19 files changed, 210 insertions, 151 deletions
diff --git a/grc/blocks/block_tree.xml b/grc/blocks/block_tree.xml
index a8775d6872..3125864d4d 100644
--- a/grc/blocks/block_tree.xml
+++ b/grc/blocks/block_tree.xml
@@ -1,11 +1,6 @@
 <?xml version="1.0"?>
-<!--
-###################################################
-##Block Tree for platform gnuradio python.
-###################################################
- -->
 <cat>
-   <name></name> <!-- Blank for Root Name -->
+   <name>[Core]</name>
    <cat>
       <name>Misc</name>
       <block>pad_source</block>
@@ -18,12 +13,16 @@
       <block>bus_structure_sink</block>
       <block>bus_structure_source</block>
 
+      <block>epy_block</block>
+      <block>epy_module</block>
+
       <block>note</block>
       <block>import</block>
    </cat>
    <cat>
       <name>Variables</name>
       <block>variable</block>
+      <block>variable_struct</block>
       <block>variable_config</block>
       <block>variable_function_probe</block>
       <block>parameter</block>
diff --git a/grc/blocks/epy_block.xml b/grc/blocks/epy_block.xml
index 3fd5aa84f1..65e78c4062 100644
--- a/grc/blocks/epy_block.xml
+++ b/grc/blocks/epy_block.xml
@@ -2,7 +2,6 @@
 <block>
     <name>Python Block</name>
     <key>epy_block</key>
-    <category>Misc</category>
     <import></import>
     <make></make>
     <param><!-- Cache the last working block IO to keep FG sane -->
diff --git a/grc/blocks/epy_module.xml b/grc/blocks/epy_module.xml
index 6d6d71804c..fa3e5f91f4 100644
--- a/grc/blocks/epy_module.xml
+++ b/grc/blocks/epy_module.xml
@@ -2,7 +2,6 @@
 <block>
 	<name>Python Module</name>
 	<key>epy_module</key>
-	<category>Misc</category>
 	<import>import $id  # embedded python module</import>
 	<make></make>
 	<param>
diff --git a/grc/blocks/options.xml b/grc/blocks/options.xml
index 937cfe82ea..55f411884d 100644
--- a/grc/blocks/options.xml
+++ b/grc/blocks/options.xml
@@ -20,8 +20,8 @@ from PyQt4 import Qt
 import sys
 #end if
 #if not $generate_options().startswith('hb')
-from optparse import OptionParser
-from gnuradio.eng_option import eng_option
+from argparse import ArgumentParser
+from gnuradio.eng_arg import eng_float, intx
 from gnuradio import eng_notation
 #end if</import>
 	<make></make>
@@ -84,7 +84,7 @@ else: self.stop(); self.wait()</callback>
 	<param>
 		<name>Category</name>
 		<key>category</key>
-		<value>Custom</value>
+		<value>[GRC Hier Blocks]</value>
 		<type>string</type>
 		<hide>#if $generate_options().startswith('hb') then 'none' else 'all'#</hide>
 	</param>
diff --git a/grc/blocks/parameter.xml b/grc/blocks/parameter.xml
index e35b8f4d1d..b0713218fd 100644
--- a/grc/blocks/parameter.xml
+++ b/grc/blocks/parameter.xml
@@ -55,9 +55,11 @@
 		</option>
 		<option>
 			<name>String</name>
-			<key>string</key>
+			<key>str</key>
 			<opt>type:string</opt>
-		</option>
+        </option>
+        <!-- Do not forget to add option value type handler import into
+            grc/python/flow_graph.tmpl for each new type. -->
 		<!-- not supported yet in tmpl
 		<option>
 			<name>Boolean</name>
diff --git a/grc/blocks/variable_function_probe.xml b/grc/blocks/variable_function_probe.xml
index baa996c0ec..47c11b29fe 100644
--- a/grc/blocks/variable_function_probe.xml
+++ b/grc/blocks/variable_function_probe.xml
@@ -10,7 +10,7 @@
 	<import>import time</import>
 	<import>import threading</import>
 	<var_make>self.$(id) = $(id) = $value</var_make>
-	<make>#slurp
+	<make>
 def _$(id)_probe():
     while True:
         #set $obj = 'self' + ('.' + $block_id() if $block_id() else '')
@@ -22,15 +22,10 @@ def _$(id)_probe():
         time.sleep(1.0 / ($poll_rate))
 _$(id)_thread = threading.Thread(target=_$(id)_probe)
 _$(id)_thread.daemon = True
-_$(id)_thread.start()</make>
+_$(id)_thread.start()
+    </make>
 	<callback>self.set_$(id)($value)</callback>
 	<param>
-		<name>Value</name>
-		<key>value</key>
-		<value>0</value>
-		<type>raw</type>
-	</param>
-	<param>
 		<name>Block ID</name>
 		<key>block_id</key>
 		<value>my_block_0</value>
@@ -55,6 +50,13 @@ _$(id)_thread.start()</make>
 		<value>10</value>
 		<type>real</type>
 	</param>
+	<param>
+		<name>Initial Value</name>
+		<key>value</key>
+		<value>0</value>
+		<type>raw</type>
+        <hide>part</hide>
+	</param>
 	<doc>
 Periodically probe a function and set its value to this variable.
 
