Keyboard navigation: Support PageUp/PageDown, Home/End

[mcsf]

Part of #2990.

Issue Overview

When editing with a keyboard, the arrow keys move the caret within and between blocks, as expected. However, a user arguably expects to be able to quickly cover great lengths of content using the PageUp, PageDown, Home and End (UDHE) virtual keys.

N.B.: These keys are nowadays less commonly found as physical keys on a keyboard, but attainable with the arrow keys combined with modifiers such as Fn, Ctrl, depending on the platform, hence the term virtual.

Currently, UDHE scroll the content as expected of a browser page, but never affect caret placement. In other words, suppose that a very long post with many paragraphs is loaded, and that the caret is sitting on the first character of the first block. Pressing PageDown or End will scroll away from that position and that block, other blocks will move into sight, but the caret disappears, since it remained at its initial position. As the user now sees the paragraph at the bottom of the editor, they may press the arrow keys (or immediately enter text) hoping to see the caret appear there; instead, the editor immediately scrolls back to the top. In the end, there is no way to move the caret to the bottom except for:

• pressing ↓ all the way to the bottom, moving the caret one line at a time, or
• using the pointer to reposition the caret.

Prior art

The described expected behavior can be experienced in conventional word processors.

Possible Solution

Screenshots / Video

Related Issues and/or PRs

Todos

• Tests
• Documentation

[karmatosed]

I just tried in Google docs and on a mac 'Fn + Arrow' seem to work. It's not super discoverable though. if we have to pick one that feels like a solid one to follow as an expected, but hidden pattern.

[mcsf]

Marked as Enhancement, since no such feature is found in Classic. Further, closing due to inactivity and inferred low interest. One can always reopen.