I hope this is not a duplicate, i tried to explain as much as possible in the image.
When half of the preview is larger than the distance between the begin of the screen and the center of the previewer, part of the viewer will be hidden, and the preview will not show the right length.
I saw that in the .previewer there is a left and a margin-left propriety.
I think that when the (margin-left*-1) > left, margin-left should be equal to left+(a few pixels for the viewer not stay too close to the end of the screen)
I hope this is not a duplicate, i tried to explain as much as possible in the image. When half of the preview is larger than the distance between the begin of the screen and the center of the previewer, part of the viewer will be hidden, and the preview will not show the right length.
I saw that in the
.previewerthere is aleftand amargin-leftpropriety. I think that when the(margin-left*-1) > left,margin-leftshould be equal toleft+(a few pixels for the viewer not stay too close to the end of the screen)