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{
  You cannot change the color of a standard TButton,
  since the windows button control always paints itself with the
  button color defined in the control panel.
  But you can derive derive a new component from TButton and handle
  the and drawing behaviour there.
}


unit ColorButton;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, Buttons, ExtCtrls;

type
  TDrawButtonEvent = procedure(Control: TWinControl;
    Rect: TRect; State: TOwnerDrawState) of object;

  TColorButton = class(TButton)
  private
    FCanvas: TCanvas;
    IsFocused: Boolean;
    FOnDrawButton: TDrawButtonEvent;
  protected
    procedure CreateParams(var Params: TCreateParams); override;
    procedure SetButtonStyle(ADefault: Boolean); override;
    procedure CMEnabledChanged(var Message: TMessage); message CM_ENABLEDCHANGED;
    procedure CMFontChanged(var Message: TMessage); message CM_FONTCHANGED;
    procedure CNMeasureItem(var Message: TWMMeasureItem); message CN_MEASUREITEM;
    procedure CNDrawItem(var Message: TWMDrawItem); message CN_DRAWITEM;
    procedure WMLButtonDblClk(var Message: TWMLButtonDblClk); message WM_LBUTTONDBLCLK;
    procedure DrawButton(Rect: TRect; State: UINT);
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    property Canvas: TCanvas read FCanvas;
  published
    property OnDrawButton: TDrawButtonEvent read FOnDrawButton write FOnDrawButton;
    property Color;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Samples', [TColorButton]);
end;

constructor TColorButton.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FCanvas := TCanvas.Create;
end;

destructor TColorButton.Destroy;
begin
  inherited Destroy;
  FCanvas.Free;
end;

procedure TColorButton.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  with Params do Style := Style or BS_OWNERDRAW;
end;

procedure TColorButton.SetButtonStyle(ADefault: Boolean);
begin
  if ADefault <> IsFocused then
  begin
    IsFocused := ADefault;
    Refresh;
  end;
end;

procedure TColorButton.CNMeasureItem(var Message: TWMMeasureItem);
begin
  with Message.MeasureItemStruct^ do
  begin
    itemWidth  := Width;
    itemHeight := Height;
  end;
end;

procedure TColorButton.CNDrawItem(var Message: TWMDrawItem);
var
  SaveIndex: Integer;
begin
  with Message.DrawItemStruct^ do
  begin
    SaveIndex := SaveDC(hDC);
    FCanvas.Lock;
    try
      FCanvas.Handle := hDC;
      FCanvas.Font := Font;
      FCanvas.Brush := Brush;
      DrawButton(rcItem, itemState);
    finally
      FCanvas.Handle := 0;
      FCanvas.Unlock;
      RestoreDC(hDC, SaveIndex);
    end;
  end;
  Message.Result := 1;
end;

procedure TColorButton.CMEnabledChanged(var Message: TMessage);
begin
  inherited;
  Invalidate;
end;

procedure TColorButton.CMFontChanged(var Message: TMessage);
begin
  inherited;
  Invalidate;
end;

procedure TColorButton.WMLButtonDblClk(var Message: TWMLButtonDblClk);
begin
  Perform(WM_LBUTTONDOWN, Message.Keys, Longint(Message.Pos));
end;

procedure TColorButton.DrawButton(Rect: TRect; State: UINT);
var
  Flags, OldMode: Longint;
  IsDown, IsDefault, IsDisabled: Boolean;
  OldColor: TColor;
  OrgRect: TRect;
begin
  OrgRect := Rect;
  Flags := DFCS_BUTTONPUSH or DFCS_ADJUSTRECT;
  IsDown := State and ODS_SELECTED <> 0;
  IsDefault := State and ODS_FOCUS <> 0;
  IsDisabled := State and ODS_DISABLED <> 0;

  if IsDown then Flags := Flags or DFCS_PUSHED;
  if IsDisabled then Flags := Flags or DFCS_INACTIVE;

  if IsFocused or IsDefault then
  begin
    FCanvas.Pen.Color := clWindowFrame;
    FCanvas.Pen.Width := 1;
    FCanvas.Brush.Style := bsClear;
    FCanvas.Rectangle(Rect.Left, Rect.Top, Rect.Right, Rect.Bottom);
    InflateRect(Rect, - 1, - 1);
  end;

  if IsDown then
  begin
    FCanvas.Pen.Color := clBtnShadow;
    FCanvas.Pen.Width := 1;
    FCanvas.Brush.Color := clBtnFace;
    FCanvas.Rectangle(Rect.Left, Rect.Top, Rect.Right, Rect.Bottom);
    InflateRect(Rect, - 1, - 1);
  end
  else
    DrawFrameControl(FCanvas.Handle, Rect, DFC_BUTTON, Flags);

  if IsDown then OffsetRect(Rect, 1, 1);

  OldColor := FCanvas.Brush.Color;
  FCanvas.Brush.Color := Color;
  FCanvas.FillRect(Rect);
  FCanvas.Brush.Color := OldColor;
  OldMode := SetBkMode(FCanvas.Handle, TRANSPARENT);
  FCanvas.Font.Color := clBtnText;
  if IsDisabled then
    DrawState(FCanvas.Handle, FCanvas.Brush.Handle, nil, Integer(Caption), 0,
    ((Rect.Right - Rect.Left) - FCanvas.TextWidth(Caption)) div 2,
    ((Rect.Bottom - Rect.Top) - FCanvas.TextHeight(Caption)) div 2,
      0, 0, DST_TEXT or DSS_DISABLED)
  else
    DrawText(FCanvas.Handle, PChar(Caption), - 1, Rect,
      DT_SINGLELINE or DT_CENTER or DT_VCENTER);
  SetBkMode(FCanvas.Handle, OldMode);

  if Assigned(FOnDrawButton) then
    FOnDrawButton(Self, Rect, TOwnerDrawState(LongRec(State).Lo));

  if IsFocused and IsDefault then
  begin
    Rect := OrgRect;
    InflateRect(Rect, - 4, - 4);
    FCanvas.Pen.Color := clWindowFrame;
    FCanvas.Brush.Color := clBtnFace;
    DrawFocusRect(FCanvas.Handle, Rect);
  end;
end;
end.