c0a8a01222
tree and verifying that there are no changes). (Also fixed a few bugs that were in the code) svn: r14427
193 lines
4.6 KiB
Racket
193 lines
4.6 KiB
Racket
#lang scribble/doc
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@(require "common.ss")
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@definterface/title[canvas<%> (subwindow<%>)]{
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A canvas is a subwindow onto which graphics and text can be drawn. Canvases also
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receive mouse and keyboard events.
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To draw onto a canvas, get its device context (see
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@method[canvas<%> get-dc]).
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The @scheme[canvas<%>] interface is implemented by two classes:
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@itemize[
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@item{@scheme[canvas%] --- a canvas for arbitrary drawing and
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event handling}
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@item{@scheme[editor-canvas%] --- a canvas for displaying
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@scheme[editor<%>] objects}
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]
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@defmethod[(get-canvas-background)
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(or/c (is-a?/c color%) false/c)]{
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Returns the color currently used to ``erase'' the canvas content before
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@method[canvas<%> on-paint] is called. See also
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@method[canvas<%> set-canvas-background].
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The result is @scheme[#f] if the canvas was created with the
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@indexed-scheme['transparent] style, otherwise it is always a
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@scheme[color%] object.
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}
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@defmethod[(get-dc)
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(is-a?/c dc<%>)]{
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Gets the canvas's device context. See
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@scheme[dc<%>] for more information about drawing.
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}
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@defmethod*[([(min-client-height)
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(integer-in 0 10000)]
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[(min-client-height [h (integer-in 0 10000)])
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void?])]{
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Gets or sets the canvas's minimum height for geometry management,
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based on the client size rather than the full size. The client height
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is obtained or changed via
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@xmethod[area<%> min-height], adding or subtracting border and scrollbar sizes as appropriate.
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The minimum height is ignored when it is smaller than the canvas's
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@tech{graphical minimum height}. See @|geomdiscuss| for
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more information.
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}
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@defmethod*[([(min-client-width)
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(integer-in 0 10000)]
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[(min-client-width [w (integer-in 0 10000)])
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void?])]{
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Gets or sets the canvas's minimum width for geometry management, based
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on the canvas's client size rather than its full size. The client
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width is obtained or changed via
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@xmethod[area<%> min-width], adding or subtracting border and scrollbar sizes as appropriate.
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The minimum width is ignored when it is smaller than the canvas's
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@tech{graphical minimum width}. See @|geomdiscuss| for
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more information.
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}
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@defmethod[(on-char [ch (is-a?/c key-event%)])
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void?]{
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@methspec{
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Called when the canvas receives a keyboard event. See also
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@|mousekeydiscuss|.
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}
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@methimpl{
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Does nothing.
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}}
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@defmethod[(on-event [event (is-a?/c mouse-event%)])
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void?]{
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@methspec{
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Called when the canvas receives a mouse event. See also
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@|mousekeydiscuss|, noting in particular that certain mouse events
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can get dropped.
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}
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@methimpl{
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Does nothing.
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}}
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@defmethod[(on-paint)
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void?]{
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@methspec{
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Called when the canvas is exposed or resized so that the image in the
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canvas can be repainted.
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When
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@method[canvas<%> on-paint] is called in response to a system expose event and only a portion of
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the canvas is newly exposed, any drawing operations performed by
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@method[canvas<%> on-paint] are clipped to the newly-exposed region; however, the clipping region
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as reported by
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@method[dc<%> get-clipping-region] does not change.
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}
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@methimpl{
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Does nothing.
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}}
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@defmethod[(on-tab-in)
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void?]{
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@methspec{
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Called when the keyboard focus enters the canvas via keyboard
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navigation events. The
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@method[window<%> on-focus] method is also called, as usual for a focus change. When the keyboard
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focus leaves a canvas due to a navigation event, only
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@method[window<%> on-focus] is called.
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See also
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@xmethod[canvas% accept-tab-focus] and
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@xmethod[top-level-window<%> on-traverse-char] .
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}
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@methimpl{
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Does nothing.
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}}
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@defmethod[(set-canvas-background [color (is-a?/c color%)])
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void?]{
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Sets the color used to ``erase'' the canvas content before
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@method[canvas<%> on-paint] is called. (This color is typically associated with the canvas at a
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low level, so that it is used even when a complete refresh of the
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canvas is delayed by other activity.)
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If the canvas was created with the @indexed-scheme['transparent] style,
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@|MismatchExn|.
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}
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@defmethod[(set-resize-corner [on? any/c])
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void?]{
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Under Mac OS X, enables or disables space for a resize tab at the
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canvas's lower-right corner when only one scrollbar is visible. This
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method has no effect under Windows or X, and it has no effect when
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both or no scrollbars are visible. The resize corner is disabled by
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default, but it can be enabled when a canvas is created with the
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@scheme['resize-corner] style.
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}
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@defmethod[(warp-pointer [x (integer-in 0 10000)]
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[y (integer-in 0 10000)])
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void?]{
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Moves the cursor to the given location on the canvas.
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}
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}
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