Users can add placeholders to their messages, eg
> …your vehicle ((registration number))
when the message is sent, this gets replaced with the data the user uploads, eg
> …your vehicle LC12 BFL
We reckon that it will be useful to see that the placeholder has been
recognised, ie that its syntax is correct, before uploading any data.
We reckon that the best way to do this is by styling it differently to the rest
of the text that the user types.
This is not a trivial problem. There are two possible ways to do it:
1 Write a Google Docs-style text rendering engine, which completely replaces
the native HTML `<textarea>` with a custom control, and programme what should
happen when the user types something that looks like a placeholder, or
presses an arrow key, or makes a selection, or…
2 Leave the `<textarea>` in place, unmodified, and duplicate layers in front
of/behind it to visually replace a placeholder with the blue lozenge
Unsurprisingly, this commit implements 2.
There are four layers. Each layer contains live-updated copy of the text in the
textbox, and each is styled differently:
- one layer behind the textbox to make the blue background
- the textbox itself
- a layer with the white text, which overlays the black text of the textbox
- a layer with an inner shadow to knock back the brackets
This is because of some interesting limitations:
- The text in the foreground and background must occupy the same physical space,
so no deleting characters from the duplicated layers
- Words can’t be split up into multiple elements,
eg `<span>((</span>regist…`:—this results in slightly different kerning to
`((regis…`, which messes up the alignment of the layers
- The textbox can’t be completely overlapped with a block of colour, because
the cursor disappears behind it. Trying to edit text when you can’t see the
cursor is hard.
Implementation
Technically this makes use of Paul Hayes work on Javascript modules in the
GOV.UK frontend toolkit[1].
It also makes use of the `oninput` event to detect changes to the textbox’s
contents. This is much more performant than `onkeydown`, `onpaste`, etc. Without
it the delay between user input and the layers all updating is too slow and you
see misalignment of the layers.
1. https://github.com/alphagov/govuk_frontend_toolkit/pull/227
Having the full history of the message is more information than is necessary.
We should only show what stage the message is at, and the time that it reached
that stage.
We can do research later on to find out if users understand or care about the
different stages.
This mocks out a data structure for a job’s messages, and renders this data:
- on the notification page, as a table, which links through to…
- …the page for an indidivual message
This commit:
- removes the row numbering so it’s easier to scan the list of phone numbers
- adds subheadings for 'first three' and 'last three'
- puts the 'see all' link at the end
Since GOV.UK Elements is versionned now it makes sense to bring it in as a
dependency. This enforces a separation between what generic stuff we’re using
from Elements and what is specific to our app.
The benefit is that when the generic stuff changes it will be easy to bring
those changes in.
This commit also bumps GOV.UK frontend toolkit to the latest version (v4.5.0).
