protocol: Add support for side mouse buttons

Side mouse buttons currently do not exist in the protocol, causing them to be inexplicably ignored by VMs in virt-manager and such. This lays the groundwork for fixing that issue.

I have also already implemented this in spice-server, spice-gtk and the Linux vd-agent. I plan on submitting MRs for those projects as well if this is accepted.

spice/enums.h

@@ -336,6 +336,8 @@ typedef enum SpiceMouseButton {
     SPICE_MOUSE_BUTTON_RIGHT,
     SPICE_MOUSE_BUTTON_UP,
     SPICE_MOUSE_BUTTON_DOWN,
+    SPICE_MOUSE_BUTTON_SIDE,
+    SPICE_MOUSE_BUTTON_EXTRA,
 
     SPICE_MOUSE_BUTTON_ENUM_END
 } SpiceMouseButton;
@@ -344,8 +346,10 @@ typedef enum SpiceMouseButtonMask {
     SPICE_MOUSE_BUTTON_MASK_LEFT = (1 << 0),
     SPICE_MOUSE_BUTTON_MASK_MIDDLE = (1 << 1),
     SPICE_MOUSE_BUTTON_MASK_RIGHT = (1 << 2),
+    SPICE_MOUSE_BUTTON_MASK_SIDE = (1 << 3),
+    SPICE_MOUSE_BUTTON_MASK_EXTRA = (1 << 4),
 
-    SPICE_MOUSE_BUTTON_MASK_MASK = 0x7
+    SPICE_MOUSE_BUTTON_MASK_MASK = 0x1F
 } SpiceMouseButtonMask;
 
 typedef enum SpiceCursorType {

[Frediano Ziglio]

Nothing wrong changing this file but it's autogenerated from spice-common/spice.proto. Change there can be done later too.

[SimonPilkington]

My mistake. I can submit a MR there if we agree to go forward with this.