Gtk signal with multiple arguments - c

Question

Context
After writing a simple application using a GtkEntry widget to process textual commands from user I would like to do some design changes.
As of now I use signal hook on key-press. If key(s) are a specified value, then show command line and process various actions on entry widget. Like e.g.
Ctrl+a: move cursor to start of input.
Ctrl+u: delete text before the cursor.
...
As well as parsing commands and saving/loading history.
I am not satisfied with how this is stitched together. The command parsing becomes a subset of:
main_window -> mode_check -> command_line_act -> parse_cmd+execute
As I see it one good approach would be to write a new widget using GtkEntry as base – and send signals on command enter. All of the internals like Ctrl+... and history handled by the new widget.
Signals emitted from new widget being e.g.:
"cmdline-abort"
"cmdline-cmd"
...
Status
Have written the base for this but I am at a hault when it comes to emitting signals with more then one argument.
I have:
gtk_signal_emit(obj, sig, 0, command)
|
+---- string.
but would like, (for now at least, most likely more/other down the line.):
gtk_signal_emit(obj, sig, 0, command, length)
gtk_emit_signal Typo fixed. Thanks to jku.. Also, now using g_signal_
In widget code:
static void
cmdline_class_init(CmdlineClass *klass)
{
With one argument I am using g_signal_new() as:
cmdline_signals[CMDLINE_CMD] = g_signal_new(
"cmdline-cmd",
G_TYPE_FROM_CLASS(klass),
G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
G_STRUCT_OFFSET(CmdlineClass, cmdline),
NULL,
NULL,
g_cclosure_marshal_VOID__VOID,
G_TYPE_NONE,
1,
G_TYPE_STRING
);
And as I see it, for two arguments, should change it to something like:
cmdline_signals[CMDLINE_CMD] = g_signal_new(
"cmdline-cmd",
G_TYPE_FROM_CLASS(klass),
G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
G_STRUCT_OFFSET(CmdlineClass, cmdline),
NULL,
NULL,
g_cclosure_user_marshal_VOID__STRING_INT,
G_TYPE_NONE,
2,
G_TYPE_STRING,
G_TYPE_INT
);
Trouble in the garden
Using glib-genmarshal to generate marshals with marshal.list holding:
VOID:STRING,INT
This works, but gives me a warning upon compile time as:
warning: ISO C forbids conversion of object pointer to function pointer type
Caused by this code generated by glib-genmarshal:
typedef void (*GMarshalFunc_VOID__STRING_INT) (gpointer data1,
gpointer arg_1,
gint arg_2,
gpointer data2);
register GMarshalFunc_VOID__STRING_INT callback;
/* GCC Warnig: conversion of object pointer to function => */
callback = (GMarshalFunc_VOID__STRING_INT) (
marshal_data ?
marshal_data :
cc->callback
);
Question
Is this the wrong approach? Is there some way to fix the conversion error? Etc.
As a note: I am fairly new to Gtk, and Gui programming in general.
Side point
There are some deprecations I also wonder if could affect the code / should be avoided:
GtkSignalMarshaller, does this indicate anything about the status of GSignalCMarshaller?
GtkCallbackMarshal, does this indicate anything about the use of marshalers in general?

Answer 1

This warning does appear (with -pedantic) on some signal marshalling code, and not just in your code. As far as I can see you are not doing anything wrong though -- except for using gtk_signal_emit() (I assume you meant that and not gtk_emit_signal() which does not exist as far as I know): you should not use any gtk_signal-prefixed code: that stuff is all deprecated. See the reference for details. Use GObject instead: g_signal_emit() or g_signal_emit_by_name() should work for you.
The signal marshaller deprecations you mention are about this same thing: GObject handles everything related to this now (and has for a long time already).
As practical advice: Often adding things to signal signatures is not worth the trouble, and this might be the case for you as well: maybe your signal does not need the command string at all, and the signal handler could just query it with your_object_get_command()?
Practical advice #2: Consider using GTK+ 3 for new code. Not having all that deprecated stuff around confusing everyone is just lovely.