First of all: many thanks for integration of curves tool. This is really great,

For this function I have some minor suggestions/requests

- The curves function is only available through the menu. In the toolbar there is the symbol for changing the image. But there the new Curves tool is missing. Please integrate it. Thanks
- For the curves tool it would be great if the size of the curves dialog on first call would be quadratic. Imho the curve display should always be quadratic (I hope you know what I mean)
- It would be nice if the histogram could be (optionally) shown in the background of the curve and changes as the curve is modified to show the current situation.