Context.Enter 在 CEF3 中总是失败

Question

我在使用存储库 (3.1750.1738) 中最新的 Delphi Chromium 嵌入式代码将 CEF1 项目转换为 CEF3 时遇到了一些问题。简而言之，我曾经有一个我会注册的扩展。然后在 html 端，我将使用本机调用向 Delphi 主机注册一个 javascript 对象。它将存储对象和对象的上下文以供以后调用。但这似乎不适用于 DCEF3。我可以获得对象及其上下文。但是后来当我调用 context.Enter 时，它失败了。我想知道这是否与 cef1 和 cef3 之间的架构变化有关。我已经不得不稍微更改扩展名以在 OnWebkitIniitalized.

中注册它

这是我的代码：

unit MainUnit;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, cefvcl, ceflib, StdCtrls;

type
  TMainForm = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    Guest: ICefv8Value;
    GuestContext: ICefv8Context;
    Browser: TChromium;
    procedure BrowserConsoleMessage(Sender: TObject; const browser: ICefBrowser;
      const message, source: ustring; line: Integer; out Result: Boolean);
  public
    function ExtensionExecute(const name: ustring; const obj: ICefv8Value;
      const arguments: TCefv8ValueArray; var retval: ICefv8Value;
      var exception: ustring): Boolean;
  end;

var
  MainForm: TMainForm;
  BrowserExt: TCefv8HandlerOwn;

implementation

{$R *.dfm}

const
  code =
   'var cef;'+
   'if (!cef)'+
   '  cef = {};'+
   'if (!cef.nes)'+
   '  cef.nes = {};'+
   '(function() {'+
   '  cef.nes.callNative = function() {'+
   '    native function callNative();'+
   '    return callNative.apply(this, arguments);'+
   '  };'+
   '})();';

type
  TCustomRenderProcessHandler = class(TCefRenderProcessHandlerOwn)
  protected
    procedure OnWebKitInitialized; override;
  end;

  TExtension = class(TCefv8HandlerOwn)
  protected
    function Execute(const name: ustring; const obj: ICefv8Value;
      const arguments: TCefv8ValueArray; var retval: ICefv8Value;
      var exception: ustring): Boolean; override;
  public
    Host: TMainForm;
  end;

function TExtension.Execute(const name: ustring; const obj: ICefv8Value;
  const arguments: TCefv8ValueArray; var retval: ICefv8Value;
  var exception: ustring): Boolean;
begin
  Result := Host.ExtensionExecute(name, obj, arguments, retval, exception);
end;

procedure TMainForm.Button1Click(Sender: TObject);
var
  o: ICefv8Value;
begin
  if GuestContext.Enter then
  begin
    o := Guest.GetValueByKey('foo');
    OutputDebugString(PChar('foo found now: ' + BoolToStr(Assigned(o), True)));
    GuestContext.Exit;
  end
  else
    OutputDebugString('GuestContext.Enter failed');
end;

function TMainForm.ExtensionExecute(const name: ustring; const obj: ICefv8Value;
  const arguments: TCefv8ValueArray; var retval: ICefv8Value;
  var exception: ustring): Boolean;
var
  o: ICefv8Value;
begin
  OutputDebugStringW(PWideChar('Execute: ' + name));
  if name = 'callNative' then
  begin
    GuestContext := TCefv8ContextRef.Current;
    Guest := arguments[0];

    o := Guest.GetValueByKey('foo');
    OutputDebugString(PChar('foo found: ' + BoolToStr(Assigned(o), True)));
  end;

  Result := True;
end;

procedure TMainForm.FormCreate(Sender: TObject);
begin
  Browser := TChromium.Create(Self);

  Browser.Options.JavascriptDomPaste := STATE_DISABLED;
  Browser.Options.CaretBrowsing := STATE_DISABLED;

  Browser.OnConsoleMessage := BrowserConsoleMessage;

  Browser.Color := clWhite;
  Browser.Align := alClient;

  Browser.DefaultUrl := 'http://localhost/test2/home.html';

  Browser.Parent := Self;

  BrowserExt := TExtension.Create;
  TExtension(BrowserExt).Host := Self;

  Browser.Load(Browser.DefaultUrl);
end;

procedure TMainForm.BrowserConsoleMessage(Sender: TObject;
    const browser: ICefBrowser; const message, source: ustring; line: Integer;
    out Result: Boolean);
begin
  OutputDebugStringW(PWideChar('[line ' + IntToStr(Line) + '] ' + message));
end;

{ TCustomRenderProcessHandler }

procedure TCustomRenderProcessHandler.OnWebKitInitialized;
begin
  inherited;

  CefRegisterExtension('v8/nes', code, BrowserExt as ICefV8Handler);
end;

initialization
  CefRemoteDebuggingPort := 9000;
  CefRenderProcessHandler := TCustomRenderProcessHandler.Create;
  CefBrowserProcessHandler := TCefBrowserProcessHandlerOwn.Create;

end.

和 javascript 代码：

console.log('startup');

var guest = {foo:function() {
  console.log('foo called');

  return 42;
}};

if (typeof(cef) !== "undefined") {
  console.log('registering guest');

  cef.nes.callNative(guest);
}
else {
  console.log('no cef');
}

console.log('startup done');

TMainForm.ExtensionExecute 被触发并发生 callNative。但是后来当我执行 Button1Click 时，上下文 Enter 总是 returns False.

Answer 1

这是由于 CEF3 架构更改为 multi-thread/process。您不能再直接调用代码，而必须使用 Browser.SendProcessMessage 来回传递消息并使用 OnProcessMessage 处理程序处理它们。

Context.Enter 在 CEF3 中总是失败

Context.Enter always fails in CEF3

delphi

chromium-embedded