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>GnomeCanvasPixbuf</TITLE
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NAME="GNOMECANVASPIXBUF">GnomeCanvasPixbuf</H1
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>GnomeCanvasPixbuf -- Canvas item to display GdkPixbuf images.</DIV
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CLASS="REFSYNOPSISDIV"
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> #include <gdk-pixbuf/gdk-pixbuf.h>
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HREF="gnomecanvaspixbuf.html#GNOME-CANVAS-PIXBUF-CAPS"
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>GNOME_CANVAS_PIXBUF</A
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>Object Hierarchy</H2
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+----GnomeCanvasPixbuf</PRE
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--PIXBUF"
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>" gpointer : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH"
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>" gdouble : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-SET"
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>" gboolean : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-IN-PIXELS"
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>" gboolean : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT"
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>" gdouble : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT-SET"
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>" gboolean : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT-IN-PIXELS"
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>" gboolean : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X"
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>" gdouble : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X-IN-PIXELS"
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>" gboolean : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y"
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>" gdouble : Read / Write
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y-IN-PIXELS"
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>" gboolean : Read / Write</PRE
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> This canvas item displays GdkPixbuf images. It handles full
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affine transformations in both GDK and antialiased modes, and also
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HREF="http://www.w3.org"
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HREF="http://www.w3.org/Graphics/SVG/"
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translation semantics for absolute pixel values.
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> GdkPixbuf structures may be shared among different pixbuf canvas
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items; the pixbuf item uses GdkPixbuf's reference counting
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>Custom Scaling and Translation</H3
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> In addition to the normal affine transformations supported by
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HREF="gnomecanvaspixbuf.html"
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>GnomeCanvasPixbuf</A
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> item supports independent
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object arguments for scaling and translation. This is useful
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for explicitly setting a size to which the pixbuf's image will
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be scaled, and for specifying translation offsets that take
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place in the item's local coordinate system.
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> By default, the pixbuf canvas item will attain the size in units
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of the GdkPixbuf it contains. If a <A
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HREF="gnomecanvaspixbuf.html"
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>GnomeCanvasPixbuf</A
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configured to use a GdkPixbuf that has a size of 300 by 200
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pixels, then the pixbuf item will automatically obtain a size of
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300 by 200 units in the item's local coordinate system. If the
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item is transformed with a scaling transformation of (0.5, 2.0),
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then the final image size will be of 150 by 400 pixels.
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> To set custom width and height values, you must set the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-SET"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT-SET"
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>, and then set the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT"
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the desired values. The former two arguments control whether
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the latter two are used when computing the final image's size;
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> by default so that the pixbuf item will
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attain a size in units equal to the size in pixels of the
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GdkPixbuf that the item contains.
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> The custom translation offsets are controlled by the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y"
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> arguments. The logical
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upper-left vertex of the image will be translated by the
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specified distance, aligned with the item's local coordinate
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>Absolute Pixel Scaling and Translation</H3
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HREF="http://www.w3.org/Graphics/SVG/"
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> specification (SVG) of the <A
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HREF="http://www.w3.org"
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>World Wide Web Consortium</A
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allows images to be translated and scaled by absolute pixel
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values that are independent of an item's normal affine
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> Normally, the pixbuf item's translation and scaling arguments
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are interpreted in units, so they will be modified by the item's
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affine transformation. The <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-IN-PIXELS"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT-IN-PIXELS"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X-IN-PIXELS"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y-IN-PIXELS"
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object arguments can be used to modify this behavior. If one of
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these arguments is <TT
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>, then the corresponding scaling or
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translation value will not be affected lengthwise by the pixbuf
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item's affine transformation.
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> For example, consider a pixbuf item whose size is (300, 200).
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If the item is modified with a scaling transformation of (0.5,
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-IN-PIXELS"
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>, then the item will appear to be (300, 400)
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pixels in size. This means that in this case the item's affine
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transformation only applies to the height value, while the width
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value is kept in absolute pixels.
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> Likewise, consider a pixbuf item whose (<A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y"
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>) arguments are set to
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(30, 40). If the item is then modified by the same scaling
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transformation of (0.5, 2.0) but the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y-IN-PIXELS"
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argument is set to <TT
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>, then the image's upper-left corner
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will appear to be at position (15, 40). In this case, the
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affine transformation is applied only to the x offset, while the
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y offset is kept in absolute pixels.
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> In short, these arguments control whether a particular dimension
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of a pixbuf item is scaled or not in the normal way by the
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item's affine transformation.
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>Resource Management</H3
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> When you set the GdkPixbuf structure that a <A
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HREF="gnomecanvaspixbuf.html"
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>GnomeCanvasPixbuf</A
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item will use by setting the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--PIXBUF"
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reference count will be added to that GdkPixbuf structure.
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When the pixbuf item no longer needs the GdkPixbuf structure,
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such as when the item is destroyed or when a new pixbuf
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structure is passed to it, then the old GdkPixbuf structure
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will be automatically unreferenced.
