unit Ruler;

interface

uses
  Classes, Controls, ExtCtrls, Forms, Graphics, SysUtils, FDUtils;


type
  TRuler = class(TPanel)
  private
    FSizePixels     : Integer;
    FSizeInches     : Double;
    FIsMetric       : Boolean;
    FIsHorizontal   : Boolean;
    FStartPosition  : Integer;
    FLoMarkPosition : Integer;
    FHiMarkPosition : Integer;
    rPixelsPerInch  : Double;
    rPixelsPerCM    : Double;  //每厘米的點數
    procedure SetSizePixels(ASizePixels : Integer);
    procedure SetSizeInches(ASizeInches : Double);
    procedure SetIsMetric(AIsMetric : Boolean);
    procedure SetIsHorizontal(AIsHorizontal : Boolean);
    procedure SetStartPosition(APosition : Integer);
    procedure SetLoMarkPosition(APosition : Integer);
    procedure SetHiMarkPosition(APosition : Integer);
  protected
    procedure Paint; override;
    property Canvas;
  public
    constructor Create(AOwner : TComponent); override;
    procedure SetMarkPositions(LoPosition, HiPosition : Integer);
    property SizePixels : Integer read FSizePixels write SetSizePixels;
    property SizeInches : Double read FSizeInches write SetSizeInches;
    property IsMetric : Boolean read FIsMetric write SetIsMetric;
    property IsHorizontal : Boolean read FIsHorizontal write SetIsHorizontal;
    property StartPosition : Integer read FStartPosition write SetStartPosition;
    property LoMarkPosition : Integer read FLoMarkPosition write SetLoMarkPosition;
    property HiMarkPosition : Integer read FHiMarkPosition write SetHiMarkPosition;
  end;


implementation

const
  ctDefaultWidth        = 16;
  ctDefaultHeight       = 16;
  ctDefaultWidthPixels  = 600;
  ctDefaultHeightPixels = 900;
  ctDefaultWidthInches  = 8.5;
  ctDefaultHeightInches = 11.0;

constructor TRuler.Create(AOwner : TComponent);
begin
  inherited Create(AOwner);
  BevelInner      := bvNone;
  BevelOuter      := bvRaised;
  BorderStyle     := bsNone;
  Color           := clWindow;
  FLoMarkPosition := -1;
  FHiMarkPosition := -1;
  SetIsHorizontal(True);  {Default to a horizontal ruler}
end;  { Create }

procedure TRuler.Paint;
var
  I       : Integer;
  BasePos : Integer;
  Offset  : Integer;
  MarkPos : Integer;
  SizeCMs : Double; //厘米
  NumStr  : string[4];
begin
  inherited Paint;
  Canvas.Font.Color := clWindowText;
  if FIsHorizontal then begin
    if FIsMetric then begin
      SizeCMs := InchesToMillimeters(FSizeInches) / 10.0;
      for I := 1 to Trunc(SizeCMs * 4) do begin
        BasePos := Round(I * rPixelsPerCM / 4) - FStartPosition;
        if BasePos > 0 then begin
          if I mod 4 = 0 then begin
            NumStr := IntToStr(I div 4);
            if Length(NumStr) = 1 then
              Offset := 2
            else
              Offset := 5;
            Canvas.TextOut(BasePos - Offset, 1, IntToStr(I div 4))
          end else if I mod 2 = 0 then
            Canvas.TextOut(BasePos - 2, 1, '+')
          else
            Canvas.Pixels[BasePos, 8] := clBlack;
        end;
      end;  { for }
    end else begin
      for I := 1 to Trunc(FSizeInches * 10) do begin
        BasePos := Round(I * rPixelsPerInch / 10) - FStartPosition;
        if BasePos > 0 then begin
          if I mod 10 = 0 then begin
            NumStr := IntToStr(I div 10);
            if Length(NumStr) = 1 then
              Offset := 3
            else
              Offset := 7;
            Canvas.TextOut(BasePos - Offset, 1, IntToStr(I div 10))
          end else if I mod 5 = 0 then
            Canvas.TextOut(BasePos - 3, 1, '+')
          else
            Canvas.Pixels[BasePos, 8] := clBlack;
        end;
      end;  
    end;
    Canvas.Pen.Color := clHighlight;
    Canvas.Pen.Width := 2;
    MarkPos := FLoMarkPosition - FStartPosition;
    if MarkPos >= 0 then
      with Canvas do begin
        MoveTo(MarkPos, 0);
        LineTo(MarkPos, Height);
      end;
    MarkPos := FHiMarkPosition - FStartPosition;
    if MarkPos >= 0 then
      with Canvas do begin
        MoveTo(MarkPos, 0);
        LineTo(MarkPos, Height);
      end;
  end else begin
    if FIsMetric then begin
      SizeCMs := InchesToMillimeters(FSizeInches) / 10.0;
      for I := 1 to Trunc(SizeCMs * 4) do begin
        BasePos := Round(I * rPixelsPerCM / 4) - FStartPosition;
        if BasePos > 0 then begin
          if I mod 4 = 0 then begin
            NumStr := IntToStr(I div 4);
            if Length(NumStr) = 1 then
              Offset := 4                        
            else
              Offset := 1;
            Canvas.TextOut(Offset, BasePos - 6, IntToStr(I div 4))
          end else if I mod 2 = 0 then
            Canvas.TextOut(4, BasePos - 7, '+')
          else
            Canvas.Pixels[7, BasePos] := clBlack;
        end;
      end;  { for }
    end else begin
      for I := 1 to Trunc(FSizeInches * 10) do begin
        BasePos := Round(I * rPixelsPerInch / 10) - FStartPosition;
        if BasePos > 0 then begin
          if I mod 10 = 0 then begin
            NumStr := IntToStr(I div 10);
            if Length(NumStr) = 1 then
              Offset := 4
            else
              Offset := 1;
            Canvas.TextOut(Offset, BasePos - 6, IntToStr(I div 10))
          end else if I mod 5 = 0 then
            Canvas.TextOut(4, BasePos - 7, '+')
          else
            Canvas.Pixels[7, BasePos] := clBlack;
        end;
      end;
    end;
    Canvas.Pen.Color := clHighlight;
    Canvas.Pen.Width := 2;
    MarkPos := FLoMarkPosition - FStartPosition;
    if MarkPos >= 0 then
      with Canvas do begin
        MoveTo(0, MarkPos);
        LineTo(Width, MarkPos);
      end;
    MarkPos := FHiMarkPosition - FStartPosition;
    if MarkPos >= 0 then
      with Canvas do begin
        MoveTo(0, MarkPos);
        LineTo(Width, MarkPos);
      end;
  end;
end;  { Paint }

