perl-win32-gui-users Mailing List for Win32::GUI (Page 215)

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<h1>The Win32::GUI FAQ</h1>
<pre>
Aldo Calpini, da...@pe...
Erick Bourgeois, er...@je...=20
Felix Gaehler, fe...@fr...

v0.1, April 14, 2001
</pre>
<p><em>This is the &quot;Frequently Asked Questions&quot; for Perl =
Win32::GUI=20
  module. The questions and answers have been collected from the =
Win32::GUI-Users=20
  mailing list. </em>=20
<hr>
<p><b>Important Notice: This is a first draft version of the FAQ. The =
document=20
  is not yet complete and the answers have not yet been =
verified.</b></p>
<hr>
<H1>General Questions</H1>
<H2>What is Win32::GUI?</H2>
<p>"Win32::GUI is a Win32-platform native graphical user interface =
toolkit for=20
  Perl. Basically, it's an XS implementation of most of the functions =
found in=20
  user32.dll and gdi32.dll, with an object oriented Perl interface and =
an event-based=20
  dialog model that mimic the functionality of visual basic. It was a =
big fun=20
  for me to put it up, hope it will be a fun for you too :-)"</p>

<H2>Where can I get Win32::GUI?</H2>
<p>The creator and chief maintainer of the Win32::GUI module is Aldo =
Calpini.=20
  The module and pertinent information can be found at <a =
href=3D"http://dada.perl.it/">http://dada.perl.it/</a>. <br>
  "The module is actually in beta testing so be warned that syntax and =
behavior=20
  can change with future builds; and of course, that there are many =
incomplete=20
  parts, sparse documentation (you can browse here the work in =
progress), and=20
  generally a lot of things to do."
<p>Win32::GUI for ActiveState Perl 5.6 can be downloaded from the =
ActiveState=20
  Archive using ppm:=20
<pre>
  ppm install Win32::GUI
</pre>
<p>Documentation is available at
<pre>  <a =
href=3D"http://dada.perl.it/gui_docs/gui.html">http://dada.perl.it/gui_do=
cs/gui.html</a>

  <a =
href=3D"http://www.jeb.ca/howto/The_Win32-GUI_HOWTO.html">http://www.jeb.=
ca/howto/The_Win32-GUI_HOWTO.html</a>
</pre>

