I think now we see the dialog in action without an Apply button, I agree with Rob. It'll be more user friendly in 1.2 to have the button to play with the canvas. After 1.2 is out, we'll have an Apply button that invokes lyxfunc code in a similar manner to the other dialogs. We'll probably need a Liason method for that, à la Print dialog.
Would someone with some time on their hands prepare a little patch? I have the logic for the code to improve the GraphicsCache to support different LyXViews of the same file (sizes, rotations, etc) sorted out here. Just need to convert it to bits. Then that'll leave the ImageLoader to sort. All seems to be going to plan. Angus