Anchoring with ‘Cvt’ Values

By default, Visual TrueType assumes that every anchor should be rounded to the nearest grid line. However, a Y anchor can refer to a ‘cvt’ value to specify a height or overshoot shared by other glyphs in the font. Instead of rounding to the nearest grid line, the point goes to the grid line specified in the ‘cvt’ value. If the height later needs global adjustment or you need to suppress or equalize an overshoot, you just change the ‘cvt’ value.

Note X anchors don’t refer to ‘cvt’ values because X links typically start at side-bearing points, which don’t need global adjustments. The left side-bearing point always has an X coordinate of 0, and the advance width (which sets the right side-bearing point) varies from glyph to glyph.

You assign a ‘cvt’ value after enabling VTT attributes on anchors in the options dialog (for details, see “Filling in the Control Value Table”. When you right-click the highway sign with a hinting tool, it displays a list of entries from the ‘cvt’ table:

The selected entry is the one already associated with the anchor 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 assign a ‘cvt’ entry to an anchor

1.       Select the Visual TrueType Options submenu of the Display menu.

2.      Set the Cvts option and optionally set the Cvt Numbers to display the large highway signs with CVT numbers.

3.       Select the appropriate hinting tool by clicking its icon in the toolbar or pressing the associated function key.

4.     Point on the highway sign for the anchor you want to control.

5.      Holding down the right mouse button, scroll to select an entry from the ‘cvt’ table that corresponds to the desired height.

OR

1.       Using the keyboard, edit the VTT Talk instruction for the link, shift, or interpolate in the VTT Talk window (Ctrl + 5).