LogarithmPlotter/LogarithmPlotter/util/latex.py

"""
 *  LogarithmPlotter - 2D plotter software to make BODE plots, sequences and distribution functions.
 *  Copyright (C) 2022  Ad5001
 * 
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 * 
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 * 
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
"""

from PySide2.QtCore import QObject, Slot, Property, QCoreApplication
from PySide2.QtGui import QImage, QColor
from PySide2.QtWidgets import QApplication, QMessageBox

from os import path, remove
from string import Template
from tempfile import TemporaryDirectory
from subprocess import Popen, TimeoutExpired, PIPE
from platform import system
from shutil import which

"""
Searches for a valid Latex and DVIPNG (http://savannah.nongnu.org/projects/dvipng/)
installation and collects the binary path in the DVIPNG_PATH variable.
If not found, it will send an alert to the user.
"""
LATEX_PATH = which('latex')
DVIPNG_PATH = which('dvipng')
#subprocess.run(["ls", "-l", "/dev/null"], capture_output=True)

DEFAULT_LATEX_DOC = Template(r"""
\documentclass[]{minimal}
\usepackage[utf8]{inputenc}
\usepackage{calligra}
\usepackage{amsfonts}

\title{}
\author{}

\begin{document}

$$$$ $markup $$$$

\end{document}
""")
    
class Latex(QObject):
    """
    Base class to convert Latex equations into PNG images with custom font color and size.
    It doesn't have any python dependency, but requires a working latex installation and
    dvipng to be installed on the system.
    """
    def __init__(self, tempdir: TemporaryDirectory):
        QObject.__init__(self)
        self.tempdir = tempdir
    
    def check_latex_install(self):
        """
        Checks if the current latex installation is valid.
        """
        if LATEX_PATH is None:
            QMessageBox.warning(None, "LogarithmPlotter - Latex setup", QCoreApplication.translate("latex", "No Latex installation found.\nIf you already have a latex distribution installed, make sure it's installed on your path.\nOtherwise, you can download a Latex distribution like TeX Live at https://tug.org/texlive/."))
        elif DVIPNG_PATH is None:
            QMessageBox.warning(None, "LogarithmPlotter - Latex setup", QCoreApplication.translate("latex", "DVIPNG was not found. Make sure you include it from your Latex distribution."))    
    
    @Property(bool)
    def latexSupported(self):
        return LATEX_PATH is not None and DVIPNG_PATH is not None
        
    @Slot(str, float, QColor, result=str)
    def render(self, latex_markup: str, font_size: float, color: QColor = True) -> str:
        """
        Renders a latex string into a png file.
        """
        export_path = path.join(self.tempdir.name, f'{hash(latex_markup)}_{font_size}_{color.rgb()}')
        print(export_path)
        if self.latexSupported and not path.exists(export_path + ".png"):
            # Generating file
            try:
                self.create_latex_doc(export_path, latex_markup)
                self.convert_latex_to_dvi(export_path)
                self.convert_dvi_to_png(export_path, font_size, color)
                self.cleanup(export_path)
            except Exception as e: # One of the processes failed. A message will be sent every time.
                raise e
        img = QImage(export_path + ".png");
        # Small hack, not very optimized since we load the image twice, but you can't pass a QImage to QML and expect it to be loaded
        return f'{export_path}.png,{img.width()},{img.height()}'
        
    def create_latex_doc(self, export_path: str, latex_markup: str):
        """
        Creates a temporary latex document with base file_hash as file name and a given expression markup latex_markup.
        """
        ltx_path = export_path + ".tex"
        f = open(export_path + ".tex", 'w')
        f.write(DEFAULT_LATEX_DOC.substitute(markup = latex_markup))
        f.close()
    
    def convert_latex_to_dvi(self, export_path: str):
        """
        Converts a DVI file to a PNG file.
        """
        self.run([
            LATEX_PATH,
            export_path + ".tex"
        ])
        
    
    def convert_dvi_to_png(self, export_path: str, font_size: float, color: QColor):
        """
        Converts a DVI file to a PNG file.
        Documentation: https://linux.die.net/man/1/dvipng
        """
        fg = color.convertTo(QColor.Rgb)
        fg = f'rgb {fg.redF()} {fg.greenF()} {fg.blueF()}'
        depth = int(font_size * 72.27 / 100) * 10
        self.run([
            DVIPNG_PATH,
            '-T', 'tight',              # Make sure image borders are as tight around the equation as possible to avoid blank space.
            '--truecolor',              # Make sure it's rendered in 24 bit colors.
            '-D',f'{depth}',            # Depth of the image
            '-bg', 'Transparent',       # Transparent background
            '-fg',f'{fg}',              # Foreground of the wanted color.
            f'{export_path}.dvi',       # Input file
            '-o',f'{export_path}.png',  # Output file
        ])
    
    def run(self, process: list):
        """
        Runs a subprocess and handles exceptions and messages them to the user.
        """
        proc = Popen(process, stdout=PIPE, stderr=PIPE, cwd=self.tempdir.name)
        try:
            out, err = proc.communicate(timeout=5) # 5 seconds is already FAR too long.
            if proc.returncode != 0:
                # Process errored
                QMessageBox.warning(None, "LogarithmPlotter - Latex", 
                                QCoreApplication.translate("latex", "An exception occured within the creation of the latex formula.\nProcess '{}' ended with a non-zero return code {}:\n{}\nPlease make sure your latex installation is correct and report a bug if so.")
                                .format(" ".join(process), proc.returncode, str(out, 'utf8')+"\n"+str(err,'utf8')))
                raise Exception(" ".join(process) + " process exited with return code " + str(proc.returncode) + ":\n" + str(out, 'utf8')+"\n"+str(err,'utf8'))
            print(out)
        except TimeoutExpired as e:
            # Process timed out
            proc.kill()
            out, err = proc.communicate()
            QMessageBox.warning(None, "LogarithmPlotter - Latex",
                                QCoreApplication.translate("latex", "An exception occured within the creation of the latex formula.\nProcess '{}' took too long to finish:\n{}\nPlease make sure your latex installation is correct and report a bug if so.")
                                    .format(" ".join(process), str(out, 'utf8')+"\n"+str(err,'utf8')))
            raise Exception(" ".join(process) + " process timed out:\n" + str(out, 'utf8')+"\n"+str(err,'utf8'))
    
    def cleanup(self, export_path): 
        """
        Removes Tex, auxiliary, logs and DVI temporary files.
        """
        for i in [".tex", ".dvi", ".aux", ".log"]:
            remove(export_path + i)
        
        
    @Slot(str, float, QColor, result=str)
    def render_legacy(self, latexstring, font_size, color = True):
        exprpath = path.join(self.tempdir.name, f'{hash(latexstring)}_{font_size}_{color.rgb()}.png')
        print("Rendering", latexstring, exprpath)
        if not path.exists(exprpath):
            fg = color.convertTo(QColor.Rgb)
            fg = f'rgb {fg.redF()} {fg.greenF()} {fg.blueF()}'
            preview('$${' + latexstring + '}$$', viewer='file', filename=exprpath, dvioptions=[
                "-T", "tight", 
                "-z", "0", 
                "--truecolor", 
                f"-D {int(font_size * 72.27 / 100) * 10}", # See https://linux.die.net/man/1/dvipng#-D for convertion
                "-bg", "Transparent", 
                "-fg", fg],
            euler=False)
        img = QImage(exprpath);
        # Small hack, not very optimized since we load the image twice, but you can't pass a QImage to QML and expect it to be loaded
        return f'{exprpath},{img.width()},{img.height()}'