diff --git a/grc/blocks/variable_struct.xml.py b/grc/blocks/variable_struct.xml.py
index e43200828b..de4411e975 100644
--- a/grc/blocks/variable_struct.xml.py
+++ b/grc/blocks/variable_struct.xml.py
@@ -6,7 +6,6 @@ HEADER = """\
 <block>
   <name>Struct Variable</name>
   <key>variable_struct</key>
-  <category>Variables</category>
   <import>def struct(data): return type('Struct', (object,), data)()</import>
   <var_make>self.$id = $id = struct({{#slurp
 #for $i in range({0}):
diff --git a/grc/core/Block.py b/grc/core/Block.py
index ff7f041dc0..9fff5afcb7 100644
--- a/grc/core/Block.py
+++ b/grc/core/Block.py
@@ -67,7 +67,7 @@ class Block(Element):
 
         self._name = n['name']
         self._key = n['key']
-        self._category = n.get('category', '')
+        self.category = [cat.strip() for cat in n.get('category', '').split('/') if cat.strip()]
         self._flags = n.get('flags', '')
         self._doc = n.get('doc', '').strip('\n').replace('\\\n', '')
 
@@ -491,12 +491,6 @@ class Block(Element):
     def get_key(self):
         return self._key
 
-    def get_category(self):
-        return self._category
-
-    def set_category(self, cat):
-        self._category = cat
-
     def get_ports(self):
         return self.get_sources() + self.get_sinks()
 
diff --git a/grc/core/Constants.py b/grc/core/Constants.py
index 8a99f8b256..992d5e7d83 100644
--- a/grc/core/Constants.py
+++ b/grc/core/Constants.py
@@ -41,6 +41,7 @@ FLOW_GRAPH_FILE_FORMAT_VERSION = 1
 # Param tabs
 DEFAULT_PARAM_TAB = "General"
 ADVANCED_PARAM_TAB = "Advanced"
+DEFAULT_BLOCK_MODULE_NAME = '(no module specified)'
 
