drag & drop is broken, can crash or deadlock app_server

[marcusoverhagen]

Drag & drop is broken and can crash or deadlock the app_server.

Michael Lotz is working on fixing this. See #269 for details.

This affects the following bugreports: #117 #231 #234 #269

[mmlr]

Simple drag & drop (like moving or dropping Tracker items) should work as of hrev17058. The negotiated drag & drop (making a bitmap clip from ShowImage) still seems to be broken. Note that we do not yet use (the faster) message delivery by shared area. This causes some flattening / unflattening that gives a noticable delay when initiating a drag.

[axeld]

Are you sure it's caused by that? Usually, drag&drop messages are pretty tiny, and (un)flattening them even hundred times shouldn't be noticeable. (I haven't yet tried it, though :))

[mmlr]

Under real hardware the delay is not noticeable but under QEMU there is one. Could come from the blending in HWInterface::_AdoptDragBitmap() as well though. The mouse moved message on the other hand certainly suffer from the constant unflattening even of tiny messages.

[mmlr]

With the BMessage fix in hrev17101 negotiated drag & drop should now work too (making bitmap clips from ShowImage for example). I'll leave this bug open until I verified that there remain no locking issues.

[diver]

I think there's no locking issues remains. The only thing is that first icon drag after Haiku boot doesn't work. After that everything is okey.