Issue: Using the up or down arrow keys when a GTK Slider widget is focused moves the slider in the opposite direction as expected.

For example, in an image editing program, a slider might represent image quality in a save dialog. If I want to increase the quality (i.e. from 75 to 80 percent) using my keyboard, I'd use the up arrow. However, this moves the slider to the left, decreasing the quality.

Another example: in a system settings app I might want to turn my brightness down, so I use the down arrow while selected on the brightness slider. However, the slider moves to the right, increasing the brightness.

The same thing is true throughout the whole OS; every time there's a GTK slider, the up and down arrows to the exact opposite of what they should.