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GTK+ Forums
Discussion forum for GTK+ and Programming. Ask questions, troubleshoot problems, view and post example code, or express your opinions.
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krisri
Familiar Face
Joined: 09 Nov 2009
Posts: 5
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 Posted: Tue Nov 24, 2009 2:51 pm Post subject: Width Of Button |
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Hi
I have 3 Buttons of one window,how can i know the width and height of each button.
rgds
kris |
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LGV
Familiar Face
Joined: 31 Dec 2009
Posts: 5
Location: Argentina
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| Posted: Fri Jan 01, 2010 6:54 pm Post subject: |
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I'm not sure if this is the correct way of doing it, but take look at the "allocation" member of the widget, it has the following variables:
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GtkWidget* button;
button->allocation.height;
button->allocation.width;
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tadeboro
Never Seen the Sunlight
Joined: 23 Jul 2008
Posts: 2114
Location: Slovenia
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| Posted: Fri Jan 01, 2010 7:28 pm Post subject: |
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Hello.
Method that LGV proposed is the right one. There is only one thing I would like to add. Since GTK+-3.0, all widgets will be opaque structures, which means that direct access to structure fields will not be possible anymore. I would recommend adding some #if preprocessor statements that will check for GTK+ version and if they detect version >= 2.18, you should use gtk_widget_get_allocation() instead.
Tadej |
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dreblen
Never Seen the Sunlight
Joined: 14 Jun 2007
Posts: 936
Location: Falun, WI USA
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| Posted: Sun Jan 03, 2010 12:59 am Post subject: |
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Just to add to the #if recommendation, I would suggest that you do something like the following once,
rather than doing and #if check every time you want an allocation (note that this is essentially the content of the gtk_widget_get_allocation function):
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| #if !GTK_CHECK_VERSION(2, 18, 0)
#define gtk_widget_get_allocation(wi, al) \
g_return_if_fail(GTK_IS_WIDGET(wi)); \
g_return_if_fail(al != NULL); \
*al = GTK_WIDGET(wi)->allocation
#endif /* !GTK_CHECK_VERSION(2, 18, 0) */ |
See here for more information on GTK_CHECK_VERSION. |
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tadeboro
Never Seen the Sunlight
Joined: 23 Jul 2008
Posts: 2114
Location: Slovenia
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| Posted: Sun Jan 03, 2010 9:22 am Post subject: |
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Hello.
| dreblen wrote: | | Code: (C) | 1
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| #if !GTK_CHECK_VERSION(2, 18, 0)
#define gtk_widget_get_allocation(wi, al) \
g_return_if_fail(GTK_IS_WIDGET(wi)); \
g_return_if_fail(al != NULL); \
*al = GTK_WIDGET(wi)->allocation
#endif /* !GTK_CHECK_VERSION(2, 18, 0) */ | |
This macro will cause code to malfunction if any of the assertions fail. Take for example this code, that assumes that last parameter passed in is valid GtkWidget:
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| static gboolean
cb_button_press( GtkWidget *widget,
GdkEventButton *event,
GtkWidget *data )
{
GtkAllocation allocation;
gtk_widget_get_allocation( data, &allocation );
/* Some important functionality here */
return( FALSE );
} |
If last parameter is not a widget by any chance, this code will still perform properly with GTK+ >= 2.18.0, but if you macro steps in, the whole cb_button_press() callback will be terminated prematurely and will even return with no value.
One way of writing this macro to emulate function would be like this:
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| #if ! GTK_CHECK_VERSION( 2, 18, 0 )
#define gtk_widget_get_allocation( wi, al ) \
if( ( al ) ) \
if( GTK_IS_WIDGET( ( wi ) ) ) \
*( al ) = GTK_WIDGET( ( wi ) )->allocation
#endif |
The way I would handle this situation would be to use autotools to detect GTK+ version and conditionally compile in a file with substitute functions for missing API. But since this is quite demanding stuff, I opted for single #if preprocessor in this case.
Tadej |
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dreblen
Never Seen the Sunlight
Joined: 14 Jun 2007
Posts: 936
Location: Falun, WI USA
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| Posted: Sun Jan 03, 2010 11:34 pm Post subject: |
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Thank you for pointing out my error.
Now that I've gone back and looked at this, I realize that gcc would have even warned me about this if I'd have had -Wall on like I usually do. |
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