Option for fullscreen qrcodes on diy jades

[akig2]

Qr-codes are very difficult to scan with a webcam. The small screen and bad autofocus on webcams makes it a nightmare or simply impossible.
The jade ui splits the screen vertically and displays the QR-code on one side. This is close to optimal for screens in landscape mode with something like a 2:1 ratio.
But for more squarish screens this reduces the possible code dimensions by a lot. It's even worse for screens in portrait mode like the waveshare touch lcd 2.

My suggestion would be to add an option to display a fullscreen qr-code on diy jades when exporting pubkeys or signatures. I don't know if this is a sensible request since it would be an almost useless feature on the original jade wallets.

[jgriffiths]

Given this only affects DIY, as a feature it would realistically be very low in priority for us given we have a large amount of outstanding features to work on, and the recent changes for QR display brightness seem to have resolved most complaints about scanning QR codes from Jade devices.

So this would have to be a user-implemented feature (at this stage at least). I could see this working with a maximize button next to the brightness button, which when pressed would display the QR fullscreen and centered with no border or buttons visible. Pressing any button from the fullscreen view would then take you back to the original view.

[akig2]

I'm no coder but grep'ing my way through I ended up changing make_show_xpub_qr_activity() in main/ui/qrmode.ci and in main/bcur.c I changed the scale factor for 114 to 7. I'm happy with the result.
Sadly it seems to break every qr that uses the same alphanumeric capacity. I can probably figure out the signature sharing part once I replace my broken cam on the waveshare.

For inspiration, this is what sharing the xpub now looks like. It's close to twice as big: