Share via

Bounding Rectangles

  • Article

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

Throughout DirectDraw and Windows Embedded CE 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 two points, the top-left corner and bottom-right corner, can describe the rectangle.

Most applications use the RECT structure to carry information about a bounding rectangle to use when blitting to the screen or performing hit detection. The RECT structure has the following definition.

typedef struct tagRECT { 
    LONG    left;    // This is the top-left corner's x-coordinate.
    LONG    top;     // The top-left corner's y-coordinate.
    LONG    right;   // The bottom-right corner's x-coordinate.
    LONG    bottom;  // The bottom-right corner's 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 top-left corner. Similarly, the right and bottom members make up the coordinates of the bottom-right corner.

Note

The right and bottom values for all rectangles in Windows Embedded CE are exclusive. Thus if you want a 100x100 square rectangle with the top-left corner at (10,10), the rectangle would be defined as (10,10,110,110).

The following illustrate shows how you can visualize these values.

Aa917114.88727284-0c48-4adb-8419-681a9d7f51b6(en-us,MSDN.10).gif

In the interest of efficiency, consistency, and ease of use, all DirectDraw blitting functions work with rectangles. However, you can create the illusion of nonrectangular blit operations by using either transparent or alpha blitting. For more information, see Transparent Blitting or Alpha Blitting.