open file

[scons]

ok another problem

I have a ListBox and I want to open the selected file on double click, with the standard windows program.

this is my code:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListBox1DblClick(Sender: TObject);
2. var
3.   i: integer;
4. begin
5.   for i:=0 to ListBox1.Count -1  do
6.   if ListBox1.ItemIndex = 1 then
7.     ShellExecute(Form1.Handle, PChar('open'),PChar(ListBox1.ItemIndex),
8.          PChar(''), PChar(''), 1);
9. end;

nothing happens, no error code.

what did I mess up this time ?

[FTurtle]

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListBox1DblClick(Sender: TObject);
2. var
3.   i: Integer;
4.   s: UnicodeString;
5. begin
6.   i := ListBox1.ItemIndex;
7.   if i<0 then Exit; // -1 means there is no selected item
8.   s := ListBox1.Items[i];
9.  
10.   ShellExecute(Handle, PWideChar('open'),PWideChar(s),
11.                PWideChar(''), PWideChar(''), 1);
12. end;
13.  

[scons]

Your solution gave me an error, but, when I changed it to:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListBox1DblClick(Sender: TObject);
2. var
3.   i: Integer;
4.   s: UnicodeString;
5. begin
6.   i := ListBox1.ItemIndex;
7.   if i<0 then Exit; // -1 means there is no selected item
8.   s := ListBox1.Items[i];
9.   ShellExecute(Handle, PChar('open'),PChar(s),
10.                PChar(''), PChar(''), 1);
11. end;

it works !!

Thank you for pointing me in the right direction FTurtle

[Bart]

Casting a UnicodeString to PChar makes no sense to me?

Bart

[balazsszekely]

It should be more like this:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListBox1DblClick(Sender: TObject);
2. var
3.   I: Integer;
4.   WS: WideString;
5. begin
6.   I := ListBox1.ItemIndex;
7.   if I < 0 then
8.     Exit;
9.   WS := WideString(ListBox1.Items[I]); //or UTF8ToUTF16(ListBox1.Items[I]) from LazUTF8
10.   ShellExecuteW(Handle, PWideChar('open'), PWideChar(WS), PWideChar(''), PWideChar(''), SW_SHOW);
11. end;  

[engkin]

Using FPC 3.0+:

Code: Pascal  [Select][+][-]

1. ShellExecuteW(Handle, PWideChar('open'), PWideChar(WS), PWideChar(''), PWideChar(''), SW_SHOW);

is identical to:

Code: Pascal  [Select][+][-]

1. ShellExecuteW(Handle, 'open', @WS[1], '', '', SW_SHOW);

and

Code: Pascal  [Select][+][-]

1. WS := WideString(ListBox1.Items[I]);

is also identical to:

Code: Pascal  [Select][+][-]

1. WS := ListBox1.Items[I];

except it shows a warning: Implicit string type conversion from "AnsiString" to "WideString"

[balazsszekely]

@engkin

Unfortunately, it has been proved many times before that the new "improved unicode support" sometimes will fail, or at least will not work as it should. I'm not saying in this particular case you're not right, but personally I prefer to do the conversion manually.

[JuhaManninen]

Unfortunately, it has been proved many times before that the new "improved unicode support" sometimes will fail, or at least will not work as it should. I'm not saying in this particular case you're not right, but personally I prefer to do the conversion manually.

When the dynamic encoding of a string is correct then the automatic conversion should work always. Otherwise FPC 3 has a bug which I don't know about.
I would like to know the cases where it does not work and then at least document them.

[scons]

I can confirm this solution works also without any errors.

It should be more like this:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ListBox1DblClick(Sender: TObject);
2. var
3.   I: Integer;
4.   WS: WideString;
5. begin
6.   I := ListBox1.ItemIndex;
7.   if I < 0 then
8.     Exit;
9.   WS := WideString(ListBox1.Items[I]); //or UTF8ToUTF16(ListBox1.Items[I]) from LazUTF8
10.   ShellExecuteW(Handle, PWideChar('open'), PWideChar(WS), PWideChar(''), PWideChar(''), SW_SHOW);
11. end;  

[scons]

This solution also works, with the warning.

Using FPC 3.0+:

Code: Pascal  [Select][+][-]

1. ShellExecuteW(Handle, PWideChar('open'), PWideChar(WS), PWideChar(''), PWideChar(''), SW_SHOW);

is identical to:

Code: Pascal  [Select][+][-]

1. ShellExecuteW(Handle, 'open', @WS[1], '', '', SW_SHOW);

and

Code: Pascal  [Select][+][-]

1. WS := WideString(ListBox1.Items[I]);

is also identical to:

Code: Pascal  [Select][+][-]

1. WS := ListBox1.Items[I];

except it shows a warning: Implicit string type conversion from "AnsiString" to "WideString"

[JuhaManninen]

I can confirm this solution works also without any errors.

Code: Pascal  [Select][+][-]

1.   WS := WideString(ListBox1.Items[I]); //or UTF8ToUTF16(ListBox1.Items[I]) from LazUTF8

If you need a typecast there then FPC has a bug.

In fact the whole ShellExecute discussion is useless. Instead of ShellExecute you should use the cross-platform

Code: Pascal  [Select][+][-]

1. function OpenDocument(APath: String): Boolean;

defined in LCLIntf.