In at least one case, it was a setting most of us had forgotten about: the Auto button. It's easy to miss, but if you turn it on accidentally, you may be unable to do anything in GIMP until you realize what's happened.
The Auto button is the one at the upper right of your Layers dialog. It's on by default, and what it does is ensure that dialogs like Layers, and GIMP's notion of the currently active layer, follow the active image. Open a new image, or click in a different image window, and your Layers dialog switches images -- so whatever you do next will apply to the image you just chose.
If you turn Auto off, then by default, no image and no layer is active. Notice, in the screenshot at left, how no image is shown in the option menu just left of the Auto button.
Even if you open a new image, you can't do anything with it until you explicitly choose an image from the menu.
I'm sure you can see why this could be confusing. So why have that button at all?
Well, it's useful when you're working with lots of images -- for
instance, if you want to drag a layer from one image into another
image, you can use the menu to switch quickly among images and layers
without needing to bring those image windows to the front.
I don't find I need it, but for those who do, I guess it can
be a real time-saver.
Just to make it even more confusing, not everyone even has the Auto button or the menu next to it. You can turn it off (and gain a little extra vertical space for your layers dialog) with the tiny menu button right above the mode menu. "Show Image Selection" controls whether the image option menu, and the Auto button next to it, will be displayed. "Auto Follow Active Image" is the same toggle as the Auto button itself.
So if you ever get stuck and the Layers dialog doesn't seem to be showing layers from your image, and you can't figure out why ... remember that pesky Auto button. It might just be the problem.
(If not, try quitting GIMP and moving your profile aside. That works
for curing all manner of mysterious ills -- including this one.
Come to think of it, that deserves an article of its own. Coming soon!)
[ 11:04 Feb 19, 2011 More gimp | permalink to this entry | ]