This app/feature first shipped on CyanogenOS 12. With each subsequent release, we were able to refine the visuals and interactions.
App Themer provides a quick way for users to adjust the look of their device by allowing them to change the theme of each app. While themes can be applied across the device, this feature is specifically geared to making adjustments in order to create sub-themes or just changing an app back to its stock appearance.
The App Themer acts as a floating button, similar to Facebook Chatheads, which can be moved anywhere on the screen. Depending on installed themes, the list will be populated with options for the app which the button is residing on top of. The button can easily be discarded via a trash tray that appears at the bottom of the screen.
Be sure to check out the video of the feature in action. It does a great job showcasing the user experience of App Themer.
