is
Checks whether a graphic block originated as a line shape.
Returns true for line graphics in their original line state, and continues to return true after the user enters vector-edit mode (the underlying shape becomes a generic vector path, but the graphic itself is still the same line-derived block). The flag only resets to false when the shape is replaced by a non-line shape via setShape.
Useful for inspector UIs that want consistent behaviour across the line lifecycle — for example keeping the Fill section visible with a "None" default before and after vector-edit, instead of having the section pop in only after conversion.
Return
true if the block originated as a line shape, false otherwise.
Parameters
block
the block to query.