From ccbd491fa48f1c43daeb1a6c5ee91a1a8fa3db88 Mon Sep 17 00:00:00 2001
From: Jan Grulich <jgrulich@redhat.com>
Date: Tue, 9 Aug 2022 14:31:07 +0200
Subject: [PATCH] x0vncserver: add new keysym in case we don't find a matching
 keycode

We might often fail to find a matching X11 keycode when the client has
a different keyboard layout and end up with no key event. To avoid a
failure we add it as a new keysym/keycode pair so the next time a keysym
from the client that is unknown to the server is send, we will find a
match and proceed with key event. This is same behavior used in Xvnc or
x11vnc, although Xvnc has more advanced mapping from keysym to keycode.
---
 unix/x0vncserver/XDesktop.cxx | 121 +++++++++++++++++++++++++++++++++-
 unix/x0vncserver/XDesktop.h   |   4 ++
 2 files changed, 122 insertions(+), 3 deletions(-)

diff --git a/unix/x0vncserver/XDesktop.cxx b/unix/x0vncserver/XDesktop.cxx
index f2046e43e..933998f05 100644
--- a/unix/x0vncserver/XDesktop.cxx
+++ b/unix/x0vncserver/XDesktop.cxx
@@ -31,6 +31,7 @@
 #include <x0vncserver/XDesktop.h>

 #include <X11/XKBlib.h>
+#include <X11/Xutil.h>
 #ifdef HAVE_XTEST
 #include <X11/extensions/XTest.h>
 #endif
@@ -50,6 +51,7 @@ void vncSetGlueContext(Display *dpy, void *res);
 #include <x0vncserver/Geometry.h>
 #include <x0vncserver/XPixelBuffer.h>

+using namespace std;
 using namespace rfb;

 extern const unsigned short code_map_qnum_to_xorgevdev[];
@@ -264,6 +266,9 @@ void XDesktop::start(VNCServer* vs) {
 void XDesktop::stop() {
   running = false;

+  // Delete added keycodes
+  deleteAddedKeysyms(dpy);
+
 #ifdef HAVE_XDAMAGE
   if (haveDamage)
     XDamageDestroy(dpy, damage);
@@ -383,6 +388,118 @@ KeyCode XDesktop::XkbKeysymToKeycode(Display* dpy, KeySym keysym) {
 }
 #endif

