Unfortunately there are no standard among touch screen based software developers. Even Floreant POS team started on doing research on existing POS system. We learnt many of the existing POS are not touch screen friendly at all. To give an example one of known Open source POS ( mostly designed for retail stores) uses thin Scroll bar which is not easy to use.
Interestingly MSDN has great tips(although I read somewhere MS Word is at the top in UI hall of shame ;)). Anyway lets share some nice efforts by them.
1. Target Area
Research indicates that the minimum target area for efficient, accurate interaction using a finger is 6x6 millimeters (mm). This area translates to layout metrics as follows:
| Font | Millimeters | Relative pixels | DLUs |
| 9 point Segoe UI | 6x6 | 23x23 | 13x13 |
| 8 point Tahoma | 6x6 | 23x23 | 15x14 |
Furthermore, research shows that a minimum size of 10x10 mm (about 40x40 pixels) enables better speed and accuracy, and also feels more comfortable to users. When practical, use this larger size for command buttons used for the most important or frequently used commands.
2. System gestures
System gestures are defined and handled by Windows. As a result, all Windows programs have access to them. These gestures have equivalent mouse, keyboard, and application command messages:| System gesture | Synthesized equivalent message |
| Hover (when supported) | Mouse hover |
| Tap (down and up) | Mouse left-click |
| Double tap (down and up twice) | Mouse double left-click |
| Press and hold (down, pause, up) | Mouse right-click |
| Drag (down, move, up) | Mouse left-drag |
| Press, hold, and drag (down, pause, move, up) | Mouse right-drag |
| Select (down, move over selectable objects, up) | Mouse select |
there are also other consideration including Control spacing, Control restrictions etc. I would recommend anyone to go through their page
