Bugzilla – Bug 12656
Touch-drag can scroll the wrong way
Last modified: 2011-11-06 23:23:11 UTC
Occasionally I've found that I've managed to get scrolling to scroll the wrong way. i.e. normally on a list, touch the screen, and move finger to drag the content around where finger goes. Sometimes a finger drag down scrolls the list the other way (as if you are dragging the scrollbar, not the list). It took a bit of fiddling to get a repeatable case, but I've managed to do it several times. This isn't easy to explain, but I'll have a go. I'd appreciate it if someone else could repeat this! Essentially I've found that if you touch the screen and roll your finger tip vertically and drag finger the other way, it starts to scroll in the direction of the initial roll of the fingertip, not the direction of the finger drag. Try this: 1. Navigate to the middle of a list of options. 2. Touch screen, with finger attacking the screen from a horizontal direction. e.g. with left index finger lying horizontally across the screen, touch with righthand edge of the finger nail. 3. Roll fingertip around (like you want to get a full fingerprint on the display), so finger is rolling slowly up the display coming close to left-hand edge of fingernail. 4. At the same time as rolling finger upwards, start to drag finger downwards. This will usually drag the screen downwards as the finger moves down, but if you get the timing just right, the screen will move upwards instead (continuing in the direction that the fingertip initiated movement). I've found this happen by accident, and it's weird - the list going off in the wrong direction!
These are marked as CAT, yet that milestone is over now. Please re-target accordingly.
Phil: are you still able to replicate this behavior on newer firmware? Try as I might, I was not able to reproduce your experience, however I know there have been some improvements to this over the last few firmware revisions. Please try again and let us know if you can still see the issue. Maybe a video of what you are seeing would help as well.
Yes, I can still repeat this with fw r7215.
Weldon: this sounds like a bad UI experience with chiral motion. What should happen here?
(In reply to comment #4) > Weldon: this sounds like a bad UI experience with chiral motion. What should > happen here? Yeah this sounds like a side-effect of chiral motion. Philip, are you aware of this behavior? If you press in the middle of the screen, then drag in a circular motion, you'll get a fast-scrolling effect that works sort of like an invisible knob. I can't tell the severity of this bug from the description, but it sounds a bit like this is as-designed, but you're accidentally triggering the behavior. I won't have time to examine this further this week, but if this remains open it will get looked at and dealt with for 8.0.
Accidental Chiral motion could be the issue. I am aware of chiral motion scrolling, and do use it for scrolling big lists. I hadn't considered that this could be the cause, as I was not doing a circular motion with my finger - only moving finger up or down. But a minute variation in x axis movement could confuse the engine into thinking it's a circular motion. Perhaps the detection of chiral motion should be made more distinct - i.e. need a larger circular gesture to invoke chiral scrolling. A small delta difference in movement should not cause chiral scrolling?
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