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: #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

1 files changed, 4 insertions, 2 deletions

diff --git a/common/rfb/VNCServer.h b/common/rfb/VNCServer.h
index 5d04da53..4535b562 100644
--- a/common/rfb/VNCServer.h
+++ b/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;