make imagelib listen to the memory-pressure observer. bug #94454. patch from nivedita@netscape.com. r=pavlov sr=brendan

modules/libpr0n/src/ImageFactory.cpp

@@ -57,10 +57,18 @@ static nsModuleComponentInfo components[] =
     imgRequestProxyConstructor, },
 };
 
+PR_STATIC_CALLBACK(nsresult)
+imgCache_Initialize(nsIModule* aSelf)
+{
+  imgCache::Init();
+  return PR_TRUE;
+}
+
 PR_STATIC_CALLBACK(void)
-ImageModuleDestructor(nsIModule *self)
+imgCache_Shutdown(nsIModule* aSelf)
 {
   imgCache::Shutdown();
 }
 
-NS_IMPL_NSGETMODULE_WITH_DTOR(nsImageLib2Module, components, ImageModuleDestructor)
+NS_IMPL_NSGETMODULE_WITH_CTOR_DTOR(nsImageLib2Module, components, imgCache_Initialize, imgCache_Shutdown)
+

modules/libpr0n/src/imgCache.cpp

@@ -30,13 +30,15 @@
 #include "nsXPIDLString.h"
 #include "nsCOMPtr.h"
 #include "nsIServiceManager.h"
+#include "nsIMemory.h"
+#include "nsIObserverService.h"
 
 #include "nsICache.h"
 #include "nsICacheService.h"
 #include "nsICacheSession.h"
 #include "nsICacheEntryDescriptor.h"
 
-NS_IMPL_ISUPPORTS1(imgCache, imgICache)
+NS_IMPL_ISUPPORTS3(imgCache, imgICache, nsIObserver, nsISupportsWeakReference)
 
 imgCache::imgCache()
 {
@@ -49,6 +51,18 @@ imgCache::~imgCache()
   /* destructor code */
 }
 
+nsresult imgCache::Init()
+{
+  imgCache* cache = new imgCache();
+  if(!cache) return NS_ERROR_OUT_OF_MEMORY;
+
+  nsresult rv;
+  nsCOMPtr<nsIObserverService> os = do_GetService("@mozilla.org/observer-service;1", &rv);
+  if (NS_SUCCEEDED(rv) && os)
+    rv = os->AddObserver(cache, "memory-pressure", PR_TRUE);
+  return rv;
+}
+
 /* void clearCache (in boolean chrome); */
 NS_IMETHODIMP imgCache::ClearCache(PRBool chrome)
 {
@@ -255,3 +269,12 @@ PRBool imgCache::Remove(nsIURI *aKey)
   return PR_TRUE;
 }
 
+
+NS_IMETHODIMP
+imgCache::Observe(nsISupports* aSubject, const char* aTopic, const PRUnichar* aSomeData)
+{
+  if (strcmp(aTopic, "memory-pressure") == 0)
+    ClearCache(PR_TRUE);
+
+  return NS_OK;
+}

modules/libpr0n/src/imgCache.h

@@ -22,6 +22,8 @@
  */
 
 #include "imgICache.h"
+#include "nsIObserver.h"
+#include "nsWeakReference.h"
 
 #include "prtypes.h"
 
@@ -37,15 +39,20 @@ class nsICacheEntryDescriptor;
     {0x83, 0x91, 0xe1, 0x42, 0x42, 0xc5, 0x9a, 0x41} \
 }
 
-class imgCache : public imgICache
+class imgCache : public imgICache, 
+                 public nsIObserver,
+                 public nsSupportsWeakReference
 {
 public:
   NS_DECL_ISUPPORTS
   NS_DECL_IMGICACHE
+  NS_DECL_NSIOBSERVER
 
   imgCache();
   virtual ~imgCache();
 
+  static nsresult Init();
+
   static void Shutdown(); // for use by the factory
 
   /* additional members */