caching screen objects to avoid repeated memory allocations. r=saari.

gfx/src/gtk/nsScreenManagerGtk.cpp

@@ -49,11 +49,17 @@ NS_IMPL_ISUPPORTS(nsScreenManagerGtk, NS_GET_IID(nsIScreenManager))
 //
 // Utility routine. Creates a new screen object from the given device handle
 //
+// NOTE: For this "single-monitor" impl, we just always return the cached primary
+//        screen. This should change when a multi-monitor impl is done.
+//
 nsIScreen* 
 nsScreenManagerGtk :: CreateNewScreenObject (  )
 {
-  nsIScreen* retval = new nsScreenGtk ( );
-  NS_IF_ADDREF(retval);
+  nsIScreen* retval = nsnull;
+  if ( !mCachedMainScreen )
+    mCachedMainScreen = new nsScreenGtk ( );
+  NS_IF_ADDREF(retval = mCachedMainScreen.get());
+  
   return retval;
 }
 

gfx/src/gtk/nsScreenManagerGtk.h

@@ -24,8 +24,8 @@
 #define nsScreenManagerGtk_h___
 
 #include "nsIScreenManager.h"
-
-class nsIScreen;
+#include "nsIScreen.h"
+#include "nsCOMPtr.h"
 
 //------------------------------------------------------------------------
 
@@ -42,6 +42,9 @@ private:
 
   nsIScreen* CreateNewScreenObject ( ) ;
 
+    // cache the primary screen object to avoid memory allocation every time
+  nsCOMPtr<nsIScreen> mCachedMainScreen;
+
 };
 
 #endif  // nsScreenManagerGtk_h___ 

gfx/src/mac/nsScreenManagerMac.cpp

@@ -22,6 +22,18 @@
 
 #include "nsScreenManagerMac.h"
 #include "nsScreenMac.h"
+#include "nsCOMPtr.h"
+
+
+class ScreenListItem
+{
+public:
+  ScreenListItem ( GDHandle inGD, nsIScreen* inScreen )
+    : mGD(inGD), mScreen(inScreen) { } ;
+  
+  GDHandle mGD;
+  nsCOMPtr<nsIScreen> mScreen;
+};
 
 
 nsScreenManagerMac :: nsScreenManagerMac ( )
@@ -36,7 +48,11 @@ nsScreenManagerMac :: nsScreenManagerMac ( )
 
 nsScreenManagerMac :: ~nsScreenManagerMac()
 {
-  // nothing to see here.
+  // walk our list of cached screens and delete them.
+  for ( int i = 0; i < mScreenList.Count(); ++i ) {
+    ScreenListItem* item = NS_REINTERPRET_CAST(ScreenListItem*, mScreenList[i]);
+    delete item;
+  }
 }
 
 
@@ -52,9 +68,25 @@ NS_IMPL_ISUPPORTS(nsScreenManagerMac, NS_GET_IID(nsIScreenManager))
 nsIScreen* 
 nsScreenManagerMac :: CreateNewScreenObject ( GDHandle inDevice )
 {
-  nsIScreen* retval = new nsScreenMac ( inDevice );
-  NS_IF_ADDREF(retval);
-  return retval;
+  nsIScreen* retScreen = nsnull;
+  
+  // look through our screen list, hoping to find it. If it's not there,
+  // add it and return the new one.
+  for ( int i = 0; i < mScreenList.Count(); ++i ) {
+    ScreenListItem* curr = NS_REINTERPRET_CAST(ScreenListItem*, mScreenList[i]);
+    if ( inDevice == curr->mGD ) {
+      NS_IF_ADDREF(retScreen = curr->mScreen.get());
+      return retScreen;
+    }
+  } // for each screen.
+  
+  // didn't find it in the list, so add it and return that item.
+  retScreen = new nsScreenMac ( inDevice );
+  ScreenListItem* listItem = new ScreenListItem ( inDevice, retScreen );
+  mScreenList.AppendElement ( listItem );
+  
+  NS_IF_ADDREF(retScreen);
+  return retScreen;
 }
 
 

gfx/src/mac/nsScreenManagerMac.h

@@ -24,10 +24,13 @@
 #define nsScreenManagerMac_h___
 
 #include "nsIScreenManager.h"
-#include <QuickDraw.h>
+#include <Quickdraw.h>
+
+#include "nsVoidArray.h"
 
 class nsIScreen;
 
+
 //------------------------------------------------------------------------
 
 class nsScreenManagerMac : public nsIScreenManager
@@ -42,7 +45,10 @@ public:
 private:
 
   nsIScreen* CreateNewScreenObject ( GDHandle inDevice ) ;
+  
+  nsAutoVoidArray mScreenList;
 
 };
 
+
 #endif  // nsScreenManagerMac_h___ 

gfx/src/windows/nsScreenManagerWin.cpp

@@ -49,11 +49,17 @@ NS_IMPL_ISUPPORTS(nsScreenManagerWin, NS_GET_IID(nsIScreenManager))
 //
 // Utility routine. Creates a new screen object from the given device handle
 //
+// NOTE: For this "single-monitor" impl, we just always return the cached primary
+//        screen. This should change when a multi-monitor impl is done.
+//
 nsIScreen* 
 nsScreenManagerWin :: CreateNewScreenObject ( HDC inScreen )
 {
-  nsIScreen* retval = new nsScreenWin ( inScreen );
-  NS_IF_ADDREF(retval);
+  nsIScreen* retval = nsnull;
+  if ( !mCachedMainScreen )
+    mCachedMainScreen = new nsScreenWin ( inScreen );
+  NS_IF_ADDREF(retval = mCachedMainScreen.get());
+  
   return retval;
 }
 

gfx/src/windows/nsScreenManagerWin.h

@@ -25,6 +25,7 @@
 
 #include "nsIScreenManager.h"
 #include <windows.h>
+#include "nsCOMPtr.h"
 
 class nsIScreen;
 
@@ -43,6 +44,8 @@ private:
 
   nsIScreen* CreateNewScreenObject ( HDC inScreen ) ;
 
+    // cache the primary screen object to avoid memory allocation every time
+  nsCOMPtr<nsIScreen> mCachedMainScreen;
 };
 
 #endif  // nsScreenManagerWin_h___