commit 5cde0849d4a865cb63af7ade8ad70ab9c66c668a
author Logan Hanks <logan@google.com> Fri Oct 05 15:56:10 2018 -0700
committer Logan Hanks <logan@google.com> Mon Oct 22 09:39:44 2018 -0700
tree 53c1c10cc2e6af733a66324191a2996545f61975
parent 4adf83cb433b4a63cae0fcb8f5af6d16801336fd

Redesign the keyboard shortcuts system

The goal of this redesign is to provide two clear concepts that are
treated as separate concerns:

1. Mapping of specific key bindings to a semantic shortcut
2. Mapping of a semantic shortcut to its behavior

Previously, there was no notion of a semantic shortcut. This required
manual crafting of the help dialog and made it difficult to find an
approach to customizing key bindings.

Although supporting key binding customization is outside the scope of
this change, the path forward is more clear. Currently key bindings are
hard-coded during the creation phase of the gr-app element. It's
conceivable that a plugin or user settings feature could override these
bindings at runtime. Or they might be read from some server-side config
and passed down to gr-app via the index.html template.

The universe of possible shortcuts is now defined in an enum by
keyboard-shortcut-behavior. This is also where all the help text is
declared and organized.

The keyboard shortcut help dialog is now a generic container that reads
the current state of actively bound shortcuts and their help content
from keyboard-shortcut-behavior.

The set of declared key bindings that are active (and registered with
suitable listeners on the body element) is determined by monitoring the
attachment and detachment of elements that mix in
keyboard-shortcut-behavior and declare a keyBindings() method. This
method replaces the keyBindings object property that
iron-a11y-keys-behavior looks for. The method should return an object
mapping Shortcut enum values to handler names.

Elements that implement a shortcut behavior but only conditionally
attach to the DOM must depend on a container element to declare the
shortcut and pass the event down. An example is SAVE_COMMENT. The
binding for this shortcut should be active on change and diff views
regardless of whether any comments exist, so that it will be listed in
the help dialog.

The result of this change produces behavior that is close to previous
behavior, but not quite identical. Shortcuts that used to be listed
under a "Change list" or "Dashboard" section header now appear as
"Actions." The exact ordering of shortcuts has not been preserved, either.

Change-Id: Ib3fe44d502a83f7012e30615fbea9da2ab112eb7