Why can’t you drop directly onto a taskbar button?

Raymond Chen


If you drag a object and drop it onto a taskbar button, you get
an error message that says,

You cannot drop an item onto a button on the taskbar.

However, if you drag the item over a button without releasing
the mouse button, the window will open after a moment,
allowing you to drop the item inside the window.

Why doesn’t the taskbar let you drop directly onto a taskbar

Ideally, if the taskbar receives a IDropTarget::Drop,
it could do something like this:

// imaginary code
IDropTarget *pdt;
if (SUCCEEDED(GetDropTargetFromWindow(hwndButton, &pdt))) {

(Warning: I said “something like” this. Forwarding a drop is
actually more complicated than this.)

The reason why the taskbar doesn’t do this is that there is no such
function GetDropTargetFromWindow function.
The taskbar can’t forward the drop operation even if it wanted to.

Why is there no GetDropTargetFromWindow function? I have no idea.
You’ll have to ask the OLE folks.
If I had to guess
(and I know I have to because you folks will just keep badgering me
until I come up with a guess),
it’s because that would create the problem of how to
prevent somebody from screwing with a program by
grabbing its drop target and never releasing it.

Now of course people will criticize my explanation, so I’m going to
say it again: I don’t know the answer. I’m just guessing.
My guess is probably wrong.

Raymond Chen
Raymond Chen

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