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Inside Macintosh: More Macintosh Toolbox /

Chapter 5 - Icon Utilities / Icon Utilities Reference

Icon Utilities Routines / Determining Whether a Point or Rectangle Is Within an Icon

PtInIconID

You can use the PtInIconID function to determine whether a specified point is within an icon. (A point is considered to be within an icon if the point is within the icon's mask.) For example, you might use this function to determine whether a user clicked an icon in a window of your application. You specify as parameters to PtInIconID the same rectangle and alignment that you last used to draw the icon. PtInIconID uses the size of this rectangle to determine which icon mask from the icon family to use for the operation. The PtInIconID function uses the location of this rectangle (along with the alignment) to determine whether a specified point is within the icon.

FUNCTION PtInIconID (testPt: Point; iconRect: Rect; 
                     align: IconAlignmentType;
                     iconID: Integer): Boolean;

testPt

The point to be tested, specified in local coordinates of the current graphics port.

iconRect

The rectangle in which the icon appears, specified in local coordinates of the current graphics port. PtInIconID determines, from the size of the rectangle specified in this parameter, which icon mask from the icon family specified by iconID to test the point against. PtInIconID then uses the location of this rectangle (and the alignment of the icon in the rectangle) to determine whether the specified point is within the icon.

align

A value that specifies how the icon against which to hit-test is aligned within the rectangle specified by iconRect. See the description of PlotIconID on page 5-20 for a list of constants you can use in this parameter.

iconID

A resource ID for an icon family.

DESCRIPTION

The PtInIconID function hit-tests the point specified by testPt against the appropriate icon mask from the icon family identified by iconID, using the destination rectangle and alignment specified by iconRect and align. The parameters iconRect and align should be the same as when the icon was last drawn. The PtInIconID function returns TRUE if the point is in the icon mask and FALSE if it is not.