User Guide

Multiple Master Fonts
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A red mark shows that the mask layer is not compatible with the master.
“Incompatible” means that mask and outline layers have different numbers
of contours, so FontLab cannot match the points and curves.
A green mark means that the mask and outline layers seem to be
compatible and you may apply the Mask to Master action. This action
replaces the contents of the active master with the contents of the Mask
layer. If the Mask layer is completely compatible with the outline you will
instantly get a properly made master for the active layer:
FontLab uses the Blend algorithm to match points in the Mask and outline
layers. Sometimes it can produce incorrect results, so we recommend you
check your outlines after you complete the Mask to Master operation.