Delphi组件:如何使用父字体?

发布于 2024-10-17 21:48:39 字数 3310 浏览 2 评论 0原文

我有一个使用 ParentFont 的自定义组件。

在构建我的组件期间,我可以看到组件的字体最初设置为默认的 MS Sans Serif

constructor TCustomWidget.Create(AOwner: TComponent);
begin
   inherited Create(AOwner);

   ...
end;

检查显示 Self.Font.Name: 'MS Sans Serif'

一段时间后,我的组件的字体被更新以反映父级的字体:

TReader.ReadComponent(nil)
   SetCompName
      TControl.SetParentComponent
         TControl.SetParent
            TWinControl.InsertControl
               AControl.Perform(CM_PARENTFONTCHANGED, 0, 0);

之后一切都很好,我的组件的字体已更改为父级的字体(例如“MS Shell Dlg 2”)。

问题是我的子控件没有与其父控件的字体(即我的组件)保持同步。

在我的组件构造函数中,我创建了子控件:

constructor TCustomWidget.Create(AOwner: TComponent);
begin
   inherited Create(AOwner);

   ...
   CreateComponents;
end;

procedure TCustomWidget.CreateComponents;
begin
   ...
   FpnlBottom := TPanel.Create(Self);
   FpnlBottom.Caption := '';
   FpnlBottom.Parent := Self;
   FpnlBottom.Align := alBottom;
   FpnlBottom.Height := 46;
   FpnlBottom.ParentFont := True;
   ...
end;

最初我的 FpnlBottom 也具有默认字体 MS Sans Serif

后来,当我的组件的字体更新为父级字体(例如MS Shell Dlg 2)时,子控件的字体没有更新,而是保持不变MS Sans Serif

  • 为什么我的子控件的 ParentFont 属性不被遵守?
  • 如何使子控件的 ParentFont 属性起作用?

示例代码

工具用两个小时将其缩减为可管理、可重现的代码:

unit WinControl1;

interface

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

type
    TWidget = class(TWinControl)
    private
        FTitleLabel: Tlabel;
        FpnlBottom: TPanel;

        procedure CreateComponents;
    protected
        procedure FontChange(Sender: TObject);
    public
        constructor Create(AOwner: TComponent); override;
    published
        {Inherited from TWinControl}
        property Align;
        property Font;
        property ParentFont;
    end;

    procedure Register;

implementation

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

{ TCustomWidget }

constructor TWidget.Create(AOwner: TComponent);
begin
    inherited Create(AOwner);

    ControlStyle := ControlStyle + [csAcceptsControls, csNoDesignVisible];

    Self.Width := 384;
    Self.Height := 240;

    Self.Font.OnChange := FontChange;

    CreateComponents;
end;

procedure TWidget.CreateComponents;
begin
    FpnlBottom := TPanel.Create(Self);
    FpnlBottom.Parent := Self;
    FpnlBottom.Align := alBottom;
    FpnlBottom.Color := clWindow;
    FpnlBottom.Caption := 'FpnlBottom';
    FpnlBottom.Height := 45;

    FTitleLabel := TLabel.Create(Self);
    FTitleLabel.Parent := FpnlBottom;
    FTitleLabel.Left := 11;
    FTitleLabel.Top := 11;
    FTitleLabel.Caption := 'Hello, world!';
    FTitleLabel.AutoSize := True;
    FTitleLabel.Font.Color := $00993300;
    FTitleLabel.Font.Size := Self.Font.Size+3;
    FTitleLabel.ParentFont := False;
end;

procedure TWidget.FontChange(Sender: TObject);
begin
    //title label is always 3 points larger than the rest of the content
    FTitleLabel.Font.Name := Self.Font.Name;
    FTitleLabel.Font.Size := Self.Font.Size+3;

    OutputDebugString(PChar('New font '+Self.Font.Name));
end;

end.

i have a custom component that uses the ParentFont.

During construction of my component, i can see that initially the component's font is set to the default MS Sans Serif:

constructor TCustomWidget.Create(AOwner: TComponent);
begin
   inherited Create(AOwner);

   ...
end;

Inspecting shows Self.Font.Name: 'MS Sans Serif'

Some time later, the font of my component is updated to reflect the parent's font:

TReader.ReadComponent(nil)
   SetCompName
      TControl.SetParentComponent
         TControl.SetParent
            TWinControl.InsertControl
               AControl.Perform(CM_PARENTFONTCHANGED, 0, 0);

And after that everything is great, my component's font has been changed to the parent's font (e.g. `MS Shell Dlg 2').

