Question

I want to make an app that shows itself when the user touches his screen. It shouldn’t work for click. I looked up for the touch hanlders in Windows 7/8. But I saw that every touch window must be registered with RegisterTouchWindow

TL;DR

Is there a way to get the touch points position outside my window (globally)?

Answer 1

RegisterTouchWindow is not necessary for Win 8 apps any more.

As far as I known, there are several ways to achieve your purpose with some limitations.

1. This article here works on both Win 7 & 8. But the vendor ID and the product ID of the touchscreen is required. There is a possibility that your application won’t work properly with some touch device.

2. Use RegisterPointerInputTarget on Win 8. From my debugging, the windows 8 touch mechanism has its unique characteristics. Between a touch down and a touch up, all the touch events will be sent to the window which receives the first touch event, no matter the window is minimized or covered by another window or set WS_EX_TRANSPARENT attribute in its later period. The touch events between one pressing and releasing can only be shared to another window if the first one is destroyed. Using this API, all the touch events will be sent to the registered window. Other windows cannot receive touch events any more until UnregisterPointerInputTarget is called by the registered window, or the touch input is injected back into the system by using InjectTouchInput. “Input injected by the registered input target will not be intercepted.” Please notice that UI Access privilege is required for using this API. A sample can be found in here.

3. Windows hook. For desktop app on Win 7/8, touch events can be easily hooked by using SetWindowsHookEx with WH_CALLWNDPROC or WH_GETMESSAGE. For metro app on Win 8, only the first pointer event can be detected in the message loop of the window. Although a pointer event can be occurred by either a click or a tap, GetPointerType can tell you if its a touch pointer or a mouse pointer. Samples for using hooks can be found at here.

A code snippet for handling pointer events:

switch(Msg)  
{  
...  
case WM_POINTERENTER:  
case WM_NCPOINTERDOWN:  
case WM_NCPOINTERUP:  
case WM_NCPOINTERUPDATE:  
case WM_POINTERACTIVATE:  
case WM_POINTERCAPTURECHANGED:  
case WM_POINTERDOWN:  
case WM_POINTERLEAVE:  
case WM_POINTERUP:  
case WM_POINTERUPDATE:  
    {  
        UINT32 pointerId = GET_POINTERID_WPARAM(wParam);  
        POINTER_INPUT_TYPE pointerType;  

        if (GetPointerType(pointerId, &pointerType))  
        {
            if (pointerType == PT_TOUCH)   
            {  
                ...  
            }  
        }  
    }  
    break;  
...