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I have a MDI application and on Windows11 I have Snap enabled. Works fine with one oddity. If I do not have my application's MDI document maximized, when I move over the maximize button, the Snap window appears. I can click and entry and my application Snaps (not the MDI child window). How can I disable this as I only want the application to snap.
I added a handler for WM_NCHITTEST to my MDI child window but if I don't return HTMAXBUTTON, I get no highlighting on the button and it doesn't react to clicks. Spying on the messages the window gets I don't see anything that I might intercept to prevent Snap from showing up. I'm trying to avoid having to implement all the NC message handlers if possible.
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If you create a MFC MDI standard template project, will the problem occur?
Hi Minxin,
Unfortunately I tried that right away and the answer is no. And, I don't see any difference when spying on messages of the MFC MDI child window and our MDI child window other than a timer that shows up in Spy right after the Snap window appears. I was hoping to find a way to "opt out" of this behavior via, for example, a call to DwmSetWindowAttribute or another API. I had to use that API to opt in to rounded corners for our application on Windows 11. We are not quite a MFC document/view application though we are an MDI application. I even debugged the non client messages involved and in both our case and the MFC sample the non client messages all route to DefMDIChildProc. I spied on the MDI client window and then our application window too but didn't see anything that I could recognize being involved in showing the Snap UI.
Can you provide a minimal reproducible example?
Try creating a new project. Copy the MDI project code step by step and remove unnecessary code until you are left with the minimal code that can reproduce the problem.
I tried that with a stock MFC sample but didn't get the Snap window. As with many issues, if it was simple to repro, it would not have made it out the door from Microsoft.