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>Aspect Frames</A
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><P
>The aspect frame widget is like a frame widget, except that it also
enforces the aspect ratio (that is, the ratio of the width to the
height) of the child widget to have a certain value, adding extra
space if necessary. This is useful, for instance, if you want to
preview a larger image. The size of the preview should vary when the
user resizes the window, but the aspect ratio needs to always match
the original image.</P
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>To create a new aspect frame use:</P
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><PRE
CLASS="PROGRAMLISTING"
>GtkWidget *gtk_aspect_frame_new( const gchar *label,
gfloat xalign,
gfloat yalign,
gfloat ratio,
gboolean obey_child);</PRE
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><P
><TT
CLASS="LITERAL"
>xalign</TT
> and <TT
CLASS="LITERAL"
>yalign</TT
> specify alignment as with Alignment
widgets. If <TT
CLASS="LITERAL"
>obey_child</TT
> is TRUE, the aspect ratio of a child
widget will match the aspect ratio of the ideal size it requests.
Otherwise, it is given by <TT
CLASS="LITERAL"
>ratio</TT
>.</P
><P
>To change the options of an existing aspect frame, you can use:</P
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><PRE
CLASS="PROGRAMLISTING"
>void gtk_aspect_frame_set( GtkAspectFrame *aspect_frame,
gfloat xalign,
gfloat yalign,
gfloat ratio,
gboolean obey_child);</PRE
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><P
>As an example, the following program uses an AspectFrame to present a
drawing area whose aspect ratio will always be 2:1, no matter how the
user resizes the top-level window.</P
><P
><SPAN
CLASS="INLINEMEDIAOBJECT"
><IMG
SRC="images/aspectframe.png"></SPAN
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><PRE
CLASS="PROGRAMLISTING"
> #include <gtk/gtk.h>
int main( int argc,
char *argv[] )
{
GtkWidget *window;
GtkWidget *aspect_frame;
GtkWidget *drawing_area;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Aspect Frame");
g_signal_connect (window, "destroy",
G_CALLBACK (gtk_main_quit), NULL);
gtk_container_set_border_width (GTK_CONTAINER (window), 10);
/* Create an aspect_frame and add it to our toplevel window */
aspect_frame = gtk_aspect_frame_new ("2x1", /* label */
0.5, /* center x */
0.5, /* center y */
2, /* xsize/ysize = 2 */
FALSE /* ignore child's aspect */);
gtk_container_add (GTK_CONTAINER (window), aspect_frame);
gtk_widget_show (aspect_frame);
/* Now add a child widget to the aspect frame */
drawing_area = gtk_drawing_area_new ();
/* Ask for a 200x200 window, but the AspectFrame will give us a 200x100
* window since we are forcing a 2x1 aspect ratio */
gtk_widget_set_size_request (drawing_area, 200, 200);
gtk_container_add (GTK_CONTAINER (aspect_frame), drawing_area);
gtk_widget_show (drawing_area);
gtk_widget_show (window);
gtk_main ();
return 0;
}</PRE
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