<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=0"/>This effectively disables the ability of the user to "pinch zoom" (aka "two-finger zoom") the entire page.
Without this, the user can pinch-zoom the page, but then in order to "pan" the entire page (for example, to find the controls), they must use a "two-finger drag" instead of using one finger, because HAniS must intercept one-finger motions on the image display.