delphi Activex and parented forms error - forms

Question

i try to fix up my activex project and i had errors , i have 2 forms in my activex project first form hold tmemo and button to call second form as parented form every thing works fine till now but i cannot set any record from second form to first form control always get access violation so i decided to show result before set tmemo.text control in the first form and actually result is showing but but cannot be set into the first form here is my project code
unit main1;
{$WARN SYMBOL_PLATFORM OFF}
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ActiveX, AxCtrls, embed_TLB, StdVcl, Vcl.StdCtrls;
type
Tform1 = class(TForm, Iform1)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
protected
{ Protected declarations }
public
{ Public declarations }
procedure showEmo(L,T:Integer);
end;
var
Form1 : Tform1;
implementation
uses ComObj, ComServ, main2;
{$R *.DFM}
{ Tform1 }
procedure Tform1.Button1Click(Sender: TObject);
var
Rect: TRect;
begin
GetWindowRect(Self.button1.Handle, Rect);
showEmo(Rect.Left + 70,(Rect.Top - 290));
end;
procedure Tform1.FormCreate(Sender: TObject);
begin
Form2 := TForm2.Createparented(0);
end;
procedure TForm1.showEmo(L,T:Integer);
var
Rect: TRect;
begin
try
GetWindowRect(button1.Handle, Rect);
begin
Form2.FormStyle := fsStayOnTop;
end;
Form2.Left := L;//Rect.Left;
Form2.top := T;//Rect.Top - emo.Height;
finally
Form2.Visible := not (Form2.visible);
end;
end;
initialization
TActiveFormFactory.Create(
ComServer,
TActiveFormControl,
Tform1,
Class_form1,
0,
'',
OLEMISC_SIMPLEFRAME or OLEMISC_ACTSLIKELABEL,
tmApartment);
end.
Form 2
unit main2;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.OleCtrls, SHDocVw_EWB, EwbCore,
EmbeddedWB, MSHTML_EWB, Vcl.StdCtrls;
type
TForm2 = class(TForm)
ewbpage: TEmbeddedWB;
load: TMemo;
procedure FormCreate(Sender: TObject);
procedure ewbpageBeforeNavigate2(ASender: TObject; const pDisp: IDispatch;
var URL, Flags, TargetFrameName, PostData, Headers: OleVariant;
var Cancel: WordBool);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form2: TForm2;
implementation
uses main1;
{$R *.dfm}
procedure TForm2.ewbpageBeforeNavigate2(ASender: TObject; const pDisp: IDispatch;
var URL, Flags, TargetFrameName, PostData, Headers: OleVariant;
var Cancel: WordBool);
var
MousePos: TPoint;
HtmlElement: IHTMLElement;
iHTMLDoc: IHtmlDocument2;
begin
if Pos('#sm',URL)>0 then
begin
if Supports(ewbpage.Document, IHtmlDocument2, iHTMLDoc) then
begin
if GetCursorPos(MousePos) then
begin
MousePos := ewbpage.ScreenToClient(MousePos);
HtmlElement := iHTMLDoc.ElementFromPoint(MousePos.X, MousePos.Y);
if Assigned(HtmlElement) then
showmessage(HtmlElement.getAttribute('id', 0));
form1.Memo1.Text := HtmlElement.getAttribute('id', 0);
Cancel := True;
Self.Close;
end;
end;
end;
end;
procedure TForm2.FormCreate(Sender: TObject);
begin
ewbpage.LoadFromStrings(load.Lines);
end;
end.
and the question is why i get this error
Access violation at address 07C734FC in module 'EMBEDA~1.OCX'. Read of
address 000003B4.
at this line
form1.Memo1.Text := HtmlElement.getAttribute('id', 0);
why i cannot set result from second form to first form ? what i did wrong here is the full project for better understand
http://www.mediafire.com/download/zn7hzoxze2390a3/embeddedactivex.zip

Answer 1

You will see this issue once you start to format your code properly
procedure TForm2.ewbpageBeforeNavigate2(ASender: TObject; const pDisp: IDispatch;
var URL, Flags, TargetFrameName, PostData, Headers: OleVariant;
var Cancel: WordBool);
var
MousePos: TPoint;
HtmlElement: IHTMLElement;
iHTMLDoc: IHtmlDocument2;
begin
if Pos('#sm',URL)>0 then
begin
if Supports(ewbpage.Document, IHtmlDocument2, iHTMLDoc) then
begin
if GetCursorPos(MousePos) then
begin
MousePos := ewbpage.ScreenToClient(MousePos);
HtmlElement := iHTMLDoc.ElementFromPoint(MousePos.X, MousePos.Y);
// if we have a valid HtmlElement ...
if Assigned(HtmlElement)
then // show a message
showmessage(HtmlElement.getAttribute('id', 0));
// now we do not care about if HtmlElement is valid or not
form1.Memo1.Text := HtmlElement.getAttribute('id', 0);
Cancel := True;
Self.Close;
end;
end;
end;
end;
To only solve your current access violation you simply put a begin end block around all the lines that will use HtmlElement.
HtmlElement := iHTMLDoc.ElementFromPoint( MousePos.X, MousePos.Y );
if Assigned( HtmlElement )
then
begin
showmessage( HtmlElement.getAttribute( 'id', 0 ) );
form1.Memo1.Text := HtmlElement.getAttribute( 'id', 0 );
end;
But there are some more issues in your code. You should not use the global variables form1 and form2. Instead pass the form instance to the created TForm2 instance or even better a callback method.