A signal equivalent to AVMakeRectWithAspectRatioInsideRect ?

[zakdances]

I've been constructing my own signal to pass a CGSize through AVFoundation's very useful AVMakeRectWithAspectRatioInsideRect function. Example:

self.videoScaledSizeSignal = [[RACSignal combineLatest:@[
    [RACAbleWithStart(self,player.currentItem.tracks) distinctUntilChanged] ,
    [RACAbleWithStart(self.maxSize) distinctUntilChanged]]
    reduce:^(NSArray *array,NSValue *maxSize){

         // If maxSize hasn't been set, just return a zero rect                                   
        CGSize videoScaledSize = CGSizeZero;
        if (CGSizeEqualToSize(maxSize.med_sizeValue, CGSizeZero)) {
                return MEDBox(videoScaledSize);
        }

        for (AVPlayerItemTrack *itemTrack in array) {
                  if ([itemTrack.assetTrack.mediaType isEqualToString:AVMediaTypeVideo]) {

                      CGSize naturalSize = itemTrack.assetTrack.naturalSize;
                      videoScaledSize = AVMakeRectWithAspectRatioInsideRect(naturalSize,  CGRectWithSize(maxSize.med_sizeValue)).size;

                      }

          }


          return MEDBox(videoScaledSize);
      }] filter:^BOOL(NSValue *videoScaledSize) {
            return !CGSizeEqualToSize(videoScaledSize.med_sizeValue, CGSizeZero);
   }];

I was going to submit a pull request for a RACSignal category containing a simplified version of my above signal, but there's a problem. AVMakeRectWithAspectRatioInsideRect requires AVFoundation, and I'm not sure it's a good idea to add a big dependency like that to RCL.

What would the best way be to add this functionality to RCL (or RAC)?

[zakdances]

I want to add something like this as a RAC extension:

- (RACSignal *)resizeWithAspect:(RACSignal *)maxSize
{
    return [[self combineLatestWith:maxSize] map:^id(RACTuple *tuple) {
        RACTupleUnpack_(NSValue *oldSize,NSValue *maxSize) = tuple;
        CGSize newSize = AVMakeRectWithAspectRatioInsideRect(oldSize.med_sizeValue, CGRectWithSize(maxSize.med_sizeValue)).size;

        return MEDBox(newSize);
    }];
}

edit here's another possibility:

- (RACSignal *)resizeWithAspect:(RACSignal *)maxSize
{
    return [RACSignal combineLatest:@[self,maxSize] reduce:^id(NSValue *currentSize,NSValue *maxSize) {

        CGSize newSize = AVMakeRectWithAspectRatioInsideRect(currentSize.med_sizeValue, CGRectWithSize(maxSize.med_sizeValue)).size;

        return MEDBox(newSize);
    }];
}

Thoughts?

[jspahrsummers]

A method like that would be useful, but we can't introduce a dependency on AVFoundation.

If you're willing to rewrite the sizing algorithm from scratch, I'd be happy to review a PR.

[zakdances]

Yeah, I tried to find the actual implementation, but of course avfoundations m files are a tightly guarded secret. I'll try to come up with something equivalent.

[jspahrsummers]

In that case, let's leave this open until a PR is merged that completes it.

[zakdances]

Instead of targeting CGSize, perhaps a better approach would be to mirror the syntax of UIViews contentMode. A signal with a name similar to UIViewContentModeScaleAspectFit like -(RACSignal *)scaleAspectFit:(RACSignal *)maxRect]. I'll push something based on that concept.

[zakdances]

First things first. Submitting pull request to Archimedes for the functions themselves.

https://github.com/github/Archimedes/pull/14

Then a special RACSignal should be added to use them.