Generic version of caching cc switches to avoid searching of switches on each function call

cc/base/switches.cc

 // Copyright (c) 2012 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.
 
 #include "cc/base/switches.h"
 
 #include "base/command_line.h"
+#include "base/logging.h"
 
 namespace cc {
 namespace switches {
 
 // On platforms where checkerboards are used, prefer background colors instead
 // of checkerboards.
 const char kBackgroundColorInsteadOfCheckerboard[] =
     "background-color-instead-of-checkerboard";
 
 // Disables LCD text.
@@ skipping 126 matching lines @@
 // Makes pixel tests write their output instead of read it.
 const char kCCRebaselinePixeltests[] = "cc-rebaseline-pixeltests";
 
 // Disable textures using RGBA_4444 layout.
 const char kDisable4444Textures[] = "disable-4444-textures";
 
 // Disable touch hit testing in the compositor.
 const char kDisableCompositorTouchHitTesting[] =
     "disable-compositor-touch-hit-testing";
 
-bool IsLCDTextEnabled() {
-  const CommandLine* command_line = CommandLine::ForCurrentProcess();
-  if (command_line->HasSwitch(cc::switches::kDisableLCDText))
-    return false;
-  else if (command_line->HasSwitch(cc::switches::kEnableLCDText))
-    return true;
 
+struct Switches {
+  typedef enum {

[danakj, 2013/11/26 15:55:50]

This is a lot of work. Can we just have 4 static bools without a struct?

[sivag, 2013/11/26 17:28:49]

As you know we cannot maintain the static bool global variables, so the only way
is to maintain the static bool local variables, for this we have to write two
functions for getting every switch value , like  CheckImplSidePaintingStatus 
and IsImplSidePaintingEnabled.
Instead of this we are trying to getswitch value from a single function just by
adding a extra enum.

[danakj, 2013/11/26 17:35:17]

Why can't we have global static bools? We do this all the time with primitive
types such as bool or pointers. The issue was a static class.

+    IMPL_SIDE_PAINTING = 0,
+    MAP_IMAGE,
+    LCD_TEXT,
+  } Type;
+
+  Switches()
+    : has_initialized_switches_(false)
+    , impl_side_painting_enabled_(false)
+    , map_image_enabled_(false)
+    , lcd_text_enabled_(false) {
+  }
+
+  bool has_initialized_switches_ : 1;
+  bool impl_side_painting_enabled_ : 1;
+  bool map_image_enabled_ : 1;
+  bool lcd_text_enabled_ : 1;
+};
+
+
+bool GetSwitchValue(Switches::Type switch_type) {
+  static Switches switch_container;
+  if (!switch_container.has_initialized_switches_) {
+    const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+    // Impl-side painting.
+    if (command_line.HasSwitch(cc::switches::kDisableImplSidePainting)) {
+      switch_container.impl_side_painting_enabled_ = false;
+    } else if (command_line.HasSwitch(cc::switches::kEnableImplSidePainting)) {
+      switch_container.impl_side_painting_enabled_ = true;
+    } else {
 #if defined(OS_ANDROID)
-  return false;
+      switch_container.impl_side_painting_enabled_ = true;
 #else
-  return true;
+      switch_container.impl_side_painting_enabled_ = false;
 #endif
+    }
+
+    // Map-Image.
+    if (command_line.HasSwitch(cc::switches::kDisableMapImage))
+      switch_container.map_image_enabled_ = false;
+    else if (command_line.HasSwitch(cc::switches::kEnableMapImage))
+      switch_container.map_image_enabled_ = true;
+    else
+      switch_container.map_image_enabled_ = false;
+
+    // LCD-Text.
+    if (command_line.HasSwitch(cc::switches::kDisableLCDText)) {
+      switch_container.lcd_text_enabled_ = false;
+    } else if (command_line.HasSwitch(cc::switches::kEnableLCDText)) {
+      switch_container.lcd_text_enabled_ = true;
+    } else {
+#if defined(OS_ANDROID)
+      switch_container.lcd_text_enabled_ = false;
+#else
+      switch_container.lcd_text_enabled_ = true;
+#endif
+    }
+    switch_container.has_initialized_switches_ = true;
+  }
+
+  switch(switch_type) {
+    case Switches::IMPL_SIDE_PAINTING:
+      return switch_container.impl_side_painting_enabled_;
+    case Switches::MAP_IMAGE:
+      return  switch_container.map_image_enabled_;
+    case Switches::LCD_TEXT:
+      return switch_container.lcd_text_enabled_;
+    default:
+      NOTREACHED();
+      return false;
+  }
 }
 
-namespace {
-bool CheckImplSidePaintingStatus() {
-  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
-
-  if (command_line.HasSwitch(cc::switches::kDisableImplSidePainting))
-    return false;
-  else if (command_line.HasSwitch(cc::switches::kEnableImplSidePainting))
-    return true;
-
-#if defined(OS_ANDROID)
-  return true;
-#else
-  return false;
-#endif
-}
-}  // namespace
-
 bool IsImplSidePaintingEnabled() {
-  static bool enabled = CheckImplSidePaintingStatus();
-  return enabled;
+  return GetSwitchValue(Switches::IMPL_SIDE_PAINTING);
 }
 
 bool IsMapImageEnabled() {
-  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  return GetSwitchValue(Switches::MAP_IMAGE);
+}
 
-  if (command_line.HasSwitch(cc::switches::kDisableMapImage))
-    return false;
-  else if (command_line.HasSwitch(cc::switches::kEnableMapImage))
-    return true;
-
-  return false;
+bool IsLCDTextEnabled() {
+  return GetSwitchValue(Switches::LCD_TEXT);
 }
 
 }  // namespace switches
 }  // namespace cc