The problem is that my child controls are not keeping in sync with their parent's font (i.e. my component).

During my components constructor, i create child controls:

constructor TCustomWidget.Create(AOwner: TComponent);
begin
   inherited Create(AOwner);

   ...
   CreateComponents;
end;

procedure TCustomWidget.CreateComponents;
begin
   ...
   FpnlBottom := TPanel.Create(Self);
   FpnlBottom.Caption := '';
   FpnlBottom.Parent := Self;
   FpnlBottom.Align := alBottom;
   FpnlBottom.Height := 46;
   FpnlBottom.ParentFont := True;
   ...
end;

And initially my FpnlBottom has the default font also MS Sans Serif.

Later, when the font of my component has been updated to its parent's font (e.g. MS Shell Dlg 2), the child controls are not having their fonts updated, and are remaining MS Sans Serif.

  • Why are my child control's ParentFont property not being honored?
  • How do i make my child control's ParentFont property work?

Sample Code

Tool two hours to trim it down to manageable, reproducible, code:

unit WinControl1;

interface

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

type
    TWidget = class(TWinControl)
    private
        FTitleLabel: Tlabel;
        FpnlBottom: TPanel;

        procedure CreateComponents;
    protected
        procedure FontChange(Sender: TObject);
    public
        constructor Create(AOwner: TComponent); override;
    published
        {Inherited from TWinControl}
        property Align;
        property Font;
        property ParentFont;
    end;

    procedure Register;

implementation

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

{ TCustomWidget }

constructor TWidget.Create(AOwner: TComponent);
begin
    inherited Create(AOwner);

    ControlStyle := ControlStyle + [csAcceptsControls, csNoDesignVisible];

    Self.Width := 384;
    Self.Height := 240;

    Self.Font.OnChange := FontChange;

    CreateComponents;
end;

procedure TWidget.CreateComponents;
begin
    FpnlBottom := TPanel.Create(Self);
    FpnlBottom.Parent := Self;
    FpnlBottom.Align := alBottom;
    FpnlBottom.Color := clWindow;
    FpnlBottom.Caption := 'FpnlBottom';
    FpnlBottom.Height := 45;

    FTitleLabel := TLabel.Create(Self);
    FTitleLabel.Parent := FpnlBottom;
    FTitleLabel.Left := 11;
    FTitleLabel.Top := 11;
    FTitleLabel.Caption := 'Hello, world!';
    FTitleLabel.AutoSize := True;
    FTitleLabel.Font.Color := $00993300;
    FTitleLabel.Font.Size := Self.Font.Size+3;
    FTitleLabel.ParentFont := False;
end;

procedure TWidget.FontChange(Sender: TObject);
begin
    //title label is always 3 points larger than the rest of the content
    FTitleLabel.Font.Name := Self.Font.Name;
    FTitleLabel.Font.Size := Self.Font.Size+3;

    OutputDebugString(PChar('New font '+Self.Font.Name));
end;

end.

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评论(2

三人与歌 2024-10-24 21:48:40

查看示例代码后,您使用的 FontChange 事件处理程序完全错误。您根本不应该使用它。您正在绕过本机 TControl.FontChanged() 事件处理程序,该处理程序会触发 CM_FONTCHANGEDCM_PARENTFONTCHANGED 通知,因此您实际上破坏了 ParentFont 逻辑。只需完全删除 TWidget.FontChanged() 事件处理程序即可。如果您需要对组件的 Font 属性的更改做出反应,则需要拦截 CM_FONTCHANGED 消息,例如:

unit WinControl1;

interface

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

type
  TWidget = class(TWinControl)
  private
    FTitleLabel: TLabel;
    FpnlBottom: TPanel;
    procedure CreateComponents;
    procedure CMFontChanged(var Message: TMessage); message CM_FONTCHANGED;
  public
    constructor Create(AOwner: TComponent); override;
  published
    {Inherited from TWinControl}
    property Align;
    property Font;
    property ParentFont;
  end;

procedure Register;

implementation

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

{ TCustomWidget }

constructor TWidget.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  ControlStyle := ControlStyle + [csAcceptsControls, csNoDesignVisible];
  Self.Width := 384;
  Self.Height := 240;
  CreateComponents;
end;

procedure TWidget.CreateComponents;
begin
  FpnlBottom := TPanel.Create(Self);
  FpnlBottom.Parent := Self;
  FpnlBottom.Align := alBottom;
  FpnlBottom.Color := clWindow;
  FpnlBottom.Caption := 'FpnlBottom';
  FpnlBottom.Height := 45;

