Implement Accessibility Support#163
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Looks like the CI is failing due to my hack in the gulp script; will remove that commit before merging. |
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Force pushed to updated inaccurate comments and commit messages to reflect that focus computations are done via a pre-order traversal of the tree, not an in-order one. |
1. The keyboard can now be used to move through the tree, expand and collapse nodes: * Home / end moves to the first and last visible node, respectively. * Up / down arrows moves to the previous / next visible node. * Right arrow expands a collapsed node, if focus is on a collapsed parent. If focus is on an expanded parent, move to its first child. * Left arrow collapses the node if focus is on an expanded parent. Otherwise, focus is moved to the parent of the currently focused node. * First letter navigation: for example, press R to move focus to the next node who's label starts with R. * Space toggles selection, as expected for a checkbox. This is implemented by computing an pre-order traversal of visible nodes updated each render which greatly simplifies computation for focus movements. Focus is managed by using the [roving tabindex pattern](https://www.w3.org/TR/wai-aria-practices-1.1/#kbd_roving_tabindex). * Each TreeNode takes in a new property, `hasFocus` which is initialized to `false` on initial render. This causes each tree item to have `tabindex=-1` set, which excludes them from tab order, but allows them to be programatically focused. * On initial focus of the top-level `CheckboxTree` component, we initialize the currently focused node index to 0. This causes the first tree node's `hasFocus` to be set to `true`, which sets `tabIndex=0`, so it is included in tab order. `TreeNode`'s `componentDidUpdate` fires a focus event when it is supposed to gain focus. * Other key presses manipulate the currently focused index, which causes the element with `tabindex=0` to move about, hence the roving tabindex. 2. Add the necessary aria attributes for screen readers to correctly read the state of the tree, whether a node is expanded/collapsed, checked etc. For more information, see https://www.w3.org/TR/wai-aria-practices-1.1/#TreeView
… be used as a dependency in package.json
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I am sorry about the radio silence. I will get to looking at this soon (ideally within a few days). |
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@jakezatecky any chance you could take a look? |
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Ping @jakezatecky |
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Fixes #162
See the commit for implementation details. I also had to temporarily disable scss-lint, since I don't have it installed.
Outstanding items: