GIF animation sometimes continues for a while even after clearing the target

[TWiStErRob]

Glide Version: 3.7.0
Integration libraries: N/A
Device/Android Version: Galaxy S4 / 4.4.2
Issue details / Repro steps / Use case background:
While investigating another issue I played around with an animated GIF (has 5 frames, and long delays). The setup is simple: show an image in a fragment on startup, and there's button to call Glide.clear(imageView).

In the below log you can see:

• the load succeeded as expected
• it showed frames 0,1,2,3
• GLIDE: Clearing target is the button press
• continued to load frames 4,0,1,2, ...

While on the UI:

• placeholder while downloading image
• frames 0,1,2,3
• placeholder after pressing button

Weirdly it doesn't always happen, if the resource is loaded from memory cache, then after clearing there are no more frames loaded. This is because there's a placeholder and TransitionDrawable (see "Proposed fix" for more).

Glide load line / GlideModule (if any) / list Adapter code (if any):

Glide
    .with(context)
    .load(url)
    .diskCacheStrategy(DiskCacheStrategy.SOURCE)
    .placeholder(R.drawable.glide_placeholder)
    .error(R.drawable.glide_error)
    .listener(new LoggingListener<String, GlideDrawable>())
    .into(new LoggingTarget<>(new GlideDrawableImageViewTarget(imageView)))
;

Stack trace / LogCat:

23.810 8055 I/GLIDE: Loading
23.820 8055 V/LoggingTarget: getRequest()
23.820 8055 V/LoggingTarget: setRequest(com.bumptech.glide.request.GenericRequest@42d00fe0)
23.820 8055 V/LoggingTarget: onStop()
23.820 8055 I/GLIDE: Loaded
23.820 8055 V/LoggingTarget: getSize(com.bumptech.glide.request.GenericRequest@42d00fe0)
23.820 8055 V/LoggingTarget: onLoadStarted(android.graphics.drawable.BitmapDrawable@42afab50)
23.820 8055 V/LoggingTarget: onStart()
23.871 8055 V/LoggingTarget: onSizeReady(com.bumptech.glide.request.GenericRequest@42d00fe0, 1080, 1677)
23.941 14390 V/DecodeJob: Decoded source from cache in 67.596434, key: EngineKey{https://cloud.githubusercontent.com/assets/2906988/14031433/1bfc4106-f20d-11e5-94c6-861bbf3f4991.gif+com.bumptech.glide.signature.EmptySignature@42d365d8+[1080x1677]+''+'ImageVideoBitmapDecoder.com.bumptech.glide.load.resource.bitmap'+''+'BitmapEncoder.com.bumptech.glide.load.resource.bitmap'+'GifBitmapWrapperDrawableTranscoder.com.bumptech.glide.load.resource.transcode'+''}
23.941 14390 V/DecodeJob: Transformed resource from source in 0.030518, key: EngineKey{https://cloud.githubusercontent.com/assets/2906988/14031433/1bfc4106-f20d-11e5-94c6-861bbf3f4991.gif+com.bumptech.glide.signature.EmptySignature@42d365d8+[1080x1677]+''+'ImageVideoBitmapDecoder.com.bumptech.glide.load.resource.bitmap'+''+'BitmapEncoder.com.bumptech.glide.load.resource.bitmap'+'GifBitmapWrapperDrawableTranscoder.com.bumptech.glide.load.resource.transcode'+''}
23.941 14390 V/DecodeJob: Transcoded transformed from source in 0.183105, key: EngineKey{https://cloud.githubusercontent.com/assets/2906988/14031433/1bfc4106-f20d-11e5-94c6-861bbf3f4991.gif+com.bumptech.glide.signature.EmptySignature@42d365d8+[1080x1677]+''+'ImageVideoBitmapDecoder.com.bumptech.glide.load.resource.bitmap'+''+'BitmapEncoder.com.bumptech.glide.load.resource.bitmap'+'GifBitmapWrapperDrawableTranscoder.com.bumptech.glide.load.resource.transcode'+''}
23.971 8055 V/GLIDE: .onResourceReady(GifDrawable@42d2f2e0(405x721), https://cloud.githubusercontent.com/assets/2906988/14031433/1bfc4106-f20d-11e5-94c6-861bbf3f4991.gif, LoggingTarget@42cfab68, async, first)
23.971 8055 V/LoggingTarget: onResourceReady(com.bumptech.glide.load.resource.gif.GifDrawable@42d2f2e0, com.bumptech.glide.request.animation.DrawableCrossFadeViewAnimation@42b01930)

23.971 8804 V/DecodeJob: Fetched data in 0.061035, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@14f35e5e+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
24.011 8804 V/DecodeJob: Decoded from source in 44.95239, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@14f35e5e+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
24.011 8804 V/DecodeJob: Transformed resource from source in 0.030517, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@14f35e5e+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
24.011 8804 V/DecodeJob: Transcoded transformed from source in 0.030518, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@14f35e5e+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

