EVALUATION

I have relocated the code for setting _NET_WM_STATE_SKIP_TASKBAR atom to XDialog.postInit() method. It is too early to invoke it in the preInit() method.From the othe hand it is not needed to set it in setVisible() method beacuse we set owner only once at the moment of a Window creation.
                                     

SUGGESTED FIX

http://hg.openjdk.java.net/jdk8/awt/jdk/rev/5255fd5b0418
                                     

EVALUATION

I took into consideration windows and now _NET_WM_STATE_SKIP_TASKBAR atom is set  in XWindowPeer.
                                     

EVALUATION

The problem connected with _NET_WM_STATE_SKIP_TASKBAR. Before we relied on WM_TRANSIENT_FOR. We expected that this hint suggests WM do not show the window in the task bar. In jdk6 we set _NET_WM_STATE_SKIP_TASKBAR atom and it explicitly asks WM to hide the window in the taskbar. From the sources I see that we set _NET_WM_STATE_SKIP_TASKBAR atom only in WWindowPeer.setBounds(). This seems incorect. The atom should not be set every time the method is called but it should be set once when a window created. Looks like we do not invoke the setBounds method in jdk 7 and 8 for decorated windows but use overriden one from XDecoratedPeer. Anyway we should place the invocation in another place to be called for Dialogs without parrents and undecorated windows.
                                     

EVALUATION

Despite the fact I do not see changes that could affect setting of this property. We set the property in the next places

    XAtom XA_NET_WM_STATE_SKIP_TASKBAR = XAtom.get("_NET_WM_STATE_SKIP_TASKBAR");
./classes/sun/awt/X11/XNETProtocol.javaabominog1
                net_wm_state.add(protocol.XA_NET_WM_STATE_SKIP_TASKBAR);
./classes/sun/awt/X11/XWindowPeer.java
                "_NET_WM_STATE_SKIP_TASKBAR", True);
./native/sun/awt/splashscreen/splashscreen_sys.c


Nither of them connected to the issue.
                                     

EVALUATION

I have compeared output of xprop for jdk8 and jdk6u31 it seems, that _NET_WM_STATE_SKIP_TASKBAR is not set in case of jdk8.

$ diff 6u31.log 8.log 
1c1,2
< XKLAVIER_STATE(INTEGER) = 0, 75497492
---
> _NET_WM_ICON_GEOMETRY(CARDINAL) = 438, 734, 203, 24
> XKLAVIER_STATE(INTEGER) = 0, 75497513
6,7c7,9
< _NET_WM_STATE(ATOM) = _NET_WM_STATE_SKIP_TASKBAR
< _NET_WM_ALLOWED_ACTIONS(ATOM) = _NET_WM_ACTION_MOVE, _NET_WM_ACTION_RESIZE, _NET_WM_ACTION_SHADE, _NET_WM_ACTION_CHANGE_DESKTOP, _NET_WM_ACTION_CLOSE, _NET_WM_ACTION_ABOVE, _NET_WM_ACTION_BELOW
---
> _NET_WM_STATE(ATOM) = 
> _NET_WM_ALLOWED_ACTIONS(ATOM) = _NET_WM_ACTION_MOVE, _NET_WM_ACTION_RESIZE, _NET_WM_ACTION_FULLSCREEN, _NET_WM_ACTION_SHADE, _NET_WM_ACTION_CHANGE_DESKTOP, _NET_WM_ACTION_CLOSE, _NET_WM_ACTION_ABOVE, _NET_WM_ACTION_BELOW
> _NET_WM_WINDOW_TYPE(ATOM) = _NET_WM_WINDOW_TYPE_NORMAL
9c11
< _MOTIF_DRAG_RECEIVER_INFO(_MOTIF_DRAG_RECEIVER_INFO) = 0x6c, 0x0, 0x5, 0x0, 0x14, 0x0, 0x80, 0x4, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, 0x0, 0x0
---
> _MOTIF_DRAG_RECEIVER_INFO(_MOTIF_DRAG_RECEIVER_INFO) = 0x6c, 0x0, 0x5, 0x0, 0x29, 0x0, 0x80, 0x4, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, 0x0, 0x0
11,15c13
< WM_NORMAL_HINTS(WM_SIZE_HINTS):
< 		user specified location: 0, 0
< 		program specified location: 0, 0
< 		program specified size: 517 by 326
< 		window gravity: NorthWest
---
> _NET_FRAME_EXTENTS(CARDINAL) = 1, 1, 29, 1
144d141
< _NET_FRAME_EXTENTS(CARDINAL) = 1, 1, 29, 1
149c146
< WM_PROTOCOLS(ATOM): protocols  WM_DELETE_WINDOW, WM_TAKE_FOCUS
---
> WM_PROTOCOLS(ATOM): protocols  WM_TAKE_FOCUS, WM_DELETE_WINDOW
155a153,157
> WM_NORMAL_HINTS(WM_SIZE_HINTS):
> 		user specified location: 0, 0
> 		program specified location: 0, 0
> 		program specified size: 517 by 326
> 		window gravity: NorthWest
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