Bug 590260 - Decode more bytes at a time during image redecodes.r=joe,a=blocker

modules/libpr0n/src/RasterImage.cpp

@@ -76,6 +76,22 @@ static PRLogModuleInfo *gCompressedImageAccountingLog = PR_NewLogModule ("Compre
 #define gCompressedImageAccountingLog
 #endif
 
+// Tweakable progressive decoding parameters
+static PRUint32 gDecodeBytesAtATime = 200000;
+static PRUint32 gMaxMSBeforeYield = 400;
+
+void
+RasterImage::SetDecodeBytesAtATime(PRUint32 aBytesAtATime)
+{
+  gDecodeBytesAtATime = aBytesAtATime;
+}
+void
+RasterImage::SetMaxMSBeforeYield(PRUint32 aMaxMS)
+{
+  gMaxMSBeforeYield = aMaxMS;
+}
+
+
 /* We define our own error checking macros here for 2 reasons:
  *
  * 1) Most of the failures we encounter here will (hopefully) be
@@ -2557,10 +2573,6 @@ RasterImage::DoError()
   LOG_CONTAINER_ERROR;
 }
 
-// Tweakable progressive decoding parameters
-#define DECODE_BYTES_AT_A_TIME 4096
-#define MAX_USEC_BEFORE_YIELD (1000 * 5)
-
 // Decodes some data, then re-posts itself to the end of the event queue if
 // there's more processing to be done
 NS_IMETHODIMP
@@ -2598,11 +2610,11 @@ imgDecodeWorker::Run()
   // synchronous. Write all the data in that case, otherwise write a
   // chunk
   PRUint32 maxBytes = image->mDecoder->IsSizeDecode()
-    ? image->mSourceData.Length() : DECODE_BYTES_AT_A_TIME;
+    ? image->mSourceData.Length() : gDecodeBytesAtATime;
 
   // Loop control
   PRBool haveMoreData = PR_TRUE;
-  nsTime deadline(PR_Now() + MAX_USEC_BEFORE_YIELD);
+  nsTime deadline(PR_Now() + 1000 * gMaxMSBeforeYield);
 
   // We keep decoding chunks until one of three possible events occur:
   // 1) We don't have any data left to decode

modules/libpr0n/src/RasterImage.h

@@ -290,6 +290,10 @@ public:
     kDisposeRestorePrevious // Restore the previous (composited) frame
   };
 
+  // Progressive decoding knobs
+  static void SetDecodeBytesAtATime(PRUint32 aBytesAtATime);
+  static void SetMaxMSBeforeYield(PRUint32 aMaxMS);
+
 private:
   struct Anim
   {

modules/libpr0n/src/imgRequest.cpp

@@ -87,6 +87,8 @@
 
 #define DISCARD_PREF "image.mem.discardable"
 #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 SVG_MIMETYPE "image/svg+xml"
 
 using namespace mozilla::imagelib;
@@ -118,6 +120,15 @@ ReloadPrefs(nsIPrefBranch *aBranch)
   if (NS_SUCCEEDED(rv))
     gDecodeOnDraw = decodeondraw;
 
+  // Progressive decoding knobs
+  PRInt32 bytesAtATime, maxMS;
+  rv = aBranch->GetIntPref(BYTESATATIME_PREF, &bytesAtATime);
+  if (NS_SUCCEEDED(rv))
+    RasterImage::SetDecodeBytesAtATime(bytesAtATime);
+  rv = aBranch->GetIntPref(MAXMS_PREF, &maxMS);
+  if (NS_SUCCEEDED(rv))
+    RasterImage::SetMaxMSBeforeYield(maxMS);
+
   // Discard timeout
   mozilla::imagelib::DiscardTracker::ReloadTimeout();
 }

modules/libpref/src/init/all.js

@@ -3154,6 +3154,12 @@ pref("image.mem.decodeondraw", false);
 // value and twice this value.
 pref("image.mem.min_discard_timeout_ms", 10000);
 
+// Chunk size for calls to the image decoders
+pref("image.mem.decode_bytes_at_a_time", 200000);
+
+// The longest time we can spend in an iteration of an async decode
+pref("image.mem.max_ms_before_yield", 400);
+
 // WebGL prefs
 pref("webgl.enabled_for_all_sites", false);
 pref("webgl.shader_validator", true);