Check if the system approves ABMsg.ABM_NEW

[Clijsters]

In AppBarFunctions.cs:137 you are assigning the return value of ABM_NEW to ret but not using it anywhere in the code: var ret = Interop.SHAppBarMessage((int)Interop.ABMsg.ABM_NEW, ref abd);

Consider using ret info.IsRegistered to determine whether the registration succeeded and if not, omit ABSetPos() (Which then would overlay other windows / bars)

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The return value of SHAppBarMessage(ABM_NEW, ref pData) is described in MSDN - ABM_NEW message:

Return value Returns TRUE if successful, or FALSE if an error occurs or if the appbar is already registered.

[PhilipRieck]

Is there a test case that would show what the issue is so that when fixed, it can be verified as fixed?

[Clijsters]

Windows server core-Installation and XP Embedded return false. Also a Rectangle which isn't in the workingArea returns false, but not in all cases.

[Clijsters]

I would suggest to combine this as an enhancement with multi screen support because with multiple screens, the WorkingArea isn't a Rectangle in every case (two displays with different resolution) and it happens more often that the system doesn't approve a SHAppBarMessage