Manual of Lua-OOCairo: path

lua-oocairo-path - Path object

Introduction

A path object represents a series of path instructions like move_to and line_to, as supplied to a context object when defining shapes for drawing. They can be created by issuing instructions on a context object and then calling cr:copy_path() or cr:copy_path_flat() (see lua-oocairo-context(3)). A path can then be added back to the current path by calling cr:append_path().

Methods

Currently only the following method can be called on a path object:

path:each ()

Returns an iterator function and initial values needed to iterate over the instructions in the path using a Lua for loop. This can be used to translate the Cairo path piece by piece, perhaps to encode it in some unusual vector graphics format, or to translate it into calls to another API like OpenGL.

The iterator function will return three values each time it is called. The first is a number, which should be ignored (but is needed to keep track of the current position in the list of instructions). The second value is a string naming the instruction to be performed, and the last value is either nil or a table (array) of numbers which are the arguments of the instruction.

This example simply prints out the instructions in the order they were issued on the context object cr:

for _, instr, args in cr:copy_path():each() do
    if args then
        print(instr, unpack(args))
    else
        print(instr)
    end
end

The following instructions can be included:

move-to

Set current point. Comes with a table of two numbers.

line-to

Draw straight line. Comes with a table of two numbers.

curve-to

Draw curved line. Comes with a table of two numbers, the two control points first and then the destination point.

close-path

Draw line back to start point. The extra arguments value will be nil.