Thank you for your thoughts.
I first created the video player in a hacked rush, just to see if I could get gifs to work, and it has kept its gif-appropriate minimalist controls. I am not sure if I want to add pause or stop buttons. I don't intend for it to be a fully fledged player, although I have let it creep into rendering mp4s and so on, which it can't do very well. Sound is something I have planned for the future.
The current controls pause the video after a drag, but play the video on a single non-drag click. Can you get frozen video to play again if you just quickly click the scanbar, or does that not work? If I coloured the bar different when the video was paused, would that be better interface feedback?
I improved some frame timings in the most recent version, but because of the language I am using, I can't easily get the raw power of a specialised video player, so large movies tend to stutter.
The memory leak is getting better in recent versions, but there is definitely still something (I think with bmps) that isn't getting cleaned up correctly. I have some ideas to improve this.
I am planning to add a page to the options where you can select default behaviours for each mimetype, which will include 'double clicking on thumbnail launches in default external program', which I hope will be a better workflow for complicated movie types (and flash, for linux and os x users).