[Bug] Gdx.input.isKey(Just)Pressed(Keys.BACKSLASH), doesn't seem to work on Linux Mint 18 KDE Edition

Issue details

Gdx.input.isKeyJustPressed(Keys.BACKSLASH) and Gdx.input.isKeyPressed(Keys.BACKSLASH) wont work on Linux Mint 18 KDE Edition, on windows it works fine, but on Linux it doesn't give any output. KeyUp and KeyDown from InputProcessor won't respond to backslash although KeyTyped will respond appropriately, thus a workaround is to check when KeyTyped returns '\'.

I tested this with the same keyboard layout and using Linux Mint 18 KDE Edition and Windows 10

The backslash will work to open (for example) CSGO's console.

Reproduction steps/code

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class DasTesten extends ApplicationAdapter {
	SpriteBatch batch;
	Texture img;
	
	//When false, displays libgdx logo, when true it won't
	private boolean testen = false;
	
	@Override
	public void create () {
		batch = new SpriteBatch();
		img = new Texture("badlogic.jpg");
	}

	@Override
	public void render () {
		Gdx.gl.glClearColor(1, 0, 0, 1);
		Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

		//Test #1, won't work on Linux (Tested on Linux Mint 18 KDE Edition)
		if(Gdx.input.isKeyJustPressed(Keys.BACKSLASH)){
			testen = !testen;
		}
		
		//Test #2, must work everywhere
		if(Gdx.input.isKeyJustPressed(Keys.A)){
			testen = !testen;
		}
		
		//The outcome
		if(!testen){
			batch.begin();
			batch.draw(img, 0, 0);
			batch.end();
		}
	}
	
	@Override
	public void dispose () {
		batch.dispose();
		img.dispose();
	}
}

Then try pressing backslash (I am using an PT-PT Keyboard layout so the backslash key is above tab)

Version of LibGDX and/or relevant dependencies

1.9.5

Stacktrace

N/A

Please select the affected platforms

• Android
• iOS (robovm)
• iOS (MOE)
• HTML/GWT
• Windows
• Linux
• MacOS

Start by reproducing the sample with Gdx.input.isKeyJustPressed(Keys.BACKSLASH) on Linux Mint 18 KDE and compare it with Keys.A. Trace the Linux input path for InputProcessor keyDown, keyUp, and keyTyped events; done means BACKSLASH polling and key events behave consistently while existing Windows behavior remains intact.