Force Pixel Alignment will snap objects, nodes and handles, and pixel selection areas to full pixels when created, moved or modified. If this option is switched off, objects and selections can occupy partial pixels.
This snapping method works together with other forms of snapping. If you snap to an object that is not aligned to a pixel, then the resulting snap will not be pixel aligned. To snap only to pixels, be sure to switch off other modes of non-pixel snapping, such as grids and guides if they are not on-pixel.
Move By Whole Pixels
In addition to Force Pixel Alignment, the Move By Whole Pixels option allows you to constrain the movement of objects, nodes and handles to whole pixels.
Move By Whole Pixels is particularly useful for repositioning an object by a particular pixel distance while also maintaining the relevant partial pixels an object occupies.
To activate/deactivate Force Pixel Alignment:
Click Force Pixel Alignment on the Toolbar.
To activate/deactivate Move By Whole Pixels:
With Force Pixel Alignment active, click Move By Whole Pixels on the Toolbar.
To temporarily override snapping:
Press the while you're positioning. Snapping won't occur while the is depressed.