Just like a window, a gadget can be invalidated.

TGadget provides two functions to invalidate the gadget:

void TGadget::Invalidate(bool erase = true);

void TGadget::InvalidateRect(const TRect& rect, bool erase = true);

These functions are similar to the TDialog functions TDialog::InvalidateRect and TDialog::Invalidate.

InvalidateRect looks and functions much like its Windows API version, except that it omits its HWND parameters. Invalidate invalidates the entire bounding rectangle of the gadget. It takes a single parameter, a bool indicating whether the invalid area should be erased when it is updated. By default, this parameter is true. So, to erase the entire area of your gadget, you need only call Invalidate, either specifying true or nothing at all for its parameter.

A related function is the TGadget::Update function,

void Update();

This function attempts to force an immediate update of the gadget. It is similar to the Windows API UpdateWindow function.

See Also