// efg, August 1998
// Break this out as a separate library since it's needed elsewhere.
UNIT LineLibrary;
{$WARN UNSAFE_TYPE OFF}
{$WARN UNSAFE_CODE OFF}
INTERFACE
USES
Windows, // TPoint, ClipCursor
ExtCtrls; // TImage
TYPE
TLineSelected = (lsNotSelected, lsPoint1, lsPoint2, lsLine);
// TLineOrientation is used as part of the heuristic algorithm that decides
// if a line is selected and if lines intersect}
TLineOrientation = (loPoint, loHorizontal, loVertical);
TVector = record
StartPoint: TPoint;
EndPoint: TPoint;
end;
TFigure = (TRectangle, TTriangle, TCircle);
TPolygon = record
X, Y: Double; // replace Real with Double
case Tipo: TFigure of
TRectangle: (Height, Width: Double); // replace Real with Double
TTriangle: (Side1, Side2, Angle: Double); // replace Real with Double
TCircle: (Radius: Double); // replace Real with Double
end;
TFigura = (toLine, toPolygon);
TObjeto = record
Numero : integer;
case Tipo: TFigura of
toLine: (linha : TVector);
toPolygon: (polygon : TPolygon);
end;
FUNCTION AddPoints(CONST PointA, PointB: TPoint): TPoint;
FUNCTION SubtractPoints(CONST PointA, PointB: TPoint): TPoint;
PROCEDURE CalcLineParameters (CONST PointA, PointB : TPoint;
VAR Slope, Intercept: DOUBLE;
VAR LineOrientation : TLineOrientation);
FUNCTION NearLine(CONST Target, Point1, Point2: TPoint): BOOLEAN;
PROCEDURE RestrictCursorToDrawingArea (CONST Image: TImage);
PROCEDURE RemoveCursorRestrictions;
FUNCTION SquareContainsPoint (CONST SquareCenter : TPoint;
CONST SquareHalfSize : INTEGER; {pixels}
CONST TestPoint : TPoint): BOOLEAN;
IMPLEMENTATION
USES
Math, // MinIntValue, MaxIntValue
Classes; // Bounds
FUNCTION AddPoints(CONST PointA, PointB: TPoint): TPoint;
BEGIN
WITH RESULT DO
BEGIN
X := PointA.X + PointB.X;
Y := PointA.Y + PointB.Y
END
END {AddPoints};
FUNCTION SubtractPoints(CONST PointA, PointB: TPoint): TPoint;
BEGIN
WITH RESULT DO
BEGIN
X := PointA.X - PointB.X;
Y := PointA.Y - PointB.Y
END
END {SubtractPoints};
// Determine whether a line is ltHorizonal or ltVertical, along with the
// appropriate slope and intercept FOR point-slope line equations. These
// parameters are used to determine if a line is selected.
PROCEDURE CalcLineParameters (CONST PointA, PointB : TPoint;
VAR Slope, Intercept: DOUBLE;
VAR LineOrientation : TLineOrientation);
VAR
Delta: TPoint;
BEGIN
Delta := SubtractPoints(PointB, PointA);
IF (Delta.X = 0) AND (Delta.Y = 0)
THEN BEGIN
// This special CASE should never happen if iMinPixels > 0
LineOrientation := loPoint;
Slope := 0.0;
Intercept := 0.0
END
ELSE BEGIN
IF ABS(Delta.X) >= ABS(Delta.Y)
THEN BEGIN
// The line is more horizontal than vertical. Determine values FOR
// equation: Y = slope*X + intercept
LineOrientation := loHorizontal;
TRY
Slope := Delta.Y / Delta.X {conventional slope in geometry}
EXCEPT
Slope := 0.0
END;
Intercept := PointA.Y - PointA.X*Slope
END
ELSE BEGIN
// The line is more vertical than horizontal. Determine values FOR
// equation: X = slope*Y + intercept
LineOrientation := loVertical;
TRY
Slope := Delta.X / Delta.Y {reciprocal of conventional slope}
EXCEPT
Slope := 0.0
END;
Intercept := PointA.X - PointA.Y*Slope;
END
END
END {CalcLineParameters};
// Determine if Target1 is "near" line segment between Point1 and Point2
FUNCTION NearLine(CONST Target, Point1, Point2: TPoint): BOOLEAN;
CONST
LineSelectFuzz = 4; // Pixel "fuzz" used in line selection
VAR
Intercept : DOUBLE;
LineOrientation: TLineOrientation;
maxX : INTEGER;
maxY : INTEGER;
minX : INTEGER;
minY : INTEGER;
Slope : DOUBLE;
xCalculated : INTEGER;
yCalculated : INTEGER;
BEGIN
RESULT := FALSE;
// If an Endpoint is not selected, was part of line selected?
CalcLineParameters (Point1, Point2, Slope, Intercept, LineOrientation);
CASE LineOrientation OF
loHorizontal:
BEGIN
minX := MinIntValue([Point1.X, Point2.X]);
maxX := MaxIntValue([Point1.X, Point2.X]);
// first check if selection within horizontal range of line
IF (Target.X >= minX) and (Target.X <= maxX)
THEN BEGIN
// Since X is within range of line, now see if Y value is close
// enough to the calculated Y value FOR the line to be selected.
yCalculated := ROUND( Slope*Target.X + Intercept );
IF ABS(yCalculated - Target.Y) <= LineSelectFuzz
THEN RESULT := TRUE
END
END;
loVertical:
BEGIN
minY := MinIntValue([Point1.Y, Point2.Y]);
maxY := MaxIntValue([Point1.Y, Point2.Y]);
// first check if selection within vertical range of line
IF (Target.Y >= minY) AND (Target.Y <= maxY)
THEN BEGIN
// Since Y is within range of line, now see if X value is close
// enough to the calculated X value FOR the line to be selected.
xCalculated := ROUND( Slope*Target.Y + Intercept );
IF ABS(xCalculated - Target.X) <= LineSelectFuzz
THEN RESULT := TRUE
END
END;
loPoint:
// Do nothing -- should not occur
END
END {NearLine};
///////////////////////////////////////////////////////////////////////
PROCEDURE RestrictCursorToDrawingArea (CONST Image: TImage);
VAR
CursorClipArea: TRect;
BEGIN
CursorClipArea := Bounds(Image.ClientOrigin.X,
Image.ClientOrigin.Y,
Image.Width, Image.Height);
Windows.ClipCursor(@CursorClipArea)
END {RestrictCursorToDrawingArea};
PROCEDURE RemoveCursorRestrictions;
BEGIN
Windows.ClipCursor(NIL)
END {RemoveCursorRestrictions};
///////////////////////////////////////////////////////////////////////
// Could use Windows PtInRect API call instead (but it excludes the
// bottom and right edges of the rectangle while including the left
// and top edges.
FUNCTION SquareContainsPoint (CONST SquareCenter : TPoint;
CONST SquareHalfSize : INTEGER; {pixels}
CONST TestPoint : TPoint): BOOLEAN;
BEGIN
RESULT := (TestPoint.X >= SquareCenter.X - SquareHalfSize) AND
(TestPoint.X <= SquareCenter.X + SquareHalfSize) AND
(TestPoint.Y >= SquareCenter.Y - SquareHalfSize) AND
(TestPoint.Y <= SquareCenter.Y + SquareHalfSize)
END {SquareContainsPoint};
END.
