3.7  canvas%

Implements: canvas<%>

A canvas% object is a general-purpose window for drawing and handling events.

• (new canvas% (parent _) [(style _)] [(paint-callback _)] [(label _)] [(gl-config _)] [(enabled _)] [(vert-margin _)] [(horiz-margin _)] [(min-width _)] [(min-height _)] [(stretchable-width _)] [(stretchable-height _)]) -> canvas% object
     parent : frame%, dialog%, panel%, or pane% object
     style = null : list of symbols in '(border control-border combo vscroll hscroll resize-corner gl deleted no-autoclear transparent)
   paint-callback = void : procedure of two arguments: a canvas% object and a dc<%> object
     label = #f : string (up to 200 characters) or #f
   gl-config = #f : gl-config% object or #f
   enabled = #t : boolean
     vert-margin = 0 : exact integer in [0, 1000]
     horiz-margin = 0 : exact integer in [0, 1000]
     min-width = 0 : exact integer in [0, 10000]
     min-height = 0 : exact integer in [0, 10000]
     stretchable-width = #t : boolean
     stretchable-height = #t : boolean

  The style argument indicates one or more of the following styles:

  • 'border -- gives the canvas a thin border

  • 'control-border -- gives the canvas a border that is like a text-field% control

  • 'combo -- gives the canvas a combo button that is like a combo-field% control; this style is intended for use with 'control-border and not with 'hscroll or 'vscroll

  • 'hscroll -- enables horizontal scrolling (initially visible but inactive)

  • 'vscroll -- enables vertical scrolling (initially visible but inactive)

  • 'resize-corner -- leaves room for a resize control at the canvas's bottom right when only one scrollbar is visible

  • 'gl -- obsolete (every canvas is an OpenGL context where supported)

  • 'deleted -- creates the canvas as initially hidden and without affecting parent's geometry; the canvas can be made active later by calling parent's add-child method

  • 'no-autoclear -- prevents automatic erasing of the canvas before calls to on-paint

  • 'transparent -- the canvas is automatically ``erased'' before an update using it's parent window's background; the result is undefined if this flag is combined with 'no-autoclear

  The 'hscroll and 'vscroll styles create a canvas with an initially inactive scrollbar. The scrollbars are activated with either init-manual-scrollbars or init-auto-scrollbars, and they can be hidden and re-shown with show-scrollbars.

  The paint-callback argument is called by the default on-paint method, using the canvas and the DC returned by get-dc as the argument.

  The label argument names the canvas for get-label, but it is not displayed with the canvas.

  The gl-config argument determines properties of an OpenGL context for this canvas, as obtained through the canvas's drawing context. See also get-dc and get-gl-context in dc<%>.

  For information about the enabled argument, see window<%>. For information about the horiz-margin and vert-margin arguments, see subarea<%>. For information about the min-width, min-height, stretchable-width, and stretchable-height arguments, see area<%>.

  
  

Methods
    accept-tab-focus
    get-canvas-background
    get-dc
    get-scroll-page
    get-scroll-pos
    get-scroll-range
    get-view-start
    get-virtual-size
    init-auto-scrollbars
    init-manual-scrollbars
    min-client-height
    min-client-width
    on-char
    on-event
    on-paint
    on-scroll
    on-tab-in
    scroll
    set-canvas-background
    set-resize-corner
    set-scroll-page
    set-scroll-pos
    set-scroll-range
    show-scrollbars
    swap-gl-buffers
    warp-pointer
    with-gl-context

All Methods
    accept-drop-files from window<%>
    accept-tab-focus from canvas%
    client->screen from window<%>
    enable from window<%>
    focus from window<%>
    get-canvas-background from canvas<%>
    get-client-size from window<%>
    get-cursor from window<%>
    get-dc from canvas<%>
    get-graphical-min-size from area<%>
    get-handle from window<%>
    get-height from window<%>
    get-label from window<%>
    get-parent from area<%>
    get-plain-label from window<%>
    get-scroll-page from canvas%
    get-scroll-pos from canvas%
    get-scroll-range from canvas%
    get-size from window<%>
    get-top-level-window from area<%>
    get-view-start from canvas%
    get-virtual-size from canvas%
    get-width from window<%>
    get-x from window<%>
    get-y from window<%>
    has-focus? from window<%>
    horiz-margin from subarea<%>
    init-auto-scrollbars from canvas%
    init-manual-scrollbars from canvas%
    is-enabled? from window<%>
    is-shown? from window<%>
    min-client-height from canvas<%>
    min-client-width from canvas<%>
    min-height from area<%>
    min-width from area<%>
    on-char from canvas<%>
    on-drop-file from window<%>
    on-event from canvas<%>
    on-focus from window<%>
    on-move from window<%>
    on-paint from canvas<%>
    on-scroll from canvas<%>
    on-size from window<%>
    on-subwindow-char from window<%>
    on-subwindow-event from window<%>
    on-superwindow-enable from window<%>
    on-superwindow-show from window<%>
    on-tab-in from canvas<%>
    popup-menu from window<%>
    refresh from window<%>
    screen->client from window<%>
    scroll from canvas%
    set-canvas-background from canvas<%>
    set-cursor from window<%>
    set-label from window<%>
    set-resize-corner from canvas<%>
    set-scroll-page from canvas%
    set-scroll-pos from canvas%
    set-scroll-range from canvas%
    show from window<%>
    show-scrollbars from canvas%
    stretchable-height from area<%>
    stretchable-width from area<%>
    swap-gl-buffers from canvas%
    vert-margin from subarea<%>
    warp-pointer from canvas<%>
    with-gl-context from canvas%