Content translation provides editors with the needed context to create good translations. While supporting translation on mobile would require a separate effort (T132900) we want to consider simple ways to improve the support provided for smaller screens (T155767). As part of that effort, this ticket proposes to better deal with cases where the viewport is too narrow to comfortably fit the three columns.

The idea is to adjust the viewport to show two columns when the window is smaller than 800px, allowing the user to navigate left and right to decide which two columns to view at each moment:

• Source and translation. Users can decide what to add from the source article, as well as proofreading their translation. Part of the tools column will still visible to provide some context, and hovering or clicking in the area will move the viewport to the other view.
• Translation and tools. Users can focus on editing the translation. Part of the source article will still be visible to provide some context, and hovering or clicking in the area will move the viewport to the other view.

In both cases, an arrow will surface the possibility to show the hidden column. Hidden columns will have a 25% opacity layer f the same color as their background when they are hidden.

This is not intended to support comfortably all sizes, but seems a simple approach to experiment and learn from users.