Revisit alt input for pH probe in the Macro screen.

[pixelzoom]

In Slack#description-tooling, @terracoda said:

Regarding Alt Input for pHS + pHSB we need to also do the Probe, not just the Eye Dropper. While the probe currently has Alternative Input, it was never decided if a single-step or two-step grab was the ideal for the interaction, and I want to know if PhET has a floating probe design or a floating probe option because for non-visual access a floating probe could be ideal - your probe is in the beaker or out of the beaker.

[pixelzoom]

it was never decided if a single-step or two-step grab was the ideal for the interaction

When we added alt input to this sim, it was decided that a single-step grab was appropriate for interaction with the pH probe in the Macro screen. That is what we have been doing as a general rule in sims that do not have description, with the expectation that it will be revisited at a point in the future when description is added. Since we’re now adding description, it sounds like the time has come to revisit.

If we change to 2-step grab, this will involve adding keyboard help for the pH probe.

[pixelzoom]

Since ph-scale has multiple probes... It's my understanding that @terracoda is referring to this pH probe in the Macro screen:

[terracoda]

@pixelzoom, apologies for my strong language. Yes, single step grab okay for Alt Input, and my guess is that a two-step grab will support a wider audience of learners better now that we are adding description.

Thanks for pointing out that pH Scale has multiple probes, but I think the pH probe is the only draggable one.

While reviewing the sim with @arouinfar and @Nancy-Salpepi, we see the benefits of a non-floatable probe. A learner can place the probe at a few useful places:

• in the solution
• in the dispensing column of the dropper
• under the water faucet
• under the drain
• back in home position outside the beaker

We'll be considering shortcuts for these positions.

Until then, @pixelzoom is it possible for you to implement the two-step drag from common code, and to consult with @jessegreenberg if needed? And note that the grab help text is platform specific:

Platform-specific help text:

Alternative Input (Keyboard):

• Look for {{pH probe}} to play. Once grabbed, use keyboard shortcuts to move {{probe}}. Space to release.

Mobile IOS

• Double tap and hold to grab {{pH probe}}. Lift to release.

[terracoda]

Assigning to @pixelzoom for comment and/or implementation.