 # Port domains
 GR_STREAM_DOMAIN = "gr_stream"
diff --git a/grc/core/Element.pyi b/grc/core/Element.pyi
new file mode 100644
index 0000000000..c81180a33e
--- /dev/null
+++ b/grc/core/Element.pyi
@@ -0,0 +1,54 @@
+# Copyright 2008, 2009, 2015, 2016 Free Software Foundation, Inc.
+# This file is part of GNU Radio
+#
+# GNU Radio Companion is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# GNU Radio Companion is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+
+from . import Platform, FlowGraph, Block
+
+def lazy_property(func):
+    return func
+
+
+class Element(object):
+
+    def __init__(self, parent=None):
+        ...
+
+    @property
+    def parent(self):
+        ...
+
+    def get_parent_by_type(self, cls):
+        parent = self.parent
+        if parent is None:
+            return None
+        elif isinstance(parent, cls):
+            return parent
+        else:
+            return parent.get_parent_by_type(cls)
+
+    @lazy_property
+    def parent_platform(self): -> Platform.Platform
+        ...
+
+    @lazy_property
+    def parent_flowgraph(self): -> FlowGraph.FlowGraph
+        ...
+
+    @lazy_property
+    def parent_block(self): -> Block.Block
+        ...
+
+
diff --git a/grc/core/Platform.py b/grc/core/Platform.py
index 069870d389..be7b60ca59 100644
--- a/grc/core/Platform.py
+++ b/grc/core/Platform.py
@@ -69,7 +69,7 @@ class Platform(Element):
 
         self.blocks = {}
         self._blocks_n = {}
-        self._category_trees_n = []
+        self._block_categories = {}
         self.domains = {}
         self.connection_templates = {}
 
@@ -79,7 +79,8 @@ class Platform(Element):
         self._flow_graph = Element.__new__(FlowGraph)
         Element.__init__(self._flow_graph, self)
         self._flow_graph.connections = []
-        self.load_blocks()
+
+        self.build_block_library()
 
     def __str__(self):
         return 'Platform - {}({})'.format(self.config.key, self.config.name)
@@ -137,14 +138,14 @@ class Platform(Element):
         self.load_block_xml(generator.file_path_xml)
         return True
 
-    def load_blocks(self):
+    def build_block_library(self):
         """load the blocks and block tree from the search paths"""
         self._docstring_extractor.start()
 
         # Reset
         self.blocks.clear()
         self._blocks_n.clear()
-        del self._category_trees_n[:]
+        self._block_categories.clear()
         self.domains.clear()
         self.connection_templates.clear()
         ParseXML.xml_failures.clear()
@@ -162,9 +163,21 @@ class Platform(Element):
                 # print >> sys.stderr, 'Warning: Block validation failed:\n\t%s\n\tIgnoring: %s' % (e, xml_file)
                 pass
             except Exception as e:
-                raise
                 print('Warning: XML parsing failed:\n\t%r\n\tIgnoring: %s' % (e, xml_file), file=sys.stderr)
 
+        # Add blocks to block tree
+        for key, block in six.iteritems(self.blocks):
+            category = self._block_categories.get(key, block.category)
+            # Blocks with empty categories are hidden
+            if not category:
+                continue
+            root = category[0]
+            if root.startswith('[') and root.endswith(']'):
+                category[0] = root[1:-1]
+            else:
+                category.insert(0, Constants.DEFAULT_BLOCK_MODULE_NAME)
+            block.category = category
+
         self._docstring_extractor.finish()
         # self._docstring_extractor.wait()
 
@@ -202,8 +215,19 @@ class Platform(Element):
     def load_category_tree_xml(self, xml_file):
         """Validate and parse category tree file and add it to list"""
         ParseXML.validate_dtd(xml_file, Constants.BLOCK_TREE_DTD)
-        n = ParseXML.from_file(xml_file).get('cat', {})
-        self._category_trees_n.append(n)
+        xml = ParseXML.from_file(xml_file)
+        path = []
+
+        def load_category(cat_n):
+            path.append(cat_n.get('name').strip())
+            for block_key in cat_n.get('block', []):
+                if block_key not in self._block_categories:
+                    self._block_categories[block_key] = list(path)
+            for sub_cat_n in cat_n.get('cat', []):
+                load_category(sub_cat_n)
+            path.pop()
+
+        load_category(xml.get('cat', {}))
 
     def load_domain_xml(self, xml_file):
         """Load a domain properties and connection templates from XML"""
@@ -248,44 +272,6 @@ class Platform(Element):
             else:
                 self.connection_templates[key] = connection_n.get('make') or ''
 
