Re: g_idle_add() clarification

Thanks Chris,
I think that not only is my code broken my idea on how to do what I want is broken. I must fix that before I start on the code.

My starting point was two button, scan off and scan on in glade. Scan on sets a flag and it scans til the off button is pressed. So the off button could not be pressed til end-of-scan, a situation commonly known as a deadly embrace in hardware design. After that g_idle_add() was pointed out to me and I've been innovating rather blindly ever since.

I interpreted g_idle_add() as inserting Scanning() into the main loop and if Scanning returned FALSE it was removed from the main loop. So I guess I'm not understanding the following explanation of
guint g_idle_add(GSourceFunc function, gpointer data); :-

Adds a function to be called whenever there are no higher priority events pending to the default main loop. The function is given the default idle priority, G_PRIORITY_DEFAULT_IDLE. If the fRegards Ian.unction returns FALSE it is automatically removed from the list of event sources and will not be called again. This internally creates a main loop source using g_idle_source_new() and attaches it to the main loop context using g_source_attach(). You can do these steps manually if you need greater control.
function,  function to call
data, data to pass to function .

Also Chris you indicated that maybe g_idle_add() should not be in a callback. Maybe it should be in main() after gtk_widget_show (window); I'm stuck for the moment not understanding.

Richard's suggestion improved things but my code and idea is still broken on exiting Scanning()

        Regards Ian.

On 01/20/2015 04:57 PM, Chris Vine wrote:
On Tue, 20 Jan 2015 16:47:27 -0500
Ian Chapman <ichapman videotron ca> wrote:
Thanks for your reply Richard.
Yes, I know that.  I thought Scanning() was a lower level than the
gtk window and thus the StartScan_active() would exit before the
mainloop would add Scanning() and then only execute Scanning() when
nothing else (signals) was active.

I was also asking about the GLib-CRITICAL stuff on exiting
Scanning().  Ian.

On 01/20/2015 03:34 PM, richard boaz wrote:

you are calling the function Scanning() in the g_idle_add() call.g_idle_add()


On Tue, Jan 20, 2015 at 3:23 PM, Ian Chapman <ichapman videotron ca
<mailto:ichapman videotron ca>> wrote:

     Hi all,

     Sorry to bother but I'm lost with the workings of

     guint g_idle_add ()

     My code is as

     extern "C"

     void on_StartScan_activate() //from gtk menu item

     { printf("Start Scan Activated. \n");

     scan_on_fg =1;

     Scanning_lvl = g_idle_add((GSourceFunc) Scanning(), (gpointer)
     printf("Exiting StartScan.\n");  //main.cpp, Line 129

     return; }

     I get to Scanning() okay but I don't exit
on_StartScan_activeat() until I exit Scanning() (not what I

     Worse still when I step through Scanning as I exit I get

     (gdb) next

     (main:24011): GLib-CRITICAL **: g_idle_add_full: assertion
     `function != NULL' failed

     on_StartScan_activate () at main.cpp:129

     (gdb) next

     Exiting StartScan.

     guint Scanning(void)

     while(1 == scan_on_fg)

     { //Bean counting with rest of GUI in control, I hoped. }

     return(FALSE); //Remove this thread.


     Regards Ian.
What Richard is telling you is that your code is broken.  Fix that
before dealing with warnings.  The point is that your broken code is
doing what the warning is telling you about - passing a FALSE value
(which equates here to NULL here), as returned by Scanning(), to the
function pointer argument of g_idle_add().

You have other problems.  You are passing a callback to g_idle_add()
which does not have the correct signature and surpressing this failure
by a cast.  (Why?.)  Fix that as well and see what warnings are left

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