To select the ‘cvt’ value for a link, Visual TrueType needs to know:
· The character group you’re working on (uppercase, lowercase, figure/numeral, or “other”). This information gets loaded into your font when you prepare it for hinting (see “Preparing the Open Font”).
· The color of the link. Visual TrueType actually “looks” at the character and checks whether your link lies entirely within the black or the white part of the character (making it a black or white link, respectively). If the color is neither back nor white, Visual TrueType assumes a gray link.
· The direction of the link. Visual TrueType determines this based on the direction of the link tool used to create the link.
· The ‘cvt’ category the link relates to. This information comes from the arrowhead you select to specify the control value category and minimum distance for the link—because the current default category applies to each new link, make sure this is the category you intended (see “Assigning a ‘Cvt’ Category to a Link”).
Once it has all this information, Visual TrueType searches the ‘cvt’ table and finds the entry that best matches the size and other attributes of the link. The search follows this order:
1. If several control value table entries have the same attribute, Visual TrueType picks the one whose control value is closest to the actual distance of the link.
2. This would be the case, for example, for uppercase black strokes of Times New Roman in the X direction because they have a dominant thin stroke with a dominant thick stroke.
3. If only one entry has that attribute, Visual TrueType picks that one, no matter how close or how far away it is from the actual distance of the link.
4. If no entry has that attribute, Visual TrueType searches the table again using the ‘cvt’ category of “distance.”
5. If “distance” doesn’t have that attribute, Visual TrueType tries one last time with the link direction set to “any.”
6. If even that fails, then the link will not refer to a ‘cvt’ value. A question mark displays in the numbered highway sign, and you may have to add an entry to the ‘cvt’ table.
Even if Visual TrueType finds a match, you may want to change it. For example, when you link to control stem thickness, Visual TrueType can pick the correct ‘cvt’ value only if the relevant ‘cvt’ entries have associated character groups and the correct character group is assigned to the current glyph.
Or Visual TrueType might choose an entry that you don’t want to use. For example, you may want two round strokes to refer to the same ‘cvt’ entry.
You can review and change the associated ‘cvt’ entry using the highway signs displayed on links. Choose between smaller, unnumbered highway signs or larger signs that include the number of the ‘cvt’ entry for each link.
In either case, holding down the right mouse button as you click the highway sign displays a list of entries from the ‘cvt’ table:
The selected entry is the one already associated with the link or, if none exists yet, Visual TrueType’s best guess, plus a dozen neighboring entries from the ‘cvt’ table. You can scroll this list to select another entry.
To change a ‘cvt’ entry for a link
1. In the Visual TrueType Options submenu of the Display menu, ensure that the Cvts option is enabled. You can also enable the Cvt Numbers option to display CVT numbers inside the highway signs on links.
2. Select the XLink or YLink tool by clicking the appropriate icon, or by pressing the F5 or F1 key, respectively
3. Point on the highway sign for the link you want to change.
4. Holding down the right mouse button, and click a rounding method from the menu (for details, see “Rounding Control Points”).