qiknob.pas

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      FIndicatorSize := Value;
      if FIndicatorSize < 1 then FIndicatorSize := 1;
      InvalidateChange;
    end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.SetPositionDisplayUnits(const Value: String);
begin
  if FPositionDisplayUnits <> Value then
    begin
      FPositionDisplayUnits := Value;
      if Trim(FPositionDisplayUnits) = '' then FPositionDisplayUnits := '';
      InvalidateChange;
    end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.iMouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
var
  X1, Y1      : Integer;
begin
  if (Button = mbLeft) and Enabled then
    begin
      PositionedChanged := False;
      SetFocus;
      X1 := x - FCenterPoint.x;
      Y1 := y - FCenterPoint.y;
      if Round(Sqrt(X1*X1 + Y1*Y1)) < FKnobRadius then
        begin
          FMouseDown := True;
          FMouseDownDegrees := RadToDeg(ArcTan2(Y-FCenterPoint.Y,X-FCenterPoint.x));
          InvalidateChange;
        end;
    end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.iMouseMove(Shift: TShiftState; X, Y: Integer);
var
  CurrentDegrees : Double;
  DeltaAngle     : Double;
begin
  if FMouseDown then
    begin
      CurrentDegrees  := RadToDeg(ArcTan2(Y-FCenterPoint.y,X-FCenterPoint.x));

      DeltaAngle      := FMouseDownDegrees - CurrentDegrees;
      if DeltaAngle >  200 then DeltaAngle := DeltaAngle - 360;
      if DeltaAngle < -200 then DeltaAngle := DeltaAngle + 360;

      UserGenerated := True;
      try
        PositionDegrees := PositionDegrees - DeltaAngle;
      finally
        UserGenerated := False;
      end;

      FMouseDownDegrees := CurrentDegrees;
      InvalidateChange;
    end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.iMouseUp(Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  InvalidateChange;
  if FMouseDown then
    begin
      FMouseDown := False;
      DoPositionChangeFinished;
    end;
end;
//****************************************************************************************************************************************************
function TiKnob.GetPositionDegrees : Double;
begin
  if PositionMax = PositionMin then Result := FRotationStartDegrees
    else Result := FRotationMaxDegrees * ValuePercent(Position);
end;
//****************************************************************************************************************************************************
function TiKnob.PositionToDegrees(Value: Double): Double;
begin
  Result := FRotationStartDegrees - FRotationMaxDegrees * ValuePercent(Value);
end;
//****************************************************************************************************************************************************
procedure TiKnob.AdjustKnobRadius(Canvas: TCanvas; const CenterPoint: TPoint);
var
  KnobDiameter : Integer;
  x            : Integer;
  TickValue    : Double;
  TextPoint    : TPoint;
  TextString   : String;

  ATextWidth   : Integer;
  ATextHeight  : Integer;
  MaxWidth     : Integer;
  MaxHeight    : Integer;
begin
  with Canvas do
    begin
      Font.Assign(TickLabelFont);
      if Width < Height then KnobDiameter := Width  - 2*FOuterMargin
        else                 KnobDiameter := Height - 2*FOuterMargin;

      MaxWidth  := 0;
      MaxHeight := 0;

      if ShowTickLabels then
        begin
          for x := 0 to TickMajorCount - 1 do
            begin
              TickValue  := (PositionMax - PositionMin)/(TickMajorCount-1) * x + PositionMin;
              TextPoint  := GetXYRadPoint(PositionToDegrees(TickValue), 1, Point(0,0));

              TextString  := Trim(Format('%.' + IntToStr(GetDecimalPoints) + 'f', [TickValue]));
              ATextWidth  := ABS(TextWidth (TextString) * TextPoint.x);
              ATextHeight := ABS(TextHeight(TextString) * TextPoint.y);

              if ATextWidth  > MaxWidth  then MaxWidth  := ATextWidth;
              if ATextHeight > MaxHeight then MaxHeight := ATextHeight;
            end;

          if MaxWidth > MaxHeight then KnobDiameter := KnobDiameter - MaxWidth
            else                       KnobDiameter := KnobDiameter - MaxHeight;

          KnobDiameter := KnobDiameter - 2*(TickMargin + TickMajorLength + TickLabelMargin + 4);

        end
      else if ShowTicksMajor or ShowTicksMinor then
        begin
          KnobDiameter := KnobDiameter - 2*(TickMargin + TickMajorLength);
        end;
      FKnobRadius := KnobDiameter div 2;
  end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.iPaintTo(Canvas: TCanvas);
begin
  FCenterPoint := GetCenterPoint(Canvas);
  if CachedDrawing then
    begin
      if BackGroundChanged then
        begin
          CreateBackGroundBitmap;
          if FAutoSize then AdjustKnobRadius(BackGroundBitmap.Canvas, FCenterPoint);
          DrawBackGround(BackGroundBitmap.Canvas, BackGroundColor);
          DrawKnob      (BackGroundBitmap.Canvas, FCenterPoint);
          DrawTicks     (BackGroundBitmap.Canvas, FCenterPoint);
          ResetBackGroundChange;
        end;

      TransferBackGround(Canvas);
    end
  else
    begin
      if FAutoSize then AdjustKnobRadius(Canvas, FCenterPoint);
      DrawBackGround(Canvas, BackGroundColor);
      DrawKnob      (Canvas, FCenterPoint);
      DrawTicks     (Canvas, FCenterPoint);
    end;

