How to perspective transform a layer and its mask?

[daiappy]

   I have an image in Gimp, that has a layer mask made from a selection I made that is also stored as a channel. I want to use a transform action, (perspective transform),  on that image and to also apply it to the layer mask. When I do this it doesn't transform the layer mask. So, how do I do perspective transform on the image and its mask, (or selection) at the same time? 

[rich2005]

I can not reproduce that problem. Make sure you have the image active (1) If the selection is active turn that off. 
Not shown, but check that the perspective tool options mode is set to 'Layer' - the first icon.

Then the layer mask and image act together.

If you want the channel to deform as well, then link together (2) You can then get the selection from the channel. The results (3) This using perspective tool but exactly the same with unified transform.

   

[daiappy]

Thank you, rich2005. It works. I've been using Gimp on my photos for over 10yrs and have never sussed how to do it. Thanks for coming back so quickly.