Trying to edit IHTMLDocument hangs an application

问题:

based on MSHTML documentation for IHTMLDocument2 I'm trying to write simple HTML parser. Unfortunately trying to set edit-mode fails, in other words resultState never gets 'complete' value so application hangs.

{$APPTYPE CONSOLE}

function ParseHtml(doc: TStringList): TStringList;
var
  iHtml: IHTMLDocument2;
  v: Variant;
  msg: tagMSG;
begin
  iHtml := CreateComObject(CLASS_HTMLDocument) as IHTMLDocument2;
  Result := TStringList.Create;
  try
    try
      iHtml.designMode := 'on';
      while iHtml.readyState <> 'complete' do
        PeekMessage(msg, 0, 0, 0, PM_NOREMOVE);
//    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//    above loop never finishes  
      v := VarArrayCreate([0, 0], varVariant);
      v[0] := doc.Text;
      iHtml.write( PSafeArray(TVarData(v).VArray) );
      iHtml.designMode := 'off';
      while iHtml.readyState <> 'complete' do
        PeekMessage(msg, 0, 0, 0, PM_NOREMOVE);
      // processing iHtml.body
      ...
    except
      ...
    end;
  finally
    ...
  end;
  ...
end;

begin
  CoInitialize(nil);
  ...
  CoUninitialize;  
end.

Just curious why readyState property of IHTMLDocument2 interface is never set to 'complete', although based by official documentation it should ?

回答1:

The readyState property is not being set to 'complete' because you have not told the IHTMLDocument2 object to actually load a document yet. You have to load a document, even a blank one (ie: the 'about:blank' URL), in order to affect the readyState property, otherwise it remains at its initial value of 'uninitialized'.

回答2:

No need to set designMode to on. no need to poll the readyState either. it will be set to "complete" as soon as you write and close the document:

program Test;
{$APPTYPE CONSOLE}
uses
  SysUtils,
  MSHTML,
  ActiveX,
  ComObj;

procedure DocumentFromString(Document: IHTMLDocument2; const S: WideString);
var
  v: OleVariant;
begin
  v := VarArrayCreate([0, 0], varVariant);
  v[0] := S;
  Document.Write(PSafeArray(TVarData(v).VArray));
  Document.Close;
end;

var
  Document: IHTMLDocument2;
  Elements: IHTMLElementCollection;
  Element: IHTMLElement;
begin
  CoInitialize(nil);

  Document := CreateComObject(CLASS_HTMLDocument) as IHTMLDocument2;
  DocumentFromString(Document, '<b>Hello</b>');
  Writeln(string(Document.readyState));

  // process the Document here
  Elements := Document.all.tags('b') as IHTMLElementCollection;
  Element := Elements.item(0, '') as IHTMLElement;
  Writeln(string(Element.innerText));
  Readln;

  CoUninitialize;
end.