tigervnc/tigervnc-fix-ghost-cursor-in-zaphod-mode.patch

From f783d5c8b567199178b6690f347e060a69d2aa36 Mon Sep 17 00:00:00 2001
From: Jan Grulich <jgrulich@redhat.com>
Date: Thu, 11 Aug 2022 13:15:29 +0200
Subject: [PATCH] x0vncserver: update/display cursor only on correct screen in
 zaphod mode

We have to check whether we update cursor position/shape only in case
the cursor is on our display, otherwise in zaphod mode, ie. when having
two instances of x0vncserver on screens :0.0 and :0.1 we would be having
the cursor duplicated and actually not funcional (aka ghost cursor) as
it would be actually not present. We also additionally watch EnterNotify
and LeaveNotify events in order to show/hide cursor accordingly.

Change made with help from Olivier Fourdan <ofourdan@redhat.com>
---
 unix/x0vncserver/XDesktop.cxx | 60 +++++++++++++++++++++++++++++++----
 1 file changed, 53 insertions(+), 7 deletions(-)

diff --git a/unix/x0vncserver/XDesktop.cxx b/unix/x0vncserver/XDesktop.cxx
index f2046e43e..f07fd78bf 100644
--- a/unix/x0vncserver/XDesktop.cxx
+++ b/unix/x0vncserver/XDesktop.cxx
@@ -192,7 +192,8 @@ XDesktop::XDesktop(Display* dpy_, Geometry *geometry_)
                    RRScreenChangeNotifyMask | RRCrtcChangeNotifyMask);
     /* Override TXWindow::init input mask */
     XSelectInput(dpy, DefaultRootWindow(dpy),
-                 PropertyChangeMask | StructureNotifyMask | ExposureMask);
+                 PropertyChangeMask | StructureNotifyMask |
+                 ExposureMask | EnterWindowMask | LeaveWindowMask);
   } else {
 #endif
     vlog.info("RANDR extension not present");
@@ -217,11 +218,13 @@ void XDesktop::poll() {
     Window root, child;
     int x, y, wx, wy;
     unsigned int mask;
-    XQueryPointer(dpy, DefaultRootWindow(dpy), &root, &child,
-                  &x, &y, &wx, &wy, &mask);
-    x -= geometry->offsetLeft();
-    y -= geometry->offsetTop();
-    server->setCursorPos(rfb::Point(x, y), false);
+
+    if (XQueryPointer(dpy, DefaultRootWindow(dpy), &root, &child,
+                      &x, &y, &wx, &wy, &mask)) {
+      x -= geometry->offsetLeft();
+      y -= geometry->offsetTop();
+      server->setCursorPos(rfb::Point(x, y), false);
+    }
   }
 }

@@ -253,7 +256,14 @@ void XDesktop::start(VNCServer* vs) {
 #endif

 #ifdef HAVE_XFIXES
-  setCursor();
+  Window root, child;
+  int x, y, wx, wy;
+  unsigned int mask;
+  // Check whether the cursor is initially on our screen
+  if (XQueryPointer(dpy, DefaultRootWindow(dpy), &root, &child,
+                    &x, &y, &wx, &wy, &mask))
+    setCursor();
+
 #endif

   server->setLEDState(ledState);
@@ -701,6 +711,15 @@ bool XDesktop::handleGlobalEvent(XEvent* ev) {
     if (cev->subtype != XFixesDisplayCursorNotify)
       return false;

+    Window root, child;
+    int x, y, wx, wy;
+    unsigned int mask;
+
+    // Check whether the cursor is initially on our screen
+    if (!XQueryPointer(dpy, DefaultRootWindow(dpy), &root, &child,
+                      &x, &y, &wx, &wy, &mask))
+      return false;
+
     return setCursor();
 #endif
 #ifdef HAVE_XRANDR
@@ -753,6 +772,33 @@ bool XDesktop::handleGlobalEvent(XEvent* ev) {

     return true;
 #endif
+#ifdef HAVE_XFIXES
+  } else if (ev->type == EnterNotify) {
+    XCrossingEvent* cev;
+
+    if (!running)
+      return true;
+
+    cev = (XCrossingEvent*)ev;
+
+    if (cev->window != cev->root)
+      return false;
+
+    return setCursor();
+  } else if (ev->type == LeaveNotify) {
+    XCrossingEvent* cev;
+
+    if (!running)
+      return true;
+
+    cev = (XCrossingEvent*)ev;
+
+    if (cev->window == cev->root)
+      return false;
+
+    server->setCursor(0, 0, Point(), NULL);
+    return true;
+#endif
   }

   return false;