Question

I’m having some troubles with javascript error handling in WebBrowser on Delphi 2010.

I’m using WebBrowser with enabled silent property. Seems OK, but there is one issue on sites with buggy scripts: it seems like part of script after error doesn’t executes. Results of some script slightly differs from IE.

Do you have any idea how this issue can be solved?

Answer 1

You can use the IOleCommandTarget and in its IOleCommandTarget.Exec method catch the OLECMDID_SHOWSCRIPTERROR command.

In the following example I’ve used the interposed class so if you put this code into your unit, only those web browsers on the form or those created in this unit dynamically will get this behavior.

uses
  SHDocVw, ActiveX;

type
  TWebBrowser = class(SHDocVw.TWebBrowser, IOleCommandTarget)
  private
    function QueryStatus(CmdGroup: PGUID; cCmds: Cardinal; prgCmds: POleCmd;
      CmdText: POleCmdText): HRESULT; stdcall;
    function Exec(CmdGroup: PGUID; nCmdID, nCmdexecopt: DWORD; 
      const vaIn: OleVariant; var vaOut: OleVariant): HRESULT; stdcall;
  end;

implementation

function TWebBrowser.QueryStatus(CmdGroup: PGUID; cCmds: Cardinal; 
  prgCmds: POleCmd; CmdText: POleCmdText): HRESULT; stdcall;
begin
  Result := S_OK;
end;

function TWebBrowser.Exec(CmdGroup: PGUID; nCmdID, nCmdexecopt: DWORD; 
  const vaIn: OleVariant; var vaOut: OleVariant): HRESULT; stdcall;
begin
  // presume that all commands can be executed; for list of available commands
  // see SHDocVw.pas unit, using this event you can suppress or create custom 
  // events for more than just script error dialogs, there are commands like 
  // undo, redo, refresh, open, save, print etc. etc.
  // be careful, because not all command results are meaningful, like the one
  // with script error message boxes, I would expect that if you return S_OK,
  // the error dialog will be displayed, but it's vice-versa
  Result := S_OK;

  // there's a script error in the currently executed script, so
  if nCmdID = OLECMDID_SHOWSCRIPTERROR then
  begin
    // if you return S_FALSE, the script error dialog is shown
    Result := S_FALSE;
    // if you return S_OK, the script error dialog is suppressed
    Result := S_OK;
  end;
end;