Pan speed not adapting during zoom

[3merillon]

Hi Tapspace team,

When panning while zooming the pan speed doesn't adapt correctly, resulting in too fast panning if zoomed out and too slow panning if zoomed in.

The issue is easier to reproduce on mobile, by moving your pinch gesture but is present when keeping the mouse button down and concurrently using the mouse wheel.

Here is a demo demonstrating the issue : https://cybercyril.com/tapspace-bug/

Thanks for your awesome library, I love it!

[axelpale]

Hi Cyril and thank you greatly for preparing a demonstration with the version data and all!

I can see what you mean. Apparently, if the zoom level changes while panning, like when the user scrolls wheel during the pan gesture, the pan executes as if no zooming happened. The issue is a bit hidden because after the gesture ends i.e. after the final pointer is lifted, things reset and the next pan works like it should.

The weird thing is that it does not seem to happen always. If I pan and zoom in sequence but without lifting the mouse button, like pan a bit, then stop and zoom a bit, and then again pan a bit, the viewport pans as expected. But if I attempt to pan and zoom concurrently the issue appears.

I have to dig deeper to find a root cause for this. Very likely it has to do with how the applied transformation is computed in Tapspace's GestureCapturer.

As a side note, the demo you prepared also exhibits another issue where the native text selection gesture of the browser overrides the viewport navigation gestures of Tapspace (at least in Chrome and Firefox). That has a known solution of styling the selectable elements with user-select: none rule. Things become a bit more complicated if there are also text that user must be able to select. This demo explores the current solutions to this situation, although we try to make that simpler before tapspace 2.0.0 exits the alpha stage.

Thank you again for finding and demonstrating the pan issue. I try to solve it for the next release, 2.0.0-alpha.25.

[3merillon]

Thank you for your prompt response Axel!

The issue is much more noticeable on a touch screen because we can pan our pinch.

I noticed it because I'm developing an app that animates the tapspace (locking onto a playhead during playback). In my case this makes the pan issue persist as long as we remain locked. My current solution is to just disable zooming when we are locked to the playhead.

Also much thanks for making me aware to the gesture/text selection issue.

Can't wait for future updates!

[axelpale]

Preparations to solve the issue in alpha.25:

• related commits: 92f0a9d a31c549 131061c 13b965c 83d10eb 392feb8 e8430e3 50457eb b0b0bf1 c2e8f64