From a39f8328cf59492e68643f499c0d0fbda910444c Mon Sep 17 00:00:00 2001
From: Armin Straub <31167361+arminstraub@users.noreply.github.com>
Date: Sun, 17 Jan 2021 15:50:49 -0600
Subject: [PATCH] Preserve links within a PDF (thanks to chrthi)

---
 ChangeLog          |  4 ++++
 krop/mainwindow.py |  1 +
 krop/pdfcropper.py | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index eb7dbb1..4ffbedb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+krop (0.6.1)  2021-00-00 -- Armin Straub
+
+  * Preserve links within a PDF (thanks to chrthi for doing this).
+
 krop (0.6.0)  2020-06-09 -- Armin Straub
 
   + Fixed aspect ratios, like letter size, can be chosen for selections.
diff --git a/krop/mainwindow.py b/krop/mainwindow.py
index fd1ae32..e8adadf 100644
--- a/krop/mainwindow.py
+++ b/krop/mainwindow.py
@@ -413,6 +413,7 @@ def slotKrop(self):
             pdf = PdfFile()
             pdf.loadFromFile(inputFileName)
             cropper = PdfCropper()
+            cropper.copyDocumentRoot(pdf)
             for nr in pages:
                 c = self.viewer.cropValues(nr)
                 cropper.addPageCropped(pdf, nr, c, alwaysinclude, rotation)
diff --git a/krop/pdfcropper.py b/krop/pdfcropper.py
index 679c6fc..db30646 100644
--- a/krop/pdfcropper.py
+++ b/krop/pdfcropper.py
@@ -55,6 +55,8 @@ def writeToFile(self, filename):
         stream.close()
     def addPageCropped(self, pdffile, pagenumber, croplist, rotate=0):
         pass
+    def copyDocumentRoot(self, pdffile):
+        pass
 
 
 class PyPdfFile(AbstractPdfFile):
@@ -110,6 +112,15 @@ def cropPage(self, page, crop, rotate):
         if rotate != 0:
             page.rotateClockwise(rotate)
 
+    def copyDocumentRoot(self, pdffile):
+        # Sounds promising in PyPDF2 (see PdfFileWriter.cloneDocumentFromReader),
+        # but doesn't seem to produce a readable PDF:
+        # self.output.cloneReaderDocumentRoot(pdffile.reader)
+        # Instead, this copies at least the named destinations for links:
+        for dest in pdffile.reader.namedDestinations.values():
+            self.output.addNamedDestinationObject(dest)
+
+
 def optimizePdfGhostscript(oldfilename, newfilename):
     import subprocess
     subprocess.check_call(('gs', '-sDEVICE=pdfwrite', '-sOutputFile=' + newfilename,