Bug 685516: Instead of decoding small images synchronously and large images asynchronously, always decode synchronously for some time, and post the remainder to the event loop if necessary. r=joe

modules/libpr0n/src/RasterImage.cpp

@@ -85,7 +85,6 @@ static PRLogModuleInfo *gCompressedImageAccountingLog = PR_NewLogModule ("Compre
 // Tweakable progressive decoding parameters
 static PRUint32 gDecodeBytesAtATime = 200000;
 static PRUint32 gMaxMSBeforeYield = 400;
-static PRUint32 gMaxBytesForSyncDecode = 150000;
 
 void
 RasterImage::SetDecodeBytesAtATime(PRUint32 aBytesAtATime)
@@ -97,11 +96,6 @@ RasterImage::SetMaxMSBeforeYield(PRUint32 aMaxMS)
 {
   gMaxMSBeforeYield = aMaxMS;
 }
-void
-RasterImage::SetMaxBytesForSyncDecode(PRUint32 aMaxBytes)
-{
-  gMaxBytesForSyncDecode = aMaxBytes;
-}
 
 /* We define our own error checking macros here for 2 reasons:
  *
@@ -2386,13 +2380,12 @@ RasterImage::RequestDecode()
   if (mBytesDecoded == mSourceData.Length())
     return NS_OK;
 
-  // If it's a smallish image, it's not worth it to do things async
-  if (!mDecoded && !mInDecoder && mHasSourceData && (mSourceData.Length() < gMaxBytesForSyncDecode))
-    return SyncDecode();
+  // If we can do decoding now, do so.  Small images will decode completely,
+  // large images will decode a bit and post themselves to the event loop
+  // to finish decoding.
+  if (!mDecoded && !mInDecoder && mHasSourceData)
+    return mWorker->Run();
 
-  // If we get this far, dispatch the worker. We do this instead of starting
-  // any immediate decoding to guarantee that all our decode notifications are
-  // dispatched asynchronously, and to ensure we stay responsive.
   return mWorker->Dispatch();
 }
 

modules/libpr0n/src/imgRequest.cpp

@@ -88,7 +88,6 @@
 #define DECODEONDRAW_PREF "image.mem.decodeondraw"
 #define BYTESATATIME_PREF "image.mem.decode_bytes_at_a_time"
 #define MAXMS_PREF "image.mem.max_ms_before_yield"
-#define MAXBYTESFORSYNC_PREF "image.mem.max_bytes_for_sync_decode"
 #define SVG_MIMETYPE "image/svg+xml"
 
 using namespace mozilla;
@@ -132,11 +131,6 @@ ReloadPrefs()
     RasterImage::SetMaxMSBeforeYield(maxMS);
   }
 
-  if (NS_SUCCEEDED(Preferences::GetInt(MAXBYTESFORSYNC_PREF,
-                                       &maxBytesForSync))) {
-    RasterImage::SetMaxBytesForSyncDecode(maxBytesForSync);
-  }
-
   // Discard timeout
   mozilla::imagelib::DiscardTracker::ReloadTimeout();
 }

modules/libpref/src/init/all.js

@@ -3276,9 +3276,6 @@ pref("image.mem.decode_bytes_at_a_time", 4096);
 // The longest time we can spend in an iteration of an async decode
 pref("image.mem.max_ms_before_yield", 5);
 
-// The maximum source data size for which we auto sync decode
-pref("image.mem.max_bytes_for_sync_decode", 150000);
-
 // WebGL prefs
 pref("webgl.force-enabled", false);
 pref("webgl.disabled", false);