procedure TRuler.SetSizePixels(ASizePixels : Integer);
var
  SizeCMs : Double;
begin
  if (ASizePixels <> FSizePixels) and (ASizePixels <> 0) then begin
    FSizePixels := ASizePixels;
    if FSizeInches = 0.0 then begin
      rPixelsPerInch := 0.0;
      rPixelsPerCM   := 0.0;
    end else begin
      SizeCMs := InchesToMillimeters(FSizeInches) / 10.0;
      rPixelsPerInch := FSizePixels / FSizeInches;
      rPixelsPerCM   := FSizePixels / SizeCMs;
    end;
    Invalidate;
  end;
end;

procedure TRuler.SetSizeInches(ASizeInches : Double);
var
  SizeCMs : Double;
begin
  if (ASizeInches <> FSizeInches) and (ASizeInches <> 0.0) then begin
    FSizeInches    := ASizeInches;
    SizeCMs        := InchesToMillimeters(FSizeInches) / 10.0;
    rPixelsPerInch := FSizePixels / FSizeInches;
    rPixelsPerCM   := FSizePixels / SizeCMs;
    Invalidate;
  end;
end;

procedure TRuler.SetIsMetric(AIsMetric : Boolean);
begin
  if AIsMetric <> FIsMetric then begin
    FIsMetric := AIsMetric;
    Invalidate;
  end;
end;

procedure TRuler.SetIsHorizontal(AIsHorizontal : Boolean);
begin
  if AIsHorizontal <> FIsHorizontal then begin
    FIsHorizontal := AIsHorizontal;
    Align := alNone;
    if FIsHorizontal then begin
      SizePixels := ctDefaultWidthPixels;
      SizeInches := ctDefaultWidthInches;
      Height     := ctDefaultHeight;
    end else begin
      SizePixels := ctDefaultHeightPixels;
      SizeInches := ctDefaultHeightInches;
      Width      := ctDefaultWidth;
    end;
  end;
end;

procedure TRuler.SetStartPosition(APosition : Integer);
begin
  if APosition <> FStartPosition then begin
    FStartPosition := APosition;
    Invalidate;
  end;
end;

procedure TRuler.SetLoMarkPosition(APosition : Integer);
begin
  if APosition <> FLoMarkPosition then begin
   FLoMarkPosition := APosition;
   Invalidate;
  end;
end;

procedure TRuler.SetHiMarkPosition(APosition : Integer);
begin
  if APosition <> FHiMarkPosition then begin
   FHiMarkPosition := APosition;
   Invalidate;
  end;
end;

procedure TRuler.SetMarkPositions(LoPosition, HiPosition : Integer);
begin
  if LoPosition < -1 then
    LoPosition := -1;
  if HiPosition < -1 then
    HiPosition := -1;
  if (LoPosition <> FLoMarkPosition) or (HiPosition <> FHiMarkPosition) then begin
    FLoMarkPosition := LoPosition;
    FHiMarkPosition := HiPosition;
    Invalidate;
  end;
end;

end.