Preview

preview is a tool for "previewing" files that require a compilatoin step, like LaTeX, Markdown, and more. It works by managing a "build" step and a "view" step, so it can be used to live-preview many different types of files, and if you filetype is not already supported, it is simple to add support for it.

Usage

Install with pip

$ pip install filepreviewer

to preview a file, just pass it to the preview command

$ preview file_to_preview.md

How it works

preview uses a handler to launch a view process in the background, and then run build process when the source file is changed. For example, the just handler can use a justfile like this

PREVIEW_INPUT_FILE := ""
PREVIEW_TMPDIR:= ""

preview-build:
    pandoc {{PREVIEW_INPUT_FILE}} -o {{PREVIEW_TMPDIR}}/out.pdf

preview-view:
    zathura {{PREVIEW_TMPDIR}}/out.pdf

to preview Markdown files by compiling them to a PDF (using Pandoc) and opening then PDF with Zathura, which does automatic reload.

You can use any tool(s) you want to build and view your file. The only requirement is that view process should block. preview will launch it in the background and exit when it returns.

Examples

To preview a Gnuplot script you could use sexpect to open gnuplot and load the script.

PREVIEW_INPUT_FILE := ""
PREVIEW_TMPDIR:= ""

preview-build:
    #! /bin/bash
    if [[ -e preview-gnuplot.sock ]]
    then
      sexpect -sock preview-gnuplot.sock send 'load "{{PREVIEW_INPUT_FILE}}"' -cr
      sexpect -sock preview-gnuplot.sock expect
    fi

preview-view:
    sexpect -sock preview-gnuplot.sock spawn gnuplot
    just --justfile {{justfile()}} PREVIEW_INPUT_FILE={{PREVIEW_INPUT_FILE}} PREVIEW_TMPDIR={{PREVIEW_TMPDIR}} preview-build
    zenity --info --no-markup --text="Click 'OK' when you are done to close the preview."
    sexpect -sock preview-gnuplot.sock send 'exit' -cr
    sexpect -sock preview-gnuplot.sock wait

The use of Zenity here is required to keep the view process from returning immediatly, which would cause preview to terminate.

Handlers

Currently, Preview supports just and Make for handing the build and view steps.

Just handler

To use the just handler, create a file named justfile.<file_extension> that defines a preview-build and preview-view recipe, as well as two variables named PREVIEW_INPUT_FILE and PREVIEW_TMPDIR. Preview will pass the name of the file being previewed, and the path to a temporary directory that is created for the hander to use.

Make handler

To use the make handler, create a file named makefile.<file_extension> that defines the preview-build and preview-view targets. Preview will set two variables named PREVIEW_INPUT_FILE and PREVIEW_TMPDIR that contain the name of the file being previewed, and the path to a temporary directory that is created for the hander to use.