Yes, that's so. The number of param passing depends on detailed signal
which is invoked. For instance, "clicked" is a signal that invokes <br><br><div class="code_highlight code-box" style="unicode-bidi: embed; direction: ltr;"><code><span style="color: rgb(0, 0, 0);">
void user_function (GtkButton *button, gpointer user_data) : Run First / Action</span>
</code></div><br>so my func should be <br><br><div class="code_highlight code-box" style="unicode-bidi: embed; direction: ltr;"><code><span style="color: rgb(0, 0, 0);">
void callback_do_test (GtkButton *button, gpointer data )</span>
</code></div> <br>instead of <br><br><div class="code_highlight code-box" style="unicode-bidi: embed; direction: ltr;"><code><span style="color: rgb(0, 0, 0);">
void callback_do_test (GtkWidget* widget, GtkAction * action, gpointer data )</span>
</code></div><br><br>Type-casting is no problem but redundant param will lead to application accessing arbitrary data as you said.<br><br>That's the reason why the app ran so unstably.<br><br>Hey, don't know why it ran well on Maemo 3.x. Is it a BUG? Don't know if 3.x is open now.<br>
<br>Thanks a lot one more time, Markku Vire!<br><br>Have a nice day!<br><br><div class="gmail_quote">On Mon, Feb 25, 2008 at 6:31 PM, Jakov <<a href="mailto:dkymail@gmail.com">dkymail@gmail.com</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>Oh my God! I didn't realize that for a long time! This morning after such a stupid prob, I removed maemo 4.0 and installed Maemo 3.2. Not tested yet, but I think it should have the same params counts as you say. I'll tell you the result soon. Just a quick msg now to say thank you! Thanks so much, Markku Vire!<div>
<div></div><div class="Wj3C7c"><br>
<br><br><br><div class="gmail_quote">On Mon, Feb 25, 2008 at 6:00 PM, Markku Vire <<a href="mailto:markku.vire@movial.fi" target="_blank">markku.vire@movial.fi</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Hi,<br>
<br>
The problem behind "changing parameters" is that you are attaching wrong<br>
type of singal handler to signal (i.e. the number/type of parameters<br>
don't match).<br>
<br>
I didn't actually try your code, but at least you cannot connect<br>
"callback_do_test" (3 parameters) to "clicked" signal (2 parameters).<br>
This will lead to you application accessing arbitrary data.<br>
<br>
Hope this helps,<br>
<br>
-Markku-<br>
<div><div></div><div><br>
Jakov wrote:<br>
> Hi,<br>
><br>
> I have a very simple app running on Maemo 4.0 with a textbox and a button.<br>
> As I click on the button, a callback function is invoked to show the content<br>
> of the textbox. I don't know why the data pointer which is passed to<br>
> callback function is sometimes NULL:<br>
> - if I click on the textbox (a virtual keyboard shown below) and then click<br>
> on the button, the callback function failed due to assertion of data pointer<br>
> - if I just click the button (don't focus on the textbox), the data pointer<br>
> is not NULL, but the child of it is NULL.<br>
><br>
> I'm so confused. It didn't happen on Maemo 3.2 before.<br>
><br>
> Here's the code of 4 files (interface.*, callbacks.*) in my project /src/ui,<br>
> I follow the structure of maemopad-2.1<br>
> <a href="http://paste.org/index.php?id=2098" target="_blank">http://paste.org/index.php?id=2098</a><br>
><br>
> If you're interested in solving this problem, please help me out. Thanks<br>
> very much!<br>
><br>
> Best regards,<br>
> Jakov<br>
><br>
><br>
><br>
</div></div>> ------------------------------------------------------------------------<br>
><br>
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<br>
</blockquote></div><br>
</div></div></blockquote></div><br>