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

[Wolf-SO]

Also a Rectangle which isn't in the workingArea returns false, but not in all cases.

@clijsters This observation seems to contradict the ABM_NEW documentation (Parameters section):

[...] You must specify the cbSize, hWnd, and uCallbackMessage members when sending this message; all other members are ignored.

[clijsters]

My comments are quite old, so I'm not 100% sure, but from what I understand, the parameters section doesn't state, when it returns true or false. My observation was just that it returns false, when the Rectangle isn't in the workingArea. When I remember it correctly, I suggested some error-handling or checking the returned value before proceeding.

[Wolf-SO]

@clijsters thanks for the quick reply. You wrote:

the parameters section doesn't state, when it returns true or false.

I think the general ABM_NEW result specification applies (emphasis mine):

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

I'm working on a completely different project and try to find nontrivial cases for the sporadic fails I observe there. So I'm currently possible reasons why an ABM_NEW call may fail if it is not already registered. At first, I was happy to find some indications here, but then, I realized that the documentation explicitly states that the rc member of APPBARDATA is ignored in the ABM_NEW call. That's why I commented on this issue in this project.

[clijsters]

Ok @Wolf-SO I understand. I was just refering to some cases when it returns false (thus, indicating an error, as cited by you already) and my initial comment or bug report was mainly focused on some "standard cases" when an error occurs, it returns false and the code should check for it.
Im not sure which Rectangle I was refering to, but maybe I meant the appBarWindow, which in turn gots referenced using hWnd.