Fix thumbnailing

This fixes thumbnailing for XDG desktops. The new script doesn't depend on GNOME libs and works either with python3 or python2.
Also, a thumbnailer config file is added to the installation in CMakeList.txt

src/Tools/freecad-thumbnailer

@@ -0,0 +1,57 @@
+#!/usr/bin/python
+"""Support file to show FreeCAD thumbnails on Free Desktop Environments (like GNOME or KDE)
+
+Installation:
+- This executable file should be on the PATH so it can be found
+	"$ sudo cp freecad-thumbnailer /usr/share/bin"
+- the application/x-extension-fcstd MIME type should be registered
+	Check that a corresponding /usr/share/mime/packages/freecad.xml file exists
+  	Make sure the MIME database is up to date
+	"$ sudo update-mime-database /usr/share/mime"
+- Register this thumbnailer
+	Adding a file /usr/share/thumbnailers/FreeCAD.thumbnailer with the following content:
+
+	[Thumbnailer Entry]
+	TryExec=freecad-thumbnailer
+	Exec=freecad-thumbnailer -s %s %i %o
+	MimeType=application/x-extension-fcstd;
+
+NOTE: To make sure FreeCAD saves thumbnail information:
+
+	Edit -> Preferences... -> Document -> Save thumbnail into project when saving document
+"""
+import sys
+import zipfile
+import getopt
+
+opt, par = getopt.getopt(sys.argv[1:], '-s:')
+input_file = par[0]
+output_file = par[1]
+
+try:
+    # Read compressed file
+    zfile = zipfile.ZipFile(input_file)
+    files = zfile.namelist()
+
+    # Check whether we have a FreeCAD document
+    if "Document.xml" not in files:
+        print(input_file, " doesn't look like a FreeCAD file")
+        sys.exit(1)
+
+    # Read thumbnail from file or use default icon
+    image = "thumbnails/Thumbnail.png"
+    if image in files:
+        image = zfile.read(image)
+    else:
+        # apps should have at least 48x48 icons
+        freecad = open("/usr/share/icons/hicolor/48x48/apps/freecad.png")
+        image = freecad.read()
+
+    # Write icon to output_file
+    thumb = open(output_file, "wb")
+    thumb.write(image)
+    thumb.close()
+
+except:
+    print("Error creating FreeCAD thumbnail for file ", input_file)
+    sys.exit(1)

src/Tools/freecad-thumbnailer.py

@@ -1,36 +0,0 @@
-#!/usr/bin/python
-
-import sys, zipfile, md5
-import getopt
-import gnomevfs
-
-opt,par = getopt.getopt(sys.argv[1:],'-s:')
-inpfile = gnomevfs.get_local_path_from_uri(par[0])
-#inpfile = par[0]
-outfile = par[1]
-
-#print "fcthumbnailer"
-#print inpfile, outfile
-
-try:
-	zfile=zipfile.ZipFile(inpfile)
-	files=zfile.namelist()
-	#print files
-	# check for meta-file if it's really a FreeCAD document
-	if files[0] != "Document.xml":
-		sys.exit(1)
-
-	image="thumbnails/Thumbnail.png"
-	if image in files:
-		image=zfile.read(image)
-	else:
-		freecad=open("/usr/share/freecad/freecad-doc.png")
-		image=freecad.read()
-
-	thumb=open(outfile,"wb")
-	thumb.write(image)
-	thumb.close()
-
-except:
-	sys.exit(1)
-

src/XDGData/CMakeLists.txt

@@ -38,3 +38,8 @@ install(
     FILES org.freecadweb.FreeCAD.xml
     DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/mime/packages
 )
+
+install(
+    FILES FreeCAD.thumbnailer
+    DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/thumbnailers
+)

src/XDGData/FreeCAD.thumbnailer

@@ -0,0 +1,4 @@
+[Thumbnailer Entry]
+TryExec=freecad-thumbnailer
+Exec=freecad-thumbnailer -s %s %i %o
+MimeType=application/x-extension-fcstd;