Connector tool: Impossible to connect object placed on top of another object
Migrated from: https://bugs.launchpad.net/inkscape/+bug/1433115
#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- Add a background shape
- Add a shape "1"
- Add a shape "2" on top of the background shape (example in attached file)
- Try to create a diagram connector from 1 to 2
#### What happened?
- The diagram connector cannot be connected to shape 2, because it is on top of a background shape -- the handle to connect to shape 2 does not appear
- Instead only the handle of the background shape appears
#### What should have happened?
Expected behavior:
- The diagram connector can be connected both to shape 2 and the background shape, however the user desires
- The shape in the foreground takes precedence over the background shape, not vice-versa
Workarounds:
- Move shape 2 to an empty area, then move back --> This is annoying
- Move shape 2 below the background shape and connect -> this works !?
#### Inkscape Version and Operating System:
* Inkscape Version: 1.1-dev (12e2a09, 2020-02-19)
* Operating System: Windows 10
* Operating System version: 10.0.18362

#### Migration info
* Reproduced on Windows XP, Inkscape 0.91 and trunk rev. 14023.
* Not reproduced with 0.48.5, Windows XP
* not reproduced with rev 10326 (merge of cairo renderer),
* not reproduced with rev 10578 (just before the merge of the rendering cache branch),
* reproduced with rev 10579 (merge of rendering cache),
* reproduced with rev >= 10588 (just before the removal of libnr in 10589);
the regression is possible related to the changes for the renderer's caching (though disabling the cache e.g. with current trunk does not restore the behavior known from earlier releases).
* Reproduced with Inkscape 0.91 r13725 and 0.91+devel r1491 on OS X 10.7.5.
issue