1865573 - Zoom ratio on double-tap-to-zoom sometimes doesn't increase monotonically

Status: NEW

(Core :: Panning and Zooming, defect, P3)

Description

[Hiroyuki Ikezoe (:hiro)]

Attachment: A mochitest to see the issue

Attaching file adds a mochitest to see this bug;

Step to reproduce the issue;

1. MOZ_LOG="apz.helper:5" ./mach mochitest --setpref="apz.subtest=helper_doubletap_zoom_bug.html" gfx/layers/apz/test/mochitest/test_group_double_tap_zoom-2.html
2. Check the log you got

An example I got is;

 0:40.72 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(0,10050), zoom=0.8, viewport=(x=0, y=10050, w=2868, h=2387.5), scrollUpdateType=1, scrollGeneration=10, scrollGenerationOnApz=0, dpMargins=(t=589.375, r=71.25, b=589.375, l=71.25)}
 0:40.79 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(0,10050), zoom=0.8, viewport=(x=0, y=10050, w=2868, h=2387.5), scrollUpdateType=1, scrollGeneration=10, scrollGenerationOnApz=0, dpMargins=(t=304.421, r=184.009, b=304.421, l=184.009)}
 0:40.79 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(9.30884,10159.5), zoom=0.840356, viewport=(x=0, y=10050, w=2868, h=2387.5), scrollUpdateType=1, scrollGeneration=10, scrollGenerationOnApz=3, dpMargins=(t=304.421, r=184.009, b=304.421, l=184.009)}
 0:40.81 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(9.30884,10159.5), zoom=0.840356, viewport=(x=0, y=10050, w=2856, h=2375.5), scrollUpdateType=0, scrollGeneration=10, scrollGenerationOnApz=3, dpMargins=(t=304.421, r=184.009, b=304.421, l=184.009)}
 0:40.83 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(22.1623,10310.6), zoom=0.903273, viewport=(x=0, y=10050, w=2856, h=2375.5), scrollUpdateType=1, scrollGeneration=10, scrollGenerationOnApz=4, dpMargins=(t=304.421, r=184.009, b=304.421, l=184.009)}
 0:40.84 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(38.5933,10503.8), zoom=0.998872, viewport=(x=0, y=10050, w=2856, h=2375.5), scrollUpdateType=1, scrollGeneration=10, scrollGenerationOnApz=5, dpMargins=(t=304.421, r=184.009, b=304.421, l=184.009)}
 0:40.84 GECKO(151732) [Child 151936: Main Thread]: D/apz.helper Handling request { scrollId=4, scrollOffset=(38.5933,10349), zoom=0.903273, viewport=(x=0, y=10071.5, w=2856, h=2365.55), scrollUpdateType=0, scrollGeneration=10, scrollGenerationOnApz=5, dpMargins=(t=304.421, r=184.009, b=304.421, l=184.009)}

At 0:40:83, the zoom value was 0.903273 and then the zoom value on next update was 0.998872 at 0:40.84, but soon after it was 0.903273 again. As far as I can tell the second 0.903273 came from a repaint request in NotifyLayersUpdated.

Due to this bug mochitests added for bug 1715179 are quite unstable.

Comment 1

[Timothy Nikkel (:tnikkel)]

Interesting. I wonder if we are getting some type of update from the content side at 0.903273 and clobbers the apz side animation?

I thought I would have run into this if it existed back when I was working on double tap zoom, so perhaps this regressed since then?

Comment 2

[Hiroyuki Ikezoe (:hiro)]

(In reply to Hiroyuki Ikezoe (:hiro) from comment #0)

At 0:40:83, the zoom value was 0.903273 and then the zoom value on next update was 0.998872 at 0:40.84, but soon after it was 0.903273 again. As far as I can tell the second 0.903273 came from a repaint request in NotifyLayersUpdated.

It turned out that the repaint request is triggered by this branch where the layout viewport size has been changed.

Adding scrollbar-width: none is a workaround for bug 1715179. That makes me suspect that we mis-include the scrollbar for the visual viewport into the layout viewport size?