100957 2012-11-01 07:15:42 -0700 [WK1] Fixed-position elements jiggle up and down slightly during scrolling on a Retina display 2012-11-01 13:58:12 -0700 1 1 1 Unclassified WebKit Layout and Rendering 528+ (Nightly build) Mac (Intel) OS X 10.8 RESOLVED FIXED InRadar P2 Normal --- 1 aroben aroben andersca bdakin dbates simon.fraser webkit.review.bot oldest_to_newest 756206 0 171842 aroben 2012-11-01 07:15:42 -0700 Created attachment 171842 testcase To reproduce: 1. Set your display to a Retina resolution 2. Load the attached test case in WebKit1 3. Scroll up and down a bit The fixed div jiggles up and down slightly while scrolling. This does not happen in WebKit2. 756233 1 aroben 2012-11-01 07:34:42 -0700 This even happens waaaaaay back in the r37376 nightly build. 756238 2 aroben 2012-11-01 07:41:14 -0700 The bug gets worse if the fixed-position element has -webkit-transform:translate3d(0,0,0) applied to it. Then it jiggles by two device pixels instead of one. 756407 3 bdakin 2012-11-01 10:18:00 -0700 Adam Roben!! I could have sworn we fixed this. Simon, did we fix this? 756429 4 aroben 2012-11-01 10:38:54 -0700 Turning off Settings::setFixedPositionCreatesStackingContext does not fix this. 756451 5 aroben 2012-11-01 10:51:29 -0700 Simon helped us realize that WebKit2 only scrolls by full pixels, even in Retina mode, while AppKit will scroll by half-pixels in Retina mode. WebCore can only represent full pixels at the moment, so this is probably the source of the bug. 756461 6 bdakin 2012-11-01 11:07:04 -0700 Ah yes, this is in Radar as <rdar://problem/11244706> 756476 7 171899 aroben 2012-11-01 11:25:11 -0700 Created attachment 171899 Patch 756477 8 171899 simon.fraser 2012-11-01 11:27:54 -0700 Comment on attachment 171899 Patch It seems unfortunate to impact the scrolling behavior of every app using WK1, whether or not they have fixed position elements. Maybe this should be opt-in somehow? 756518 9 171904 aroben 2012-11-01 12:02:31 -0700 Created attachment 171904 Patch 756522 10 aroben 2012-11-01 12:03:10 -0700 OK, added a new patch that only affects pages with position:fixed or position:sticky elements. It is not currently opt-in. Simon, were you imagining a new preference key? Or some other opt-in mechanism? 756593 11 171904 webkit.review.bot 2012-11-01 13:58:09 -0700 Comment on attachment 171904 Patch Clearing flags on attachment: 171904 Committed r133225: <http://trac.webkit.org/changeset/133225> 756594 12 webkit.review.bot 2012-11-01 13:58:12 -0700 All reviewed patches have been landed. Closing bug. 171842 2012-11-01 07:15:42 -0700 2012-11-01 07:15:42 -0700 testcase fixed-scrolling.html text/html 396 aroben PCFET0NUWVBFIGh0bWw+CjxzdHlsZT4KICAjZml4ZWQgewogICAgcG9zaXRpb246IGZpeGVkOwog ICAgYm9yZGVyOiAxcHggc29saWQgcmVkOwogICAgbGVmdDogMDsKICAgIHJpZ2h0OiAwOwogICAg Ym90dG9tOiAwOwogICAgaGVpZ2h0OiAzMHB4OwogIH0KICAjaHVnZSB7CiAgICBoZWlnaHQ6IDQw MDBweDsKICB9Cjwvc3R5bGU+CjxwPlNjcm9sbCB0aGlzIHBhZ2Ugb24gYSBSZXRpbmEgZGlzcGxh eSBpbiBXZWJLaXQxLiBUaGUgZml4ZWQgPGNvZGU+ZGl2PC9jb2RlPgphdCB0aGUgYm90dG9tIGpp Z2dsZXMgdXAgYW5kIGRvd24gc2xpZ2h0bHkuIFRoaXMgZG9lcyBub3QgaGFwcGVuIGluIFdlYktp dDIuPC9wPgo8ZGl2IGlkPWh1Z2U+PC9kaXY+CjxkaXYgaWQ9Zml4ZWQ+Rml4ZWQ8L2Rpdj4K 171899 2012-11-01 11:25:11 -0700 2012-11-01 12:02:27 -0700 Patch bug-100957-20121101142332.patch text/plain 1968 aroben U3VidmVyc2lvbiBSZXZpc2lvbjogMTMzMTUxCmRpZmYgLS1naXQgYS9Tb3VyY2UvV2ViS2l0L21h Yy9DaGFuZ2VMb2cgYi9Tb3VyY2UvV2ViS2l0L21hYy9DaGFuZ2VMb2cKaW5kZXggMTY3NzY1YTIx 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