Component (similar to trackbar) to enter a range of values

Question

I need a component for entering ranges. I was thinking along the lines of a trackbar with two markers. Are there "native Delphi" components that are meant for this purpose or that can simulate it easily?

Answer 1

I got a few minutes over and wrote this:

unit RangeSelector;

interface

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

type
  TRangeSelectorState = (rssNormal, rssDisabled, rssThumb1Hover, rssThumb1Down, rssThumb2Hover, rssThumb2Down, rssBlockHover, rssBlockDown);

  TRangeSelector = class(TCustomControl)
  private
    { Private declarations }
    FBuffer: TBitmap;
    FMin,
    FMax,
    FSelStart,
    FSelEnd: real;
    FTrackPos,
    FSelPos,
    FThumbPos1,
    FThumbPos2: TRect;
    FState: TRangeSelectorState;
    FDown: boolean;
    FPrevX,
    FPrevY: integer;
    FOnChange: TNotifyEvent;
    FDblClicked: Boolean;
    FThumbSize: TSize;
    procedure SwapBuffers;
    procedure SetMin(Min: real);
    procedure SetMax(Max: real);
    procedure SetSelStart(SelStart: real);
    procedure SetSelEnd(SelEnd: real);
    function GetSelLength: real;
    procedure UpdateMetrics;
    procedure SetState(State: TRangeSelectorState);
    function DeduceState(const X, Y: integer; const Down: boolean): TRangeSelectorState;
    function BarWidth: integer; inline;
    function LogicalToScreen(const LogicalPos: real): real;
    procedure UpdateThumbMetrics;
  protected
    { Protected declarations }
    procedure Paint; override;
    procedure WndProc(var Message: TMessage); override;
    procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X: Integer; Y: Integer); override;
    procedure MouseMove(Shift: TShiftState; X: Integer; Y: Integer); override;
    procedure MouseUp(Button: TMouseButton; Shift: TShiftState; X: Integer; Y: Integer); override;
    procedure MouseLeave(Sender: TObject);
    procedure DblClick; override;
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  published
    { Published declarations }
    property Anchors;
    property Min: real read FMin write SetMin;
    property Max: real read FMax write SetMax;
    property SelStart: real read FSelStart write SetSelStart;
    property SelEnd: real read FSelEnd write SetSelEnd;
    property SelLength: real read GetSelLength;
    property Enabled;
    property Visible;
    property OnChange: TNotifyEvent read FOnChange write FOnChange;
  end;

procedure Register;

implementation

uses Math;

procedure Register;
begin
  RegisterComponents('Rejbrand 2009', [TRangeSelector]);
end;

function IsIntInInterval(x, xmin, xmax: integer): boolean; inline;
begin
  IsIntInInterval := (xmin <= x) and (x <= xmax);
end;

function PointInRect(const X, Y: integer; const Rect: TRect): boolean; inline;
begin
  PointInRect := IsIntInInterval(X, Rect.Left, Rect.Right) and
                 IsIntInInterval(Y, Rect.Top, Rect.Bottom);
end;

function IsRealInInterval(x, xmin, xmax: extended): boolean; inline;
begin
  IsRealInInterval := (xmin <= x) and (x <= xmax);
end;

{ TRangeSelector }

function TRangeSelector.BarWidth: integer;
begin
  result := Width - 2*FThumbSize.cx;
end;

constructor TRangeSelector.Create(AOwner: TComponent);
begin
  inherited;
  FBuffer := TBitmap.Create;
  FMin := 0;
  FMax := 100;
  FSelStart := 20;
  FSelEnd := 80;
  FDown := false;
  FPrevX := -1;
  FPrevY := -1;
  FDblClicked := false;
end;

procedure TRangeSelector.UpdateThumbMetrics;
var
  theme: HTHEME;
const
  DEFAULT_THUMB_SIZE: TSize = (cx: 12; cy: 20);
begin
  FThumbSize := DEFAULT_THUMB_SIZE;
  if UxTheme.UseThemes then
  begin
    theme := OpenThemeData(Handle, 'TRACKBAR');
    if theme <> 0 then
      try
        GetThemePartSize(theme, FBuffer.Handle, TKP_THUMBTOP, TUTS_NORMAL, nil, TS_DRAW, FThumbSize);
      finally
        CloseThemeData(theme);
      end;
  end;
end;

destructor TRangeSelector.Destroy;
begin
  FBuffer.Free;
  inherited;
end;

function TRangeSelector.GetSelLength: real;
begin
  result := FSelEnd - FSelStart;
end;

function TRangeSelector.LogicalToScreen(const LogicalPos: real): real;
begin
  result := FThumbSize.cx + BarWidth * (LogicalPos - FMin) / (FMax - FMin)
end;

