The Tool Behavior dialog

The Tool Behavior dialog box is essential to configure most of the tools. If it was closed, you can still bring it back using View | Tool Behavior. It looks like the following:

The first two buttons configure whether a drawn rectangle or ellipse is filled or just the outline is drawn. The other four buttons after the separator line control the shape of the brush tip. You can draw with square, circle, slash and backslash-shaped brushes.

The controls in the second row are used to set the line width and the brush width. There is some difference between them: the line width is used when drawing outlined shapes, and the brush width affects e.g. the Brush (B) and Retouch (U) tools. The line and brush width can both range from 1 to 50.

The scroll bar in the third row controls the color tolerance of some tools, for instance, the Wand (W) tool. The higher the value set, the more pixels will be affected by the tool. Set the value to 0 to select only pixels of exactly the same color.

The controls in the fourth row affect the Gradient (G) tool. You can configure the gradient kind and repetition with them. Below is a picture which helps you understand the three repetition types, which are: none, symmetric and asymmetric, respectively:

Finally, you can set the mode used by the Retouch (U) tool and the behavior of the Eyedropper (Y) using the remaining controls.