Live Filters
A live filter lets you try a change to an outline while keeping the drawing that produced it. You can round a corner, cut one shape out of another, attach a serif, or distort an entire element, then adjust the result as the design develops.
Live Filter Principles
An element transformation changes where existing content appears: its position, scale, slant, or rotation. A live filter generates or modifies the geometry shown for that content. The source remains available for editing, and FontLab recalculates the result when the source or filter settings change.
For example, you can draw two overlapping shapes and subtract one from the other with Fusion. Moving the cutter changes the cut immediately. Expanding that construction produces the resulting outline; it no longer contains a live cutter that you can reposition.
Apply, adjust, and resolve
Start with the element or nodes that the operation needs. Filter commands are distributed by function: Element > Add Filter contains Skin, Delta, and Mesh; Element > Fusion contains Boolean operations; and Element > Brush & Stroke contains skeleton-based treatments. Smart Corners act on selected corner nodes. Some filters also have controls in a tool's property bar or context menu.
Once a filter is active, edit its source geometry or use its controls to change the result. Keep the filtered construction in a native FontLab working file if you want to adjust it later.
Before expanding, save a native version with the live construction if you may need to revise it: expansion gives up the filter’s controls. Select the intended element and inspect its structure in the Elements panel, especially if it contains several nested operations.
Two different decisions end this stage:
- Expand Filters, in the Element menu, converts an eligible filter construction into ordinary editable contours. Use it when you need to edit the generated outline directly. This parallels Expand Transformation in Element Transformations: the calculated result becomes geometry.
- Remove Filter, in the Element menu, removes the filter construction and exposes its source content. Use it when you want to discard the generated treatment.
The result after removal reflects the source as it is now; it does not undo edits you made to that source while the filter was active. Smart Corners also have node-level controls for applying or removing an individual corner.
Filters are resolved into supported geometry when you export a production font. You do not need to expand them manually just to deliver ordinary outlines. Keep the editable source and inspect the exported font separately: exporting is a conversion, while saving the native working file preserves the construction.
Choose a filter by the change you need
| Design task | Filter or tool |
|---|---|
| Add, subtract, intersect, or exclude stacked shapes | Fusion |
| Clip content with the uppermost selected shape | Clipping Group |
| Choose which enclosed regions are solid or hollow | Fill tool and Fill filter |
| Round a corner or open an ink trap | Smart Corner |
| Fasten a drawn open contour to a body | Glue |
| Apply reusable corner, terminal, or edge details from named source glyphs | Skin |
| Move selected coordinates and interpolate the rest of an outline | Delta |
| Warp content through an adjustable envelope | Mesh |
| Generate an outline around a skeleton | Power Stroke |
| Draw with a calligraphic nib along a skeleton | Power Brush |
These features do not all store their controls in the same way. A Smart Corner belongs to a node, for example, while a Glue construction contains participating elements. The common principle is that editable inputs produce a live result.
You may encounter the term compound contour for a contour carrying construction data, such as Smart Corners or skin details, beyond a plain sequence of outline segments. A production font needs the resulting supported outline geometry. Retaining that construction in the working file lets you continue editing its inputs.
Filters on Element References
An element reference shares content with its other occurrences. If the shared content includes a filter construction, editing that construction can change every reference. This is useful when a stem should receive the same treatment throughout the font; it is less useful when only one alternate needs the change.
For a supported filtered reference, Element > Reference > Unlink Filter moves the filter outside the shared content. The current occurrence retains its filtered result, while the other references use the shared source without that filter. The source itself remains shared: a contour edit can still propagate even though the current filter settings are local.
This distinction matters. Unlinking the filter does not give every occurrence an independent copy of the filtered appearance. Check another referencing glyph after the operation, especially if you had already relied on the shared treatment there.
Element > Reference > Link Filter moves an eligible outside filter back into the referenced content. Its result then becomes part of what the references share again.
These commands are available for eligible constructions with a single included source. Do not expect them to apply to every operation in the filter directory: a group, component, multi-input construction, or node-level Smart Corner has a different structure. When the command is unavailable, inspect the selected construction rather than assuming that the source has become independent.
For a local experiment:
- Open the glyph containing the referenced element and select its filtered construction.
- Choose Element > Reference > Unlink Filter if it is available.
- Adjust the filter and compare the current glyph with another reference to the same source.
- Keep the local filter, or use Link Filter if you decide that its treatment should become shared.
If you need both the drawing and the treatment to become independent, unlink the element reference itself. That is a different decision from keeping a shared drawing with a local filter.