-    def load_block_tree(self, block_tree):
-        """
-        Load a block tree with categories and blocks.
-        Step 1: Load all blocks from the xml specification.
-        Step 2: Load blocks with builtin category specifications.
-
-        Args:
-            block_tree: the block tree object
-        """
-        # Recursive function to load categories and blocks
-        def load_category(cat_n, parent=None):
-            # Add this category
-            parent = (parent or []) + [cat_n.get('name')]
-            block_tree.add_block(parent)
-            # Recursive call to load sub categories
-            for cat in cat_n.get('cat', []):
-                load_category(cat, parent)
-            # Add blocks in this category
-            for block_key in cat_n.get('block', []):
-                if block_key not in self.blocks:
-                    print('Warning: Block key "{}" not found when loading category tree.'.format(block_key), file=sys.stderr)
-                    continue
-                block = self.blocks[block_key]
-                # If it exists, the block's category shall not be overridden by the xml tree
-                if not block.get_category():
-                    block.set_category(parent)
-
-        # Recursively load the category trees and update the categories for each block
-        for category_tree_n in self._category_trees_n:
-            load_category(category_tree_n)
-
-        # Add blocks to block tree
-        for block in six.itervalues(self.blocks):
-            # Blocks with empty categories are hidden
-            if not block.get_category():
-                continue
-            block_tree.add_block(block.get_category(), block)
-
     def _save_docstring_extraction_result(self, key, docstrings):
         docs = {}
         for match, docstring in six.iteritems(docstrings):
diff --git a/grc/core/generator/Generator.py b/grc/core/generator/Generator.py
index c3308d6c32..9c7d07e76b 100644
--- a/grc/core/generator/Generator.py
+++ b/grc/core/generator/Generator.py
@@ -144,16 +144,16 @@ class TopBlockGenerator(object):
                 pass
             return code
 
-        blocks = expr_utils.sort_objects(
+        blocks_all = expr_utils.sort_objects(
             [b for b in fg.blocks if b.get_enabled() and not b.get_bypassed()],
             operator.methodcaller('get_id'), _get_block_sort_text
         )
-        deprecated_block_keys = set(block.get_name() for block in blocks if block.is_deprecated)
+        deprecated_block_keys = set(b.get_name() for b in blocks_all if b.is_deprecated)
         for key in deprecated_block_keys:
             Messages.send_warning("The block {!r} is deprecated.".format(key))
 
         # List of regular blocks (all blocks minus the special ones)
-        blocks = [b for b in blocks if b not in imports and b not in parameters]
+        blocks = [b for b in blocks_all if b not in imports and b not in parameters]
 
         for block in blocks:
             key = block.get_key()
@@ -220,18 +220,20 @@ class TopBlockGenerator(object):
 
         # List of variable names
         var_ids = [var.get_id() for var in parameters + variables]
-        # Prepend self.
-        replace_dict = dict([(var_id, 'self.%s' % var_id) for var_id in var_ids])
-        # List of callbacks
-        callbacks = [
-            expr_utils.expr_replace(cb, replace_dict)
-            for cb in sum([block.get_callbacks() for block in fg.get_enabled_blocks()], [])
-            ]
+        replace_dict = dict((var_id, 'self.' + var_id) for var_id in var_ids)
+        callbacks_all = []
+        for block in blocks_all:
+            callbacks_all.extend(expr_utils.expr_replace(cb, replace_dict) for cb in block.get_callbacks())
+
         # Map var id to callbacks
-        var_id2cbs = dict([
-            (var_id, [c for c in callbacks if expr_utils.get_variable_dependencies(c, [var_id])])
-            for var_id in var_ids
-        ])
+        def uses_var_id():
+            used = expr_utils.get_variable_dependencies(callback, [var_id])
+            return used and 'self.' + var_id in callback  # callback might contain var_id itself
+
+        callbacks = {}
+        for var_id in var_ids:
+            callbacks[var_id] = [callback for callback in callbacks_all if uses_var_id()]
+
         # Load the namespace
         namespace = {
             'title': title,
@@ -245,7 +247,7 @@ class TopBlockGenerator(object):
             'connection_templates': connection_templates,
             'msgs': msgs,
             'generate_options': self._generate_options,
-            'var_id2cbs': var_id2cbs,
+            'callbacks': callbacks,
         }
         # Build the template
         t = Template(open(FLOW_GRAPH_TEMPLATE, 'r').read(), namespace)
@@ -265,8 +267,9 @@ class HierBlockGenerator(TopBlockGenerator):
             file_path: where to write the py file (the xml goes into HIER_BLOCK_LIB_DIR)
         """
         TopBlockGenerator.__init__(self, flow_graph, file_path)
+        platform = flow_graph.parent
 