  FTitleLabel := TLabel.Create(Self);
  FTitleLabel.Parent := FpnlBottom;
  FTitleLabel.Left := 11;
  FTitleLabel.Top := 11;
  FTitleLabel.Caption := 'Hello, world!';
  FTitleLabel.AutoSize := True;
  FTitleLabel.Font.Color := $00993300;
  FTitleLabel.Font.Size := Self.Font.Size+3;
  FTitleLabel.ParentFont := False;
end;

procedure TWidget.CMFontChanged(var Message: TMessage);
begin
  inherited; // let TControl and TWinControl react first
  //title label is always 3 points larger than the rest of the content
  FTitleLabel.Font.Name := Self.Font.Name;
  FTitleLabel.Font.Size := Self.Font.Size + 3;
  OutputDebugString(PChar('New font ' + Self.Font.Name));
end;

end. 

After seeing your sample code, you are using the FontChange event handler all wrong. You should not be using it at all. You are bypassing the native TControl.FontChanged() event handler, which triggers CM_FONTCHANGED and CM_PARENTFONTCHANGED notifications, so you are actually breaking the ParentFont logic. Just get rid of your TWidget.FontChanged() event handler altogether. If you need to react to changed to your component's Font property, you need to intercept the CM_FONTCHANGED message instead, eg:

unit WinControl1;

interface

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

type
  TWidget = class(TWinControl)
  private
    FTitleLabel: TLabel;
    FpnlBottom: TPanel;
    procedure CreateComponents;
    procedure CMFontChanged(var Message: TMessage); message CM_FONTCHANGED;
  public
    constructor Create(AOwner: TComponent); override;
  published
    {Inherited from TWinControl}
    property Align;
    property Font;
    property ParentFont;
  end;

procedure Register;

implementation

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

{ TCustomWidget }

constructor TWidget.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  ControlStyle := ControlStyle + [csAcceptsControls, csNoDesignVisible];
  Self.Width := 384;
  Self.Height := 240;
  CreateComponents;
end;

procedure TWidget.CreateComponents;
begin
  FpnlBottom := TPanel.Create(Self);
  FpnlBottom.Parent := Self;
  FpnlBottom.Align := alBottom;
  FpnlBottom.Color := clWindow;
  FpnlBottom.Caption := 'FpnlBottom';
  FpnlBottom.Height := 45;

  FTitleLabel := TLabel.Create(Self);
  FTitleLabel.Parent := FpnlBottom;
  FTitleLabel.Left := 11;
  FTitleLabel.Top := 11;
  FTitleLabel.Caption := 'Hello, world!';
  FTitleLabel.AutoSize := True;
  FTitleLabel.Font.Color := $00993300;
  FTitleLabel.Font.Size := Self.Font.Size+3;
  FTitleLabel.ParentFont := False;
end;

procedure TWidget.CMFontChanged(var Message: TMessage);
begin
  inherited; // let TControl and TWinControl react first
  //title label is always 3 points larger than the rest of the content
  FTitleLabel.Font.Name := Self.Font.Name;
  FTitleLabel.Font.Size := Self.Font.Size + 3;
  OutputDebugString(PChar('New font ' + Self.Font.Name));
end;

end. 
长不大的小祸害 2024-10-24 21:48:40

每次更新组件的 Font 属性时,组件都会自动向其每个子控件发送 CM_PARENTFONTCHANGED 消息,此时每个控件都会检查其 ParentFont code> 属性是否为 True。您是否检查过以确保子控件的 ParentFont 属性仍设置为 True?也许在它们自己的 DFM 流期间,子控件正在设置它们的 Font 属性,这会将 ParentFont 重置为 False。

Every time your component's Font property is updated, the component automatically sends CM_PARENTFONTCHANGED messages to each of its child controls, at which time each control checks whether its ParentFont property is True or not. Have you checked to make sure your child control's ParentFont properties are still set to True? Perhaps during their own DFM streaming, the child controls are setting their Font properties, which wouuld reset the ParentFont to False.

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