Add LLDB command to PrintViewGraph docs

Bug: None
Change-Id: Ia919cbafa827280b4fc999085b0cc0281338cc5c
Reviewed-on: https://chromium-review.googlesource.com/1150425
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579407}

docs/graphical_debugging_aid_chromium_views.md

@@ -7,7 +7,11 @@ debugging. It consists of 4 components:
 
 1.  The function `views::PrintViewGraph()` (in the file
     `ui/views/debug_utils.h`),
-1.  a gdb script file `viewg.gdb` (see below),
+1.  a custom debugger command
+  - For GDB, use `tools/gdb/viewg.gdb`
+  - For LLDB, use `tools/lldb/lldb_viewg.py`
+  - For other debuggers, it should be relatively easy to adapt the
+    above scripts.
 1.  the graphViz package (http://www.graphviz.org/ - downloadable for Linux,
     Windows and Mac), and
 1.  an SVG viewer (_e.g._ Chrome).
@@ -17,8 +21,11 @@ debugging. It consists of 4 components:
 To use the tool,
 
 1.  Make sure you have 'dot' installed (part of graphViz),
-1.  run gdb on your build and
-1.  `source viewg.gdb` (this can be done automatically in `.gdbinit`),
+1.  run gdb/lldb on your build and
+    1. For GDB `source tools/gdb/viewg.gdb` (this can be done automatically
+    in `.gdbinit`),
+    1. For LLDB `command script import tools/lldb/lldb_viewg.py` (this can
+    be done automatically in `.lldbinit`),
 1.  stop at any breakpoint inside class `View` (or any derived class), and
 1.  type `viewg` at the gdb prompt.
 
@@ -31,32 +38,10 @@ representation of the state of the views hierarchy that is always up to date.
 It is easy to modify the gdb script to generate PDF in case viewing with evince
 (or other PDF viewer) is preferred.
 
-If you don't use gdb, you may be able to adapt the script to work with your
-favorite debugger. The gdb script invokes
+If you don't use gdb or lldb, you may be able to adapt the script to work with
+your favorite debugger. The gdb script invokes
 
     views::PrintViewGraph(this)
 
 on the current object, returning `std::string`, whose contents must then be
 saved to a file in order to be processed by dot.
-
-## viewg.gdb
-
-```
-define viewg
-  if $argc != 0
-    echo Usage: viewg
-  else
-    set pagination off
-    set print elements 0
-    set logging off
-    set logging file ~/state.dot
-    set logging overwrite on
-    set logging redirect on
-    set logging on
-    printf "%s\n", view::PrintViewGraph(this).c_str()
-    set logging off
-    shell dot -Tsvg -o ~/state.svg ~/state.dot
-    set pagination on
-  end
-end
-```

tools/gdb/viewg.gdb

@@ -0,0 +1,34 @@
+# Copyright 2018 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Creates a SVG graph of the view hierarchy, when stopped in a
+# method of an object that inherits from views::View. Requires
+# graphviz.
+#
+# For more info see
+# chromium/src/+/HEAD/docs/graphical_debugging_aid_chromium_views.md
+#
+# To make this command available, add the following to your ~/.lldbinit:
+# source {Path to SRC Root}/tools/gdbviewg.gdb
+#
+# Usage: type `viewg` at the GDB prompt, given the conditions above.
+
+
+define viewg
+  if $argc != 0
+    echo Usage: viewg
+  else
+    set pagination off
+    set print elements 0
+    set logging off
+    set logging file ~/state.dot
+    set logging overwrite on
+    set logging redirect on
+    set logging on
+    printf "%s\n", view::PrintViewGraph(this).c_str()
+    set logging off
+    shell dot -Tsvg -o ~/state.svg ~/state.dot
+    set pagination on
+  end
+end

tools/lldb/lldb_viewg.py

@@ -0,0 +1,47 @@
+# Copyright 2018 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+    Creates a SVG graph of the view hierarchy, when stopped in a
+    method of an object that inherits from views::View. Requires
+    graphviz.
+
+    For more info see
+    chromium/src/+/HEAD/docs/graphical_debugging_aid_chromium_views.md
+
+    To make this command available, add the following to your ~/.lldbinit:
+    command script import {Path to SRC Root}/tools/lldb/lldb_viewg.py
+
+    Usage: type `viewg` at the LLDB prompt, given the conditions above.
+"""
+
+import lldb
+import os
+
+def view_graph(debugger, command, result, internal_dict):
+  dot = os.path.expanduser("~/state.dot")
+  svg = os.path.splitext(dot)[0] + ".svg"
+
+  process = debugger.GetSelectedTarget().GetProcess()
+  frame = process.GetSelectedThread().GetSelectedFrame()
+
+  cstr_address = frame.EvaluateExpression("views::PrintViewGraph(this).c_str()")
+  if not cstr_address.GetError().Success():
+    return
+  str_size = frame.EvaluateExpression("(size_t)strlen(%s)"
+                                      % cstr_address.GetValue())
+  if not str_size.GetError().Success():
+    return
+  error = lldb.SBError()
+  dot_str = process.ReadCStringFromMemory(int(cstr_address.GetValue(), 16),
+                                          str_size.GetValueAsUnsigned(), error)
+  if not error.Success():
+    return
+
+  with open(dot, "w") as f:
+    f.write(dot_str)
+    os.system("dot -Tsvg -o %s %s" % (svg, dot))
+
+def __lldb_init_module(debugger, internal_dict):
+  debugger.HandleCommand('command script add -f lldb_viewg.view_graph viewg')