Toolbar buttons tooltip: show help instead of label

[manics]

Currently the tooltip for a toolbar button with just an icon is the help text for the action/command.
If a toolbar button has a label the label text is shown alongside the button icon as expected, but it also replaces the tooltip help.

With this PR the help text is always shown as the tooltip.

Old behaviour:

New behaviour:

[lresende]

What is the accessibility side effect of this change? @jasongrout @takluyver any thoughts here?

[kevin-bates]

@jasongrout - can you please comment on Luciano's accessibility question? Otherwise, I think this looks good.

[kevin-bates]

My review is based purely on the excellent screenshots - thank you.

There's still the question of accessibility that should be resolved.

[kevin-bates]

@tgeorgeux - I believe you deal in the realm of UX. Do these changes introduce any accessibility issues and, if so, might there be a way they can be addressed while still providing this improved behavior?

[afshin]

Thanks for the PR!

I rebased your branch against master and pushed. I would suggest adding an aria-label and also defaulting to the el.label in cases where help is not available and just switching the default order instead of removing it altogether. Something like this diff:

diff --git a/notebook/static/notebook/js/toolbar.js b/notebook/static/notebook/js/toolbar.js
index 0e47e3470..295975c30 100644
--- a/notebook/static/notebook/js/toolbar.js
+++ b/notebook/static/notebook/js/toolbar.js
@@ -94,7 +94,8 @@ define(['jquery','base/js/i18n'], function($, i18n) {
                 }
                 var button  = $('<button/>')
                     .addClass('btn btn-default')
-                    .attr("title", i18n.msg._(action.help))
+                    .attr("aria-label", el.label)
+                    .attr("title", i18n.msg._(action.help)||el.label)
                     .append(
                         $("<i/>").addClass(el.icon||(action||{icon:'fa-exclamation-triangle'}).icon).addClass('fa')
                     );

I'm happy to push a commit with this myself since this PR was opened quite some time ago and you may be otherwise occupied.

[tgeorgeux]

@kevin-bates Sorry I missed this ping. I don't really know enough about the mechanics of what's going on to know if this change will negatively impact accessibility. It looks like a net improvement to me, with @afshin's changes mentioned above.

[manics]

Thanks for looking, I've made the requested change.

[afshin]

Thank you!