Rectangles

Throughout Microsoft?Direct3D?and Microsoft Windows?programming, objects on the screen are referred to in terms of bounding rectangles. The sides of a bounding rectangle are always parallel to the sides of the screen, so the rectangle can be described by two points, the upper-left corner and lower-right corner. Most applications use the RECT structure to carry information about a bounding rectangle to use when blitting to the screen or performing hit detection.

In C++, the RECT structure has the following definition.

typedef struct tagRECT { 
    LONG    left;    // This is the upper-left corner x-coordinate.
    LONG    top;     // The upper-left corner y-coordinate.
    LONG    right;   // The lower-right corner x-coordinate.
    LONG    bottom;  // The lower-right corner y-coordinate.
} RECT, *PRECT, NEAR *NPRECT, FAR *LPRECT; 

In the preceding example, the left and top members are the x- and y-coordinates of a bounding rectangle's upper-left corner. Similarly, the right and bottom members make up the coordinates of the lower-right corner. The following diagram illustrates how you can visualize these values.

In the interest of efficiency, consistency, and ease of use, all Direct3D presentation functions work with rectangles.