+msw just fyi, since he's reviewing my refactor change

Note that there's a touch_hud mus app [1] that we worked on a long time back when we were looking into breaking ash into smaller pieces. I think this would be a really good step to move towards the direction of splitting off smaller rarely used features into their own mus apps that can be launched/terminated as needed. (The other one we looked into was autoclick [2])

[1] https://cs.chromium.org/chromium/src/ash/touch_hud/mus/
[2] https://cs.chromium.org/chromium/src/ash/autoclick/mus/

Note that for testing or explaining videos, this is useful internally.
As we can record the touch points for showing when things don't work.

That being said, agreed that for users there is no benefit.

at least no clear benefit compared to the chances a user would accidentally invoke it.

1-day usage on this ranges from 0.04% to 0.08% in the course of a week. I have a strong suspicion that most of that is accidental usage.

There are only 2 use cases that I know of for this:
1: Touch debugging.
2: Demo projecting (showing where the user touched on screen)

My strong preference here is to keep the feature (For now. Eventually moving it to an installable mus app as sadrul@ suggests makes a lot of sense) but remove the pref. That will accomplish a few things:
1: Simplify the code
2: Make the feature available everywhere
3: Allow users who accidentally turn this on to escape with a reboot (rather than having to track down help as they do now).

I want PM input on this before we make a call though.

omrilio@ what do you think?

I have the same feeling as you -> most usage is accidental.

Also agree with you about removal -> I think it would be good to only have a more advanced entry point and remove the shortcut. Perhaps via a flag?

Thoughts? 

If you'd like it to become a flag just assign this bug to me and I'll take care of it.

Note that we already have a flag show-touch-hud, which shows a trail of colored dots for the last ~10 touches. It'll be a bit confusing to have both, but the colored dots definitely aren't suitable for projecting.

(You can try show-touch-hud in about:flags today.)

Thanks James!
Regarding the touch hud flag - from past experience it is extremely slow and adds other information on the screen. I'll check it out later when I get to a touch Chromebook.

Assuming it's also okay with you Albert, I'll do a quick check with UI Review to make sure there is no concern.

Sounds good Omri.

I tested it per comment #9 and I stand corrected about it being slow, it worked nicely now. However, the colors remaining on the screen make use-case 2. in comment #5 impossible.

I'll reach out to UI review and get back to you if there are any concerns.

Hi there, just looping back that we have agreement from UI review to move this to a flag.
In addition, I'd recommend to default the setting to off for all users (including ones who accidentally enabled it) when we do the switch. I've also reviewed that with UI review and they are okay with it.

James, can you take ownership?

I'm going to call the flag "Show taps" to match the Android Oreo developer option that does the same thing.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0ba192bf79dbac1cc72bd8d677570719b46f761e

commit 0ba192bf79dbac1cc72bd8d677570719b46f761e
Author: James Cook <jamescook@chromium.org>
Date: Fri Dec 01 20:53:11 2017

cros: Convert "touch hud projection" from key shortcut/pref to flag

This debugging/presentation feature was tied to Ctrl-Alt-P. Usage is
very low per UMA metrics. We suspect most usage was from users
mistakenly hitting it when pressing Ctrl-P to print. Since it was tied
to a pref the user could get stuck in this state. It also didn't work
at the login screen and would turn on and off when switching
multiprofile users.

This feature is useful for debugging, recording videos of touch bugs,
and for projecting demos. UI review suggested moving it to about:flags
alongside the other touch debug flags.

* Remove the pref and add cleanup code to wipe the existing value.
* Remove the accelerator key.
* Add --show-taps. The name is inspired by the Android OS developer
  option that does the same thing.

TBR=rockot@chromium.org

Bug:  786115 
Test: existing ash_unittests
Change-Id: I07579bff6ab3dd16ec5c14347df1a047b1aa935c
Reviewed-on: https://chromium-review.googlesource.com/802075
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: Dominic Battré <battre@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521058}
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Are there any people who record screencasts for bugs or who use projection for demos that I should notify about this change?