Sorry I don't see any issues with hanging a rod from the wall with the supports set in from the edges and then sliding on a grommet drapery panel. The panel will run along side the fireplace mantle and the extended portion of the mantle will be in the shadow of the drapery.

Should be fine to hang the width of the door. The rod pendent will be up to the trim & you can adjust your furthest curtain ring to the inside if needed. Also if you hang your rod right under the ceiling molding instead center of the wall it will give illusion of higher ceilings. Here's a photo of my living room curtains next to the mantle

Thanks Beverly but the mantle comes out a further than the curtains would so the curtain will hit the mantle. I guess I can try it and just move the curtain in on that side a little so it doesn't hit - it may end up looking like maicoursey's where it looks like if the curtain were pulled out to the edge of the rod it would hit the mantle but it's pulled back a little to miss it.

Do you have to have drapes? or could you go with blinds? Home Depot makes blinds custom fit and they can be placed directly on to the doors.

Your photo was not taken close enough to the mantle to illustrate what your concern is exactly so I'm not able to address your specific worry. So the curtain touches the mantle............so what?

If you use a rod that has brackets and the rod is telescoping, you can adjust all this to get all the pieces to work together. BTW NO BIG FINIAL on the end of the rod is possible to get this to work. Something minimal so the drapes don't fall off the end of the rod.

If you would simply like to experiment before making a big purchase, buy a pair of grommet curtain panels at Home Goods and do a temporary install with a tension shower rod suspended between the wall and the fireplace pilaster. Hang the panels from the rod and see what happens. You should be able to allay all your fears and work out any quirks.

I went to bed bath and beyond, looked at all the curtains, then I went on line and ordered them plus got a discount. I like mine longer and has the linen feel but is synthetic and doesn't wrinkle, which I love, I like that they still let the light in without blocking it completely, i used two panels on each side and had them stitched together like they are one. I think you would like this. Put the bar high, measure the length you like and when they are opened, they will be fine by the fireplace, these curtains are very thin, don't take to much space. Good luck!!