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POInherited TShape.Paint does not work after overriding Shape property
 

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  1. POInherited TShape.Paint does not work after overriding Shape property
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    <p>I'm to code a TExpandedShape class inherited from TShape. TExpandedShape must act like TShape and be able to draw extra shapes: Polygon and Star. Here is my code </p> <pre><code>unit ExpandedShape; interface uses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, Windows; type TExpandedShapeType = ( stRectangle, stSquare, stRoundRect, stRoundSquare, stEllipse, stCircle, stPolygon, stStar ); TExpandedShape = class(TShape) private FShape: TExpandedShapeType; FEdgeCount: integer; procedure SetShape(const Value: TExpandedShapeType); procedure SetEdgeCount(const Value: integer); public procedure Paint; override; published property Shape : TExpandedShapeType read FShape write SetShape;// default stPolygon; property EdgeCount : integer read FEdgeCount write SetEdgeCount default 5; end; procedure Register; implementation procedure Register; begin RegisterComponents('Course', [TExpandedShape]); end; // TExpandedShape procedure TExpandedShape.Paint; begin case Shape of stStar : begin {Draw Star} end; stPolygon : begin {Draw Polygon} end; else begin </code></pre> <p><strong>{It is supposed to draw Circle, Rectangle etc, but it does not}</strong> </p> <pre><code> inherited; end; end; end; procedure TExpandedShape.SetEdgeCount(const Value: integer); begin FEdgeCount := Value; Repaint; end; procedure TExpandedShape.SetShape(const Value: TExpandedShapeType); begin FShape := Value; Repaint; end; end. </code></pre> <p>So, what is wrong?<br> IMO TShape.Paint checks private value like FShape in case section and then decides what to draw. When inherited Paint method is called in my code it checks FShape value sees default 0 value [stRectangle] in there and draws it. </p> <p>PS: I did solve it with blackmagic way using Shape1 property instead of Shape one and if Shape1 value is not stPolygon or stStar i do like this: begin Shape := TShapeType(Shape1); inherited end; But this option is not really an option. I need a good short nice-looking one.</p>
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