DWMWA_CAPTION_BUTTON_BOUNDS constant
int
const DWMWA_CAPTION_BUTTON_BOUNDS
Use with DwmGetWindowAttribute. Retrieves the bounds of the caption button area in the window-relative space. The retrieved value is of type RECT. If the window is minimized or otherwise not visible to the user, then the value of the RECT retrieved is undefined. You should check whether the retrieved RECT contains a boundary that you can work with, and if it doesn't then you can conclude that the window is minimized or otherwise not visible.
Implementation
static const DWMWA_CAPTION_BUTTON_BOUNDS = 5;