This application uses a WebAssembly, a.k.a. WASM, build of pikchr to provide a so-called "fiddle" app, for "fiddling around" with pikchr. It requires:

• The Emscripten SDK (see below)
• A modern browser

First, install the Emscripten SDK, as documented here and summarized below for Linux environments:

# Clone the emscripten repository:
$ git clone https://github.com/emscripten-core/emsdk.git
$ cd emsdk

# Download and install the latest SDK tools:
$ ./emsdk install latest

# Make the "latest" SDK "active" for the current user:
$ ./emsdk activate latest

Those parts only need to be run once. To update that tree to the latest version, use:

$ git pull
$ ./emsdk install latest
$ ./emsdk activate latest

The following needs to be run for each shell instance which needs the emcc compiler:

# Activate PATH and other environment variables in the current terminal:
$ source /path/tp/emsdk/emsdk_env.sh

$ which emcc
/path/to/emsdk/upstream/emscripten/emcc

Adding alternate builds for non-Emscripten toolchains is on the TODO list. Doing so requires:

• WASM builds of libc and libm. wasi-sdk "should" be suitable but is as yet untested.
• Replacing much of the "glue code" which Emscripten installs. This work has already been done in other trees closely related to this project.

The makefile for the fiddle app requires GNU Make (installed as "make" on Linux and typically "gmake" on BSD systems). From the top of the pikchr tree, simply do:

$ source /path/to/emsdk/emsdk_env.sh # see previous section
$ cd fiddle
$ make
# or, depending on the platform (e.g. BSD):
$ gmake

The EMSDK environment setup is only needed for building, not running the app.

Due to limitations in WASM module loading in some browsers, the fiddle app must be run via an HTTP server rather than by opening its HTML file directly. There are many options for doing so, but one of the simplest is to use althttpd:

$ althttpd -page fiddle.html

That will start up a local HTTP server on the next available network port at or above 8080, start up your browser, and point it to http:https://localhost:THAT_PORT/fiddle.html.

From highest level to lowest:

• fiddle.html is the entry point for...
• fiddle.js is the main hand-written JS part of the app. It loads...
• pikchr-worker.js is a hand-written Worker-API binding to...
• pikchr.js is the Emscripten-generated module code. It loads pikchr.wasm (the WASM-compiled from of pikchr.c) and makes it available to JS.