Swipe gesture not detected if started by tiny motion in other direction. Make swipe detection more robust?
Looking at the swipe-up for the lockscreen as an example, but I think this is a general thing with how a swipe gesture is identified, it is not specific to the lockscreen and perhaps also not specific to phosh.
It easily happens that a touch gesture that the user intended to be a swipe in a certain direction, like a swipe up to unlock the lockscreen, is ignore. Here is what it can look like:
In that video each swipe is started with a small movement in a "wrong" direction, a direction that is not up, followed by a large motion upwards. I think what happens is that the software processing the touch events is looking at the direction of the swipe for the very first part of the motion and at that point decides the possible swipe direction. If the motion then changes direction, that is not treated as a swipe but is instead ignored.
Someone might argue that the user should learn to swipe properly, but I think this is an important accessibility issue: if you give a phone or tablet to a child, or an old person, or a person with slightly shaky hands due to whatever reason, then they will have trouble using the device because of this. For the user, it is very confusing that the device does not react when you as a user think you made a clear swipe.
Example: the finger first touches a point near the center of the screen. From there it moves down very slightly, perhaps as little as one or two pixels, and then it starts moving upwards a much longer distance. That should, I think, be interpreted as a swipe up even if the first few pixels of movement had another direction.
Another way of looking at it is to say that swipe detection should be robust to small disturbances; if there is a small random "noise" in the touch movement superimposed on a larger consistent movement, then the small noise should not destroy the touch gesture, the gesture should be detected anyway based on the larger movement that is very likely what the user intended.
I don't know where in the software stack this happens, but probably somewhere there is an algorithm that processes touch events to decide what gets interpreted as a swipe, then I think that algorithm would need tweaking to make it more robust.