25.973 8598 V/DecodeJob: Fetched data in 0.12207, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@afb05e7d+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
26.063 8598 V/DecodeJob: Decoded from source in 86.364746, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@afb05e7d+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
26.063 8598 V/DecodeJob: Transformed resource from source in 0.061035, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@afb05e7d+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
26.063 8598 V/DecodeJob: Transcoded transformed from source in 0.030518, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@afb05e7d+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

29.977 8715 V/DecodeJob: Fetched data in 0.122071, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@808e194b+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
30.077 8715 V/DecodeJob: Decoded from source in 97.198487, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@808e194b+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
30.077 8715 V/DecodeJob: Transformed resource from source in 0.091552, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@808e194b+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
30.077 8715 V/DecodeJob: Transcoded transformed from source in 0.12207, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@808e194b+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

30.977 8787 V/DecodeJob: Fetched data in 0.12207, key: EngineKey{3+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@74444e25+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
31.058 8787 V/DecodeJob: Decoded from source in 79.62035999999999, key: EngineKey{3+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@74444e25+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
31.058 8787 V/DecodeJob: Transformed resource from source in 0.061035, key: EngineKey{3+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@74444e25+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
31.058 8787 V/DecodeJob: Transcoded transformed from source in 0.030517, key: EngineKey{3+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@74444e25+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

31.848 8055 I/GLIDE: Clearing target android.support.v7.widget.AppCompatImageView{42bfbe28 V.ED..C. ........ 0,0-1080,1677 #1020006 android:id/icon}
31.848 8055 V/LoggingTarget: onLoadCleared(android.graphics.drawable.BitmapDrawable@42afab50)
31.848 8055 I/GLIDE: Clearing target android.support.v7.widget.AppCompatImageView{42bfbe28 V.ED..C. ......ID 0,0-1080,1677 #1020006 android:id/icon} finished

34.991 8804 V/DecodeJob: Fetched data in 0.12207, key: EngineKey{4+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e3a47037+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
35.051 8804 V/DecodeJob: Decoded from source in 68.206786, key: EngineKey{4+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e3a47037+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
35.051 8804 V/DecodeJob: Transformed resource from source in 0.061035, key: EngineKey{4+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e3a47037+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
35.061 8804 V/DecodeJob: Transcoded transformed from source in 0.091554, key: EngineKey{4+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e3a47037+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

35.992 8598 V/DecodeJob: Fetched data in 0.091552, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@559405aa+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
36.062 8598 V/DecodeJob: Decoded from source in 73.486328, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@559405aa+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
36.062 8598 V/DecodeJob: Transformed resource from source in 0.030518, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@559405aa+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
36.062 8598 V/DecodeJob: Transcoded transformed from source in 0.030517, key: EngineKey{0+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@559405aa+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

38.004 8715 V/DecodeJob: Fetched data in 0.12207, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@ce952f7a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
38.074 8715 V/DecodeJob: Decoded from source in 71.13647499999999, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@ce952f7a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
38.074 8715 V/DecodeJob: Transformed resource from source in 0.061035, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@ce952f7a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
38.074 8715 V/DecodeJob: Transcoded transformed from source in 0.061035, key: EngineKey{1+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@ce952f7a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

41.988 8787 V/DecodeJob: Fetched data in 0.12207, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e6191b1a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
42.088 8787 V/DecodeJob: Decoded from source in 97.53417999999999, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e6191b1a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
42.088 8787 V/DecodeJob: Transformed resource from source in 0.061035, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e6191b1a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}
42.088 8787 V/DecodeJob: Transcoded transformed from source in 0.030518, key: EngineKey{2+com.bumptech.glide.load.resource.gif.GifFrameLoader$FrameSignature@e6191b1a+[1080x1677]+''+'GifFrameResourceDecoder.com.bumptech.glide.load.resource.gif'+''+''+''+''}

...

Workaround:
Most of the time users won't experience this issue, becuase this continuous loading is stopped when a GC happens, but it's still a good idea to properly free resources.

Proposed fix:
I think the problem is in GlideDrawableImageViewTarget where onResourceReady resource.start() is called, but the animation is only stopped when the activity/fragment is stopped. I think that class needs to override another method too:

@Override public void onLoadCleared(Drawable placeholder) {
    if (resource != null) {
        resource.stop();
        resource = null;
    }
    super.onLoadCleared(placeholder);
}

The comment in GifDrawable.stop() says there's an automatic detection of "no longer in use". This doesn't work when the GifDrawable is part of a TransitionDrawable because that sets itself as callback to the GifDrawable. So the check that would clean up resources fails in onFrameReady. This only happens when a thumbnail or a placeholder was displayed with crossFade before the GIF load finished. This may worth fixing as well as part of this issue, for example changing getCallback() to something like findCallback():

/**
 * Find out if there's a real Callback registered to this Drawable.
 * In case of multiple layers of drawables, like in case of `TransitionDrawable`,
 * find the topmost callback.
 */
private Callback findCallback() {
    Callback callback = getCallback();
    while (callback instanceof Drawable) {
        callback = ((Drawable)callback).getCallback();
    }
    return callback;
}