Address keyboard commands in certain patterns that may be problematic on MacOS

[mcking65]

The following remarks are pulled from a comment by @jnurthen in issue #484.

There are other patterns where we recommend control + (something) for a function. We should probably modify those too.

Accordion

• control + page up/down (mac keyboards don't have page up/down). While I don't think this will conflict with anything as it is a pretty contrived keystroke it is certainly not natural for a mac user

Grid Popup, Feed, Data Grids

• control + Home/End (mac keyboards don't have home/end). Again - probably won't conflict but fn+control+left/right arrow is a pretty tricky shortcut.

Data Grids

• Control + space - I don't think I have seen this conflict. We definately don't want to suggest using command + space as that conflicts with selecting alternate keyboard layouts which is essential for anyone using a language that uses an IME.
• Control + A - this seems to conflict with "Move to the beginning of the line or paragraph." which probably isn't a big deal in a web document as all it seems to do it scroll up. Command + A would be the mac way of doing select all.

Listbox (multiple selection) & Multi-select Trees.

• Control + Shift + Home/End - becomes Fn+Control+Shift+left/right arrow - probably not practical
• Control + A - as before
• Control + Down Arrow: This needs fixing as this does an OS function (application windows)
• Control + Up Arrow: This needs fixing as this does an OS function (Mission control)
• Control + Space As above

[devongovett]

Came across this same problem when implementing the alternative multi-selection pattern. I did some research across platforms, and I think it's best to alter the keyboard commands depending on the platform:

• Mac
  • Alt + Up Arrow/Down Arrow – Moves focus up or down without changing selection. macOS has default handling for Control + arrow keys. We initially considered Control + Alt but this conflicts with VoiceOver. Command + up/down does not conflict, but Command + Space does.
  • Alt + Space – Selects the focused row. Control + Space also works without conflict, but it's nice to match Alt + arrow keys here.
  • Command + A – Select all.
• Windows/Linux
  • Control + Up Arrow/Down Arrow – Moves focus up or down without changing selection. This matches Windows Explorer.
  • Control + Space – Alt + Space does conflict with a global handler (showing the window menu, e.g. minimize/maximize), so best to avoid matching Mac here.
  • Control + A – Select all.