94 lines
2.6 KiB
Plaintext
94 lines
2.6 KiB
Plaintext
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{ Copyright (c) 1989 by Borland Interational, Inc. }
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program FigureDemo;
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{ From P-47 of the Object-Oriented Programming Guide.
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Extending FIGURES.PAS with type Arc.
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}
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uses Crt, DOS, Graph, Figures;
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type
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Arc = object (Circle)
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StartAngle, EndAngle : Integer;
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constructor Init(InitX, InitY : Integer;
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InitRadius : Integer;
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InitStartAngle, InitEndAngle : Integer);
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procedure Show; virtual;
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procedure Hide; virtual;
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end;
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var
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GraphDriver : Integer;
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GraphMode : Integer;
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ErrorCode : Integer;
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AnArc : Arc;
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ACircle : Circle;
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{--------------------------------------------------------}
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{ Arc's method declarations: }
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{--------------------------------------------------------}
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constructor Arc.Init(InitX,InitY : Integer;
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InitRadius : Integer;
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InitStartAngle, InitEndAngle : Integer);
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begin
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Circle.Init(InitX, InitY, InitRadius);
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StartAngle := InitStartAngle;
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EndAngle := InitEndAngle;
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end;
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procedure Arc.Show;
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begin
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Visible := True;
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Graph.Arc(X, Y, StartAngle, EndAngle, Radius);
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end;
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procedure Arc.Hide;
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var
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TempColor : Word;
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begin
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TempColor := Graph.GetColor;
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Graph.SetColor(GetBkColor);
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Visible := False;
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{ Draw the arc in the background color to hide it }
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Graph.Arc(X, Y, StartAngle, EndAngle, Radius);
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SetColor(TempColor);
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end;
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{--------------------------------------------------------}
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{ Main program: }
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{--------------------------------------------------------}
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begin
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GraphDriver := Detect; { Let the BGI determine what board
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you're using }
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DetectGraph(GraphDriver, GraphMode);
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InitGraph(GraphDriver, GraphMode,'');
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if GraphResult <> GrOK then
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begin
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WriteLn('>>Halted on graphics error:',
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GraphErrorMsg(GraphDriver));
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Halt(1)
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end;
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{ All descendents of type Point contain virtual methods and }
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{ *must* be initialized before use through a constructor call. }
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ACircle.Init(151, 82, { Initial X,Y at 151,82 }
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50); { Initial radius of 50 pixels }
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AnArc.Init(151, 82, { Initial X,Y at 151,82 }
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25, 0, 90); { Initial radius of 50 pixels }
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{ Start angle: 0; End angle: 90 }
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{ Replace AnArc with ACircle to drag a circle instead of an }
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{ arc. Press Enter to stop dragging and end the program. }
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ACircle.Drag(5); { Parameter is # of pixels to drag by }
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CloseGraph;
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RestoreCRTMode;
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end.
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