No matter what I do my Brush Editor options remain grayed out. I'm trying to edit a custom brush as I know the default ones are read-only.
I have no idea what's causing this, the way that I make new brushes is by copying something and using the Paste as new brush option.
In Gimp there are really two kind of brushes:
bitmap: these are those you create as an image and export as GBR (or GIH). They can have any shape/color. The "color" ones (for instance, the "Pepper" brush) are used as is, the grayscales ones (saved from a grayscale image) are considered "masks": they assume the foreground color, the white-to-black value indicates opacity. Like all bitmaps they cannot be scaled indefinitely.
parametric: these are really described internally a bit like paths/vectors. They can be scaled at will but can only have a few simple shapes (circle, square, diamond, star...) and always behave like grayscale brushes.
The brush editor is only meant to create/edit these "parametric" brushes.