-        hier_block_lib_dir = flow_graph.parent_platform.config.hier_block_lib_dir
+        hier_block_lib_dir = platform.config.hier_block_lib_dir
         if not os.path.exists(hier_block_lib_dir):
             os.mkdir(hier_block_lib_dir)
 
diff --git a/grc/core/generator/flow_graph.tmpl b/grc/core/generator/flow_graph.tmpl
index c86808455b..5eef3d2042 100644
--- a/grc/core/generator/flow_graph.tmpl
+++ b/grc/core/generator/flow_graph.tmpl
@@ -13,7 +13,7 @@
 ##@param connections the connections
 ##@param msgs the msg type connections
 ##@param generate_options the type of flow graph
-##@param var_id2cbs variable id map to callback strings
+##@param callbacks variable id map to callback strings
 ########################################################
 #def indent($code)
 #set $code = '\n        '.join(str($code).splitlines())
@@ -301,12 +301,12 @@ gr.io_signaturev($(len($io_sigs)), $(len($io_sigs)), [$(', '.join($size_strs))])
     #if $flow_graph.get_option('thread_safe_setters')
         with self._lock:
             self.$id = $id
-        #for $callback in $var_id2cbs[$id]
+        #for $callback in $callbacks[$id]
             $indent($callback)
         #end for
     #else
         self.$id = $id
-        #for $callback in $var_id2cbs[$id]
+        #for $callback in $callbacks[$id]
         $indent($callback)
         #end for
     #end if
@@ -336,19 +336,22 @@ $short_id#slurp
 
 
 def argument_parser():
-    #set $desc_args = 'usage="%prog: [options]", option_class=eng_option'
+    #set $arg_parser_args = ''
     #if $flow_graph.get_option('description')
-        #set $desc_args += ', description=description'
+        #set $arg_parser_args = 'description=description'
     description = $repr($flow_graph.get_option('description'))
     #end if
-    parser = OptionParser($desc_args)
+    parser = ArgumentParser($arg_parser_args)
     #for $param in $parameters
         #set $type = $param.get_param('type').get_value()
         #if $type
             #silent $params_eq_list.append('%s=options.%s'%($param.get_id(), $param.get_id()))
-    parser.add_option(
-        "$make_short_id($param)", "--$param.get_id().replace('_', '-')", dest="$param.get_id()", type="$type", default=$make_default($type, $param),
-        help="Set $($param.get_param('label').get_evaluated() or $param.get_id()) [default=%default]")
+    parser.add_argument(
+        #if $make_short_id($param)
+        "$make_short_id($param)", #slurp
+        #end if
+        "--$param.get_id().replace('_', '-')", dest="$param.get_id()", type=$type, default=$make_default($type, $param),
+        help="Set $($param.get_param('label').get_evaluated() or $param.get_id()) [default=%(default)r]")
         #end if
     #end for
     return parser
@@ -358,7 +361,7 @@ def argument_parser():
 def main(top_block_cls=$(class_name), options=None):
     #if $parameters
     if options is None:
-        options, _ = argument_parser().parse_args()
+        options = argument_parser().parse_args()
     #end if
     #if $flow_graph.get_option('realtime_scheduling')
     if gr.enable_realtime_scheduling() != gr.RT_OK:
diff --git a/grc/core/utils/expr_utils.py b/grc/core/utils/expr_utils.py
index 0577f06a75..555bd709b1 100644
--- a/grc/core/utils/expr_utils.py
+++ b/grc/core/utils/expr_utils.py
@@ -61,7 +61,7 @@ class graph(object):
         return self._graph[node_key]
 
