How to get the default caption bar height of a window in Windows?

win32gui, winapi, windows

Solution

Source code ported from Firefox:

// mCaptionHeight is the default size of the NC area at
// the top of the window. If the window has a caption,
// the size is calculated as the sum of:
//      SM_CYFRAME        - The thickness of the sizing border
//                          around a resizable window
//      SM_CXPADDEDBORDER - The amount of border padding
//                          for captioned windows
//      SM_CYCAPTION      - The height of the caption area
//
// If the window does not have a caption, mCaptionHeight will be equal to
// `GetSystemMetrics(SM_CYFRAME)`
int height = (GetSystemMetrics(SM_CYFRAME) + GetSystemMetrics(SM_CYCAPTION) +
    GetSystemMetrics(SM_CXPADDEDBORDER));
return height;

PS: the height is dpi-dependent.

Problem

I am developing an application which employs a self-drawn titlebar, which needs to mimic the system default titlebar. So how could I get the default titlebar height of an overloapped window in Windows?

Original source