1643461 - Pinch to Zoom on built-in PDF viewer does not allow zooming out

Status: VERIFIED FIXED

(Core :: Panning and Zooming, defect)

Description

[Savvy Raghuvanshi]

+++ This bug was initially created as a clone of Bug #1643097 +++

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:79.0) Gecko/20100101 Firefox/79.0

Steps to reproduce:

I am on Windows 10. I have the following about:config settings enabled:
apz.windows.use_direct_manipulation to true
apz.allow_zooming to true

Open a PDF file using the built-in PDF viewer. Then, try to pinch to zoom on a precision trackpad.

Actual results:
Regardless of the current zoom level, I cannot zoom out, only in.

Expected results:

Compare it to the old Microsoft Edge PDF viewer (not the new Chromium-based Edge), where pinching to zoom in and out is butter-smooth.

Comment 1

[Timothy Nikkel (:tnikkel)]

This might be a bug in the direct manipulation code as it doesn't reproduce on mac.

Comment 2

[Timothy Nikkel (:tnikkel)]

Attachment: Bug 1643461. Fix calculation of deltaY when creating a widget wheel event from pinch input data on Windows. r?kats

The originally code make the mistake of thinking that [event magnification] was a multiplicative quantity (ie if the scale changed from a to b then [event magnification] would be b/a). But it is an additive quantity (so b-a). If we then apply this knowledge to how we calculate the value from the Windows code we get the new formula.

The macOS and non-macOS code could be merged because mCurrentSpan is always 100.0 on macOS, but I'm not going to do that just yet because the Windows specific code isn't mature yet, so I'm not sure if we will need to tweak it more and my goal with this change was to just get the signs right to fix the worst bug. The scale can be addressed later if needed.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7966e39bfe36
Fix calculation of deltaY when creating a widget wheel event from pinch input data on Windows. r=kats

Comment 4

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/7966e39bfe36

Comment 5

[Savvy Raghuvanshi]

Looks like this patch landed in the latest nightly. However, now, when I pinch to zoom, bug 1625462 is back. When I pinch to zoom on a PDF, the entire webpage zooms. And it's kind of janky because the PDF.js menus zoom unevenly compared to the actual webpage content. It's hard to describe what's going on.

Technically, though, this bug is fixed since I can zoom out again. But bug 1643097 is still active, and bug 1625462 has reappeared.

Comment 6

[Timothy Nikkel (:tnikkel)]

That's odd. I would expect that those two bugs could never happen at the same time. Do you think you could make a video of what you are seeing to help me understand?

Comment 7

[Savvy Raghuvanshi]

See a screen recording here: https://youtu.be/40l7S2A-Zzo

I pinch to zoom in and out using my trackpad a few times. I also hit Ctrl-0 a couple times --- that only affects the content zoom, not the overall page zoom. Please let me know if you need anything else.

Comment 8

[Timothy Nikkel (:tnikkel)]

Thank you for the screen recording. Could you please file a new bug for that? Thanks.

Comment 9

[Savvy Raghuvanshi]

Done: https://bugzilla.mozilla.org/show_bug.cgi?id=1644529

Comment 10

[Gyula Palko[:gpalko]]

Verified-Fixed on latest Nightly 80 and Beta 79.0b2. Pinch zoom out is working in the built-in PDF viewer.