Follow-up to D7427.
Here are various examples of before/after layouts:
We use column or row headings here to bring more structure, and to give the eye visual anchors which aid eye-scanning. The left-aligned checkboxes likewise help with this. And we keep the adherence to the center line, so the alignment matches up between the various buttons and controls.
* Changes the property split percentage from 50/50% to 40/60%.
This is needed to give enough space for the checkboxes:
But in most cases this looks better anyway - see Transform panel:
Or here - this split % just fills out the available space more efficiently:
* Fix various hacks where we previously used manually defined splits. When we did this, the alignment was never quite right, and the layout code was a mess.
* Adds column headings to many places where a list of checkboxes all share a common purpose or leading text:
* Add checkbox + value configurations various places where a checkbox only serves to enable the value slider:
* Removes most uses of grid flow layout. The grid flow layouts combine poorly with column headings, and also they would mess alignment up badly. The grid flow layouts also often made buttons and controls jump around on the screen if you would just resize editors slightly, causing visual confusion, making users lose their place. The logic for at what time the list of items would re-flow was often flawed, jumping to multiple columns too fast or too late - and frankly, the grid flow layouts would often just look bad.
Most changes here are by @billreynish.