  DrawPosition (Canvas, FCenterPoint);
  DrawIndicator(Canvas, FCenterPoint);

  if FShowFocusRect and HasFocus then iDrawFocusRect(Canvas, ClientRect, BackGroundColor);
end;
//****************************************************************************************************************************************************
procedure TiKnob.DrawKnob(Canvas: TCanvas; const CenterPoint: TPoint);
var
  OuterRect     : TRect;
  InnerRect     : TRect;
  ReverseColors : Boolean;
begin
  case FKnobStyle of
    iksRaisedEdge : ReverseColors := False;
    iksRaised     : ReverseColors := False;
    iksSunken     : ReverseColors := True;
    iksSunkenEdge : ReverseColors := True;
    else            ReverseColors := False;
  end;

  with Canvas do
    begin
      OuterRect   := Rect(CenterPoint.x - (FKnobRadius),
                          CenterPoint.y - (FKnobRadius),
                          CenterPoint.x + (FKnobRadius),
                          CenterPoint.y + (FKnobRadius));

      InnerRect   := Rect(CenterPoint.x - (FKnobRadius - FKnobEdgeWidth),
                          CenterPoint.y - (FKnobRadius - FKnobEdgeWidth),
                          CenterPoint.x + (FKnobRadius - FKnobEdgeWidth),
                          CenterPoint.y + (FKnobRadius - FKnobEdgeWidth));

      DrawGradientCircle(Canvas, CenterPoint, FKnobRadius, ReverseColors);

      Pen.Color := BackGroundColor;

      if (FKnobStyle = iksRaisedEdge) or (FKnobStyle = ikssunkenEdge) then
        begin
          Brush.Style := bsSolid;
          Brush.Color := clBtnFace;
          Pen.Color   := clBtnFace;
          with InnerRect do
            Ellipse(Left, Top, Right, Bottom);
        end;
    end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.DrawIndicator(Canvas: TCanvas; const CenterPoint: TPoint);
var
  InnerPoint           : TPoint;
  OuterPoint           : TPoint;
  IndicatorCenterPoint : Tpoint;
  IndicatorRect        : TRect;
  IndicatorDegrees     : Double;
  PointerEndPoint      : TPoint;
  PointerBasePoint     : TPoint;
  Point1               : TPoint;
  Point2               : Tpoint;
begin
  IndicatorDegrees := RotationStartDegrees - PositionDegrees;

  with Canvas, IndicatorRect do
    begin
      Brush.Style := bsSolid;
      IndicatorCenterPoint := GetXYRadPoint(IndicatorDegrees, FKnobRadius - FIndicatorMargin - FIndicatorSize, CenterPoint);

      IndicatorRect := Rect(IndicatorCenterPoint.x - FIndicatorSize,
                            IndicatorCenterPoint.y - FIndicatorSize,
                            IndicatorCenterPoint.x + FIndicatorSize,
                            IndicatorCenterPoint.y + FIndicatorSize);

      if FMouseDown or FKeyDown then begin Pen.Color := FIndicatorActiveColor;   Brush.Color := FIndicatorActiveColor    end
        else                         begin Pen.Color := FIndicatorInactiveColor; Brush.Color := FIndicatorInactiveColor; end;

      case FIndicatorStyle of
        ikisDotLowered : begin
                           Ellipse(Left, Top, Right, Bottom);
                           Pen.Color := clGray;  Arc(Left, Top, Right, Bottom, Right, Top   , Left , Bottom);
                           Pen.Color := clWhite; Arc(Left, Top, Right, Bottom, Left , Bottom, Right, Top   );
                         end;
        ikisDotRaised  : begin
                           Ellipse(Left, Top, Right, Bottom);
                           Pen.Color := clWhite; Arc(Left, Top, Right, Bottom, Right, Top   , Left , Bottom);
                           Pen.Color := clGray;  Arc(Left, Top, Right, Bottom, Left , Bottom, Right, Top   );
                         end;
        ikisDot        : begin
                           Ellipse(Left, Top, Right, Bottom);
                         end;
        ikisLineCenter : begin
                           OuterPoint:=GetXYRadPoint(IndicatorDegrees,FKnobRadius-FIndicatorMargin,CenterPoint);
                           PolyLine([OuterPoint, CenterPoint]);
                         end;
        ikisLineCustom : begin
                           OuterPoint:=GetXYRadPoint(IndicatorDegrees,FKnobRadius-FIndicatorMargin,               CenterPoint);
                           InnerPoint:=GetXYRadPoint(IndicatorDegrees,FKnobRadius-FIndicatorMargin-FIndicatorSize,CenterPoint);
                           PolyLine([OuterPoint, InnerPoint]);
                         end;
        ikisTriangle   : begin
                           PointerEndPoint :=GetXYRadPoint(IndicatorDegrees,FKnobRadius-FIndicatorMargin,               CenterPoint);
                           PointerBasePoint:=GetXYRadPoint(IndicatorDegrees,FKnobRadius-FIndicatorMargin-FIndicatorSize,CenterPoint);
                           Point1 := GetXYRadPoint(IndicatorDegrees + 90, FIndicatorSize/2, PointerBasePoint);
                           Point2 := GetXYRadPoint(IndicatorDegrees - 90, FIndicatorSize/2, PointerBasePoint);
                           Polygon([Point1, Point2, PointerEndPoint]);
                         end;
      end;
    end;
end;
//****************************************************************************************************************************************************
procedure TiKnob.DrawTicks(Canvas: TCanvas; const CenterPoint: TPoint);
var
  OuterPoint      : TPoint;
  InnerPoint      : TPoint;
  MajorRadius1    : Double;
  MajorRadius2    : Double;
  MinorRadius1    : Double;