TChromium : GetSourceProc and Incompatible types: 'regular procedure and method pointer'

I need to get the source HTML from a page loaded in TChromium, but i need to store the source inside a variable of another class. In other words, the callback function needs to be inside another class and i can't do it because this exception :

E2009 Incompatible types: 'regular procedure and method pointer'

Here is my code. It works only if 'StringVisitor' function is outside of 'Form1' class.

Any ideas ?

unit simple1;

interface

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

type
  TForm1 = class(TForm)
    Chromium1: TChromium;
    procedure FormCreate(Sender: TObject);
    procedure Chromium1LoadEnd(Sender: TObject; const browser: ICefBrowser; const frame: ICefFrame;
      httpStatusCode: Integer);
  public
  mySource : string;
  procedure StringVisitor(const str: ustring);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Chromium1LoadEnd(Sender: TObject; const browser: ICefBrowser; const frame: ICefFrame;
  httpStatusCode: Integer);
begin
  Chromium1.Browser.MainFrame.GetSourceProc(StringVisitor);  // error on this line
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
chromium1.load('http://www.google.com');
end;

procedure TForm1.StringVisitor(const str: ustring);
begin
mySource := str;
end;

end.

Ok Using Delphi 7 I was able to reproduce the problem.

After digging into the problem I found out that there are two diffrnet ways of getting the source of the loaded page:

1) procedure GetSourceProc(const proc: TCefStringVisitorProc); as you are using. The problem with that solution is in pre Dlephi 2009 it only accepts a stand-alone procedure, which gives you problems when you have multible instances of you object in which you want to keep you HTML.

2) procedure GetSource(const visitor: ICefStringVisitor);

Let's start by looking at the expected interface

  ICefStringVisitor = interface(ICefBase)
    ['{63ED4D6C-2FC8-4537-964B-B84C008F6158}']
    procedure Visit(const str: ustring);
  end;

So I started looking into that. Aftter digging in unit ceflib; I found TCefStringVisitorOwn and that is the key to your solution.

The interface of TCefStringVisitorOwn is quite simple:

  TCefStringVisitorOwn = class(TCefBaseOwn, ICefStringVisitor)
  protected
    procedure Visit(const str: ustring); virtual;
  public
    constructor Create; virtual;
  end;

So with this in hand I created a descendant of TCefStringVisitorOwn:

unit SourceContainerU;

interface

uses
  ceflib;

type
  ISourceContainer = interface(ICefStringVisitor)
    function Source: ustring;
  end;

  TSourceContainer = class(TCefStringVisitorOwn, ISourceContainer)
  private
    FSource: ustring;
  protected
    procedure Visit(const str: ustring); override;
  public
    function Source: ustring;
  end;

implementation

{ TSourceContainer }

function TSourceContainer.Source: ustring;
begin
  Result := FSource;
end;

procedure TSourceContainer.Visit(const str: ustring);
begin
  FSource := str;
end;

end.

Nothing magic here.

Only thing left is to create a demo project using this class. In my example I create TChromium at runtime. The form contains a button and a Memo and then this code:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    Chromium1: TChromium;
    SourceContainer : ISourceContainer;
    procedure Chromium1LoadEnd(Sender: TObject; const browser: ICefBrowser; const frame: ICefFrame;  httpStatusCode: Integer);
  public
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TForm1 }

procedure TForm1.Chromium1LoadEnd(Sender: TObject;  const browser: ICefBrowser; const frame: ICefFrame;  httpStatusCode: Integer);
begin
  if Frame = nil then
    exit;

  SourceContainer := TSourceContainer.Create;
  Frame.GetSource(SourceContainer);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Chromium1 := TChromium.Create(self);
  Chromium1.Parent := self;
  Chromium1.OnLoadEnd := Chromium1LoadEnd;
  Chromium1.load('http://www.google.com');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if Assigned(SourceContainer) then
    Memo1.Lines.Text := SourceContainer.Source;
end;

end.

This solution has been tested osing the latest version of Chromium, and I've tested it in Delphi 7, Delphi XE and Delphi XE6. I do not own any Delphi 2007 installation, but I belive it should work in wotk in that aswell.