I can see from searching images that KDE3 and KDE5 appear to support mouse gestures that respond to button 1. KDE4 only allows the user to choose button 2 or 3. Using button 1 would allow for some interesting uses for touchscreens, especially the resistive kind that only sends a simple left click. Currently with KDE4 I am having to set mouse gestures to respond to button 2, evdev mouse emulation to button 2 with a (instant) 1ms timeout and send custom commands through scripts with mouse gestures and through scripts with evrouter. In my mind at least, everything would just work properly if KDE would respond to button 1 with mouse gestures. I can probably work around all this but I thought it was an interesting point to raise.