如何在无边界的窗口中保持阴影

Question

I'm trying to drop a shadow on a borderless window using Qt in windows. I succeeded in dropping the shadow when launching the application, referring to the following article.

• Borderless Window Using Areo Snap, Shadow, Minimize Animation, and Shake

• Borderless Window with Drop Shadow

But I encountered the problem that the shadow will disappear if the application is deactivated and reactivated ( In other words, click the other applications, and click my application again.)

Perhaps my implementation is not good enough. I'm glad if you have some ideas for this issue.

I'm trying to imprement Qt with Go bindings Here is the code snippet:

package qframelesswindow

import (
    "unsafe"

    "github.com/therecipe/qt/core"
    "github.com/therecipe/qt/widgets"

    win "github.com/akiyosi/w32"
)

func (f *QFramelessWindow) SetNativeEvent(app *widgets.QApplication) {
    filterObj := core.NewQAbstractNativeEventFilter()
    filterObj.ConnectNativeEventFilter(func(eventType *core.QByteArray, message unsafe.Pointer, result int) bool {
        msg := (*win.MSG)(message)
        lparam := msg.LParam
        hwnd := msg.Hwnd
        var uflag uint
        uflag = win.SWP_NOZORDER | win.SWP_NOOWNERZORDER | win.SWP_NOMOVE | win.SWP_NOSIZE | win.SWP_FRAMECHANGED
        var nullptr win.HWND
        shadow := &win.MARGINS{0, 0, 0, 1}

        switch msg.Message {
        case win.WM_CREATE:
            style := win.WS_POPUP | win.WS_THICKFRAME | win.WS_MINIMIZEBOX | win.WS_MAXIMIZEBOX | win.WS_CAPTION
            win.SetWindowLong(hwnd, win.GWL_STYLE, uint32(style))

            win.DwmExtendFrameIntoClientArea(hwnd, shadow)
            win.SetWindowPos(hwnd, nullptr, 0, 0, 0, 0, uflag)

            return true

        case win.WM_NCCALCSIZE:
            if msg.WParam == 1 {
                // this kills the window frame and title bar we added with WS_THICKFRAME and WS_CAPTION
                result = 0
                return true
            }
            return false

        case win.WM_GETMINMAXINFO:
            mm := (*win.MINMAXINFO)((unsafe.Pointer)(lparam))
            mm.PtMinTrackSize.X = int32(f.minimumWidth)
            mm.PtMinTrackSize.Y = int32(f.minimumHeight)
            return true

        default:
        }
        return false
    })
    app.InstallNativeEventFilter(filterObj)
}

All source code is in my repository; akiyosi/goqtframelesswindow

Answer 1

WM_NCCALCSIZE:

If wParam is TRUE, the application should return zero or a combination of the following values.(In document)

And also:

When wParam is TRUE, simply returning 0 without processing the NCCALCSIZE_PARAMS rectangles will cause the client area to resize to the size of the window, including the window frame. This will remove the window frame and caption items from your window, leaving only the client area displayed.

Starting with Windows Vista, simply returning 0 does not affect extended frames, only the standard frame will be removed.

EDIT:

Set the return value with the DWL_MSGRESULT instead of result = 0.