 
-def expr_split(expr):
+def expr_split(expr, var_chars=VAR_CHARS):
     """
     Split up an expression by non alphanumeric characters, including underscore.
     Leave strings in-tact.
@@ -77,7 +77,7 @@ def expr_split(expr):
     tok = ''
     quote = ''
     for char in expr:
-        if quote or char in VAR_CHARS:
+        if quote or char in var_chars:
             if char == quote:
                 quote = ''
             tok += char
@@ -104,7 +104,7 @@ def expr_replace(expr, replace_dict):
     Returns:
         a new expression with the prepend
     """
-    expr_splits = expr_split(expr)
+    expr_splits = expr_split(expr, var_chars=VAR_CHARS + '.')
     for i, es in enumerate(expr_splits):
         if es in list(replace_dict.keys()):
             expr_splits[i] = replace_dict[es]
@@ -195,7 +195,3 @@ def sort_objects(objects, get_id, get_expr):
     # Return list of sorted objects
     return [id2obj[id] for id in sorted_ids]
 
-
-if __name__ == '__main__':
-    for i in sort_variables({'x': '1', 'y': 'x+1', 'a': 'x+y', 'b': 'y+1', 'c': 'a+b+x+y'}):
-        print(i)
diff --git a/grc/gui/ActionHandler.py b/grc/gui/ActionHandler.py
index 8d4dc7841f..25c779b4d2 100644
--- a/grc/gui/ActionHandler.py
+++ b/grc/gui/ActionHandler.py
@@ -608,9 +608,8 @@ class ActionHandler:
         elif action == Actions.PAGE_CHANGE:  # pass and run the global actions
             pass
         elif action == Actions.RELOAD_BLOCKS:
-            self.platform.load_blocks()
-            main.btwin.clear()
-            self.platform.load_block_tree(main.btwin)
+            self.platform.build_block_library()
+            main.btwin.repopulate()
             Actions.XML_PARSER_ERRORS_DISPLAY.set_sensitive(bool(
                 ParseXML.xml_failures))
             Messages.send_xml_errors_if_any(ParseXML.xml_failures)
diff --git a/grc/gui/BlockTreeWindow.py b/grc/gui/BlockTreeWindow.py
index 26086f58e9..89aac53a0e 100644
--- a/grc/gui/BlockTreeWindow.py
+++ b/grc/gui/BlockTreeWindow.py
@@ -27,7 +27,8 @@ from gi.repository import Gdk
 from gi.repository import GObject
 
 from . import Actions, Utils
-from .Constants import DEFAULT_BLOCKS_WINDOW_WIDTH, DND_TARGETS
+from . import Constants
+
 
 NAME_INDEX, KEY_INDEX, DOC_INDEX = range(3)
 
@@ -51,6 +52,18 @@ def _format_doc(doc):
     return out or 'undocumented'
 
 
+def _format_cat_tooltip(category):
+    tooltip = '{}: {}'.format('Category' if len(category) > 1 else 'Module', category[-1])
+
+    if category == ('Core',):
+        tooltip += '\n\nThis subtree is meant for blocks included with GNU Radio (in-tree).'
+
+    elif category == (Constants.DEFAULT_BLOCK_MODULE_NAME,):
+        tooltip += '\n\n' + Constants.DEFAULT_BLOCK_MODULE_TOOLTIP
+
+    return tooltip
+
+
 class BlockTreeWindow(Gtk.VBox):
     """The block selection panel."""
 