+KeyCode XDesktop::addKeysym(Display* dpy, KeySym keysym)
+{
+  int types[1];
+  unsigned int key;
+  XkbDescPtr xkb;
+  XkbMapChangesRec changes;
+  KeySym *syms;
+  KeySym upper, lower;
+
+  xkb = XkbGetMap(dpy, XkbAllComponentsMask, XkbUseCoreKbd);
+
+  if (!xkb)
+    return 0;
+
+  for (key = xkb->max_key_code; key >= xkb->min_key_code; key--) {
+    if (XkbKeyNumGroups(xkb, key) == 0)
+      break;
+  }
+
+  if (key < xkb->min_key_code)
+    return 0;
+
+  memset(&changes, 0, sizeof(changes));
+
+  XConvertCase(keysym, &lower, &upper);
+
+  if (upper == lower)
+    types[XkbGroup1Index] = XkbOneLevelIndex;
+  else
+    types[XkbGroup1Index] = XkbAlphabeticIndex;
+
+  XkbChangeTypesOfKey(xkb, key, 1, XkbGroup1Mask, types, &changes);
+
+  syms = XkbKeySymsPtr(xkb,key);
+  if (upper == lower)
+    syms[0] = keysym;
+  else {
+    syms[0] = lower;
+    syms[1] = upper;
+  }
+
+  changes.changed |= XkbKeySymsMask;
+  changes.first_key_sym = key;
+  changes.num_key_syms = 1;
+
+  if (XkbChangeMap(dpy, xkb, &changes)) {
+    vlog.info("Added unknown keysym %s to keycode %d", XKeysymToString(keysym), key);
+    addedKeysyms[keysym] = key;
+    return key;
+  }
+
+  return 0;
+}
+
+void XDesktop::deleteAddedKeysyms(Display* dpy) {
+  XkbDescPtr xkb;
+  xkb = XkbGetMap(dpy, XkbAllComponentsMask, XkbUseCoreKbd);
+
+  if (!xkb)
+    return;
+
+  XkbMapChangesRec changes;
+  memset(&changes, 0, sizeof(changes));
+
+  KeyCode lowestKeyCode = xkb->max_key_code;
+  KeyCode highestKeyCode = xkb->min_key_code;
+  std::map<KeySym, KeyCode>::iterator it;
+  for (it = addedKeysyms.begin(); it != addedKeysyms.end(); it++) {
+    if (XkbKeyNumGroups(xkb, it->second) != 0) {
+      // Check if we are removing keysym we added ourself
+      if (XkbKeysymToKeycode(dpy, it->first) != it->second)
+        continue;
+
+      XkbChangeTypesOfKey(xkb, it->second, 0, XkbGroup1Mask, NULL, &changes);
+
+      if (it->second < lowestKeyCode)
+        lowestKeyCode = it->second;
+
+      if (it->second > highestKeyCode)
+        highestKeyCode = it->second;
+    }
+  }
+
+  changes.changed |= XkbKeySymsMask;
+  changes.first_key_sym = lowestKeyCode;
+  changes.num_key_syms = highestKeyCode - lowestKeyCode + 1;
+  XkbChangeMap(dpy, xkb, &changes);
+
+  addedKeysyms.clear();
+}
+
+KeyCode XDesktop::keysymToKeycode(Display* dpy, KeySym keysym) {
+  int keycode = 0;
+
+  // XKeysymToKeycode() doesn't respect state, so we have to use
+  // something slightly more complex
+  keycode = XkbKeysymToKeycode(dpy, keysym);
+
+  if (keycode != 0)
+    return keycode;
+
+  // TODO: try to further guess keycode with all possible mods as Xvnc does
+
+  keycode = addKeysym(dpy, keysym);
+
+  if (keycode == 0)
+    vlog.error("Failure adding new keysym 0x%lx", keysym);
+
+  return keycode;
+}
+
+
 void XDesktop::keyEvent(rdr::U32 keysym, rdr::U32 xtcode, bool down) {
 #ifdef HAVE_XTEST
   int keycode = 0;
@@ -398,9 +515,7 @@ void XDesktop::keyEvent(rdr::U32 keysym, rdr::U32 xtcode, bool down) {
     if (pressedKeys.find(keysym) != pressedKeys.end())
       keycode = pressedKeys[keysym];
     else {
-      // XKeysymToKeycode() doesn't respect state, so we have to use
-      // something slightly more complex
-      keycode = XkbKeysymToKeycode(dpy, keysym);
+      keycode = keysymToKeycode(dpy, keysym);
     }
   }

diff --git a/unix/x0vncserver/XDesktop.h b/unix/x0vncserver/XDesktop.h
index 840d43316..6ebcd9f8a 100644
--- a/unix/x0vncserver/XDesktop.h
+++ b/unix/x0vncserver/XDesktop.h
@@ -55,6 +55,9 @@ class XDesktop : public rfb::SDesktop,
                                const char* userName);
   virtual void pointerEvent(const rfb::Point& pos, int buttonMask);
   KeyCode XkbKeysymToKeycode(Display* dpy, KeySym keysym);
+  KeyCode addKeysym(Display* dpy, KeySym keysym);
+  void deleteAddedKeysyms(Display* dpy);
+  KeyCode keysymToKeycode(Display* dpy, KeySym keysym);
   virtual void keyEvent(rdr::U32 keysym, rdr::U32 xtcode, bool down);
   virtual void clientCutText(const char* str);
   virtual unsigned int setScreenLayout(int fb_width, int fb_height,
@@ -78,6 +81,7 @@ class XDesktop : public rfb::SDesktop,
   bool haveXtest;
   bool haveDamage;
   int maxButtons;
+  std::map<KeySym, KeyCode> addedKeysyms;
   std::map<KeySym, KeyCode> pressedKeys;
   bool running;
 #ifdef HAVE_XDAMAGE