在VCL风格的表单上禁用TButton问题 [英] Disabling TButton issue on a VCL styled form

问题描述

当我尝试在风格的VCL上禁用一个Button，使用以下代码行

When I try to disable a Button on a styled VCL from using the follwing line of code

TButton(Sender).enabled:= False;

我得到这个结果（在运行时禁用了按钮）

I get the this result (Button disabled at runtime)

而不是这个！ （在设计时禁用按钮）

instead of this!! (Button disabled at design time)

让两个或更多个具有相同颜色的按钮彼此相隔真的很困惑，一个被禁用，另一个被启用

It's really confusing to have two or more Buttons with the same color beside each other, one is disabled and the other is enabled

推荐答案

此问题的原因位于 TButtonStyleHook （在Vcl.StdCtrls单元中）样式钩子类。

The cause of this issue is located in the Paint method of the TButtonStyleHook (in the Vcl.StdCtrls unit) style hook class.

在方法中找到此代码

if FPressed then
  Details := StyleServices.GetElementDetails(tbPushButtonPressed)
else if MouseInControl  then //this condition is triggered even if the button is disabled
  Details := StyleServices.GetElementDetails(tbPushButtonHot)
else if Focused then //this condition is triggered even if the button is disabled
  Details := StyleServices.GetElementDetails(tbPushButtonDefaulted)
else if Control.Enabled then
  Details := StyleServices.GetElementDetails(tbPushButtonNormal)
else
  Details := StyleServices.GetElementDetails(tbPushButtonDisabled);

替换此代码

if FPressed then
  Details := StyleServices.GetElementDetails(tbPushButtonPressed)
else if MouseInControl and Control.Enabled then
  Details := StyleServices.GetElementDetails(tbPushButtonHot)
else if Focused and Control.Enabled then
  Details := StyleServices.GetElementDetails(tbPushButtonDefaulted)
else if Control.Enabled then
  Details := StyleServices.GetElementDetails(tbPushButtonNormal)
else
  Details := StyleServices.GetElementDetails(tbPushButtonDisabled);

另一个选项是重写TButton的Style钩子：

Another option is rewrite the Style hook for the TButton :

根据这篇文章检查此代码修复TButton组件中的VCL风格错误。这些代码的优点是您正在修复两个问题 103708 和 103962 。

Check this code based in this article Fixing a VCL Style bug in the TButton component. The advantage of ths code is which you are fixing two issues 103708 and 103962.

Uses
 Winapi.CommCtrl,
 Vcl.Themes,
 Vcl.Styles;

type
  TCustomButtonH=class(TCustomButton);

  //we need this helper to access some strict private fields
  TButtonStyleHookHelper = class Helper for TButtonStyleHook
  protected
   function Pressed : Boolean;
   function DropDown: Boolean;
  end;

  //to avoid writting a lot of extra code we are to use TButtonStyleHook class and override the paint method
  TButtonStyleHookFix = class(TButtonStyleHook)
  protected
    procedure Paint(Canvas: TCanvas); override;
  end;


{ TButtonStyleHookFix }

procedure TButtonStyleHookFix.Paint(Canvas: TCanvas);
var
  LDetails          : TThemedElementDetails;
  DrawRect          : TRect;
  pbuttonImagelist  : BUTTON_IMAGELIST;
  IW, IH, IY        : Integer;
  LTextFormatFlags  : TTextFormatFlags;
  ThemeTextColor    : TColor;
  Buffer            : string;
  BufferLength      : Integer;
  SaveIndex         : Integer;
  X, Y, I           : Integer;
  BCaption          : String;
begin

  if StyleServices.Available then
  begin
    BCaption := Text;

    if Pressed then
      LDetails := StyleServices.GetElementDetails(tbPushButtonPressed)
    else
    if MouseInControl and Control.Enabled then
      LDetails := StyleServices.GetElementDetails(tbPushButtonHot)
    else
    if Focused and Control.Enabled  then
      LDetails := StyleServices.GetElementDetails(tbPushButtonDefaulted)
    else
    if Control.Enabled then
      LDetails := StyleServices.GetElementDetails(tbPushButtonNormal)
    else
      LDetails := StyleServices.GetElementDetails(tbPushButtonDisabled);

    DrawRect := Control.ClientRect;
    StyleServices.DrawElement(Canvas.Handle, LDetails, DrawRect);

    if Button_GetImageList(handle, pbuttonImagelist) and (pbuttonImagelist.himl <> 0) and ImageList_GetIconSize(pbuttonImagelist.himl, IW, IH) then
    begin
      if (GetWindowLong(Handle, GWL_STYLE) and BS_COMMANDLINK) = BS_COMMANDLINK then
        IY := DrawRect.Top + 15
      else
        IY := DrawRect.Top + (DrawRect.Height - IH) div 2;

