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This section describes each of the canvas items that come
with Gnome, giving a table of arguments and describing any
non-obvious arguments.
The GnomeCanvasRect and
GnomeCanvasEllipse canvas
items share exactly the same interface, via a GnomeCanvasRE base class. Their
shape is given as a bounding box: a top left coordinate
(x1, y1) and a bottom right coordinate (x2, y2). The
rectangle item matches the shape of the bounding box; the
ellipse is inscribed in the bounding box, touching the
center of each side. Rectangles and ellipses can be
filled or simply an outline. If they are only an outline,
they are considered to be "hollow"; that is, the
transparent area inside the shape is not part of the
canvas item and events that occur in that area will not
be relayed to the item.
GnomeCanvasRE does not
behave gracefully if you give the coordinates in the
wrong order. That is, x2 must be greater than x1, and y2
must be greater than y1; otherwise GnomeCanvasRE gets confused.
Table 1.
GnomeCanvasRE Arguments
|
Name
|
Type
|
Read/Write
|
Description
|
|
x1
|
double
|
Both
|
Leftmost coordinate
|
|
y1
|
double
|
Both
|
Topmost coordinate
|
|
x2
|
double
|
Both
|
Rightmost coordinate
|
|
y2
|
double
|
Both
|
Bottommost coordinate
|
|
fill_color
|
gchar*
|
Write-only
|
Fill color; string for
gdk_color_parse(), or NULL for transparent
|
|
fill_color_gdk
|
GdkColor*
|
Both
|
Fill color; specified as already-allocated GdkColor
|
|
fill_color_rgba
|
guint32
|
Both
|
Fill color; specified as 32-bit value packing red,
green, blue, and alpha into bytes 1, 2, 3, and 4;
alpha of 255 is opaque, 0 is invisible
|
|
outline_color
|
gchar*
|
Write-only
|
Outline color; string for
gdk_color_parse, or
NULL for transparent
|
|
outline_color_gdk
|
GdkColor*
|
Both
|
Outline color; specified as already-allocated GdkColor
|
|
outline_color_rgba
|
guint32
|
Both
|
Outline color; specified as 32-bit value packing
red, green, blue, and alpha into bytes 1, 2, 3, and
4; alpha of 255 is opaque, 0 is invisible
|
|
fill_stipple
|
GdkBitmap*
|
Both
|
Stipple to use when drawing fill; GDK mode only
|
|
outline_stipple
|
GdkBitmap*
|
Both
|
Stipple to use when drawing outline; GDK mode only
|
|
width_pixels
|
guint
|
Write-only
|
Width of the outline, in pixels (independent of
zoom)
|
|
width_units
|
double
|
Write-only
|
Width of the outline, in canvas units; pixel width
changes with zoom factor (pixels per unit)
|
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