I would like to play Widelands on my Microsoft Surface Pro 3 and only use the pen on the touch screen. Everything else seemed to work very well with the pen (left click, right click and scrolling with the right click), but I was not able to change the game speed. Even the on-screen keyboard is missing the Page Up and Page Down keys.
If there were UI buttons for changing the game speed, I could play the game without a keyboard.
Unless you want to get very creative, the icons could be the familiar ones from a VCR: << >>
You could add pause button as well if you like. Then it would need three buttons: << || >>
But since pausing can be done just by pressing the speed down to x0, maybe a separate pause button is not needed.
Ofcourse the most awesome thing would be to fully support the touch controls for scrolling and zooming, but even then the game speed needs to be changed somehow and, I think, clear UI buttons is the best way to do it.
PS. Please let me know, if there are other crucial hotkeys I shoud be using, which are not available on the UI. I haven't played the game much yet and might be missing something.