FontForge Font View Color Indicator Bars Explained

When working in the FontForge Font View, small colored indicator bars appear above or across glyph cells to provide real-time feedback on glyph status, outline integrity, and instructions. This guide explains what the red, green, and blue indicator bars represent, how FontForge triggers them, and how type designers can use them to monitor glyph health and production progress.

The Blue Indicator Bar: Modified Glyphs

A blue line appearing at the top edge of a glyph cell indicates that the glyph has been modified since the font file was last saved. Any action that alters the glyph—such as moving points, adjusting advance widths, modifying kerning pairs, or transforming components—flags the glyph with this blue marker. Once you save the font file (via File > Save or File > Generate Fonts), the blue bar clears until further edits are made.

The Red Indicator Bar: Validation and Outline Errors

A red indicator bar highlights an error or structural issue within the glyph geometry. FontForge continuously evaluates outlines against standard OpenType and PostScript specifications. A red bar typically appears when:

• Self-intersecting paths exist: Contours cross over themselves, creating non-manifold geometry.
• Incorrect contour orientation: Overlapping paths have conflicting winding directions (clockwise versus counterclockwise), confusing the rasterizer about which areas are solid or cut out.
• Open contours: A path has unjoined endpoints where a closed loop is required.
• Missing extrema: Control points do not properly mark the local horizontal or vertical maximums and minimums of a curve.
• Outdated hints or invalid references: Dependent composite glyphs link to missing or corrupt base glyphs.

To locate and resolve these issues, double-click the flagged glyph to open the Outline View, then navigate to Element > Validation > Find Problems to inspect and repair the outline.

The Green Indicator Bar: TrueType Instructions and Hinting

A green indicator bar signifies the presence of valid TrueType instructions or up-to-date hints. When TrueType hinting is applied—either through FontForge’s autohinting tools or manual instruction coding via the Instruction Editor—the green line informs you that low-resolution grid-fitting instructions are compiled and active for that specific glyph. In some FontForge workflows, green also denotes that a glyph has undergone validation testing and satisfies all geometric checks.

Distinguishing Indicator Bars from Manual Mark Colors

It is important to differentiate between FontForge’s automated indicator bars and manual glyph color marks:

• Indicator bars are thin, colored horizontal stripes at the top boundary of a glyph box generated automatically by the application to reflect modification, validation, and hinting states.
• Mark colors are user-defined background highlights applied to the entire glyph cell (accessible via Glyph Info > Mark Color or by right-clicking a cell). Type designers commonly assign their own red, green, and blue cell fills as a project management tool (for example, marking red for "to do," blue for "in progress," and green for "approved").