Differentiate between Windows Ink (pen) and regular touch input

[Susko3]

Description

Allows consumers to differentiate pen from touch input.

Windows will send WM_TOUCH messages for both regular touch input, and for pen/tablet PC/Windows Ink input.
Pen events will have the TOUCHEVENTF_PEN flag is set in TOUCHINPUT.dwFlags.

Consumers can use SDL_GetTouchName to get the device type ("pen" or "touch") for a SDL_TouchFingerEvent:

SDL_Event event; // from event loop
int index = -1;

for (int i = 0; i < SDL_GetNumTouchDevices(); i++) {
    if (event.tfinger.touchId == SDL_GetTouchDevice(i)) {
        index = i;
        break;
    }
}

if (SDL_strncmp(SDL_GetTouchName(index), "pen", 3) == 0) {
    // pen/tablet handling
} else {
    // touchscreen handling
}

Existing Issue(s)

• Dragging on tablet hides cursor and acts as touch input ppy/osu#19150

Testing

I've tested this on a Windows Ink compatible drawing tablet. Not tested on a touchscreen, but I have faith in the flags set by windows.

Wiki

If this goes trough, I will add the above code and a short description to https://wiki.libsdl.org/SDL_TouchFingerEvent/

[flibitijibibo]

Might be related: #5481