PyGerber internal API V2

Introduction

Since PyGerber 2.2.0, there is alternative improved internal API to PyGerber. It was created to aid problems with design of API V2 build around Tokenizer, Parser and AbstractBackend classes and way they interact. They were designed to closely interact and made extension of PyGerber complicated due to multiple design flaws. Therefore, implementation of new features was becoming much harder than anticipated. To avoid breaking backward compatibility and forcing major refactoring, we have decided to introduce alternative API alongside existing one. To make it easier to distinguish parts of API V2 modules which contain parts of it contain a suffix or infix 2, for example parser2, renderer2, commands2.

API V2 contains new parser implementation, in form of Parser2 class and new rendering implementation(s) based on Renderer2, eg. SvgRenderer2 (experimental). We still rely on original Tokenizer and Token classes, although their interfaces were extended to provide integration with Parser2 separate from how Parser (API V1) worked.

New parser from the very begging was equipped with Visitor pattern based design and allows for easy substitution of implementation of various tokens. Most of Gerber file state is stored in immutable state which allows for quick jumping back in time. Additionally state is divided into multiple sub-objects each representing related set of state properties (compliant to Gerber standard). This separation simplifies process of sharing information about states with interested parties, eg. draw commands.

Rendering

Parser2 does not rely in any way on Renderer2, differently than how Parser interacted with AbstractBackend. API V2 parser generates command buffer containing draw commands which describe what should appear in the image. Those commands are later interpreted by Renderer2, but latter one knows nothing about the source of commands, making it possible to generate in arbitrary ways. Each command makes use of some aperture in a way described by The Gerber Format Specification. Set of commands is defined and quite small, same goes for apertures, so implementation of rendering of them can be very compact.

In API V2 some parts of Gerber images are resolved at parser level into individual draws. This happens for SR blocks and AB apertures. These concepts doesn't exist at Renderer2 level, they are resolved by Parser2 into correctly transformed series of draw commands. Macros however remain as apertures and are used to create flashes consisting of multiple simple commands.

Usage

Here's some sample code showing how to manually create objects from API V2 to parse and render Gerber file.

from pygerber.gerberx3.parser2.parser2 import Parser2
from pygerber.gerberx3.renderer2.svg import SvgRenderer2
from pygerber.gerberx3.tokenizer.tokenizer import Tokenizer

source = r"""
%FSLAX26Y26*%
%MOMM*%
%ADD100R,1.5X1.0X0.5*%
%ADD200C,1.5X1.0*%
%ADD300O,1.5X1.0X0.6*%
%ADD400P,1.5X3X5.0*%
D100*
X0Y0D03*
D200*
X0Y2000000D03*
D300*
X2000000Y0D03*
D400*
X2000000Y2000000D03*
M02*
"""

ast = Tokenizer().tokenize(source)
cmd_buf = Parser2().parse(ast)
img_ref = SvgRenderer2().render(cmd_buf)
img_ref.save_to("output.png")