我如何自定義繪製的TEdit控制文本？

Question

我想繪製一段TEdit.Text使用Font.Color不同於默認。有沒有例子如何做到這一點？

我試圖做這樣的事情：

_{注：這張截圖的圖片是什麼僅僅是一個毛茸茸的草案，但它使我相信有什麼問題可以解決。}

Answer 1

Edit控件沒有所有者繪製支持，但由子類它和處理WM_PAINT（許多其他消息中），您可以自定義繪製。這是可行的，但實際上實現100％是一個痛苦的世界。從文檔：Developing Custom Draw Controls in Visual C++：

注意，所有者繪製將大部分控制工作。但是，它不適用於編輯控件;與問候列表控件，它僅適用於報告視圖風格

我也有興趣瞭解兔子洞有多深，所以，
下面是使用一箇中介類代碼示例（還需要落實的選擇，但是當插入符號是自定義繪製工作在控制）：

type 
    TEdit = class(StdCtrls.TEdit) 
    private 
    FCanvas: TCanvas; 
    procedure WMPaint(var Message: TWMPaint); message WM_PAINT; 
    protected 
    procedure WndProc(var Message: TMessage); override; 
    procedure Paint; virtual; 
    procedure PaintWindow(DC: HDC); override; 
    property Canvas: TCanvas read FCanvas; 
    public 
    constructor Create(AOwner: TComponent); override; 
    destructor Destroy; override; 
    end; 

... 

constructor TEdit.Create(AOwner: TComponent); 
begin 
    inherited Create(AOwner); 
    FCanvas := TControlCanvas.Create; 
    TControlCanvas(FCanvas).Control := Self; 
end; 

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

procedure TEdit.Paint; 
var 
    R: TRect; 
    I: Integer; 
    S: String; 
begin 
    R := ClientRect; 
    Inc(R.Left, 1); 
    Inc(R.Top, 1); 
    Canvas.Brush.Assign(Self.Brush); 
    Canvas.Font.Assign(Self.Font); 
    for I := 1 to Length(Text) do 
    begin 
    if Text[I] in ['0'..'9'] then 
     Canvas.Font.Color := clRed 
    else 
     Canvas.Font.Color := clGreen; 
    S := Text[I]; 
    DrawText(Canvas.Handle, PChar(S), -1, R, DT_LEFT or DT_NOPREFIX or 
     DT_WORDBREAK or DrawTextBiDiModeFlagsReadingOnly); 
    Inc(R.Left,Canvas.TextWidth(S)); 
    end; 
end; 

procedure TEdit.PaintWindow(DC: HDC); 
begin 
    FCanvas.Lock; 
    try 
    FCanvas.Handle := DC; 
    try 
     TControlCanvas(FCanvas).UpdateTextFlags; 
     Paint; 
    finally 
     FCanvas.Handle := 0; 
    end; 
    finally 
    FCanvas.Unlock; 
    end; 
end; 

procedure TEdit.WMPaint(var Message: TWMPaint); 
begin 
    ControlState := ControlState+[csCustomPaint]; 
    inherited; 
    ControlState := ControlState-[csCustomPaint]; 
end; 

procedure TEdit.WndProc(var Message: TMessage); 
begin 
    inherited WndProc(Message); 
    with Message do 
    case Msg of 
     CM_MOUSEENTER, CM_MOUSELEAVE, WM_LBUTTONUP, WM_LBUTTONDOWN, 
     WM_KEYDOWN, WM_KEYUP, 
     WM_SETFOCUS, WM_KILLFOCUS, 
     CM_FONTCHANGED, CM_TEXTCHANGED: 
     begin 
     Invalidate; 
     end; 
    end; 
end; 

Answer 2

號標準TEDIT不具有自定義繪製或文本有多種顏色的支持。作爲替代，你可以使用tRichEdit和WantReturns = False。

Answer 3

一些改進，kobik solusion：

procedure TMyEdit.Paint; 
var 
    R: TRect; 
    I: Integer; 

    NewColor : TColor; 
    NewBackColor : TColor; 

    procedure DrawEx(S: String); 
    begin 
    if ((i-1)>=Self.SelStart) and ((i-1)<=(Self.SelStart+(Self.SelLength-1))) 
     and (Self.SelLength>0) and (Self.focused) 
     then begin 
     Canvas.Font.Color := clWhite; 
     Canvas.Brush.Color := NewColor; 
     end else begin 
     Canvas.Font.Color := NewColor; 
     Canvas.Brush.Color := NewBackColor; 
     end; 
    Canvas.Brush.Style := bsSolid; 
    DrawText(Canvas.Handle, PChar(S), -1, R, DT_LEFT or DT_NOPREFIX or 
     DT_WORDBREAK or DrawTextBiDiModeFlagsReadingOnly); 
    end; 

begin 
    R := ClientRect; 
    Inc(R.Left, 1); 
    Inc(R.Top, 1); 
    Canvas.Brush.Assign(Self.Brush); 
    Canvas.Font.Assign(Self.Font); 

    if Self.Focused then begin 
     NewBackColor  := clYellow; 
     Canvas.Brush.Color := NewBackColor; 
     Canvas.Brush.Style := bsSolid; 
     Canvas.FillRect(ClientRect); 
     Canvas.DrawFocusRect(ClientRect); 
    end else NewBackColor := clWhite; 

    for I:=1 to Length(Text) do begin 
    if PasswordChar=#0 then begin 
    if Text[I] in ['0'..'9'] then begin 
     NewColor := clRed; 
     DrawEx(Text[I]); 
     end else begin 
     NewColor := clGreen; 
     DrawEx(Text[I]); 
     end; 
    Inc(R.Left,Canvas.TextWidth(Text[I])); 
    end else begin //with passwordchar 
     NewColor := clBlack; 
     DrawEx(PasswordChar); 
    Inc(R.Left,Canvas.TextWidth(PasswordChar)); 
    end; 
    end; 
end;