Streamline skia.h construction.

This moves the work of finding headers from `gn gen` time into the action itself.  We can do this safely now because we're constructing a skia.h.d deps file, which Ninja uses to track if-these-are-dirty-then-this-is-dirty relationships.  Everything can now live in one handy find_headers.py.

Upshot is, `gn gen` runs ~50ms faster, and I think the code's clearer this way too.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4065

Change-Id: I2f1e7adf68be8e961eb77596786a795134bbb9a6
Reviewed-on: https://skia-review.googlesource.com/4065
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/gn/find_headers.py b/gn/find_headers.py
new file mode 100644
index 0000000000..4ade28de71
--- /dev/null
+++ b/gn/find_headers.py
@@ -0,0 +1,54 @@
+#!/usr/bin/env python
+#
+# Copyright 2016 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import sys
+
+# We'll recursively search each include directory for headers,
+# then write them to skia.h with a small blacklist.
+
+# We'll also write skia.h.deps, which Ninja uses to track dependencies. It's the
+# very same mechanism Ninja uses to know which .h files affect which .cpp files.
+
+skia_h       = sys.argv[1]
+include_dirs = sys.argv[2:]
+
+blacklist = {
+  "GrGLConfig_chrome.h",
+  "GrVkBackendContext.h",
+  "GrVkDefines.h",
+  "GrVkInterface.h",
+  "GrVkTypes.h",
+  "SkFontMgr_fontconfig.h",
+}
+
+headers = []
+for directory in include_dirs:
+  for d, _, files in os.walk(directory):
+    for f in files:
+      if f.endswith('.h') and f not in blacklist:
+        headers.append(os.path.join(d,f))
+headers.sort()
+
+with open(skia_h, "w") as f:
+  f.write('// skia.h generated by GN.\n')
+  f.write('#ifndef skia_h_DEFINED\n')
+  f.write('#define skia_h_DEFINED\n')
+  for h in headers:
+    f.write('#include "' + h + '"\n')
+  f.write('#endif//skia_h_DEFINED\n')
+
+with open(skia_h + '.deps', "w") as f:
+  f.write(skia_h + ':')
+  for h in headers:
+    f.write(' ' + h)
+  f.write('\n')
+
+# Temporary: during development this file wrote skia.h.d, not skia.h.deps,
+# and I think we have some bad versions of those files laying around.
+if os.path.exists(skia_h + '.d'):
+  os.remove(skia_h + '.d')