Grid snapping, guides, and alignment

Snapping pulls what you draw and what you move onto exact positions, so shapes line up with the grid, with the ruler, and with the middle of the canvas without you having to aim.

View > Snap to grid/ruler/center (Ctrl+Alt+G) turns it on and off. When it is on, a checkmark shows next to the menu item.

What it snaps to

Snapping picks its target from whatever is visible on the canvas, in this order:

The last case is a fallback rather than a quantising step: the canvas edges and centre lines are only three lines per axis, so snapping is a magnet rather than a ruler. A point within 8 screen pixels of one of those lines is pulled onto it, and the guide it landed on is drawn while the drag lasts, so you can see which line is holding it. The tolerance is measured in screen pixels, so it stays equally easy to hit at any zoom.

With no grid, no rulers, and no canvas guide within reach, nothing happens: a point is left exactly where you put it rather than being forced onto an invisible grid. If snapping is on but the grid and the rulers are both hidden, the canvas guides are what you are snapping to - which is why turning the rulers on changes snapping’s behaviour even though the rulers themselves only draw decorations.

Ruler units decide the step

When the rulers are the snapping target, View > Ruler Units picks the step as well as the labels:

The rulers choose their tick spacing from the zoom level and from how wide their labels are, so at low zoom a “one inch” step may actually be a coarser round number of pixels. Impasto snaps to the ticks you can see, not to a fixed conversion, which keeps the grid of ticks and the grid of snapping targets the same thing.

Whole objects, not just the pointer

A dragged shape, a moved text object, and a moved selection snap by their whole bounding box rather than by the corner under the pointer. Each edge of the box and its centre line is offered to the snapping target, and the nearest match within tolerance wins, so a box being dragged onto the canvas centre falls into place by its own centre and a box being dragged toward an edge aligns by that edge.

The canvas grid

View > Show Grid draws the grid; View > Edit Canvas Grid opens a dialog with:

• Show Grid - the same toggle as the menu item.
• Width and Height - the cell size in pixels. These are also the snap step while the grid is visible.
• Color - any color and opacity, chosen with Impasto’s own color picker, so a bright grid can be made subtle or a dark one made loud.
• Show Axonometric Grid - a lattice at a given Width and Angle, for isometric and other angled work. While it is showing, it takes over both drawing and snapping, and points snap to its lattice lines instead of to rectangular cells.

The grid’s settings are saved with your other preferences and are shared by every image, not stored per document. The Canvas pad in the right-hand dock holds the same grid and ruler settings, so they are reachable without the menu.

Other snaps

Snapping is separate from a few tool-specific alignment behaviours that work even when it is off:

• Holding Shift while dragging a shape’s control point snaps the adjacent segment to a 15° angle.
• Holding Shift while drawing an ellipse constrains it to a circle, and the same key constrains other shape tools as documented on the shape tools page.
• The Rotate / Zoom Layer… dialog takes exact numbers rather than relying on snapping for alignment.

Where snapping shows up

The painting tools - paintbrush, pencil, eraser, bucket, gradient, clone stamp, recolor - are not snapping tools: their input follows the pointer exactly, because a brush stroke pulled onto a grid line would not be what you painted.

Because snapping follows the grid and the rulers rather than replacing them, the way to change how tightly things snap is to change the grid’s cell size or the ruler’s unit, not to look for a separate tolerance setting.