procedure TRangeSelector.DblClick;
var
  str: string;
begin
  FDblClicked := true;
  case FState of
    rssThumb1Hover, rssThumb1Down:
      begin
        str := FloatToStr(FSelStart);
        if InputQuery('Initial value', 'Enter new initial value:', str) then
          SetSelStart(StrToFloat(str));
      end;
    rssThumb2Hover, rssThumb2Down:
      begin
        str := FloatToStr(FSelEnd);
        if InputQuery('Final value', 'Enter new final value:', str) then
          SetSelEnd(StrToFloat(str));
      end;
  end;
end;

function TRangeSelector.DeduceState(const X, Y: integer; const Down: boolean): TRangeSelectorState;
begin
  result := rssNormal;

  if not Enabled then
    Exit(rssDisabled);

  if PointInRect(X, Y, FThumbPos1) then
    if Down then
      result := rssThumb1Down
    else
      result := rssThumb1Hover

  else if PointInRect(X, Y, FThumbPos2) then
    if Down then
      result := rssThumb2Down
    else
      result := rssThumb2Hover

  else if PointInRect(X, Y, FSelPos) then
    if Down then
      result := rssBlockDown
    else
      result := rssBlockHover;


end;

procedure TRangeSelector.MouseDown(Button: TMouseButton; Shift: TShiftState; X,
  Y: Integer);
begin
  inherited;
  if FDblClicked then
  begin
    FDblClicked := false;
    Exit;
  end;
  FDown := Button = mbLeft;
  SetState(DeduceState(X, Y, FDown));
end;

procedure TRangeSelector.MouseLeave(Sender: TObject);
begin
  if Enabled then
    SetState(rssNormal)
  else
    SetState(rssDisabled);
end;

procedure TRangeSelector.MouseMove(Shift: TShiftState; X, Y: Integer);
begin
  inherited;
  if FState = rssThumb1Down then
    SetSelStart(FSelStart + (X - FPrevX) * (FMax - FMin) / BarWidth)
  else if FState = rssThumb2Down then
    SetSelEnd(FSelEnd + (X - FPrevX) * (FMax - FMin) / BarWidth)
  else if FState = rssBlockDown then
  begin
    if IsRealInInterval(FSelStart + (X - FPrevX) * (FMax - FMin) / BarWidth, FMin, FMax) and
       IsRealInInterval(FSelEnd + (X - FPrevX) * (FMax - FMin) / BarWidth, FMin, FMax) then
    begin
      SetSelStart(FSelStart + (X - FPrevX) * (FMax - FMin) / BarWidth);
      SetSelEnd(FSelEnd + (X - FPrevX) * (FMax - FMin) / BarWidth);
    end;
  end
  else
    SetState(DeduceState(X, Y, FDown));

  FPrevX := X;
  FPrevY := Y;
end;

procedure TRangeSelector.MouseUp(Button: TMouseButton; Shift: TShiftState; X,
  Y: Integer);
begin
  inherited;
  FDown := false;
  SetState(DeduceState(X, Y, FDown));
end;

procedure TRangeSelector.Paint;
var
  theme: HTHEME;
begin
  inherited;

  FBuffer.Canvas.Brush.Color := Color;
  FBuffer.Canvas.FillRect(ClientRect);

  if UxTheme.UseThemes then
  begin

    theme := OpenThemeData(Handle, 'TRACKBAR');
    if theme <> 0 then
      try

        DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_TRACK, TRS_NORMAL, FTrackPos, nil);

        case FState of
          rssDisabled:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMB, TUS_DISABLED, FSelPos, nil);
          rssBlockHover:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMB, TUS_HOT, FSelPos, nil);
          rssBlockDown:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMB, TUS_PRESSED, FSelPos, nil);
        else
          DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMB, TUS_NORMAL, FSelPos, nil);
        end;


        case FState of
          rssDisabled:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBBOTTOM, TUBS_DISABLED, FThumbPos1, nil);
          rssThumb1Hover:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBBOTTOM, TUBS_HOT, FThumbPos1, nil);
          rssThumb1Down:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBBOTTOM, TUBS_PRESSED, FThumbPos1, nil);
        else
          DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBBOTTOM, TUBS_NORMAL, FThumbPos1, nil);
        end;

        case FState of
          rssDisabled:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBTOP, TUTS_DISABLED, FThumbPos2, nil);
          rssThumb2Hover:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBTOP, TUTS_HOT, FThumbPos2, nil);
          rssThumb2Down:
            DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBTOP, TUTS_PRESSED, FThumbPos2, nil);
        else
          DrawThemeBackground(theme, FBuffer.Canvas.Handle, TKP_THUMBTOP, TUTS_NORMAL, FThumbPos2, nil);
        end;

      finally
        CloseThemeData(theme);
      end;

  end

  else

  begin

    DrawEdge(FBuffer.Canvas.Handle, FTrackPos, EDGE_SUNKEN, BF_RECT);

