`Process.MainWindowHandle` should prefer non-popup windows

[miloush]

Description

The Process.MainWindowHandle currently grabs the first window that 1) does not have owner 2) is visible:

runtime/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/ProcessManager.Win32.cs

Lines 43 to 46 in 7715391

	private static bool IsMainWindow(IntPtr handle)
	{
	return (Interop.User32.GetWindow(handle, GW_OWNER) == IntPtr.Zero) && Interop.User32.IsWindowVisible(handle) != Interop.BOOL.FALSE;
	}

Arguably if the process has multiple windows meeting this criteria with one of them having WS_POPUP, the popup is probably not the main window.

Reproduction Steps

Create a process with normal and a popup window. The repro relies on EnumWindow returning the popup first, but the order is not guaranteed.

Expected behavior

Popup windows are returned as main window even when non-popup windows exist.

Actual behavior

Prefer non-popup windows.

Regression?

No, same in .NET Framework.

Known Workarounds

Do not use Process.MainWindowHandle but do your own interop.

Configuration

.NET: not specific
OS: not specific (27793 x64)

Other information

No response

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