It sounds like you're encountering a problem with KWin, the window manager for KDE, on an X11 display. Here are a few steps you can try to resolve this issue:
1. **Restart KWin**:
Open a terminal and try restarting KWin with the following command:
```bash
kwin_x11 --replace &
```
2. **Check Display Environment Variable**:
Ensure that the `DISPLAY` environment variable is set correctly. You can check it with:
```bash
echo $DISPLAY
```
It should typically be set to `:0` or another appropriate value. If it's not set, you can set it with:
```bash
export DISPLAY=:0
```
3. **Check for Running X Server**:
Make sure that an X server is running. You can check for running X servers with:
```bash
ps aux | grep X
```
If no X server is running, you might need to start one. For example:
```bash
startx
```
4. **Check Log Files**:
Look at the X server logs for any errors. These logs are usually located in `/var/log/` and might be named something like `Xorg.0.log`. You can view the log with:
```bash
less /var/log/Xorg.0.log
```
Look for any errors or warnings that might indicate what went wrong.
5. **Update System**:
Make sure your system and all packages are up to date. On a Debian-based system, you can do this with:
```bash
sudo apt update
sudo apt upgrade
```
On an Arch-based system, use:
```bash
sudo pacman -Syu
```
6. **Check for Configuration Issues**:
Sometimes, configuration files can cause issues. Check your KWin configuration files located in `~/.config/kwinrc` or other related configuration files for any anomalies.
7. **Reinstall KWin**:
If none of the above steps work, you might try reinstalling KWin. On a Debian-based system:
```bash
sudo apt-get install --reinstall kwin-x11
```
On an Arch-based system:
```bash
sudo pacman -S kwin
```
If the problem persists after these steps, providing more specific details about your system setup and any error messages you're seeing would be helpful.
