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GnomeDbCanvas

<!-- ##### SECTION Short_Description ##### -->
Base class for all the #GnomeCanvas derived widgets in libgnomedb.

<!-- ##### SECTION Long_Description ##### -->
<para>
This abstract class adds some basic functionnalities on top of the #GnomeCanvas canvas such as:
<itemizedlist>
<listitem><para>synchronisation with a #GdaGraph object (to be able to save the position of each canvas
item) and management of the list of items drawn on the canvas.</para></listitem>
<listitem><para>zoom settings</para></listitem>
</itemizedlist>
</para>
<para>
The #GnomeDbCanvas widget can be used with or without any associated #GdaGraph object.
</para>

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<para>

</para>

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<!-- ##### STRUCT GnomeDbCanvas ##### -->
<para>

</para>


<!-- ##### SIGNAL GnomeDbCanvas::drag-action ##### -->
<para>

</para>

@dbcanvas: the object which received the signal.
@arg1: 
@arg2: 

<!-- ##### ARG GnomeDbCanvas:graph ##### -->
<para>

</para>

<!-- ##### STRUCT GnomeDbCanvasClass ##### -->
<para>

</para>

@parent_class: 
@create_canvas_items: 
@clean_canvas_items: 
@graph_item_added: 
@graph_item_dropped: 
@build_context_menu: 
@drag_action: 

<!-- ##### FUNCTION gnome_db_canvas_get_graph ##### -->
<para>

</para>

@canvas: 
@Returns: 


<!-- ##### FUNCTION gnome_db_canvas_set_in_scrolled_window ##### -->
<para>

</para>

@canvas: 
@Returns: 


<!-- ##### FUNCTION gnome_db_canvas_declare_item ##### -->
<para>

</para>

@canvas: 
@item: 


<!-- ##### FUNCTION gnome_db_canvas_set_zoom_factor ##### -->
<para>

</para>

@canvas: 
@n: 


<!-- ##### FUNCTION gnome_db_canvas_get_zoom_factor ##### -->
<para>

</para>

@canvas: 
@Returns: 


<!-- ##### FUNCTION gnome_db_canvas_fit_zoom_factor ##### -->
<para>

</para>

@canvas: 
@Returns: 


<!-- ##### FUNCTION gnome_db_canvas_auto_layout_enabled ##### -->
<para>

</para>

@canvas: 
@Returns: 


<!-- ##### FUNCTION gnome_db_canvas_perform_auto_layout ##### -->
<para>

</para>

@canvas: 
@animate: 
@algorithm: 


<!-- ##### FUNCTION gnome_db_canvas_center ##### -->
<para>

</para>

@canvas: 


