Smart Guides

Smart guides line things up while you work. When the item you drag comes close to lining up with another item, or to matching the spacing between two others, it snaps into place and a guide line shows what it matched. Guides also appear while you nudge with the arrow keys and while you drag out a new shape or text box. This page explains what counts as a match, which match wins, and how to move without snapping.

Turning guides on and off

Toggle smart guides from View > Smart Guides, the Smart Guides button in the action bar, or Ctrl+;. They are on by default, and the setting is remembered in your browser.

Turning guides off also turns off the 15 degree angle snap of the Bond tool (see Bond Tool). When the grid is on with snapping enabled, grid snap places the item instead of smart guides; see Grid Settings.

What lines up with what

While you drag, the edges and centre of the dragged item are compared with the items around it. Lines pair only like with like:

Box edges line up with box edges, and centres with centres.
A line of text lines up with the same line of other text: baseline with baseline. Cap-height, x-height, and descender lines pair only between text of the same size.
A molecule’s centre line lines up with another molecule’s centre line.
Atoms of another molecule line up only with the atom you grabbed to start the drag.
An arrow offers its middle and its two ends, not the box around its arrowhead.

A group you are not dragging counts as one block, measured by its outline, so its members do not offer lines of their own. A group you drag also moves as one block. Inside a group you have entered, the members are separate again.

Which items count

Only items that are on screen count, and the list follows the view if you pan or the canvas scrolls during the drag. Zoom in to narrow the field.

A neighbour pulls from 5 screen pixels away. The pull weakens with distance on screen: full strength up to 80 px away, falling to 0.3 of that for items more than 480 px away. A far item still lines up when you are nearly there, but it does not grab the drag from a distance.

Once a match has taken hold, it is kept until another one is at least twice as good, so the guides do not flicker between candidates as you move.

Which match wins

Each direction (sideways and up-down) shows at most one guide. When several matches are in reach, the first of these wins:

Text beside an arrow end: text dragged near the end of an arrow settles beside it at a standard gap. The arrow’s line must pass through the text, and the rule reaches 12 px along the arrow.
Bond length: when you drag an atom, its bond snaps to the drawn length of a neighbouring bond in the chain.
Equal spacing.
The standard gap between two boxes.
Plain alignment of edges, centres, and text lines.

Reading a guide

A guide line runs only between the dragged item and the item it matched, and the matched item is outlined with a thin dashed box (or a ring around a matched atom). When the match is a line of text, the guide is labelled with its name, such as “baseline”. An open circle marks the dragged item’s end of the guide and filled chevrons mark the matched item’s end; a circled plus marks a match on a text line or a molecule’s centre line. A guide cut off by the edge of the view ends in a short tick. On release, the guides flash briefly to confirm the snap. Guide lines follow the light or dark theme.

Equal spacing

When the gap between the dragged item and a neighbour can match a gap between two other items in the same row or column, the item snaps to make the gaps equal, and pills show the gap distance. A long chain of equal gaps shows its three nearest gaps, with a ”× N” count for the whole chain.

Equal spacing has its own limits:

Only items on screen count.
A gap wider than a third of the visible width (or height, for a column) is not treated as a gap.
Gaps between items you are not dragging must match within 1 screen pixel to count as equal, and a chain is compared with its first gap, so the spacing does not drift along a long row.
Only the chain the item snaps to draws its pills.

Dragging several items

When you drag several items at once (two molecules, or a molecule and its caption), each item is compared with its neighbours by the same rules as a single item, and one match wins per direction. Its guide runs from the item that matched.

Guides while nudging

After each arrow-key nudge, the guides the selection now lines up with exactly are shown. A nudge never snaps: each press still moves exactly 1 px, 10 px with Shift, or 1 screen pixel with Ctrl+Shift. The guides clear 0.7 seconds after the last key.

Guides while drawing a shape or text box

When you drag out a new shape with the Shape tool, or a text box with the Text tool, the moving corner snaps to other items’ edges and centres: sideways to their left, right, and middle lines, up and down to their top, bottom, and middle lines. The item you are drawing lands where the preview showed it. The point where you pressed does not snap. A plain click with the Text tool places text where you click, without snapping.

Hold Ctrl while drawing to turn the snap off. With grid snap on, the grid places the shape instead. With the Shape tool, Alt still draws from the centre.

Moving without snapping

While dragging	Effect
`Alt`	Turns off every snap, guides and grid alike. A text box or shape you drag also pulls free of the arrows drawn from it: the arrows stay where they are, and on release they let go of it. Release `Alt` before the mouse to keep the arrows attached. One undo puts back the move and the attachment.
`Ctrl`	Turns off every snap and keeps attached arrows attached, so they follow the item.

For atoms, Ctrl also arms merging and fusing; see Select Tool.