A class to toggle image display in Internet Explorer 5

Problem/Question/Abstract:

Internet Explorer 5 (and others) allows you to toggle image displays. If you are using Twebbrowser this can speed up retrieving webpages as the graphics are not longer fetched.

Answer:

A year ago I had an article published in Delphi Developer on writing Web-robots using the twebbrowser that is part of Internet Explorer and which you can install in Delphi 3 or 4 and comes pre-installed in Delphi 5.

My only gripes with using Twebbrowser are that there is a fair bit of baggage- it renders every web-page which slows things down (especially when it has to retrieve every image on the page).  The class below implements a way of disabling image display (toggling the IE switch programmatically) in IE 5 to speed up web-robots written using it. It hasn’t beeen tested in IE 4 or IE 5.5 though I suspect it will probably work.

type
  TViewIEImage = class
  private
    fSavedimagesVisible: Boolean;
    function GetState: Boolean;
    procedure SetVisible(Visible: Boolean);
  public
    BroadcastChange: Boolean;
    constructor Create;
    destructor Destroy; override;
    property ImagesVisible: Boolean read GetState write SetVisible;
    property SavedImagesVisible: Boolean read fSavedimagesVisible write
      fSavedimagesVisible;
  end;

constructor TViewIEImage.Create;
begin
  fSavedimagesVisible := GetState;
  BroadcastChange := True;
end;

destructor TViewIEImage.Destroy;
begin
  SetVisible(fSavedimagesVisible);
end;

function TViewIEImage.GetState: Boolean;
begin
  Result := GetRegistryValue = 'yes';
end;

procedure TViewIEImage.SetVisible(Visible: Boolean);
var
  Reg: TRegistry;
  Str: string;
begin
  if Visible then
    Str := 'yes'
  else
    Str := 'no';
  Reg := TRegistry.Create;
  try
    Reg.RootKey := HKEY_CURRENT_USER;
    if Reg.OpenKey('\Software\Microsoft\Internet Explorer\Main',
      False) then
      Reg.WriteString('Display Inline Images', Str);
  finally
    Reg.CloseKey;
    Reg.Free;
    inherited;
  end;
  if BroadcastChange or Visible then
    PostMessage(
      HWND_BROADCAST,
      WM_WININICHANGE,
      0,
      Longint(pchar('HKEY_CURRENT_USER\Software\Microsoft\Internet
      Explorer\Main')));
end;

In future articles I will look at writing web robots without using twebbrowser.