Using WM_MOUSEMOVE/WM_NCMOUSEMOVE to update specified area - windows

Question

My perpose: When cursor hover on the specified area , a rectangle, filled with red brush. When cursor out of this area, filled with blue brush.
So I handle with WM_MOUSEMOVE/WM_NCMOUSEMOVE message(depend on the area, client zone or non-client zone), according the paramater of the cursor positon, I do defferent paintings.
Howerver,If I spliped faster, it do not work correctly.
case WM_NCMOUSEMOVE: {
UINT HITPOS = wParam;
POINT pt={GET_X_LPARAM(lParam),GET_Y_LPARAM(lParam)};
BOOL active_flag=(GetActiveWindow()==hwnd);
Frame_NCDraw(hwnd,&active_flag);
if(HITPOS==HTMENU) Frame_PopMenu(hwnd,pt);
TRACKMOUSEEVENT tme;
tme.cbSize=sizeof(TRACKMOUSEEVENT);
tme.dwFlags=TME_NONCLIENT;
tme.hwndTrack=hwnd;
tme.dwHoverTime=HOVER_DEFAULT;
TrackMouseEvent(&tme);
return 0;
} break;
case WM_NCMOUSELEAVE: {
BOOL active_flag=(GetActiveWindow()==hwnd);
Frame_NCDraw(hwnd,&active_flag);
TRACKMOUSEEVENT tme;
tme.cbSize=sizeof(TRACKMOUSEEVENT);
tme.dwFlags=TME_CANCEL;
tme.hwndTrack=hwnd;
tme.dwHoverTime=HOVER_DEFAULT;
TrackMouseEvent(&tme);
} break;
I think this may be something with the spin of each WM_MOUSEMOVE message has been triggered.
Compared with the max/min/close button on window non-client zone, no matter how fast I sliped over , it still can work well. How did it do that ?

Answer 1

If the mouse is moving fast, your program can receive not all mouse messages. I think in your case, while the mouse moves to a new position, your program still handles a message with an older position, thus the wrong output.
To handle this you can check mouse position in other handlers, for example WM_TIMER.
At startup (typically in WM_CREATE handler) you should create the timer:
#define ID_MY_TIMER 750
void SetupTimer(HWND hwnd)
{
//Set timer for every second
if( !SetTimer(hwnd, ID_MY_TIMER, 1000, (TIMERPROC) NULL))
handle error;
}
In your WndProc add WM_TIMER handler:
case WM_TIMER:
{
if( wParam == ID_MY_TIMER )
{
TODO:
Get mouse position (for example GetCursorPos, it returns cursor
position in screen coordinates), compare it with the previous position.
If the position changed, issue a redraw command (seems it is Frame_NCDraw
call in your case).
Save the current position as previous position
//Set timer
SetupTimer(hwnd);
}
break;
}
At closing (typically WM_DESTROY) kill the timer:
KillTimer(hwnd, 1);