[SDK] Toolkit lacks radio buttons

[Matthew Paul Thomas]

Currently the toolkit has no radio buttons.

As a result, developers are using checkboxes for groups of options where only one can be selected at a time.
<https://launchpadlibrarian.net/187978147/new.jpg>

This is misleading. Everywhere else, checking a checkbox toggles its state, whereas here special code is used to ensure it remains checked. And on every other platform, checking a checkbox doesn't uncheck another checkbox.

<http://goo.gl/6fWvFg>: “Radio buttons are one of the three types of radio control (along with the radio list and the radio menu), letting you choose exactly one from a group of options…”

[Tim Peeters (tpeeters)]

This is a bug for design, because we don't have designs for radio buttons (and maybe we won't ever have them at all?).

In the meantime, we have either the CheckBoxes shown in the screenshot, or the ItemSelector.

[Giorgio Venturi (giorgio-venturi-deactivatedaccount)]

We are going to use the ListItem selector. It currently shows the checkmark at the right.

We will need to explore the implications of this decision on larger form factors for the Convergence SDK.

[Matthew Paul Thomas (mpt)]

On the PC, toolkits have radio lists like ListItem as well. But they *also* have radio buttons, because for a couple of reasons, sometimes radio lists just don't work.

First, just as with boolean options, radio options may have secondary controls. An example of this is shown, albeit with a visual glitch, in the bug description <https://launchpadlibrarian.net/187978147/new.jpg>: the second option has a caption containing a tappable link to the "Nokia HERE terms and conditions". That wouldn't be possible with ListItems.

If only one radio item has secondary controls, you can work around this by ordering the option with secondary controls last, so that the secondary controls are outside the list. But sometimes the order is already important: for example in that Location screen, the "Not at all" option really should be last. And sometimes, more than one option has secondary controls. An example of this is the "Connect to the Internet" screen of the installer <https://launchpadlibrarian.net/195464902/internet.png>, where both "Connect to this Wi-Fi network" and "Connect to a hidden Wi-Fi network" have secondary controls (and again, the negative option really should be last).

Second, radio options should sometimes be presented horizontally if they can fit, which ListItems can't do. For example in System Settings on the PC, "Time & Date" has "Set the time: ( ) Manually (*) Automatically from the Internet", while "Mouse & Touchpad" has "Primary button: (*) Left ( ) Right".

Let me know if you need any further info.

[Femma (femma)]

Part of the UI Toolkit/SDK project.

[Matthew Paul Thomas (mpt)]

I have now fully specified radio buttons in the toolkit specification. Let me know if you have any questions. <https://goo.gl/tnwf5y> (Canonical-only link, unfortunately)