    FBuffer.Canvas.Brush.Color := clHighlight;
    FBuffer.Canvas.FillRect(FSelPos);

    case FState of
      rssDisabled:
        DrawEdge(FBuffer.Canvas.Handle, FSelPos, EDGE_BUMP, BF_RECT or BF_MONO);
      rssBlockHover:
        DrawEdge(FBuffer.Canvas.Handle, FSelPos, EDGE_RAISED, BF_RECT);
      rssBlockDown:
        DrawEdge(FBuffer.Canvas.Handle, FSelPos, EDGE_SUNKEN, BF_RECT);
    else
      DrawEdge(FBuffer.Canvas.Handle, FSelPos, EDGE_ETCHED, BF_RECT);
    end;

    case FState of
      rssDisabled:
        DrawEdge(FBuffer.Canvas.Handle, FThumbPos1, EDGE_BUMP, BF_RECT or BF_MONO);
      rssThumb1Hover:
        DrawEdge(FBuffer.Canvas.Handle, FThumbPos1, EDGE_RAISED, BF_RECT);
      rssThumb1Down:
        DrawEdge(FBuffer.Canvas.Handle, FThumbPos1, EDGE_SUNKEN, BF_RECT);
    else
      DrawEdge(FBuffer.Canvas.Handle, FThumbPos1, EDGE_ETCHED, BF_RECT);
    end;

    case FState of
      rssDisabled:
        DrawEdge(FBuffer.Canvas.Handle, FThumbPos2, EDGE_BUMP, BF_RECT or BF_MONO);
      rssThumb2Hover:
        DrawEdge(FBuffer.Canvas.Handle, FThumbPos2, EDGE_RAISED, BF_RECT);
      rssThumb2Down:
        DrawEdge(FBuffer.Canvas.Handle, FThumbPos2, EDGE_SUNKEN, BF_RECT);
    else
      DrawEdge(FBuffer.Canvas.Handle, FThumbPos2, EDGE_ETCHED, BF_RECT);
    end;

  end;

  SwapBuffers;
end;

procedure TRangeSelector.UpdateMetrics;
begin
  UpdateThumbMetrics;
  FBuffer.SetSize(Width, Height);
  FTrackPos := Rect(FThumbSize.cx, FThumbSize.cy + 2, Width - FThumbSize.cx, Height - FThumbSize.cy - 2);
  FSelPos := Rect(round(LogicalToScreen(FSelStart)),
                  FTrackPos.Top,
                  round(LogicalToScreen(FSelEnd)),
                  FTrackPos.Bottom);
  with FThumbPos1 do
  begin
    Top := 0;
    Left := round(LogicalToScreen(FSelStart) - FThumbSize.cx / 2);
    Right := Left + FThumbSize.cx;
    Bottom := Top + FThumbSize.cy;
  end;
  with FThumbPos2 do
  begin
    Top := Self.Height - FThumbSize.cy;
    Left := round(LogicalToScreen(FSelEnd) - FThumbSize.cx / 2);
    Right := Left + FThumbSize.cx;
    Bottom := Top + FThumbSize.cy;
  end;
end;

procedure TRangeSelector.WndProc(var Message: TMessage);
begin
  inherited;
  case Message.Msg of
    WM_SIZE:
      UpdateMetrics;
  end;
end;

procedure TRangeSelector.SetMax(Max: real);
begin
  if FMax <> Max then
  begin
    FMax := Max;
    UpdateMetrics;
    Paint;
  end;
end;

procedure TRangeSelector.SetMin(Min: real);
begin
  if FMin <> Min then
  begin
    FMin := Min;
    UpdateMetrics;
    Paint;
  end;
end;

procedure TRangeSelector.SetSelEnd(SelEnd: real);
begin
  if (FSelEnd <> SelEnd) and IsRealInInterval(SelEnd, FMin, FMax) then
  begin
    FSelEnd := SelEnd;
    if FSelStart > FSelEnd then
      FSelStart := FSelEnd;
    UpdateMetrics;
    Paint;
    if Assigned(FOnChange) then
      FOnChange(Self);
  end;
end;

procedure TRangeSelector.SetSelStart(SelStart: real);
begin
  if (FSelStart <> SelStart) and IsRealInInterval(SelStart, FMin, FMax) then
  begin
    FSelStart := SelStart;
    if FSelStart > FSelEnd then
      FSelEnd := FSelStart;
    UpdateMetrics;
    Paint;
    if Assigned(FOnChange) then
      FOnChange(Self);
  end;
end;

procedure TRangeSelector.SetState(State: TRangeSelectorState);
begin
  if State <> FState then
  begin
    FState := State;
    Paint;
  end;
end;

procedure TRangeSelector.SwapBuffers;
begin
  BitBlt(Canvas.Handle,
         0,
         0,
         Width,
         Height,
         FBuffer.Canvas.Handle,
         0,
         0,
         SRCCOPY);
end;

end.

There are still a few things to improve, such as 1) add keyboard interface, 2) make the display of the markers optional and add more appearance settings, 4) snap to integer grid, and 3) add the ability to enter a value by numbers Try double-clicking a thumb!.

The control works both with and without visual themes enabled and is completely double-buffered.