      //here the image is drawn properly according to the ImageAlignment value
      case TCustomButton(Control).ImageAlignment of
        iaLeft  :
                  begin
                    ImageList_Draw(pbuttonImagelist.himl, 0, Canvas.Handle, DrawRect.Left + 3, IY, ILD_NORMAL);
                    Inc(DrawRect.Left, IW + 3);
                  end;
        iaRight :
                  begin
                    ImageList_Draw(pbuttonImagelist.himl, 0, Canvas.Handle, DrawRect.Right - IW -3, IY, ILD_NORMAL);
                    Dec(DrawRect.Right, IW - 3);
                  end;

        iaCenter:
                  begin
                   ImageList_Draw(pbuttonImagelist.himl, 0, Canvas.Handle, (DrawRect.Right - IW) div 2, IY, ILD_NORMAL);
                  end;


        iaTop   :
                  begin
                   ImageList_Draw(pbuttonImagelist.himl, 0, Canvas.Handle, (DrawRect.Right - IW) div 2, 3, ILD_NORMAL);
                  end;


        iaBottom:
                  begin
                   ImageList_Draw(pbuttonImagelist.himl, 0, Canvas.Handle, (DrawRect.Right - IW) div 2, (DrawRect.Height - IH) - 3, ILD_NORMAL);
                  end;

      end;


    end;

    if (GetWindowLong(Handle, GWL_STYLE) and BS_COMMANDLINK) = BS_COMMANDLINK then
    begin
      if pbuttonImagelist.himl = 0 then
        Inc(DrawRect.Left, 35);

      Inc(DrawRect.Top, 15);
      Inc(DrawRect.Left, 5);
      Canvas.Font := TCustomButtonH(Control).Font;
      Canvas.Font.Style := [];
      Canvas.Font.Size := 12;
      LTextFormatFlags := TTextFormatFlags(DT_LEFT);
      if StyleServices.GetElementColor(LDetails, ecTextColor, ThemeTextColor) then
         Canvas.Font.Color := ThemeTextColor;
      StyleServices.DrawText(Canvas.Handle, LDetails, BCaption, DrawRect, LTextFormatFlags, Canvas.Font.Color);
      SetLength(Buffer, Button_GetNoteLength(Handle) + 1);
      if Length(Buffer) <> 0 then
      begin
        BufferLength := Length(Buffer);
        if Button_GetNote(Handle, PChar(Buffer), BufferLength) then
        begin
          LTextFormatFlags := TTextFormatFlags(DT_LEFT or DT_WORDBREAK);
          Inc(DrawRect.Top, Canvas.TextHeight('Wq') + 2);
          Canvas.Font.Size := 8;
          StyleServices.DrawText(Canvas.Handle, LDetails, Buffer, DrawRect,
            LTextFormatFlags, Canvas.Font.Color);
        end;
      end;

      if pbuttonImagelist.himl = 0 then
      begin
        if Pressed then
          LDetails := StyleServices.GetElementDetails(tbCommandLinkGlyphPressed)
        else if MouseInControl then
          LDetails := StyleServices.GetElementDetails(tbCommandLinkGlyphHot)
        else if Control.Enabled then
          LDetails := StyleServices.GetElementDetails(tbCommandLinkGlyphNormal)
        else
          LDetails := StyleServices.GetElementDetails(tbCommandLinkGlyphDisabled);
        DrawRect.Right := 35;
        DrawRect.Left := 3;
        DrawRect.Top := 10;
        DrawRect.Bottom := DrawRect.Top + 32;
        StyleServices.DrawElement(Canvas.Handle, LDetails, DrawRect);
      end;

    end
    else
    if (GetWindowLong(Handle, GWL_STYLE) and BS_SPLITBUTTON) = BS_SPLITBUTTON then
    begin
      Dec(DrawRect.Right, 15);
      DrawControlText(Canvas, LDetails, Text, DrawRect, DT_VCENTER or DT_CENTER);
      if DropDown then
      begin
        LDetails := StyleServices.GetElementDetails(tbPushButtonPressed);
        SaveIndex := SaveDC(Canvas.Handle);
        try
          IntersectClipRect(Canvas.Handle, Control.Width - 15, 0,
            Control.Width, Control.Height);
          DrawRect := Rect(Control.Width - 30, 0, Control.Width, Control.Height);
          StyleServices.DrawElement(Canvas.Handle, LDetails, DrawRect);
        finally
          RestoreDC(Canvas.Handle, SaveIndex);
        end;
      end;

      with Canvas do
      begin
        Pen.Color := StyleServices.GetSystemColor(clBtnShadow);
        MoveTo(Control.Width - 15, 3);
        LineTo(Control.Width - 15, Control.Height - 3);
        if Control.Enabled then
          Pen.Color := StyleServices.GetSystemColor(clBtnHighLight)
        else
          Pen.Color := Font.Color;
        MoveTo(Control.Width - 14, 3);
        LineTo(Control.Width - 14, Control.Height - 3);
        Pen.Color := Font.Color;
        X := Control.Width - 8;
        Y := Control.Height div 2 + 1;
        for i := 3 downto 0 do
        begin
          MoveTo(X - I, Y - I);
          LineTo(X + I + 1, Y - I);
        end;
      end;

    end
    else
    begin
      //finally the text is aligned and drawn depending of the value of the ImageAlignment property
      case TCustomButton(Control).ImageAlignment of
        iaLeft,
        iaRight,
        iaCenter : DrawControlText(Canvas, LDetails, BCaption, DrawRect, DT_VCENTER or DT_CENTER);
        iaBottom : DrawControlText(Canvas, LDetails, BCaption, DrawRect, DT_TOP or DT_CENTER);
        iaTop    : DrawControlText(Canvas, LDetails, BCaption, DrawRect, DT_BOTTOM or DT_CENTER);
      end;
    end;
  end;
end;

{ TButtonStyleHookHelper }

function TButtonStyleHookHelper.DropDown: Boolean;
begin
  Result:=Self.FDropDown;
end;

function TButtonStyleHookHelper.Pressed: Boolean;
begin
  Result:=Self.FPressed;
end;


initialization
 TStyleManager.Engine.RegisterStyleHook(TButton, TButtonStyleHookFix);

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