Backdrop Navigation UI

[carljbowman]

Breaking out from: https://github.com/LLK/scratch-gui/issues/514

@carljbowman to flesh out and to provide icons

[carljbowman]

Overview

This was an UI exploration to allow a user to easily select a backdrop without having to use blocks or navigate to the Paint Editor.

1 of 1 Backdrops

• Here is exploration that use the language "Backdrops 1 of n", but we could simplify and remove the "of n" text.

1 of 3 Backdrops - Clicking next UI

• UI could only appear when there are more than one backdrops.
• Arrow should always be active and backdrop lists should wrap. So when "Backdrop 1 of 3" is selected and the left arrow should wrap to "Backdrop 3 of 3"

2 of 3 Backdrops

[carljbowman]

There are still some layout issues to dial in regarding responsive behavior. Since this is not a 2.0 feature I am backlogging until we have some more time to iron out these details.