Unintended zoom/keyboard behavior

[KatieWoe]

Test device
Dell
Operating System
Win 10
Browser
Chrome
Problem description
For phetsims/qa#582
It seems to be possible to manipulate both the hands in the sim and the magnification at the same time, which can lead to unintended behavior that can cause some confusion. If keyboard nav focus is on both hands and you are zoomed in, you can use ctrl + 0 to zoom out to normal, but in doing so you will press 0, which moves both hands to the bottom. Since ctrl was pressed, presumably only the zooming out behavior was intended.

Visuals

Troubleshooting information:

!!!!! DO NOT EDIT !!!!!
Name: ‪Ratio and Proportion‬
URL: https://phet-dev.colorado.edu/html/ratio-and-proportion/1.0.0-dev.77/phet/ratio-and-proportion_all_phet.html
Version: 1.0.0-dev.77 2020-12-08 00:32:10 UTC
Features missing: applicationcache, applicationcache, touch
Flags: pixelRatioScaling
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36
Language: en-US
Window: 1280x658
Pixel Ratio: 1.5/1
WebGL: WebGL 1.0 (OpenGL ES 2.0 Chromium)
GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.0 Chromium)
Vendor: WebKit (WebKit WebGL)
Vertex: attribs: 16 varying: 30 uniform: 4096
Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32)
Max viewport: 32767x32767
OES_texture_float: true
Dependencies JSON: {}

[jessegreenberg]

I think the best way to fix this would be to not have the sim specific behavior on "0" key if the "ctrl" key is down. However, let me know if that isn't possible @zepumph.

I considered adding a way "reserve" the Pointer for this case but it started to get complicated. Presumably we want to continue to allow zoom, we just want to prevent behavior on "0". So we would need an Intent on Pointer that would reserve behavior for a specific key. In my opinion that shouldn't be Pointer's responsibility which is why I am recommending a sim change.

[zepumph]

@jessegreenberg does this feel like a slippery slope, in which a Sim specific issues needs to know about all global functionality in the sim and manually avoid duplicating it? If the future might there be a Sim with general listeners for zoom, playback, and perhaps other things? Is it solely a design consideration to know about these all and avoid overloading keys?

I think the answer is probably to handle this in a Sim specific way, and I'm fine with that here.

If we can forget about the overlap in this case, we can certainly forget again.

Do you have any thoughts about at least marking certain keys as "reserved" so we can fail loudly if we overload key commands?

[jessegreenberg]

I am not sure. This does seem like a problem, and if we cannot catch in code then we need a well documented list of the taken hotkeys. Currently, the overlapping key is in an arbitrary listener somewhere in the sim code, and I can't think of a way to detect this. Not sure how it would work, but perhaps one day we could have "hot key registration" class that keeps track of this for us.

[zepumph]

@jessegreenberg and I decided that the manual approach seemed acceptable for now, and we added doc in the code review checklist to look for these overlaps in the future.