https://bugs.kde.org/show_bug.cgi?id=519973
Bug ID: 519973
Summary: fakeinput keyboard_keysym broadcasts modifier state to
all Wayland clients causing key corruption on
non-QWERTY layouts
Classification: Plasma
Product: kwin
Version First 6.6.4
Reported In:
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: virtual-keyboard
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Overview
When using org_kde_kwin_fake_input protocol's keyboard_keysym request (used by
KDE Connect via xdg-desktop-portal-kde's RemoteDesktop portal), uppercase
letters and AltGr characters are injected incorrectly on non-QWERTY keyboard
layouts (confirmed on French AZERTY).
Root cause
In src/backends/fakeinput/fakeinputbackend.cpp,
org_kde_kwin_fake_input_keyboard_keysym calls
input()->keyboard()->xkb()->updateModifiers() to temporarily set the
Shift/AltGr modifier state before sending the key. This function broadcasts the
modifier state change to all connected Wayland clients via forwardModifiers().
The terminal or application receiving the keypress sees the Shift modifier
arrive, then the key, then Shift release — but the timing and ordering causes
the modifier state to bleed into subsequent keystrokes, resulting in random
capitalization and symbol corruption on AZERTY and other non-QWERTY layouts.
Steps to reproduce
Use a French AZERTY keyboard layout on KDE Plasma Wayland
Use KDE Connect Android app with the remote keyboard feature
Type uppercase letters or AltGr characters
Observe that characters arrive incorrectly — uppercase letters appear as
lowercase, numbers appear as their shifted symbols (e.g. 1 → &, 2 → é), and
modifier state bleeds into subsequent keystrokes
Fix
Instead of calling updateModifiers() (which broadcasts globally), send explicit
KEY_LEFTSHIFT / KEY_RIGHTALT key press and release events around the actual
keypress. The key level from keycodeFromKeysym() already tells us which
modifier is needed:
cppstd::optional<Xkb::KeyCode> keyCode =
input()->keyboard()->xkb()->keycodeFromKeysym(keySym);
if (keyCode) {
const bool needsShift = keyCode->level == 1;
const bool needsAltGr = keyCode->level == 2;
if (needsShift) sendKey(device, KEY_LEFTSHIFT, KeyboardKeyState::Pressed);
if (needsAltGr) sendKey(device, KEY_RIGHTALT, KeyboardKeyState::Pressed);
sendKey(device, keyCode->keyCode, nativeState);
if (needsAltGr) sendKey(device, KEY_RIGHTALT, KeyboardKeyState::Released);
if (needsShift) sendKey(device, KEY_LEFTSHIFT, KeyboardKeyState::Released);
return;
}
KEY_LEFTSHIFT (42) and KEY_RIGHTALT (100) are already defined in
linux/input-event-codes.h which is included via the existing headers.
Tested on
Nobara Linux 43, KDE Plasma 6.6.2 / KWin 6.6.4
French AZERTY layout (localectl set-x11-keymap fr pc105)
KDE Connect Android 1.35.5 → xdg-desktop-portal-kde → KWin fakeinput
Patch confirmed working on both KWin 6.6.2 and 6.6.4.
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