add "max" button to amount fields

[jbibla]

Is your feature request related to a problem? Please describe.

Often, users want to do make a tx with all the atoms. since there are 6 decimal places, this can be tedious to type out.

Describe the solution you'd like

It is common in these situations to include a max button, which will automagically add the total amount left to the amount field for the user.

Additional context

Something to consider is the relationship with #2674.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[jbibla]

simple UI feature. would be nice to have!

[mariopino]

Set Max button is working on branch mario/2670-add-max-amount.

Currently set the entire available balance, so want to discuss about best way to subtract the fee from the available balance. If we click on the button, in the step 2 the fee is 0.000000 ATOM, is this a validation error?

It would be cool to include a fee slider to let user set the fee they want. We can include it in step 1 to let us calculate max = (available balance - fee).

[jbibla]

Set Max button is working on branch mario/2670-add-max-amount.

awesome! if you make a draft PR we can see the link to the build and test out the feature 😉

If we click on the button, in the step 2 the fee is 0.000000 ATOM, is this a validation error?

no this is actually correct. if the user has no ATOMs left to pay fees we let them submit a tx without fees.

can you add a warning to this section that explains this? i will help with the language.

discuss about best way to subtract the fee from the available balance.

good thought here. a fee slider could work. i don't know what the best approach is.

we could...

1. allow the user to set the true max with the max button on step 1
2. have a fee selector on step 1 (either a slider or three button/options)

alternatively...

1. allow the user to set the true max with the max button on step 1
2. show a warning that they are not leaving any for fees which may be required
3. turn the button into a "subtract fees" button

@faboweb what do you think?

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this is related to #2530

[faboweb]

We decided against a fee selector in favor of less mental overhead for the user.
We could run the simulation already on step 1 to know the fees there to calculate the max. Never the less we need to show a warning that the max already has subtracted fees.
But I vote for show a warning that they are not leaving any for fees which may be required. It is the least complex. And this way we don't block the user in their intended behavior but educate him about the consequences.

[jbibla]

so what you're proposing is:

1. when the user clicks max we run the fee simulation and subtract this from the max?
2. show a message explaining this is what happened and why

are you opposed to the following proposal?

1. allow the user to set the true max with the max button on step 1
2. show a warning that they are not leaving any for fees which may be required
3. turn the button into a "subtract fees" button

[faboweb]

Why do you want to make it more complex? Do we want to force the user to pay for fees?

[jbibla]

my intention is to make it as simple as possible while also letting the user know what's happening.

i am in favour of the simplest solution - which i guess at this point is having a max button that doesn't know anything about fees and a message (#2530) that says "hey, you should probably leave some left over for fees".

that would be simplest and easiest IMO.