textures: implement proper fallback loading

Sometimes a texture pack is not complete, but system textures are
available to make up the difference. In that case, we should load
those.

Current caveat is that we might not notice texture names changing
with newer minecraft clients because we have old ones installed.

I'll have to think some more about that one.

overviewer_core/textures.py

@@ -86,8 +86,8 @@ class Textures(object):
         self.texture_cache = {}
 
         # once we find a jarfile that contains a texture, we cache the ZipFile object here
-        self.jar = None
+        self.jars = []
-        self.jarpath = ""
+        self.jarpaths = []
     
     ##
     ## pickle support
@@ -101,7 +101,7 @@ class Textures(object):
                 del attributes[attr]
             except KeyError:
                 pass
-        attributes['jar'] = None
+        attributes['jars'] = []
         return attributes
     def __setstate__(self, attrs):
         # regenerate textures, if needed
@@ -116,6 +116,17 @@ class Textures(object):
     ##
     
     def generate(self):
+        # Make sure we have the foliage/grasscolor images available
+        try:
+            self.load_foliage_color()
+            self.load_grass_color()
+        except TextureException as e:
+            logging.error(
+                "Your system is missing either assets/minecraft/textures/colormap/foliage.png "
+                "or assets/minecraft/textures/colormap/grass.png. Either complement your "
+                "resource pack with these texture files, or install the vanilla Minecraft "
+                "client to use as a fallback.")
+            raise e
         
         # generate biome grass mask
         self.biome_grass_texture = self.build_block(self.load_image_texture("assets/minecraft/textures/block/grass_block_top.png"), self.load_image_texture("assets/minecraft/textures/block/grass_block_side_overlay.png"))
@@ -173,11 +184,17 @@ class Textures(object):
 
         # we've sucessfully loaded something from here before, so let's quickly try
         # this before searching again
-        if self.jar is not None:
+        # We might already know some jarpaths from other processes though.
+        if len(self.jarpaths) > len(self.jars):
+            for p in self.jarpaths:
+                self.jars.append(zipfile.ZipFile(p))
+        if len(self.jars) > 0:
+            for jar_num, jar in enumerate(self.jars):
                 try:
-                self.jar.getinfo(filename)
+                    jar.getinfo(filename)
-                if verbose: logging.info("Found (cached) %s in '%s'", filename, self.jarpath)
+                    if verbose: logging.info("Found (cached) %s in '%s'", filename,
-                return self.jar.open(filename)
+                                             self.jarpaths[jar_num])
+                    return jar.open(filename)
                 except (KeyError, IOError) as e:
                     pass
 
@@ -199,7 +216,8 @@ class Textures(object):
                     pack.getinfo(filename)
                     if verbose: logging.info("Found %s in '%s'", filename,
                                              self.find_file_local_path)
-                    self.jar, self.jarpath = pack, self.find_file_local_path
+                    self.jars.append(pack)
+                    self.jarpaths.append(self.find_file_local_path)
                     return pack.open(filename)
                 except (zipfile.BadZipfile, KeyError, IOError):
                     pass
@@ -283,7 +301,8 @@ class Textures(object):
                 try:
                     jar.getinfo(filename)
                     if verbose: logging.info("Found %s in '%s'", filename, jarpath)
-                    self.jar, self.jarpath = jar, jarpath
+                    self.jars.append(jar)
+                    self.jarpaths.append(jarpath)
                     return jar.open(filename)
                 except (KeyError, IOError) as e:
                     pass