So I got the touchscreen working last night, however for DOS games to successfully use the mouse, it listens to movement, rather than absolute position. I have implemented it like a touchpad but want to see if people like the way I have done it, or can suggest a better way. For simplicity, touching the screen doesn't activate a mouse button, but enables mouse move mode. When you touch and move, the cursor moves like a touchpad ie. the cursor moves. To generate a mouse button, you double tap. If two taps occur within a fast timeframe (ie. 300ms), it activates a left mouse down. If the taps are within a slower timeframe (600ms), it activates the right button. To click and drag, double tap but don't lift your finger. To get an actual double click, you tripple tap. I can't find an SDL routing to detect multiple touches. So:
1) press and release screen (tap): nothing
2) press and drag: mouse move in trackpad style mode
3) tap then press less than 300ms apart: left mouse button down
4) tap then press more than 300ms, but less than 600ms: right mouse button down
5) release after either 3 or 4: mouse button up
You can do 3 or 4, and move your finger to do a "click and drag".
Works well in all the games I have tried so far.
I have also installed word 5.5 (the now free version), and it works. The mouse functionality works, as do the Fn keys etc.