The explanation of the tool goes like this: the tool is supposed to fill closed regions inside the enclosing region (those regions that are entirely inside the enclosing shape that the user makes). If one of the regions touches the boundary of the enclosing region, then it is not considered closed, and it is not filled.
The different modes under the “what to fill” section are variants on that:
- all regions: fills all the regions of any color that are entirelly inside the shape made by the user. It is supposed that the user don’t want to fill the regions that touch the boundary of the enclosing shape, otherwise everything would be filled.
- regions of specific color / transparent / both: fills regions of that color that lie inside the enclosing shape. If the “include contour regions” option is selected then the regions of that color that touch the boundary of the enclosing shspe are also filled, it can be useful in some situations.
- all regions except specific color / transparent / both: the same as the previous one but instead of selecting the regions of that color for filling, it selects the regions that are not of that color. Again, it selects only the regions that are entirely inside the enclosing shape, unless you select “include contour regions”.
- regions surrounded by specific color / transparent / both: selects regions of any color that are inside the enclosing shape and that are surrounded by the selected color. If “include surrounding color” is selected then the shapes with the selected color that surround the other regions, are considered part of the shape that needs to be selected and filled.
The “transparent” and “specific color or transparent” variants are there to allow selecting transparent as the color and to mix transparent and a color, for example transparent and white seems convenient since those are the most common colors used for backgrounds in lineart.
I’m open to any suggestions for the text.
Please, tell me more about that glitch (a video showing it would be great).