UI and BRect — how it actually works?

Development
1

I always thought that BRect provides two cords for position and two cords for dimensions — X-pos, Y-pos, Width, Height. But everytime I’m trying to get it works I’m getting strange results. Looks like actual width and height are bound to position, so when I change position cords, visual dimensions changing too.
Someone, please explain this until I get to a nuthouse.

2

The [BeBook](file:///boot/system/documentation/BeBook/BRect.html) shows these constructors:

inline BRect(float left,
float top,
float right,
float bottom);

inline BRect(BPoint leftTop,
BPoint rightBottom);

So either the coordinates for the top-left and bottom-right of the rectangle, or their coordinates as BPoints. To move the BRect, you should probably use it’s OffsetBy() or OffsetTo().

Regards,
Humdinger

1 Like
3

A BRect does not store the width and height internally, but the left-top and bottom-right coordinates (in appropriately named left, top, right, bottom variables). This makes it possible to move any side of the rectangle without complex math (just change one of the 4 “sides”).

If you need the width and height, simply use the Width() and Height() methods. Use OffsetBy/OffsetTo to move the rectangle, and so on. In most cases you won’t need to mess with the coordinates directly.

1 Like
4

Ooops…
Thank you all, guys, for cool functions and for cool explanation.