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Custom operations are invoked using the procedure
graphics-operation. For example,
(graphics-operation device 'set-foreground-color "blue")
operation+: x-graphics-device set-background-color color-name
operation+: x-graphics-device set-foreground-color color-name
operation+: x-graphics-device set-border-color color-name
operation+: x-graphics-device set-mouse-color color-name
These operations change the colors associated with a window.
Color-name must be a string, which is the X server's name for the
desired color. set-border-color and set-mouse-color
immediately change the border and mouse-cursor colors.
set-background-color and set-foreground-color change the
colors to be used when drawing, but have no effect on anything drawn
prior to their invocation. Because changing the background color
affects the entire window, we recommend calling graphics-clear on
the window's device afterwards. Color names include both mnemonic
names, like "red", and intensity names specified in the
"#rrggbb" notation.
operation+: x-graphics-device draw-arc x y radius-x radius-y angle-start angle-sweep fill?
Operation draw-arc draws or fills an arc. An arc is a segment of
a circle, which may have been stretched along the x- or y- axis to form
an ellipse.
The parameters X, Y, RADIUS-X and RADIUS-Y describe the circle and ANGLE-START and ANGLE-SWEEP choose which part of the circle is drawn. The arc is drawn on the graphics device with the center of the circle at the virtual coordinates given by X and Y. RADIUS-X and RADIUS-Y determine the size of the circle in virtual coordinate units.
The parameter ANGLE-START determines where the arc starts. It is measured in degrees in an anti-clockwise direction, starting at 3 o'clock. ANGLE-SWEEP determines how much of the circle is drawn. It too is measured anti-clockwise in degrees. A negative value means the measurement is in a clockwise direction.
Note that the angles are determined on a unit circle before it is stretched into an ellipse, so the actual angles that you will see on the computer screen depends on all of: RADIUS-X and RADIUS-Y, the window size, and the virtual coordinates.
If fill? is #F then just the segment of the circle is
drawn, otherwise the arc is filled in a pie-slice fashion.
This draws a quarter circle pie slice, standing on its point, with point at virtual coordinates (3,5):
(graphics-opereration g 'draw-arc 3 5 .5 .5 45 90 #T)
operation+: x-graphics-device draw-circle x y radius
operation+: x-graphics-device fill-circle x y radius
These operations draw a circle (outline) or a filled circle (solid) at
on the graphics device at the virtual coordinates given by X and
Y. These operations could be implemented trivially interms of the
draw-arc operation.
operation+: x-graphics-device set-border-width width
operation+: x-graphics-device set-internal-border-width width
These operations change the external and internal border widths of a
window. Width must be an exact non-negative integer, specified in
pixels. The change takes place immediately. Note that changing the
internal border width can cause displayed graphics to be garbled; we
recommend calling graphics-clear on the window's device after
doing so.
operation+: x-graphics-device set-font font-name
Changes the font used when drawing text in a window. Font-name must be a string that is a font name known to the X server. This operation does not affect text drawn prior to its invocation.
operation+: x-graphics-device set-mouse-shape shape-number
Changes the shape of the mouse cursor. Shape-number is an exact non-negative integer that is used as an index into the mouse-shape font; when multiplied by 2 this number corresponds to an index in the file `/usr/include/X11/cursorfont.h'.
operation+: x-graphics-device map-window
operation+: x-graphics-device withdraw-window
These operations control the mapping of windows. They correspond
directly to the Xlib procedures XMapWindow and
XWithdrawWindow.
operation+: x-graphics-device resize-window width height
Changes the size of a window. Width and height must be
exact non-negative integers. The operation corresponds directly to the
Xlib procedure XResizeWindow.
This operation resets the virtual coordinate system and the clip rectangle.
operation+: x-graphics-device move-window x y
Changes the position of a window on the display. X and y
must be exact integers. The operation corresponds directly to the Xlib
procedure XMoveWindow. Note that the coordinates x and
y do not take the external border into account, and therefore will
not position the window as you might like. The only reliable way to
position a window is to ask a window manager to do it for you.
operation+: x-graphics-device get-default resource property
This operation corresponds directly to the Xlib procedure
XGetDefault. Resource and property must be strings.
The operation returns the character string corresponding to the
association of resource and property; if no such association
exists, #f is returned.
operation+: x-graphics-device copy-area source-x-left source-y-top width height destination-x-left destination-y-top
This operation copies the contents of the rectangle specified by source-x-left, source-y-top, width, and height to the rectangle of the same dimensions at destination-x-left and destination-y-top.
operation+: x-graphics-device font-structure font-name
Returns a Scheme equivalent of the X font structure for the font named
font-name. If the string font-name does not name a font
known to the X server, or names a 16-bit font, #f is returned.
procedure+: x-font-structure/name font-structure
procedure+: x-font-structure/direction font-structure
procedure+: x-font-structure/all-chars-exist font-structure
procedure+: x-font-structure/default-char font-structure
procedure+: x-font-structure/min-bounds font-structure
procedure+: x-font-structure/max-bounds font-structure
procedure+: x-font-structure/start-index font-structure
procedure+: x-font-structure/character-bounds font-structure
procedure+: x-font-structure/max-ascent font-structure
procedure+: x-font-structure/max-descent font-structure
These procedures extract the components of the font description
structure returned by the X graphics operation font-structure. A
more complete description of these components appears in documentation
of the XLoadQueryFont Xlib call. start-index is the index
of the first character available in the font. The min-bounds and
max-bounds components are structures of type
x-character-bounds, and the character-bounds component is
a vector of the same type.
procedure+: x-character-bounds/lbearing character-bounds
procedure+: x-character-bounds/rbearing character-bounds
procedure+: x-character-bounds/width character-bounds
procedure+: x-character-bounds/ascent character-bounds
procedure+: x-character-bounds/descent character-bounds
These procedures extract components of objects of type
x-character-bounds. A more complete description of them appears
in documentation of the XLoadQueryFont Xlib call.
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