Dragging an editor to another monitor with different zoom is positioning it wrong

[akoch-yatta]

Important setup: the primary monitor is at 200% and the second monitor is on 100% and placed right from the 200% monitor

The problem occurs, when a view is dragged from the 200% monitor to a position on tje 100% monitor. The new view will not be visible after that, because it is position out of sight.
As far as I have investigated, the flow is as follows:

1. a new Shell is created und it inherits the zoom from the parent or uses it from the primary monitor (=200%).
2. the position is set (from WBWRenderer::createWidget) to its target position, e.g. mouse drop at position 4000/200 (is on 100% monitor)
3. Shell:.setBounds is called with point 4000/200
4. Shell has zoom of 200% and there the points will scaled up to 8000/400 and positioned out of sight.

There will be no DPI changed event, because the shell was never positioned correctly on the second monitor.

Question is, what is the expected behaviour here. I see two different options:

1. The caller takes care of this
   Hard to achieve, because the target location comes from the OS (= drop location of the mouse cursor). How should the caller adept to this (windows specific) behaviour
2. Shell:setBounds takes care of this
   Probably easier to achieve. This would mean that setBounds must be adapted to:

• calculate monitor where the the shell will be placed onto (see org.eclipse.jface.util.Util::getClosestMonitor)
• adapt nativeZoom attribute the zoom of the monitor

[akoch-yatta]

Closed with eclipse-platform/eclipse.platform.swt#1349
Remaining limitations are discussed in #125