how to keep shadow in borderless window - qt

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.