@@ -100,66 +113,68 @@ class BlockTreeWindow(Gtk.VBox):
         renderer = Gtk.CellRendererText()
         column = Gtk.TreeViewColumn('Blocks', renderer, text=NAME_INDEX)
         self.treeview.append_column(column)
-        # try to enable the tooltips (available in pygtk 2.12 and above)
-        try:
-            self.treeview.set_tooltip_column(DOC_INDEX)
-        except:
-            pass
+        self.treeview.set_tooltip_column(DOC_INDEX)
         # setup sort order
         column.set_sort_column_id(0)
         self.treestore.set_sort_column_id(0, Gtk.SortType.ASCENDING)
         # setup drag and drop
-        self.treeview.enable_model_drag_source(Gdk.ModifierType.BUTTON1_MASK, DND_TARGETS, Gdk.DragAction.COPY)
+        self.treeview.enable_model_drag_source(Gdk.ModifierType.BUTTON1_MASK, Constants.DND_TARGETS, Gdk.DragAction.COPY)
         self.treeview.connect('drag-data-get', self._handle_drag_get_data)
         # make the scrolled window to hold the tree view
         scrolled_window = Gtk.ScrolledWindow()
         scrolled_window.set_policy(Gtk.PolicyType.AUTOMATIC, Gtk.PolicyType.AUTOMATIC)
         scrolled_window.add_with_viewport(self.treeview)
-        scrolled_window.set_size_request(DEFAULT_BLOCKS_WINDOW_WIDTH, -1)
+        scrolled_window.set_size_request(Constants.DEFAULT_BLOCKS_WINDOW_WIDTH, -1)
         self.pack_start(scrolled_window, True, True, 0)
         # map categories to iters, automatic mapping for root
         self._categories = {tuple(): None}
         self._categories_search = {tuple(): None}
-        # add blocks and categories
-        self.platform.load_block_tree(self)
         self.platform.block_docstrings_loaded_callback = self.update_docs
+        self.repopulate()
 
     def clear(self):
-        self.treestore.clear();
-        self._categories = {tuple(): None}
+        self.treestore.clear()
+        self._categories = {(): None}
+
+    def repopulate(self):
+        self.clear()
+        for block in six.itervalues(self.platform.blocks):
+            if block.category:
+                self.add_block(block)
+        self.expand_module_in_tree()
+
+    def expand_module_in_tree(self, module_name='Core'):
+        self.treeview.collapse_all()
+        core_module_iter = self._categories.get((module_name,))
+        if core_module_iter:
+            self.treeview.expand_row(self.treestore.get_path(core_module_iter), False)
 
     ############################################################
     ## Block Tree Methods
     ############################################################
-    def add_block(self, category, block=None, treestore=None, categories=None):
+    def add_block(self, block, treestore=None, categories=None):
         """
         Add a block with category to this selection window.
         Add only the category when block is None.
 
