[Qemu-devel] [PATCH] Support VNC PointerTypeChange psuedo-encoding

[Anthony Liguori]

The following patch adds support to the VNC server for the 
PointerTypeChange.  This is a new encoding I've defined specifically for 
virtualization.  It allows a VNC client to support a server that has a 
relative mouse (such as a PS/2 mouse in QEMU).  If you're familiar with 
the mouse being offset in a VNC session, this patch is the proper way to 
address that.

This extension is documented at http://tocm.wikidot.com/pointertypechange

It uses a type that I've reserved in the latest RFB spec.

Currently, the only client that supports this encoding is my PoC client 
available at http://hg.codemonkey.ws/vnc-gui.  I've also talked to Dan 
Berrange, the virt-manager maintainer, and I believe he plans on 
supporting this extension in virt-manager too.  Once QEMU supports the 
encoding, I suspect some of the other more popular VNC clients will 
considering also supporting it.

Regards,

Anthony Liguori

diff -r a137f714c033 vnc.c
--- a/vnc.c     Sun Dec 17 23:58:38 2006 -0600
+++ b/vnc.c     Sun Dec 17 23:58:51 2006 -0600
@@ -68,6 +68,11 @@ struct VncState
     int depth; /* internal VNC frame buffer byte per pixel */
     int has_resize;
     int has_hextile;
+    int has_pointer_type_change;
+    int absolute;
+    int last_x;
+    int last_y;
+
     Buffer output;
     Buffer input;
     kbd_layout_t *kbd_layout;
@@ -671,6 +676,19 @@ static void client_cut_text(VncState *vs
 {
 }
 
+static void check_pointer_type_change(VncState *vs, int absolute)
+{
+    if (vs->has_pointer_type_change && vs->absolute != absolute) {
+       vnc_write_u8(vs, 0);
+       vnc_write_u8(vs, 0);
+       vnc_write_u16(vs, 1);
+       vnc_framebuffer_update(vs, absolute, 0,
+                              vs->ds->width, vs->ds->height, -257);
+       vnc_flush(vs);
+    }
+    vs->absolute = absolute;
+}
+
 static void pointer_event(VncState *vs, int button_mask, int x, int y)
 {
     int buttons = 0;
@@ -686,21 +704,26 @@ static void pointer_event(VncState *vs, 
        dz = -1;
     if (button_mask & 0x10)
        dz = 1;
-           
-    if (kbd_mouse_is_absolute()) {
+
+    if (vs->absolute) {
        kbd_mouse_event(x * 0x7FFF / vs->ds->width,
                        y * 0x7FFF / vs->ds->height,
                        dz, buttons);
+    } else if (vs->has_pointer_type_change) {
+       x -= 0x7FFF;
+       y -= 0x7FFF;
+
+       kbd_mouse_event(x, y, dz, buttons);
     } else {
-       static int last_x = -1;
-       static int last_y = -1;
-
-       if (last_x != -1)
-           kbd_mouse_event(x - last_x, y - last_y, dz, buttons);
-
-       last_x = x;
-       last_y = y;
-    }
+       if (vs->last_x != -1)
+           kbd_mouse_event(x - vs->last_x,
+                           y - vs->last_y,
+                           dz, buttons);
+       vs->last_x = x;
+       vs->last_y = y;
+    }
+
+    check_pointer_type_change(vs, kbd_mouse_is_absolute());
 }
 
 static void reset_keys(VncState *vs)
@@ -829,6 +852,8 @@ static void set_encodings(VncState *vs, 
 
     vs->has_hextile = 0;
     vs->has_resize = 0;
+    vs->has_pointer_type_change = 0;
+    vs->absolute = -1;
     vs->ds->dpy_copy = NULL;
 
     for (i = n_encodings - 1; i >= 0; i--) {
@@ -845,10 +870,15 @@ static void set_encodings(VncState *vs, 
        case -223: /* DesktopResize */
            vs->has_resize = 1;
            break;
+       case -257:
+           vs->has_pointer_type_change = 1;
+           break;
        default:
            break;
        }
     }
+
+    check_pointer_type_change(vs, kbd_mouse_is_absolute());
 }
 
 static int compute_nbits(unsigned int val)
@@ -1124,6 +1154,8 @@ void vnc_display_init(DisplayState *ds, 
     vs->lsock = -1;
     vs->csock = -1;
     vs->depth = 4;
+    vs->last_x = -1;
+    vs->last_y = -1;
 
     vs->ds = ds;