Pinch to zoom

[starypatyk]

Here is my initial pinch-to-zoom implementation. This should resolve #916 and #917.

I have not committed the compiled code yet, to make rebasing easier.

Some explanation of the changes:

In https://github.com/nextcloud/viewer/pull/1952/commits/003f31fe70550da3c8046e80124784a425335b4c I have switched from mouse events to more generic pointer events (see https://developer.mozilla.org/en-US/docs/Web/API/Pointer_events).

https://github.com/nextcloud/viewer/pull/1952/commits/e96662cc299e6d665b7b7d7112ee98fbe744b649 is the actual implementation.

• I have re-used the original zoom handling code - a significant part of the old updateZoom method was extracted to updateZoomAndShift and I created an additional common method updateShift.
• Co-ordinates of the two touches are kept in pointerCache.
• Pinch-zoom calculations are explained in the comments.

I committed https://github.com/nextcloud/viewer/pull/1952/commits/aeab2bd8f159fae5553150b293d2c12fa7f353ca separately, to make it easier to follow the changes.

https://github.com/nextcloud/viewer/pull/1952/commits/1f0fcedc9dfa1ecc86a3ab59418c1e151425a1b7 was required after recent changes in master - as I removed the width/height: 100% from CSS.

I have the following questions:

• Regarding https://github.com/nextcloud/viewer/pull/1952/commits/1f0fcedc9dfa1ecc86a3ab59418c1e151425a1b7 - an alternative solution would be to bring back width/height: 100%. I am not sure which one is better. Any suggestions?
• The pointerMove and pointerUp handlers are now attached all the time. I am not sure what should be done here: https://github.com/nextcloud/viewer/blob/698afa42df0c8976e797a68dec8c8ee8f2dc9c89/src/components/Images.vue#L219 and here: https://github.com/nextcloud/viewer/blob/698afa42df0c8976e797a68dec8c8ee8f2dc9c89/src/components/Images.vue#L223 Probably also a permanent handler for pointerOut that would invoke resetZoom? I do not know how to test this case. Suggestions welcome.
• I have tested on Android and iPad. Would be good to verify on an iPhone.
• I have noticed that recent changes to NcModal (https://github.com/nextcloud-libraries/nextcloud-vue/pull/4350) affect zooming behaviour. Now, when the image is enlarged a bit from 100%, a scrollbar is shown, and this causes a slight shift in image position. This happens on Chrome and Chrome Mobile (for some reason Firefox does not show the scrollbar). This is not a major problem, but is ~~quite~~ a bit annoying. I wonder if we should try to have some workaround in this PR or leave it for a separate PR.

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[skjnldsv]

@starypatyk I don't have much time for Viewer lately, thank you for this PR (and your patience :see_no_evil:)

[starypatyk]

@skjnldsv No worries. :wink: Thanks for letting me know. Waiting patiently then. :snail:

[starypatyk]

@starypatyk I don't have much time for Viewer lately, thank you for this PR (and your patience 🙈)

Hi @skjnldsv,

Any chance to go forward with this PR?

FYI - I have rebased and re-checked the implementation. Seems to behave decently. Tested as previously on Android and iPad.

This still requires some clean-up - see my questions in the first comment (I have updated commit references after rebase in the original comment).

[skjnldsv]

/compile /

[skjnldsv]

Patience came to an end, let get this in! Sorry again @starypatyk!

Btw, if you're interested, I sketched an RFC for an improved Viewer version 3.0. If you have some commens or feedback, feel free to check #2395 :tada:

[skjnldsv]

cypress fix: https://github.com/nextcloud/viewer/pull/2436

[skjnldsv]

Fixing the public view rendering :)

[starypatyk]

@skjnldsv - Great to see this merged finally! :wink: Thanks :+1: