Bootstrap 3 vs Bootstrap 4
Support for Bootstrap 3 was added in AppStudio 6. Since that release, the developers of Bootstrap have released Version 4.
They made a lot of changes in Bootstrap 4: more than we could build a migration for in AppStudio 7. We ended up making Bootstrap 4 a separate framework. We will continue to support Bootstrap 3 for existing projects, but recommend using Bootstrap 4 for new projects.
We were able to make most of the changes in our code, so the controls work pretty much the same way. The code emitted by AppStudio is quite different.
Since Bootstrap 3 and Bootstrap 4 share many internal variable names, controls from the two frameworks cannot be included in the same project.
Summary of notable changes
Button: Extra small size is gone. No more 'default' appearance.
Button: New outline property.
Card: New control for displaying formatted information.
Icons: Now using Open Iconic. Names of some icons have changed. Rotation no longer built in. Much smaller!
Labels: Replaced by Badges and Alerts. We left a simple Label control in BS4.
Media: No more imageHorizontal or imageAlignment.
Navs: New control.