[DUG] Venn Diagrams

[Alister Christie]

I was feeling bored today so I wrote a component to do Venn Diagrams (as 
you do when bored) - now can anybody find a use for it?

I did have in the back of my mind that it could be a way for the users 
of my software to select stuff out of a database.  If tomorrow is 
equally exciting I may extend it to 3 sets and have it create some SQL 
along similar lines to the LogicString property (although with 3 sets 
the number of combinations would be huge)

Anyway Comments...

unit VennDiagram;

interface

uses
   Windows, Messages, SysUtils, Classes, Controls, Graphics;

type
   TVennDiagram = class(TGraphicControl)
   private
     FSelectedOutside: boolean;
     FSelectedMiddle: boolean;
     FSelectedLeft: boolean;
     FSelectedRight: boolean;
     FRightDescription: string;
     FLeftDescription: string;
     FShowDescriptions: boolean;
     FOnChange: TNotifyEvent;
     function GetCircleRadius: integer;
     function GetLeftCircleCenter: TPoint;
     function GetRightCircleCenter: TPoint;
     procedure SetSelectedLeft(const Value: boolean);
     procedure SetSelectedMiddle(const Value: boolean);
     procedure SetSelectedOutside(const Value: boolean);
     procedure SetSelectedRight(const Value: boolean);
     procedure VennDiagramMouseDown(Sender: TObject; Button: TMouseButton;
       Shift: TShiftState; X, Y: Integer);
     procedure SetLeftDescription(const Value: string);
     procedure SetRightDescription(const Value: string);
     procedure SetShowDescriptions(const Value: boolean);
     function GetLogicString: string;
     { Private declarations }
   protected
     { Protected declarations }
     property OnMouseDown;

   public
     { Public declarations }
     procedure Paint; override;
     function InCircle(aPoint, Center: TPoint; Radius: integer): boolean;
     function InsideLeftCircle(aPoint : TPoint) : boolean;
     function InsideRightCircle(aPoint : TPoint) : boolean;
     function InsideMiddle(aPoint : TPoint) : boolean;
     constructor Create(AOwner: TComponent); override;

     property LogicString : string read GetLogicString;

   published
     { Published declarations }
     Property SelectedOutside : boolean read FSelectedOutside write 
SetSelectedOutside;
     Property SelectedLeft : boolean read FSelectedLeft write 
SetSelectedLeft;
     Property SelectedRight : boolean read FSelectedRight write 
SetSelectedRight;
     Property SelectedMiddle : boolean read FSelectedMiddle write 
SetSelectedMiddle;
     Property LeftCircleCenter : TPoint read GetLeftCircleCenter;
     Property RightCircleCenter : TPoint read GetRightCircleCenter;
     property CircleRadius : integer read GetCircleRadius;
     property LeftDescription : string read FLeftDescription write 
SetLeftDescription;
     Property RightDescription : string read FRightDescription write 
SetRightDescription;
     Property ShowDescriptions : boolean read FShowDescriptions write 
SetShowDescriptions;
     Property Font;
     property OnChange: TNotifyEvent read FOnChange write FOnChange;
   end;

procedure Register;

implementation

procedure Register;
begin
   RegisterComponents('Additional', [TVennDiagram]);
end;

{ TVennDiagram }

constructor TVennDiagram.Create(AOwner: TComponent);
begin
   inherited;
   Canvas.Font.Assign(Font);
   Canvas.Brush.Color := clBtnFace;
   OnMouseDown := VennDiagramMouseDown;
   FSelectedOutside := FALSE;
   FSelectedMiddle := FALSE;
   FSelectedLeft := FALSE;
   FSelectedRight := FALSE;
end;

function TVennDiagram.GetCircleRadius: integer;
begin
   result := Width div 4;
end;

function TVennDiagram.GetLeftCircleCenter: TPoint;
begin
   result.X := Width div 3;
   result.Y := Height div 2;
end;

function TVennDiagram.GetLogicString: string;
begin
   //all things selected
   if SelectedOutside and SelectedLeft and SelectedMiddle and 
SelectedRight then
     result := 'TRUE'
   //3 things selected
   else if SelectedLeft and SelectedMiddle and SelectedRight then
     result := LeftDescription + ' or ' + RightDescription
   else if SelectedOutside and SelectedLeft and SelectedMiddle then
     result := LeftDescription + ' and not ' + RightDescription
   else if SelectedOutside and SelectedMiddle and SelectedRight then
     result := 'not ' + LeftDescription + ' and ' + RightDescription
   else if SelectedOutside and SelectedLeft and SelectedRight then
     result := 'not (' + LeftDescription + ' and ' + RightDescription + ')'
   //2 things selected
   else if SelectedOutside and SelectedLeft then
     result := 'not ' + RightDescription
   else if SelectedOutside and SelectedRight then
     result := 'not ' + LeftDescription
   else if SelectedOutside and SelectedMiddle then
     result := 'not (' + LeftDescription + ' xor ' + RightDescription + ')'
   else if SelectedMiddle and SelectedLeft then
     result := LeftDescription
   else if SelectedMiddle and SelectedRight then
     result := RightDescription
   else if SelectedRight and SelectedLeft then
     result := LeftDescription + ' xor ' + RightDescription
   //1 thing Selected
   else if SelectedOutside then
     result := 'not (' + LeftDescription + ' or ' + RightDescription + ')'
   else if SelectedLeft then
     result := LeftDescription + ' and not ' + RightDescription
   else if SelectedRight then
     result := 'not ' + LeftDescription + ' and ' + RightDescription
   else if SelectedMiddle then
     result := LeftDescription + ' xor ' + RightDescription
   else
   //only possibility remaining
     result := 'FALSE';
end;

