Bug 378313

Created attachment 104830 [details]
Patch

Hi, for a while I noticed the following message in my console when starting Krita:

    QLayout: Attempting to add QLayout "" to QWidget "", which already has a layout

Today while testing the appimage for 3.1.3-alpha-2 I decided to check why that was happening.

Learned that when you create a Layout passing a widget via constructor, it then sets itself as the main layout for that widget. Then debugging the Docker factory creation loop, found that the HistoryDocker was being created with a QVBoxLayout(this) and QHBoxLayout(this). So the second time a layout was created, the warning was raised.

Spent some time searching the web for example on how people create widgets with V+H box layouts, and the general consensus seems to create the horizontal passing nothing in the constructor, then the vertical with the widget in the constructor, and finally add the hboxlayout to the vboxlayout (e.g. http://zetcode.com/gui/qt4/layoutmanagement/).

Attached a patch created against the latest commit to the master branch.

Testing locally, the behaviour of the History Docker seemed to be the same (both H + V scroll bars working, can successfully go back and forth in history, etc).

Hope that helps!
Bruno