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> This means that if an application just needs to load a pixbuf
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image and set it into a pixbuf canvas item, it can do the
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following to ‘forget’ about the pixbuf structure:
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CLASS="PROGRAMLISTING"
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GnomeCanvasItem *item;
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pixbuf = gdk_pixbuf_new_from_file ("foo.png");
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g_assert (pixbuf != NULL);
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item = gnome_canvas_item_new (gnome_canvas_root (my_canvas),
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gnome_canvas_pixbuf_get_type(),
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gdk_pixbuf_unref (pixbuf);
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> After this happens, the reference count of the pixbuf structure
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HREF="gdk-pixbuf-file-loading.html#GDK-PIXBUF-NEW-FROM-FILE"
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>gdk_pixbuf_new_from_file</A
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>() function creates it
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with a reference count of 1, then setting the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--PIXBUF"
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HREF="gnomecanvaspixbuf.html"
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>GnomeCanvasPixbuf</A
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> item increases it to 2, and then it is
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decremented to 1 by the call to <A
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HREF="gdk-pixbuf-refcounting.html#GDK-PIXBUF-UNREF"
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canvas item is destroyed, it will automatically unreference the
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pixbuf structure again, causing its reference count to drop to
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zero and thus be freed.
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NAME="GNOME-CANVAS-PIXBUF-CAPS"
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>GNOME_CANVAS_PIXBUF()</H3
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CLASS="PROGRAMLISTING"
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>#define GNOME_CANVAS_PIXBUF(obj)</PRE
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> Casts a GtkOjbect to a <A
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HREF="gnomecanvaspixbuf.html"
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>GnomeCanvasPixbuf</A
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CLASS="INFORMALTABLE"
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NAME="GNOMECANVASPIXBUF--PIXBUF"
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>" (gpointer : Read / Write)</DT
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> Contains a pointer to a GdkPixbuf structure that will be used by
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the pixbuf canvas item as an image source. When a pixbuf is set
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its reference count is incremented; if the pixbuf item kept a
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pointer to another GdkPixbuf structure, the reference count of
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this structure will be decremented. Also, the GdkPixbuf's
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reference count will automatically be decremented when the
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HREF="gnomecanvaspixbuf.html"
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>GnomeCanvasPixbuf</A
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> item is destroyed. When a pixbuf is queried, a
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reference count will not be added to the return value; you must do
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this yourself if you intend to keep the pixbuf structure around.
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NAME="GNOMECANVASPIXBUF--WIDTH"
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>" (gdouble : Read / Write)</DT
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> Indicates the width the pixbuf will be scaled to. This argument
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will only be used if the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-SET"
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-IN-PIXELS"
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>, the width will be taken to be in canvas units,
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and thus will be scaled along with the canvas item's affine
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transformation. If width_in_pixels is <TT
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taken to be in pixels, and will visually remain a constant size
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even if the item's affine transformation changes.
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NAME="GNOMECANVASPIXBUF--WIDTH-SET"
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>" (gboolean : Read / Write)</DT
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> Determines whether the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH"
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into account when scaling the pixbuf item. If this argument is
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>, then the width value of the pixbuf will be used instead.
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NAME="GNOMECANVASPIXBUF--WIDTH-IN-PIXELS"
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>" (gboolean : Read / Write)</DT
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> If this argument is <TT
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>, then the width of the pixbuf will be
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considered to be in pixels, that is, it will not be visually
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scaled even if the item's affine transformation changes. If this
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>, then the width of the pixbuf will be considered to be
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in canvas units, and so will be scaled normally by affine
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transformations. The default is <TT
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NAME="GNOMECANVASPIXBUF--HEIGHT"
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>" (gdouble : Read / Write)</DT
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> Indicates the height the pixbuf will be scaled to. This argument
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will only be used if the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT-SET"
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>. Works in the same way as the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH"
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NAME="GNOMECANVASPIXBUF--HEIGHT-SET"
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>" (gboolean : Read / Write)</DT
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> Determines whether the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--HEIGHT"
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taken into account when scaling the pixbuf item. Works in the
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-SET"
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NAME="GNOMECANVASPIXBUF--HEIGHT-IN-PIXELS"
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>height-in-pixels</TT
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>" (gboolean : Read / Write)</DT
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> Works in the same way as the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--WIDTH-IN-PIXELS"
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argument. The default is <TT
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NAME="GNOMECANVASPIXBUF--X"
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>" (gdouble : Read / Write)</DT
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> Indicates the horizontal translation offset of the pixbuf item's
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image. This offset may not actually appear horizontal, since it
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will be affected by the item's affine transformation. The default
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NAME="GNOMECANVASPIXBUF--X-IN-PIXELS"
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>" (gboolean : Read / Write)</DT
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> If this argument is <TT
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>, the pixbuf's translation with respect
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to its logical origin in item-relative coordinates will be in
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pixels, that is, the visible offset will not change even if the
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item's affine transformation changes. If it is <TT
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pixbuf's translation will be taken to be in canvas units, and thus
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will change along with the item's affine transformation. The
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NAME="GNOMECANVASPIXBUF--Y"
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>" (gdouble : Read / Write)</DT
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> Indicates the vertical translation offset of the pixbuf item's
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image. Works in the same way as the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X"
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> argument. The default is
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NAME="GNOMECANVASPIXBUF--Y-IN-PIXELS"
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>" (gboolean : Read / Write)</DT
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> Works in the same way as the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--X-IN-PIXELS"
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argument, but controls whether the <A
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HREF="gnomecanvaspixbuf.html#GNOMECANVASPIXBUF--Y"
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> translation offset is
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scaled or not. The default is <TT
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> GnomeCanvas, GdkPixbuf
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CLEAR="all"><BR><TABLE
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HREF="gdkpixbufloader.html"
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> Xlib initialization</B
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