Re: Releasing client-side pixmaps

[Olexiy Avramchenko <ath beast stu cn ua>]

Dag Helstad wrote:

> Hi, I'm trying to minimize the memory usage of a GTK application which uses
> a GtkPixmap to show a background pixmap. 
>
> The X server keeps a server-side copy of the pixmap, but it seems a
> client-side copy is kept in my application.
X pixmaps unlike the X images are always (except the MIT-SHM shared pixmaps)
stored on the Xserver side. The copy you mean is only small structure 
(GdkPixmap)
gdk uses to represent the X pixmap.

> Here is the code fragment which creates a gtk_pixmap from my bitmap (which
> is stored in PNG format):
>
> /****************************/
> GtkWidget* LoadImage(const std::string& location)
> {
>   GtkWidget* widget = NULL;
>   GdkPixbuf* image = NULL;
>   GdkPixmap* pixmap = NULL;
>   GdkBitmap* mask = NULL;
>
>   image=gdk_pixbuf_new_from_file(location.c_str());
image's ref count == 1

>   gdk_pixbuf_render_pixmap_and_mask(image, &pixmap, &mask, 100);
pixmap's and mask's ref counts == 1

>   widget = gtk_pixmap_new(pixmap, mask);
GtkPixmap adds its own references to pixmap and mask, so
pixmap's and mask's ref counts == 2

>   gdk_pixmap_unref(pixmap);
pixmap's ref count == 1, so its still alive

>   gdk_bitmap_unref(mask);
mask's ref count == 1, so its still alive

>   gdk_pixbuf_unref(image);
image's ref count reaches 0 - it freed.

>   
>   return widget;
> }
> /****************************/
>
> I unref() the GdkPixbuf, GdkPixmap and GdkBitmap. Does the GtkPixmap widget
> keep a client-side copy of the pixmap? Can I free the client-side pixmap
> without destroying my GtkPixmap widget?
The GtkPixmap widget (deprecated in gtk+-2.0, by the way) doesnt create 
a copy
of the GdkPixmap and GdkBitmap it increases thier ref counts instead.

Olexiy