         Args:
-            category: the category list or path string
             block: the block object or None
         """
-        if treestore is None:
-            treestore = self.treestore
-        if categories is None:
-            categories = self._categories
-
-        if isinstance(category, (str, six.text_type)):
-            category = category.split('/')
-        category = tuple(x for x in category if x)  # tuple is hashable
+        treestore = treestore or self.treestore
+        categories = categories or self._categories
+
+        category = tuple(filter(str, block.category))  # tuple is hashable, remove empty cats
+
         # add category and all sub categories
-        for i, cat_name in enumerate(category):
-            sub_category = category[:i+1]
-            if sub_category not in categories:
-                iter_ = treestore.insert_before(categories[sub_category[:-1]], None)
-                treestore.set_value(iter_, NAME_INDEX, cat_name)
+        for level, parent_cat_name in enumerate(category, 1):
+            parent_category = category[:level]
+            if parent_category not in categories:
+                iter_ = treestore.insert_before(categories[parent_category[:-1]], None)
+                treestore.set_value(iter_, NAME_INDEX, parent_cat_name)
                 treestore.set_value(iter_, KEY_INDEX, '')
-                treestore.set_value(iter_, DOC_INDEX, 'Category: ' + Utils.encode(cat_name))
-                categories[sub_category] = iter_
+                treestore.set_value(iter_, DOC_INDEX, _format_cat_tooltip(parent_cat_name))
+                categories[parent_category] = iter_
         # add block
-        if block is None:
-            return
         iter_ = treestore.insert_before(categories[category], None)
         treestore.set_value(iter_, NAME_INDEX, block.get_name())
         treestore.set_value(iter_, KEY_INDEX, block.get_key())
@@ -212,7 +227,7 @@ class BlockTreeWindow(Gtk.VBox):
         key = widget.get_text().lower()
         if not key:
             self.treeview.set_model(self.treestore)
-            self.treeview.collapse_all()
+            self.expand_module_in_tree()
         else:
             matching_blocks = [b for b in list(self.platform.blocks.values())
                                if key in b.get_key().lower() or key in b.get_name().lower()]
@@ -220,8 +235,7 @@ class BlockTreeWindow(Gtk.VBox):
             self.treestore_search.clear()
             self._categories_search = {tuple(): None}
             for block in matching_blocks:
-                self.add_block(block.get_category() or 'None', block,
-                               self.treestore_search, self._categories_search)
+                self.add_block(block, self.treestore_search, self._categories_search)
             self.treeview.set_model(self.treestore_search)
             self.treeview.expand_all()
 
diff --git a/grc/gui/Constants.py b/grc/gui/Constants.py
index 8bb15acc09..035a7f8ca9 100644
--- a/grc/gui/Constants.py
+++ b/grc/gui/Constants.py
@@ -96,6 +96,13 @@ SCROLL_DISTANCE = 15
 # How close the mouse click can be to a line and register a connection select.
 LINE_SELECT_SENSITIVITY = 5
 
+DEFAULT_BLOCK_MODULE_TOOLTIP = """\
+This subtree holds all blocks (from OOT modules) that specify no module name. \
+The module name is the root category enclosed in square brackets.
+
+Please consider contacting OOT module maintainer for any block in here \
+and kindly ask to update their GRC Block Descriptions or Block Tree to include a module name."""
+
 
 def update_font_size(font_size):
     global PORT_SEPARATION, BLOCK_FONT, PORT_FONT, PARAM_FONT, FONT_SIZE
diff --git a/grc/main.py b/grc/main.py
index 810ac7c66f..ff0811e22a 100755
--- a/grc/main.py
+++ b/grc/main.py
@@ -15,8 +15,7 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 
-from __future__ import absolute_import
-import optparse
+import argparse
 
 import gi
 gi.require_version('Gtk', '3.0')
@@ -38,10 +37,10 @@ This is free software, and you are welcome to redistribute it.
 
 
 def main():
-    parser = optparse.OptionParser(
-        usage='usage: %prog [options] [saved flow graphs]',
-        version=VERSION_AND_DISCLAIMER_TEMPLATE % gr.version())
-    options, args = parser.parse_args()
+    parser = argparse.ArgumentParser(
+        description=VERSION_AND_DISCLAIMER_TEMPLATE % gr.version())
+    parser.add_argument('flow_graphs', nargs='*')
+    args = parser.parse_args()
 
     try:
         Gtk.window_set_default_icon(Gtk.IconTheme().load_icon('gnuradio-grc', 256, 0))
@@ -54,6 +53,6 @@ def main():
         version_parts=(gr.major_version(), gr.api_version(), gr.minor_version()),
         install_prefix=gr.prefix()
     )
-    ActionHandler(args, platform)
+    ActionHandler(args.flow_graphs, platform)
     Gtk.main()
 
diff --git a/grc/test/.cache/v/cache/lastfailed b/grc/test/.cache/v/cache/lastfailed
new file mode 100644
index 0000000000..9c73bf7055
--- /dev/null
+++ b/grc/test/.cache/v/cache/lastfailed
@@ -0,0 +1,3 @@
+{
+  "test_no_re_cheetah_find.py::test_nested": true
+}
+\ No newline at end of file