Create overriding loaders.cache on win32 platform

If loaders.cache specifies absolute paths to the GDK Pixbuf loader DLLs, the loader DLLs are always found regardless of their otherwise relative location to the name returned by win32 function GetModuleFileName

Author: RedFantom

gttk/__init__.py

@@ -5,6 +5,8 @@
 """
 import contextlib
 import os
+import sys
+from tempfile import gettempdir
 import tkinter as tk
 from typing import Optional, Tuple
 
@@ -26,7 +28,8 @@ class GTTK(object):
 
     FOLDER = os.path.abspath(os.path.dirname(__file__))
 
-    def __init__(self, window: tk.Tk, theme: Optional[str] = None, theme_dir_prefix: Optional[str] = None):
+    def __init__(self, window: tk.Tk, theme: Optional[str] = None, theme_dir_prefix: Optional[str] = None,
+                 temp_dir: str = gettempdir()):
         """
         Initialize gttk and load it into a window
 
@@ -36,14 +39,31 @@ def __init__(self, window: tk.Tk, theme: Optional[str] = None, theme_dir_prefix:
             given, defaults to the current working directory. If this
             has the special value "LIB", the script will use the
             site-packages directory where it is installed.
+        :param temp_dir: Absolute path to temporary files directory that
+            may be used by the library
         """
         self.tk = window.tk
-        folder = os.path.dirname(os.path.abspath(__file__)).replace("\\", "/")
+        folder = os.path.dirname(os.path.abspath(__file__))
+
         if theme_dir_prefix is not None:
             os.environ["GTK_DATA_PREFIX"] = theme_dir_prefix
 
+        # Create loaders.cache on win32 platforms to find pixbuf loaders properly
+        if "win" in sys.platform:
+            target = os.path.join(temp_dir, "loaders.cache")
+            with open(os.path.join(folder, "loaders.cache")) as fi, open(target, "w") as fo:
+                cache = fi.read()
+                abspath = (os.path.join(folder, "lib", "gdk-pixbuf-2.0", "2.10.0", "loaders") + "\\")\
+                    .replace("\\", "\\\\")  # loaders.cache uses double \ everywhere
+                cache_w_abspaths = cache.replace("\\\\lib", abspath)
+                fo.write(cache_w_abspaths)
+            # Set GDK_PIXBUF_MODULE_FILE to the path of the new cache file
+            # GDK_PIXBUF_MODULEDIR does not do anything for plain GDK!
+            os.environ["GDK_PIXBUF_MODULE_FILE"] = target
+
         with chdir(folder):
-            self.tk.eval("set dir {0}; source {0}/pkgIndex.tcl".format(folder))
+            # Evaluate pkgIndex.tcl, Tcl does not handle \ as a pathsep, so with /
+            self.tk.eval("set dir {0}; source {0}/pkgIndex.tcl".format(folder.replace("\\", "/")))
             self.tk.call("package", "require", "ttk::theme::gttk")
 
         if theme is not None:

setup.py

@@ -159,7 +159,7 @@ def copy_to_target(self, target: str):
     specials={
         "libpixmap.dll": "/lib/gtk-2.0/2.10.0/engines/", 
         "libwimp.dll": "/lib/gtk-2.0/2.10.0/engines/",
-        "loaders.cache": "/lib/gdk-pixbuf-2.0/2.10.0/"}
+        "loaders.cache": "/"}  # loaders.cache is used to specify abspaths to the loaders
     specials.update({"libpixbufloader-{}.dll".format(fmt): "/lib/gdk-pixbuf-2.0/2.10.0/loaders/"
                      for fmt in ["ani", "bmp", "gif", "icns", "ico", "jpeg", "png", "pnm", "qtif", "svg", "tga", "tiff", "xbm", "xpm"]})
     DependencyWalker("libgttk.dll", specials=specials).copy_to_target("gttk")