resolve when screens are mirrors, desktop item view disappear.when screens are mirrors, desktop item view disappear.

when create template failed, show error message.

style change will relayout items in view by default, restore their positions manually.

since i use inpositive response model for list view, there is no need to do that.

   1.Use semaphroe to ensure thread safety.
    the current insert/remove operation of thumbnail hash is not thread-safety.
    that might let peony crashed sometimes.
   2.ThumbnailJob: handle the unexpected watcher's parent (a file item).
    note that a image which's parent is a deleted file item should not be thumbnailed.

sometimes it might lead a crash when edit a index when location change started.

list view with inpositive response model will generate files thumbnails correctly after all files enumerated and their infos queried.

IconViewIndexWidget: fix the bottom does not draw rounded bottom when item's icon is not a standard size (for example, a image 200x100).

1. fix when using arrow keys for selecting new item, current index widget does not be cleared.
2. when double clicked an item, clear its index widget.

for now, when dragging the item it will be dragged correctly, not show a unexpected rubberband instead.

the old code is not safe and might let peony-desktop crash.

1. icon view: improve the text painting.
   Allow draw 2 line with ellipsis ending for default long name file items.
2. desktop icon view: improve item text displaying.
3. IconViewTextHelper::paintText: fix the pen color proplem.
   Add option for using system palette or not.

note that the point passing to icon view might have offsets,
which decided by contents margins between DesktopWindow and DesktopIconView.

note that after user login, view might be resized due to other components, such as ukui-panel.

when right click on a selected index, do not clear current selection.

For now, slow double click rename perform much better than last version.