<H2>What about licensing?</H2>
<p>If I develop a product in Perl with usage of the Win32::GUI module, =
and I spread=20
  (well lets asume for FREE) to the public.. is it still under GNU =
license or=20
  do we have to pay the win32::gui team something ?=20
<p> &quot;No, you don't have to pay anything. I'm not a lawyer and I =
don't want=20
  to pay a lawyer :-) Win32::GUI is released under the Artistic License, =
eg. you=20
  can redistribute it under the same terms of Perl itself.&quot;
<hr>
<H1>Frequent Problems</H1>
<H2>Why does my window seem to freeze when my program is in a loop?</H2>
<p>I can help here. Put a call to DoEvents() inside the
loop. this will ensure that all queued messages are processed
before going on with the loop:
<pre>    Textfield-&gt;change(-text &quot;Processing...&quot;);    =
$$$verify
    foreach $line (<INFILE>) {
        $Window->DoEvents();
        # body of the loop...
    }
    Textfield-&gt;change(-text &quot;completed&quot;);
</pre>
<p>This will, of course, make your loop run slightly slower (almost =
irrelevant=20
  if there is no activity on the window). But there is the advantage =
(other than=20
  having the Textfield saying "Processing...") of being able to stop the =
loop=20
  in the middle by killing the window, or with a 'dedicated' stopbutton, =
for example.=20
<H2>Can I use a window handle in more than one process?</H2>
<p>If you run some lengthy processing like web page retrieval with LWP, =
database=20
  search, file processing etc, and you cannot call =
$Window-&gt;DoEvents() within=20
  that processing, your window will seem to freeze during your =
processing. The=20
  solution to that is, to do the processing in a separate Windows thread =
or process.=20
  ActivePerl 5.6 simulates the &quot;fork&quot; command using Windows =
threads.
<p>&quot;Well, from Windows point of view, it is a thread. From Perl's =
point of=20
  view, it is a process. The Perl interpreter is busily keeping the data =
separate=20
  between the two threads (I'm not sure I understand the complete =
technique of=20
  the magic that does that, but I'm sure it can be made to work because =
the Perl=20
  language doesn't expose "real" addresses (much)).&quot;=20
<p> &quot;On the other hand, the (Unix) model for "fork" is that the =
multiple=20
  processes (threads on Perl for Windows) start off with identical =
data/variables/file=20
  handles. And the Windows model for "windows" is that the windows are =
owned by=20
  a process (not a thread), and can be accessed by any thread that has =
the window=20
  handle. (And in fact, because Windows was developed on DOS, the =
windows are=20
  even a bit visible to other processes, but that doesn't concern us =
here.)&quot;
<p>&quot;By creating the Win32::GUI objects before forking, both the =
parent and=20
  child threads get copies (?) of the object variables. Because of the =
nature=20
  of Windows, the embedded Window handles inside both copies of the =
object variables=20
  are equally usable. Because of the (present) nature of Win32::GUI, =
whereby most=20
  of the parameter data is pumped into Win32 API parameters, and most of =
the return=20
  values are obtained by calling Win32 APIs to obtain it, I have shown =
experimentally=20
  that it is possible to use the Win32::GUI object references from both =
a parent=20
  and a child thread. Now it is important to remember that Windows only =
delivers=20
  window messages to the first thread of a program, so in the Perl =
"fork" environment,=20
  this gets translated to <b>only the parent process of a group of =
Perl-forked=20
  processes can successfully run Win32::GUI::Dialog</b> (Yep, I tried it =
the other=20
  way first, figuring that the parent could more easily monitor the =
child process=20
  for death, since fork returns the child pid, and waitpid works that =
way--but=20
  it just hung, and the windows never appeared). However, <b>the child =
can use=20
  the object references created by Win32::GUI</b> [before the fork] to =
access=20
  the "IsEnabled", "IsVisible" attributes of the window widgets, and =
they are=20
  dynamically updated (not cached in the object). The child can access =
the current=20
  selection from combo boxes. The child can enable and disable widgets, =
and the=20
  display gets updated appropriately. This is quite adequate for my =
application,=20
  which now can do its "long" operations in the child "process", and =
keep the=20
  GUI window "active" (except that certain parts get disabled during =
"long" operations).&quot;
<H2>How can I use Win32::GUI functions in EVAL?</H2>
<p>Yes, Win32::GUI supports things like these (it's really Perl that =
supports=20
  it :-), but you need to escape your window-handler variable $W:=20
<pre>
    eval qq (
        sub main::$subtxt {
            print "button clicked\n";
            <b>\$W</b>->SimpleLabel->Text("Got a click");
        }
    );
    $@ or die &quot;Error in eval: $@&quot;;   $$$verify
</pre>
...and always check for $@ after an eval!

<hr>
<H1>Text Fields</H1>
<H2>How can I change the background color of a text field?</H2>
<p>To change the background color of a Richedit field, use</p>
<pre>  Richedit->SendMessage(EM_SETBKGNDCOLOR, 0, hex('00FF00')); </pre>
<p>This sets the background color to green. Note that the hex() format =
for the=20
  color is expressed as BBGGRR (BB=3Dblue, GG=3Dgreen, RR=3Dred).  </p>
<p>Textfield does not support EM_SETBKGNDCOLOR. have you tried this: =
</p>
<pre>
  # change to red
  Textfield->Change( -background =3D> [ 255, 0, 0 ] );=20
  # repaint the control
  Textfield->InvalidateRect(1); =20
</pre>
<p>Note: Colors can now be given in the HTML notation too (eg. =
"#E3E2CC").

<H2>How can I get a vertical scrollbar in a textfield?</H2>
Add this option when you create the Textfield:
<pre>
  -autovscroll =3D> 1
</pre>
This should do the trick.

<H2>How can I get the selected portion of a textfield?</H2>
<p>There is a Selection method that returns the start and end of the =
selection.=20
  then you just make a substr on the Textfield content:=20
<pre>
  ($from, $to) =3D $Textfield->Selection();
  $var =3D substr($Textfield->Text, $from, $to-$from);
</pre>

<H2>How can I get the _Change event from a RichEdit control?</H2>
<p>&quot;I'd like to share a solution to a problem that has been driving =
me nuts=20
  for a while. I changed a Textfield control to a RichEdit and it would =
not give=20
  me the _Change event. I dug in the GUI.xs and could find nothing =
wrong. I finally=20
  tracked it down to the eventmask being zero, which means that the =
notification=20
  messages don't come to the GUI message loop in the first place. The =
workaround=20
  is to do=20
<pre>
  $MainWindow->myRichEditField->SendMessage (0x445, 0, 1);
</pre>
<p>That sends EM_SETEVENTMASK (0x445) to the control with the ENM_CHANGE =
bit set.=20
  Hope that spares somebody else a headache.&quot;
<hr>
<H1>ListView</H1>
<H2> How can I prevent the user from choosing more than one item in a =
Listview?</H2>
You can use the -singlesel option on the ListView to achieve what you =
want.

