177646 2017-09-29 04:02:47 -0700 Scroll containers with "-webkit-overflow-scrolling: touch" don't always show scrollbars on scroll 2019-02-11 14:51:45 -0800 1 1 1 Unclassified WebKit CSS Safari 10 iPhone / iPad iOS 10.3 NEW InRadar P2 Normal --- 1 contact webkit-unassigned simon.fraser tahoon webkit-bug-importer oldest_to_newest 1354489 0 contact 2017-09-29 04:02:47 -0700 This is iOS specific so view the following reduction on an iOS device: https://codepen.io/benfrain/full/rGwWae All of the horizontal panes are identical. However, only some of the scroll panes get the scroll handle when scrolled. If the problem doesn't occur first time, try refreshing and immediately scrolling some of the panes. Live site example: https://mobile.bet365.com/#type=Splash;key=2;ip=0;lng=1 Scroll down that page a little to the list of race times and scroll those. Again, some exhibit the scroll bar handle, some don't. 1355219 1 webkit-bug-importer 2017-10-02 07:00:02 -0700 <rdar://problem/34766358> 1355727 2 simon.fraser 2017-10-03 01:04:55 -0700 By "get the scroll handle" do you mean that they don't show scrollbars? Or that they don't handle the scroll (i.e. are not scrollable)? 1355736 3 contact 2017-10-03 01:35:56 -0700 I mean the scroll but the handle doesn't always appear when scrolled. 1505004 4 361714 tahoon 2019-02-11 14:51:45 -0800 Created attachment 361714 Repro case: rapid changes to scrollable height This bug is timing-dependent. The symptom is that the user can swipe up and down to scroll an element; however, the scrollbar does not appear. Workaround is to change "-webkit-overflow-scrolling" to "auto" and then back to "touch" after a delay. Attachment provides two ways to reproduce this bug in iOS. The first way is reliable: 1. Check the "Add items automatically" checkbox. This adds items continuously to a scrollable area. 2. Flick finger up and down to scroll the list. Note that the scrollbar disappears (or does not appear in the first place). 3. Uncheck checkbox. This stops adding items. 4. Flick finger up and down. The list scrolls but there is no scrollbar. The second way is to add items manually. It is more difficult to reproduce. 1. Click "Add item" button quickly 4 to 5 times. 2. Lightly and quickly flick finger up on the scrollable area. 3. Area scrolls but scrollbar does not appear. 4. If cannot reproduce, click "Clear all" and try again. I have also managed to reproduce this bug with static HTML (no dynamic DOM modifications), but very rarely. 361714 2019-02-11 14:51:45 -0800 2019-02-11 14:51:45 -0800 Repro case: rapid changes to scrollable height noScrollbar.html text/html 1547 tahoon PCFET0NUWVBFIGh0bWw+DQo8aHRtbD4NCiAgPGhlYWQ+DQogICAgPHRpdGxlPkJ1ZyAxNzc2NDY6 IFNjcm9sbCBjb250YWluZXJzIHdpdGggIi13ZWJraXQtb3ZlcmZsb3ctc2Nyb2xsaW5nOiB0b3Vj aCIgZG9uJ3QgYWx3YXlzIHNob3cgc2Nyb2xsYmFycyBvbiBzY3JvbGw8L3RpdGxlPg0KICA8L2hl YWQ+DQogIDxtZXRhIG5hbWU9InZpZXdwb3J0IiBjb250ZW50PSJ3aWR0aD1kZXZpY2Utd2lkdGgi Pg0KICA8c3R5bGU+DQogICAgI2NvbnRhaW5lciB7DQogICAgICB3aWR0aDogMTUwcHg7DQogICAg ICBoZWlnaHQ6IDIwMHB4Ow0KICAgICAgYm9yZGVyOiAxcHggc29saWQgYmxhY2s7DQogICAgICBt YXJnaW46IDEwcHggMDsNCiAgICAgIG92ZXJmbG93OiBhdXRvOw0KICAgICAgLXdlYmtpdC1vdmVy Zmxvdy1zY3JvbGxpbmc6IHRvdWNoOw0KICAgIH0NCg0KICAgIC5pdGVtIHsNCiAgICAgIGhlaWdo dDogODBweDsNCiAgICAgIHdpZHRoOiAxMDBweDsNCiAgICAgIGJhY2tncm91bmQtY29sb3I6IGdy ZWVuOw0KICAgICAgb3V0bGluZTogMXB4IHNvbGlkIGJsYWNrOw0KICAgIH0NCiAgPC9zdHlsZT4N CjwvaGVhZD4NCjxib2R5Pg0KICA8ZGl2Pg0KICAgIDxidXR0b24gaWQ9J2FkZCc+QWRkIGl0ZW08 L2J1dHRvbj4NCiAgICA8YnV0dG9uIGlkPSdjbGVhcic+Q2xlYXIgYWxsPC9idXR0b24+DQogICAg PGxhYmVsPjxpbnB1dCBpZD0nYXV0b2FkZCcgdHlwZT0nY2hlY2tib3gnIC8+QWRkIGl0ZW1zIGF1 dG9tYXRpY2FsbHk8L2xhYmVsPg0KICA8L2Rpdj4NCiAgPGRpdiBpZD0nY29udGFpbmVyJz4NCiAg PC9kaXY+DQoNCiAgPHNjcmlwdD4NCiAgICB2YXIgY29udGFpbmVyID0gZG9jdW1lbnQuZ2V0RWxl bWVudEJ5SWQoJ2NvbnRhaW5lcicpOw0KDQogICAgdmFyIGFkZEl0ZW0gPSBmdW5jdGlvbigpIHsN CiAgICAgIHZhciBpdGVtID0gZG9jdW1lbnQuY3JlYXRlRWxlbWVudCgnZGl2Jyk7DQogICAgICBp dGVtLmNsYXNzTGlzdC5hZGQoJ2l0ZW0nKTsNCiAgICAgIGNvbnRhaW5lci5hcHBlbmRDaGlsZChp dGVtKTsNCiAgICB9Ow0KDQogICAgZG9jdW1lbnQuZ2V0RWxlbWVudEJ5SWQoJ2FkZCcpLmFkZEV2 ZW50TGlzdGVuZXIoJ2NsaWNrJywgYWRkSXRlbSk7DQogICAgZG9jdW1lbnQuZ2V0RWxlbWVudEJ5 SWQoJ2NsZWFyJykuYWRkRXZlbnRMaXN0ZW5lcignY2xpY2snLCBmdW5jdGlvbigpIHsNCiAgICAg IGNvbnRhaW5lci5pbm5lckhUTUwgPSAnJzsNCiAgICB9KTsNCg0KICAgIHZhciBjaGVja2JveCA9 IGRvY3VtZW50LmdldEVsZW1lbnRCeUlkKCdhdXRvYWRkJyk7DQogICAgdmFyIGF1dG9BZGRJZCA9 IDA7DQoNCiAgICBjaGVja2JveC5hZGRFdmVudExpc3RlbmVyKCdjaGFuZ2UnLCBmdW5jdGlvbigp IHsNCiAgICAgIHdpbmRvdy5jbGVhckludGVydmFsKGF1dG9BZGRJZCk7DQogICAgICBpZiAoY2hl Y2tib3guY2hlY2tlZCkgew0KICAgICAgICBhdXRvQWRkSWQgPSB3aW5kb3cuc2V0SW50ZXJ2YWwo YWRkSXRlbSwgMTAwKTsNCiAgICAgIH0NCiAgICB9KTsNCiAgPC9zY3JpcHQ+DQo8L2JvZHk+DQo8 L2h0bWw+DQo=