Erroneous sort call when maximizing window via title bar double-click

[UskovM]

With specific window layouts, a double-click on the title bar mistakenly triggers sorting in Column 1. A reproduction demo project is attached in Vt2Bug.zip.

VTBug2.zip

[UskovM]

I couldn't fix the behavior of TVTHeader.HandleMessage + fWasDoubleClick, so I implemented my own workaround by launching an additional timer on the WM_WINDOWPOSCHANGED event and adding a new tsColumnClickLock state

and processing it into VirtualTrees.Header.pas

[joachimmarder]

With specific window layouts, a double-click on the title bar mistakenly triggers sorting in Column 1. A reproduction demo project is attached in Vt2Bug.zip.

I compiled your sample project with Delphi 12.3 and the latest VTV source code, double-clicked on the title bar, but the sort order didn't change. See this screen recording:

Any idea what I am doing wrong when reproducing this issue?

[UskovM]

To reproduce the effect, the initial window position is important. I have drawn an explanation in the attached images

[UskovM]

2026-06-02.17-31-36.-.Trim.mp4

[luebbe]

Interesting find. This looks like after maximizing there is a click going to the position where the windows title bar has been before (and where the VTV header is now)

[UskovM]

The issue was reported by users of our software, which uses TVirtualStringTree. Therefore, this is not an isolated case of a faulty mouse on my end. However, the issue is likely tied to the Windows 'Double-click speed' setting.

[joachimmarder]

There is already code there to circumvent such double click issues, and the member TVTHeader.FWasDoubleClick. But it seem that the control does not receive any mouse event when the double click on the title bar occurs. That makes it difficult to intercept.

These are the message I saw in this situation:

Breakpoint Expression Message.Msg: 641 WM_IME_SETCONTEXT
Breakpoint Expression Message.Msg: 642 WM_IME_NOTIFY
Breakpoint Expression Message.Msg: 61 WM_GETOBJECT
Breakpoint Expression Message.Msg: 61 WM_GETOBJECT
Breakpoint Expression Message.Msg: 7 WM_SETFOCUS
Breakpoint Expression Message.Msg: 45108 WM_APP + 0x3034
Breakpoint Expression Message.Msg: 45097 WM_APP +
Breakpoint Expression Message.Msg: 15 WM_PAINT
Breakpoint Expression Message.Msg: 20 WM_ERASEBKGND
Breakpoint Expression Message.Msg: 792 WM_PRINTCLIENT
Breakpoint Expression Message.Msg: 70 WM_WINDOWPOSCHANGING
Breakpoint Expression Message.Msg: 131 WM_NCCALCSIZE
Breakpoint Expression Message.Msg: 133 WM_NCPAINT
Breakpoint Expression Message.Msg: 20 WM_ERASEBKGND
Breakpoint Expression Message.Msg: 71 WM_WINDOWPOSCHANGED
Breakpoint Expression Message.Msg: 5 WM_SIZE
Breakpoint Expression Message.Msg: 131 WM_NCCALCSIZE
Breakpoint Expression Message.Msg: 131 WM_NCCALCSIZE
Breakpoint Expression Message.Msg: 133 WM_NCPAINT
Breakpoint Expression Message.Msg: 133 WM_NCPAINT
Breakpoint Expression Message.Msg: 20 WM_ERASEBKGND
Breakpoint Expression Message.Msg: 20 WM_ERASEBKGND
Breakpoint Expression Message.Msg: 71 WM_WINDOWPOSCHANGED
Breakpoint Expression Message.Msg: 71 WM_WINDOWPOSCHANGED
Breakpoint Expression Message.Msg: 47106 WM_APP +
Breakpoint Expression Message.Msg: 45148 WM_APP +
Breakpoint Expression Message.Msg: 132 WM_NCHITTEST 
Breakpoint Expression Message.Msg: 132 WM_NCHITTEST 
Breakpoint Expression Message.Msg: 132 WM_NCHITTEST 
Breakpoint Expression Message.Msg: 32 WM_SETCURSOR
Breakpoint Expression Message.Msg: 32 WM_SETCURSOR
Breakpoint Expression Message.Msg: 160 WM_NCMOUSEMOVE
Breakpoint Expression Message.Msg: 15 WM_PAINT
Breakpoint Expression Message.Msg: 133 WM_NCPAINT
Breakpoint Expression Message.Msg: 20 WM_ERASEBKGND
Breakpoint Expression Message.Msg: 792 WM_PRINTCLIENT
Breakpoint Expression Message.Msg: 132 WM_NCHITTEST
Breakpoint Expression Message.Msg: 132 WM_NCHITTEST
Breakpoint Expression Message.Msg: 32 WM_SETCURSOR
Breakpoint Expression Message.Msg: 32 WM_SETCURSOR
Breakpoint Expression Message.Msg: 162 WM_NCLBUTTONUP

Any ideas?

[UskovM]

As I showed above, I simply blocked the header click event handler for 50ms using a timer, starting from when WM_WINDOWPOSCHANGED is received. Couldn't make it look pretty, but it gets the job done.
The WM_NCLBUTTONDBLCLK event, which TVTHeader.fWasDoubleClick relies on, doesn't fire in this scenario