add script

README.md

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+# Relative Xournal++ background paths
+
+Replace absolute paths of Xournal++ PDF backgrounds with relative ones.
+
+## Installation
+
+Place [relative-xopp-background](relative-xopp-background) in `~/.local/share/nautilus/scripts/relative-xopp-background` and make it executable.
+
+If missing, install [notify2](https://pypi.org/project/notify2/) and (optionally)
+[dbus-python](https://pypi.org/project/dbus-python/) with your package manager or with pip.

relative-xopp-background

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+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+
+import gzip
+import traceback
+from os import getenv
+from pathlib import Path
+from sys import argv, stderr
+from typing import List
+from xml.etree import ElementTree
+from datetime import datetime
+from xml.etree.ElementTree import Element
+
+# Set to true if notify2 was successfully imported and initialized
+NOTIFY2 = False
+MSG_FALLBACK_STR = 'Messages will only be printed to stdout.'
+try:
+    # DEPENDENCIES
+    # -> https://pypi.org/project/notify2/
+    # -> https://pypi.org/project/dbus-python/
+    import notify2
+
+    notify2.init('Relative Xournal++ Background Paths')
+    NOTIFY2 = True
+except ImportError as e:
+    print(f'Optional dependency "notify2" is not available. {MSG_FALLBACK_STR}')
+except Exception as e:
+    print(f'Error during import or initialization of notify2. Is the dependency "dbus-python" missing? {MSG_FALLBACK_STR}')
+
+
+def main():
+    modified_files=0
+    xopp_files: List[Path] = []
+    try:
+        xopp_files = parse_args()
+        for xopp_file in xopp_files:
+            modified_files += save_relative_paths(xopp_file=xopp_file)
+
+    # Catch exception, print it to stderr and save as file
+    except Exception as ex:
+        traceback.print_exc()
+
+        log_file = Path.home().joinpath('relative_paths.error')
+        with open(file=log_file, mode='w') as file:
+            traceback.print_exc(file=file)
+
+        notify(summary='Exception', message=getattr(ex, 'message', str(ex)))
+        exit(1)
+
+    notify(summary='Success!', message=f'Modified {modified_files} out of {len(xopp_files)} files.')
+
+
+def parse_args() -> List[Path]:
+    NAUTILUS_SELECTION = 'NAUTILUS_SCRIPT_SELECTED_FILE_PATHS'
+    SCRIPT_NAME = 'relative-xopp-background'
+
+    selected_files_str = getenv(NAUTILUS_SELECTION)
+    if selected_files_str:
+        selected_files = selected_files_str.split('\n')
+        if len(selected_files[-1]) < 1:
+            selected_files = selected_files[:-1]
+        return [Path(file) for file in selected_files]
+
+    if len(argv) < 2:
+        usage_str = f'Usage:\n' \
+                    f'\t{SCRIPT_NAME} <xopp-file-1> [<xopp-file-2>] [...]\n' \
+                    f'\tenv {NAUTILUS_SELECTION}=<newline-delimited-list-of-xopp-files> {SCRIPT_NAME}'
+        print(usage_str, file=stderr)
+        raise Exception(usage_str)
+    return [Path(file) for file in argv[1:]]
+
+
+def save_relative_paths(xopp_file: Path) -> int:
+    """
+    Xournal++ stores XML content into gz compressed `.xopp` files.
+
+    This method modifies the content a given `.xopp` file "xopp_file":
+    In case there are PDF background files with an absolute path and they do
+    not exist at that location but instead reside next to the "xopp_file"
+    (located in the same directory), then their path is replaced with a relative one.
+
+    :returns the number of modified .xopp files (0 or 1)
+    """
+
+    xml_modified = False
+    print(f'=== RELATIVE PATHS ===\nxopp_file: {xopp_file}')
+
+    if not xopp_file.exists():
+        raise Exception(f'The given file does not exist: {xopp_file}')
+    if not xopp_file.suffix == '.xopp':
+        raise Exception(f'Expected a Xournal++ file ending in .xopp: {xopp_file.suffix}')
+
+    # Open gz-compressed file
+    with gzip.open(xopp_file, mode="rt", encoding="utf-8") as fi:
+        xopp_str = fi.read()
+
+    root: Element = ElementTree.fromstring(xopp_str)
+    #
+    # xml_file: Path = Path('2019_SozialeMedien_Umgang-mit-Social-Media.xopp.xml')
+    # tree: ElementTree = ElementTree.parse(xml_file)
+    # root: Element = tree.getroot()
+
+    if not root.tag == 'xournal':
+        raise Exception(f'Unexpected root element: {root.tag}')
+
+    child1: Element
+    for child1 in root:
+        if child1.tag == 'page':
+            child2: Element
+            for child2 in child1:
+                if child2.tag == 'background' \
+                        and 'type' in child2.attrib \
+                        and child2.attrib['type'] == 'pdf' \
+                        and 'domain' in child2.attrib \
+                        and child2.attrib['domain'] == 'absolute' \
+                        and 'filename' in child2.attrib:
+                    print(f'type: {child2.tag}, attrib: {child2.attrib}')
+                    abs_pdf: Path = Path(child2.attrib['filename'])
+
+                    if not abs_pdf.is_absolute():
+                        continue  # No action required as the path is already relative
+                    if abs_pdf.exists():
+                        continue  # No action required as the background pdf will be found by Xournal++
+                    if len(abs_pdf.name) < 1:
+                        raise Exception(f'Expected the PDF file name to be non empty: {abs_pdf}')
+
+                    rel_pdf: Path = xopp_file.parent.joinpath(abs_pdf.name)
+                    if rel_pdf.exists():
+                        # Replace absolute with relative path
+                        child2.attrib['filename'] = abs_pdf.name
+                        xml_modified = True
+                    else:
+                        print("The PDF file was neither found at it's absolute path"
+                              f" nor in the same directory as this Xournal++ file: {abs_pdf}")
+
+    if not xml_modified:
+        print('No modifications.')
+        return 0
+
+    print('The xml was modified!')
+
+    # Current date as string including milliseconds
+    date_str = datetime.today().strftime('%Y-%m-%d_%H-%M-%S_%f')[:-3]
+
+    xopp_file: Path
+    # Optional: Backup old .xopp file
+    # xopp_file.rename(xopp_file.parent.joinpath(xopp_file.name + '.' + date_str + '.backup'))
+
+    # Open in binary mode
+    encoding = 'utf-8'
+    fo = gzip.open(filename=xopp_file, mode='wb')
+
+    # Write xml header
+    # Default xml encoding: us-ascii
+    # -> https://stackoverflow.com/a/28208190/6334421
+    fo.write(f'<?xml version="1.0" encoding="{encoding}" standalone="no"?>\n'.encode(encoding=encoding))
+
+    # Write xml content
+    fo.write(ElementTree.tostring(root, encoding=encoding, method='xml'))
+    fo.close()
+
+    return 1
+
+
+def notify(summary: str, message: str) -> None:
+    """
+    If notify2 is initialized, the user is informed of the given
+    message via a graphical dbus notification.
+
+    If notify2 is not available, the message is instead printed to stdout.
+    """
+    if NOTIFY2:
+        n = notify2.Notification(summary=summary, message=message)
+        n.show()
+    else:
+        print(f'=== MESSAGE ===\n{summary}\n{message}\n')
+
+
+if __name__ == '__main__':
+    main()