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

cc/base/switches.cc

Index: cc/base/switches.cc
diff --git a/cc/base/switches.cc b/cc/base/switches.cc
index be4a2c55adfbcb22214a0a92439f59da8fd112e2..71e87f8f1a75eba932a3b5a59d9958053147678f 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -5,6 +5,7 @@
 #include "cc/base/switches.h"
 
 #include "base/command_line.h"
+#include "base/logging.h"
 
 namespace cc {
 namespace switches {
@@ -151,51 +152,91 @@ const char kDisable4444Textures[] = "disable-4444-textures";
 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
-}
-
-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;
-
+    }
+
+    // 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)
-  return true;
+      switch_container.lcd_text_enabled_ = false;
 #else
-  return false;
+      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 IsImplSidePaintingEnabled() {
-  static bool enabled = CheckImplSidePaintingStatus();
-  return enabled;
+  return GetSwitchValue(Switches::IMPL_SIDE_PAINTING);
 }
 
 bool IsMapImageEnabled() {
-  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
-
-  if (command_line.HasSwitch(cc::switches::kDisableMapImage))
-    return false;
-  else if (command_line.HasSwitch(cc::switches::kEnableMapImage))
-    return true;
+  return GetSwitchValue(Switches::MAP_IMAGE);
+}
 
-  return false;
+bool IsLCDTextEnabled() {
+  return GetSwitchValue(Switches::LCD_TEXT);
 }
 
 }  // namespace switches