diff options
| -rw-r--r-- | common/rect.h | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/common/rect.h b/common/rect.h index 7eeec875f2..40b01044a7 100644 --- a/common/rect.h +++ b/common/rect.h @@ -46,7 +46,20 @@ struct Point { /*! @brief simple class for handling a rectangular zone. This small class is an helper for rectangles. - It is mostly used by the blitter class. + Note: This implementation is built around the assumption that (top,left) is + part of the rectangle, but (bottom,right) is not! This is reflected in + various methods, including contains(), intersects() and others. + + Another very wide spread approach to rectangle classes treats (bottom,right) + also as a part of the rectangle. + + Coneptually, both are sound, but the approach we use saves many intermediate + computations (like computing the height in our case is done by doing this: + height = bottom - top; + while in the alternate system, it would be + height = bottom - top + 1; + + When writing code using our Rect class, always keep this principle in mind! */ struct Rect { int16 top, left; //!< The point at the top left of the rectangle (part of the rect). |