Use $XDG_CONFIG_HOME

Fixes #3.

pdf-sign

@@ -4,8 +4,6 @@
 
 import argparse, os, queue, re, subprocess, sys, tempfile, time
 
-signatureDir=os.path.expanduser(os.environ['PDF_SIGNATURE_DIR'] if 'PDF_SIGNATURE_DIR' in os.environ else "~/.pdf_signatures")
-
 # Inspired by https://unix.stackexchange.com/a/141496
 def main(args):
     filePath=args.input
@@ -35,7 +33,10 @@ def main(args):
         # The chosen signature
         if not args.signature and args.batch:
             die('In batch mode, signature must be specified.')
+        signatureDir=getSignatureDir()
         signatures=[*filter(lambda x: m("^.*\.pdf$", x), os.listdir(signatureDir))] if not args.signature else [None]
+        if not signatures:
+            die(f'No .pdf files found in {signatureDir}')
         signatureIndex=Cell(0)
         signaturePath=Cell(lambda: args.signature if args.signature else os.path.join(signatureDir, signatures[signatureIndex()]))
         signatureSize=Cell(lambda: pdfGetSize(signaturePath()))
@@ -281,6 +282,22 @@ def main(args):
         else:
             print(f'Aborted')
 
+def getSignatureDir():
+    if 'PDF_SIGNATURE_DIR' in os.environ:
+        sd=os.environ['PDF_SIGNATURE_DIR']
+    elif 'XDG_CONFIG_HOME' in os.environ:
+        sd=os.path.join(os.environ['XDG_CONFIG_HOME'], 'pdf_signatures')
+    elif os.path.exists(os.path.expanduser("~/.config/pdf_signatures")):
+        sd="~/.config/pdf_signatures"
+    else:
+        sd="~/.pdf_signatures"
+    sd=os.path.expanduser(sd)
+    if not os.path.exists(sd):
+        raise Exception(f'Signature directory {sd} does not exist')
+    if not os.path.isdir(sd):
+        raise Exception(f'Signature directory {sd} is not a directory')
+    return sd
+
 # Simple dependency tracking.
 # Init with a value or function to calculate the value.
 # Update by calling with one argument (as in init).
@@ -384,7 +401,7 @@ if not 'BooleanOptionalAction' in dir(argparse):
 parser = argparse.ArgumentParser(description='Sign a PDF file.')
 parser.add_argument('input', metavar='input.pdf', type=str, help='Input PDF file.')
 parser.add_argument('-p', '--page', type=int, default=-1, help='The page to sign, negative for counting from the end. (default: -1)')
-parser.add_argument('-s', '--signature', type=str, help='Path to file used as signature. Required in batch mode. In GUI mode, the user can choose among files in $PDF_SIGNATURE_DIR or ~/.pdf_signatures.')
+parser.add_argument('-s', '--signature', type=str, help='Path to file used as signature. Required in batch mode. In GUI mode, the user can choose among files in $PDF_SIGNATURE_DIR, $XDG_CONFIG_HOME/pdf_signatures (defaulting to ~/.config/pdf_signatures), or ~/.pdf_signatures.')
 parser.add_argument('-x', '--x-coordinate', type=float, default=0.5, help='Horizontal coordinate of signature center, in page width units. (default: 0.5)')
 parser.add_argument('-y', '--y-coordinate', type=float, default=0.75, help='Vertical coordinate of signature center, in page height units. (default: 0.75)')
 parser.add_argument('-W', '--width', type=float, default=0.28, help='Width of box to fit signature to, in page width units. (default: 0.28)')