Wondering about the new units (px and em) introduced into develop-1.8

[besh81]

New units system introduced in develop-1.8 seems to work fine from the point of view of control arrangement inside place's fields.
Now what isn't working properly are the controls themselves.

For example, imagine to use an HighDPI screen and the treebox control, while the text is properly scaled the others parts are not:
- handlebars
- elements like "arrows"
- node images should support different resolution too

The same happens with almost all the other controls.

The question is:
@cnjinhao would you like to completely support the High DPI screen or leave the lib as it is?

In case you would support High DPI please give us some guidelines so we can help you with this task.

[cnjinhao]

The contents in a widget are not enlarged is a known issue.