On Android, we disallow screenshots on screens where the seed is visible.
(The seed is extremely sensitive data that should not be stored digitally without
significant precautions but it's also cumbersome to write down or memorise, so
some people instinctively just try to take a screenshot of it when creating a wallet.)
We do this by using the built-in OS mechanism of setting FLAG_SECURE on the window.
However, on some devices with custom ROMs (one report from LineageOS, one from /e/OS),
unsetting FLAG_SECURE crashes the application for some reason.
As a workaround, this commit adds a config setting into the Preferences,
to disable this mechanism and just always allow screenshots.
(note that you can get into the qml Preferences before creating/opening any wallet)
ref https://github.com/spesmilo/electrum/issues/8522
A new config API is introduced, and ~all of the codebase is adapted to it.
The old API is kept but mainly only for dynamic usage where its extra flexibility is needed.
Using examples, the old config API looked this:
```
>>> config.get("request_expiry", 86400)
604800
>>> config.set_key("request_expiry", 86400)
>>>
```
The new config API instead:
```
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS
604800
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS = 86400
>>>
```
The old API operated on arbitrary string keys, the new one uses
a static ~enum-like list of variables.
With the new API:
- there is a single centralised list of config variables, as opposed to
these being scattered all over
- no more duplication of default values (in the getters)
- there is now some (minimal for now) type-validation/conversion for
the config values
closes https://github.com/spesmilo/electrum/pull/5640
closes https://github.com/spesmilo/electrum/pull/5649
Note: there is yet a third API added here, for certain niche/abstract use-cases,
where we need a reference to the config variable itself.
It should only be used when needed:
```
>>> var = config.cv.WALLET_PAYREQ_EXPIRY_SECONDS
>>> var
<ConfigVarWithConfig key='request_expiry'>
>>> var.get()
604800
>>> var.set(3600)
>>> var.get_default_value()
86400
>>> var.is_set()
True
>>> var.is_modifiable()
True
```
(this somehow escaped attention before, as most objects usually don't have multiple instances,
unless multiple wallets are open at the same time.)
Also, move all signal declarations, class constants and variables to the top of class definitions.
preference from the GUI, because the mempoolfullrbf option in
Bitcoin 0.24 makes RBF signaling pretty meaningless. Fixes#8088.
Note: RBF remains disabled for channel funding transactions.
In that case, the flag is actually only used as a semaphore
between different instances of the same wallet.
If enabled, we log to stderr, which can get inspected via logcat.
Not user-friendly at all - but previously there was no way to get logs from a release build.
closes https://github.com/spesmilo/electrum/issues/7409
