Using Rect and Point Structures
The userint.h include file defines two structures, Rect and Point. You use these structures to specify locations and areas in Cartesian coordinate systems, such as those in canvas controls, table controls, and bitmaps. Many canvas and table control functions use these structures.
The Rect structure specifies the location and size of a rectangle. Define a rectangle as follows:
typedef struct
{
int top;
int left;
int height;
int width;
} Rect;
A Point structure specifies the location of a point. The point can be a pixel, as is the case when programming with canvas controls or bitmaps, or it can be a cell, when programming with table controls. Define a point as follows:
typedef struct
{
int x;
int y;
} Point;
Functions and Macros for Making Rects and Points
Instead of creating new variables, use MakeRect and MakePoint when you only need to pass the values to another function. MakePoint creates a Point in the following example:
CanvasDrawPoint (panel, ctrl, MakePoint (30, 40));
You also can use these functions to initialize variables, as in the following example:
Rect r = MakeRect (10, 20, 100, 130);
The following table lists other macros used for creating commonly used rectangles. The Rect height and width can have special values.
| Name | Value or Definition | Description |
| VAL_TO_EDGE | 1 | Set the Rect width (or height) to the distance from the Rect left (or top) to the right (or bottom) edge of the object. |
| VAL_KEEP_SAME_SIZE | 2 | When copying objects such as bitmaps, make the destination object the same size as the source object. |
| VAL_EMPTY_RECT | MakeRect (0, 0, 0, 0) | An empty rectangle. |
| VAL_ENTIRE_OBJECT | MakeRect (0, 0, VAL_TO_EDGE, VAL_TO_EDGE) | Make the Rect the size of the object, for example, the canvas or bitmap. |
| VAL_TABLE_ROW_RANGE (r) | MakeRect ((r), 1, 1, VAL_TO_EDGE) | A specific row of table cells. |
| VAL_TABLE_COLUMN_RANGE (c) | MakeRect (1, (c), 1, VAL_TO_EDGE) | A specific column of table cells. |
| VAL_TABLE_ENTIRE_RANGE | MakeRect (1, 1, VAL_TO_EDGE, VAL_TO_EDGE) | A range consisting of all the cells in a table. |
| VAL_TABLE_SINGLE_CELL_RANGE (r, c) | MakeRect ((r), (c), 1, 1) | A range consisting of a single, specific table cell. |
Functions for Modifying Rects and Points
Use the following functions to set or modify the values in a Rect or Point structure.
- RectSet sets each of the four values of an existing Rect structure.
- RectSetFromPoints sets a Rect so that it defines the smallest rectangle that encloses two points.
- RectSetBottom sets the height of a Rect so that the bottom is a given value. The bottom is not enclosed by the rectangle.
- RectSetRight sets the height of a Rect so that the right edge is a given value. The right edge is not enclosed by the rectangle.
- RectSetCenter sets the top and left of a Rect so that it is centered around a given value, while keeping the same size.
- RectOffset modifies the top and left of a Rect so as to shift the location of the rectangle.
- RectMove sets the top and left of Rect to a given Point.
- RectGrow modifies the values in a Rect so that the rectangle grows or shrinks around its current center point.
- PointSet sets the two values in an existing Point structure.
Functions for Comparing or Obtaining Values from Rects and Points
Use the following functions to compare or obtain values from a Rect or Point structure.
- RectBottom obtains the location of the bottom of a rectangle.
- RectRight obtains the location of the right edge of a rectangle.
- RectCenter obtains the location of the center of a rectangle.
- RectEqual determines if two rectangles are identical.
- RectEmpty determines if a rectangle is empty.
- RectContainsPoint determines if a rectangle encloses a given point.
- RectContainsRect determines if a rectangle completely encloses another rectangle.
- RectSameSize determines if two rectangles are the same size.
- RectUnion sets a Rect to the smallest rectangle that encloses two given rectangles.
- RectIntersection sets a Rect to the largest rectangle that is enclosed by two given rectangles.
- PointEqual determines whether two points are at the same location.
- PointPinnedToRect modifies a Point structure, if necessary, to ensure that it is within a given rectangle.