function TVennDiagram.GetRightCircleCenter: TPoint;
begin
   result.X := 2 * Width div 3;
   result.Y := Height div 2;
end;

function TVennDiagram.InCircle(aPoint, Center: TPoint;
   Radius: integer): boolean;
var
  DistanceFromCenter : TPoint;
begin
   DistanceFromCenter.X := abs(aPoint.X-Center.X);
   DistanceFromCenter.Y := abs(aPoint.Y-Center.Y);
   result :=  Sqrt(Sqr(DistanceFromCenter.X) + 
Sqr(DistanceFromCenter.Y)) < radius;
end;

function TVennDiagram.InsideLeftCircle(aPoint: TPoint): boolean;
begin
   result := InCircle(aPoint, LeftCircleCenter, CircleRadius)
end;

function TVennDiagram.InsideMiddle(aPoint: TPoint): boolean;
begin
   result := InsideRightCircle(aPoint) and InsideLeftCircle(aPoint)
end;

function TVennDiagram.InsideRightCircle(aPoint: TPoint): boolean;
begin
   result := InCircle(aPoint, RightCircleCenter, CircleRadius)
end;

procedure TVennDiagram.Paint;
   procedure CenterCircle(C : TCanvas; X, Y, R : Integer);
   begin
     C.Ellipse(x-r, y-r, x+r, y+r);
   end;
begin
   inherited;
   Canvas.Brush.Color := clBtnFace;
   Canvas.Rectangle(0,0,width, height);

   Canvas.Brush.Style := bsClear;

   CenterCircle(Canvas, LeftCircleCenter.X, LeftCircleCenter.Y, 
CircleRadius);
   CenterCircle(Canvas, RightCircleCenter.X, RightCircleCenter.Y, 
CircleRadius);

   Canvas.Brush.Style := bsSolid;
   Canvas.Brush.Color := clRed;

   if FSelectedOutside then
     Canvas.FloodFill(2, 2, clBlack, fsBorder);
   if FSelectedLeft then
     Canvas.FloodFill(LeftCircleCenter.X, LeftCircleCenter.Y, clBlack, 
fsBorder);
   if FSelectedMiddle then
     Canvas.FloodFill(width div 2, Height div 2, clBlack, fsBorder);
   if FSelectedRight then
     Canvas.FloodFill(RightCircleCenter.X, RightCircleCenter.Y, clBlack, 
fsBorder);

   if ShowDescriptions then
   begin
     Canvas.Font := Font;
     Canvas.Brush.Style := bsClear;
     Canvas.TextOut(2,2,LeftDescription);
     Canvas.TextOut(width - Canvas.TextWidth(RightDescription)-2 
,2,RightDescription);
   end;

end;

procedure TVennDiagram.SetLeftDescription(const Value: string);
begin
   FLeftDescription := Value;
   Invalidate;
end;

procedure TVennDiagram.SetRightDescription(const Value: string);
begin
   FRightDescription := Value;
   Invalidate;
end;

procedure TVennDiagram.SetSelectedLeft(const Value: boolean);
begin
   FSelectedLeft := Value;
   invalidate;
end;

procedure TVennDiagram.SetSelectedMiddle(const Value: boolean);
begin
   FSelectedMiddle := Value;
   invalidate;
end;

procedure TVennDiagram.SetSelectedOutside(const Value: boolean);
begin
   FSelectedOutside := Value;
   invalidate;
end;

procedure TVennDiagram.SetSelectedRight(const Value: boolean);
begin
   FSelectedRight := Value;
   invalidate;
end;

procedure TVennDiagram.SetShowDescriptions(const Value: boolean);
begin
   FShowDescriptions := Value;
   Invalidate;
end;

procedure TVennDiagram.VennDiagramMouseDown(Sender: TObject;
   Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
   if DebugHook <> -1 then
   begin
     if InsideMiddle(Point(X,Y)) then
       FSelectedMiddle := not FSelectedMiddle
     else if InsideLeftCircle(Point(X,Y)) then
       FSelectedLeft := not FSelectedLeft
     else if InsideRightCircle(Point(X,Y)) then
       FSelectedRight := not FSelectedRight
     else
       FSelectedOutside := not FSelectedOutside;
   end;
   Invalidate;
   if Assigned(FOnChange) then
     FOnChange(Self);
end;

end.


-- 
Alister Christie
Computers for People
Ph: 04 471 1849 Fax: 04 471 1266
http://www.salespartner.co.nz
PO Box 13085
Johnsonville
Wellington