate());
-        server->setCursorPos(desktopPos);
+        server->setCursorPos(desktopPos, false);
 
         old_cursor = info;
       }