Revamp event handling in text boxes and add continuous_update option

[jasongrout]

• Check the width of float/int/bounded text boxes now - they seem to be shorter.
• deprecate the on_submit handler for text boxes, and handle the events similar to how things are done in this PR (with input and change events).

Also, specialize those inputs to type number, and add a step option.

I default continuous_update to False for the textboxes because I figured if people were typing, that's typically what is wanted.

FIxes #584 and #1401.

[jasongrout]

CC @mpacer

[jasongrout]

@mpacer (or anyone), if you have a better name than "continuous_update", I'm all ears...

[jasongrout]

@mpacer, I think this is ready to go. Would you like to give it a spin before merging, or would it be easier to merge and spin off another beta for you to take a look at?

[mpacer]

I can give it a spin before the end of the day :) thanks for getting to this so quickly!

[mpacer]

I think it would help to include in the docstrings what the default behaviour is (i.e., when continuous_update is set to False). E.g., does it send when either you hit enter/return or change focus as asked for in #584?

[mpacer]

Also it'd be good to have an example in the docs of both kinds of behaviour. Probably in the Widgets Event section. This shouldn't need backend connections as far as I can tell so it should explain the behaviour nicely in the docs with two appropriate examples.

Also, you probably want to remove the Special Events on_submit section from the docs if it's deprecated.

[mpacer]

So this almost works, but there is bug in the continuous_update version of this if you select text and then delete it (rather than just deleting single characters):

[jasongrout]

So this almost works,

I'm entirely relying on the browser events, hoping that they Do The Right Thing [1]. Does it have the behavior in other browsers too?

[1] Perhaps too optimistic? Our hopes have been dashed many times before...

[jasongrout]

Oh, the issue there is that when you delete, it recognizes it's not a number, so it's patiently waiting for you to type something that is a number.

[jasongrout]

(that's also why it resets when you click out - if the value is not valid, it resets to the previous value)

[jasongrout]

Also, you probably want to remove the Special Events on_submit section from the docs if it's deprecated.

Right - doc changes coming up...

[jasongrout]

Oh, the issue there is that when you delete, it recognizes it's not a number, so it's patiently waiting for you to type something that is a number.

What if we put in a placeholder like "Type a number" or something? That would show if you deleted everything in the box. Would that be enough of a hint?

[jasongrout]

@mpacer, I updated the docs. Thoughts?

[jasongrout]

Merging - @mpacer, feel free to open another issue if you see something we missed.