Dynamic Video Dimensions in Custom Widgets... HOW?!

How the heck do we account for presenting videos in their native aspect ratio when custom widgets require a predetermined pixel count for width and height? Along the same lines, when using a custom video widget - how do we make a 16:9 youtube style video span the whole width of the screen (when held in portrait orientation) while making the height dynamically adjust to make sure the video is shown in the proper aspect ration? PLEASE HELP AHHHHH

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