<H2>How can I display a popup menu within a ListView?</H2>
<p>Here is an example how it can be done:
<pre>
# define popup menu for listview
my $PopupMenu =3D new Win32::GUI::Menu(
    "Item Properties" =3D> "ItemProp",
    ">&Properties" =3D> "ItemProperties",
);
=20
# get right-click in listview
sub DataView_RightClick {
   my($X, $Y) =3D Win32::GUI::GetCursorPos();
=20
   $MainWindow->TrackPopupMenu($PopupMenu->{ItemProp},$X, $Y);
}
=20
# clicked on particular menu item in popup menu
sub ItemProperties_Click {
   ## code you want to process;
}
</pre>

<hr>
<H1>MessageBox</H1>
<H2>What are the icon, button and modality values for MessageBox?</H2>
<p>&quot;I think these will work, I haven't tried them all.=20
<pre>
Settings
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D
0 - display only the OK button
1 - display OK and Cancel buttons
2 - display Abort, Retry, and Ignore buttons
3 - display Yes, No, and Cancel buttons
4 - display Yes and No buttons
5 - display Retry and Cancel buttons

16 - display Critical Message icon
32 - display Warning Query icon
48 - display Warning Message icon
64 - display Information Message icon

0 - set first button as default
256 - set second button as default
512 - set third button as default
768 - set fourth button as default

=20
Return Values
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
1 - OK
2 - Cancel
3 - Abort
4 - Retry
5 - Ignore
6 - Yes
7 - No&quot;
</pre>
<H1>Cursors</H1>
<H2>How can I change the cursor to hourglass and back?</H2>
<p>$$$tbd (find out first...)
<hr>
<H1>Extensions to Win32::GUI</H1>
<H2>Is there a spreadsheet (grid) look-a-like solution or =
component?</H2>
<p>&quot;No, but I'm thinking about implementing one (just thinking for =
now :-).=20
  &quot;
<H2>Is there a inline webbrowser somewhere ? or a HTML or XML =
parser?</H2>
&quot;No, and I don't think I will try to implement one :-) You should =
instead=20
look at Win32::OLE, to see if you can embed an InternetExplorer instance =
in a=20
window. That said, it seems that RichEdit 3.0 (available in Windows =
2000) has=20
a lot of nice features, that I'll try to implement if time =
permits.&quot;=20
<H2>Is there support for JPG or common image formats like .PNG or =
.GIF?</H2>
<p>&quot;Support is for .BMP files only. There is something in the Win32 =
API about=20
  JPGs, but I have not yet investigated it thoroughly.&quot;=20
<p>$$$How to convert JPG and GIF to BMP in Perl (tbd)

<H2>Is there a Win32-GUI-Builder available (i.e. a visual aid in =
designing the GUI)?</H2>
<p>yes, well.. at least a basic one. Download
<pre>
  <a =
href=3D"ftp://ftp.wh.whoi.edu/pub/gb109.zip">ftp://ftp.wh.whoi.edu/pub/gb=
109.zip</a>
</pre>
For more information, see in the Win32::GUI mailing-list, the mails from =
David Hiltz.

<H2>How can I deal with moving and resizing stuff when a window is =
resized?</H2>
<p>&quot;Dealing with moving and resizing stuff when a window is resized =
is really=20
  annoying, not to mention boring. So I created a class to make that =
easier. That=20
  was a lot more fun for some reason :) Anyway, the result is =
Win32::GUI::Resizer.=20
<pre>
  <a =
href=3D"http://www.bahnhof.se/~johanl/perl/Win32GUI/">http://www.bahnhof.=
se/~johanl/perl/Win32GUI/</a>
</pre>
Please try it out if you like and let me know what you think. &quot;=20
<p>$$$Source: mail from Johan Lindstr=F6m, Sourcerer, Boss Casinos Ltd, =
Antigua,=20
  jp...@bo...=20
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perl-win32-gui-users Mailing List for Win32::GUI (Page 215)

perl-win32-gui-users — Using the Win32::GUI Perl extension