Zoom issue on iOS - How can I help debug?

[GuilhermeAnchieta]

Continuing the discussion on the iOS zoom bug (Issue #2939). I understand it's a tricky issue to resolve.

I'd like to help debug this. To do that, I need to run a local, modifiable version of "Orbe" inside my own Angular/Nx project.

Could you give me some quick guidance on the correct steps to "vendor" the library?

I'm trying to create a local copy of the source code to add logs and test fixes, but I'm not sure about the correct build steps, required assets, or dependencies I need to configure.

Any tips on how to get a local dev setup running would be a huge help.

Thanks!

[stephanrauh]

Sounds good! Have a look at this document - I hope it answers most of your questions: https://github.com/stephanrauh/ngx-extended-pdf-viewer/blob/main/projects/ngx-extended-pdf-viewer/how-to-build.md

As for debugging: set the attribute [minifiedJSLibraries]=false, and you're rewarded with the non-minified JavaScript code.

If you still need help - just tell me. I'm looking forward to your insights! Obrigado!

[GuilhermeAnchieta]

Even after following the steps, I'm running into some problems, but the main one is not finding the file:

Cannot GET /assets/viewer-5.4.1093.mjs

[stephanrauh]

Is the file in the assets folder of the source folder of ngx-extended-pdf-viewer? I always run "npm run run:all:old", and it works.

Oh, wait - which branch of pdf.js did you check out? If it's the bleeding edge branch, you have to activate it in the constructor, as described here: https://pdfviewer.net/extended-pdf-viewer/pdfjs-versions

[GuilhermeAnchieta]

@stephanrauh Hi Stephan,

I've successfully set up the local debug environment (showcase + mypdf.js + ngx-extended-pdf-viewer). I have reproduced the pinch-to-zoom stuttering bug on iOS (18.5+).

After extensive debugging, here are the key findings:

The Event Fires: The scalechanging event (from mypdf.js) is firing during the pinch gesture.

The Scale Value is Broken: The event is dispatching an incorrect scale value. It sends for exemple 0.1, 0.11, 0.1, 0.12 ,0.1, 0.13, instead of the expected 1.0, 1.1, 1.2.

The Stuttering/Freezing: The "agarrado" (stuttering) happens because the motor seems to be trying to render this 10% zoom (scale 0.1) before jumping to the correct zoom, causing a visual "flicker" or "jump" on every frame of the gesture.

Location Found: We confirmed this happens inside the mypdf.js motor, in the #setScaleUpdatePages function, right before the eventBus.dispatch('scalechanging', ...) call.

this.eventBus.dispatch("scalechanging", {
source: this,
scale: newScale,
presetValue: preset ? newValue : undefined,
previousScale,
previousPresetValue: previousScaleValue,
noScroll,
});

This seems to be a deep issue in how pdf.js is handling the touchmove coordinates or gestures specifically on the new iOS 18.5 WebKit. The passive: false and defaultZoomDelay suggestions did not solve the stuttering.

[stephanrauh]

Sorry for the late response - I was ill.

TBH, I'm puzzled. I don't have a clue why the event sends 0.1 instead of 1.0. But it's a hot trace!

[GuilhermeAnchieta]

I believe my problem is directly related to issue #3069

[stephanrauh]

I don't think so - but it's not impossible. It's only my gut feeling that says "no!".

[stephanrauh]

I've been trying to find out what's going wrong, but I failed. You've mentioned the "0.1" (aka 10%) zoom. What happens if you increase minZoom, e.g. [minZoom]="0.5"?