如何获得Windows中窗口的默认标题栏高度？

Question

我正在开发一个应用程序，该应用程序采用了自绘标题栏，需要模仿系统默认的标题栏。

那么，我如何在Windows中获得一个被覆盖的窗口的默认标题栏高度？

Answer 1

源代码移植自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：高度是依赖于dpi的。

Answer 2

一个解决方案是使用 AdjustWindowRectEx函数 它还可以计算其他窗口边框的宽度，并允许窗口风格的变化。

RECT rcFrame = { 0 };
AdjustWindowRectEx(&rcFrame, WS_OVERLAPPEDWINDOW, FALSE, 0);
// abs(rcFrame.top) will contain the caption bar height

对于现代的Windows(10+)，还有DPI感知版本。

// get DPI from somewhere, for example from the GetDpiForWindow function
const UINT dpi = GetDpiForWindow(myHwnd);
...
RECT rcFrame = { 0 };
AdjustWindowRectExForDpi(&rcFrame, WS_OVERLAPPEDWINDOW, FALSE, 0, dpi);
// abs(rcFrame.top) will contain the caption bar height