`primitives` Module

Synopsis

Racket	`(require (planet murphy/canvas-draw:1:0/primitives))`
CHICKEN	`(require-extension canvas-draw-primitives)`
CHICKEN 5	`(require-library canvas-draw) (import canvas-draw-primitives)`

Drawing primitives.

Points

`(canvas-pixel! [canvas canvas?] [x integer?] [y integer?] [color integer? (canvas-foreground canvas)]) → void?`

Draws a single pixel of the given color on the given canvas.

`(canvas-mark! [canvas canvas?] [x integer?] [y integer?]) → void?`

Draws a marker symbol on the given canvas.

`(canvas-mark-type [canvas canvas?]) → symbol?`

Retrieves the current marker symbol type for the given canvas. Possible values are

'+ or 'plus
'* or 'star
'0 or 'circle
'O or 'hollow-circle
'X or 'x
'box
'hollow-box
'diamond
'hollow-diamond

`(canvas-mark-type-set! [canvas canvas?] [mark-type symbol?]) → void? (set! (canvas-mark-type [canvas canvas?]) [mark-type symbol?]) → void?`

Sets the current marker symbol type for the given canvas.

`(canvas-mark-size [canvas canvas?]) → integer?`

Retrieves the current marker symbol size for the given canvas.

`(canvas-mark-size-set! [canvas canvas?] [size integer?]) → void? (set! (canvas-mark-size [canvas canvas?]) [size integer?]) → void?`

Sets the current marker symbol size for the given canvas.

Lines

`(canvas-line! [canvas canvas?] [x0 real?] [y0 real?] [x1 real?] [y1 real?]) → void?`

Draws a line on the given canvas.

`(canvas-rectangle! [canvas canvas?] [x0 real?] [x1 real?] [y0 real?] [y1 real?]) → void?`

Draws a hollow rectangle on the given canvas.

`(canvas-arc! [canvas canvas?] [x real?] [y real?] [width real?] [height real?] [alpha0 real?] [alpha1 real?]) → void?`

Draws a hollow ellipsis segment on the given canvas.

`(canvas-line-style [canvas canvas?]) → symbol?`

Retrieves the current line style of the given canvas. Possible values are

'continuous
'dashed
'dotted
'dash-dotted
'dash-dot-dotted
'custom

`(canvas-line-style-set! [canvas canvas?] [line-style (or/c symbol? list?)]) → symbol? (set! (canvas-line-style [canvas canvas?]) [line-style (or/c symbol? list?)]) → symbol?`

Sets the current line style of the given canvas and returns the previous value.

In addition to the possible return values of canvas-line-style a custom line-style can be fully specified using the form (list 'custom [len integer?] ...).

`(canvas-line-width [canvas canvas?]) → integer?`

Retrieves the current line width of the given canvas.

`(canvas-line-width-set! [canvas canvas?] [line-width integer?]) → integer? (set! (canvas-line-width [canvas canvas?]) [line-width integer?]) → integer?`

Sets the current line width of the given canvas and returns the previous value.

`(canvas-line-join [canvas canvas?]) → symbol?`

Retrieves the current line join style of the given canvas. Possible values are

'miter
'bevel
'round

`(canvas-line-join-set! [canvas canvas?] [line-join symbol?]) → symbol? (set! (canvas-line-join [canvas canvas?]) [line-join symbol?]) → symbol?`

Sets the current line join style of the given canvas and returns the previous value.

`(canvas-line-cap [canvas canvas?]) → symbol?`

Retrieves the current line cap style of the given canvas.

'flat
'square
'round

`(canvas-line-cap-set! [canvas canvas?] [line-cap symbol?]) → symbol? (set! (canvas-line-cap [canvas canvas?]) [line-cap symbol?]) → symbol?`

Sets the current line cap style of the given canvas and returns the previous value.

Filled Areas

`(canvas-box! [canvas canvas?] [x0 real?] [x1 real?] [y0 real?] [y1 real?]) → void?`

Draws a filled rectangle on the given canvas.

`(canvas-sector! [canvas canvas?] [x real?] [y real?] [width real?] [height real?] [alpha0 real?] [alpha1 real?]) → void?`

Draws a filled ellipsis sector on the given canvas.

`(canvas-chord! [canvas canvas?] [x real?] [y real?] [width real?] [height real?] [alpha0 real?] [alpha1 real?]) → void?`

Draws a filled ellipsis arc on the given canvas.

`(canvas-background-opacity [canvas canvas?]) → symbol?`

Retrieves the current background opacity of the given canvas. Possible values are

'transparent
'opaque

`(canvas-background-opacity-set! [canvas canvas?] [background-opacity symbol?]) → symbol? (set! (canvas-background-opacity-set! [canvas canvas?]) [background-opacity symbol?]) → symbol?`

Sets the current background opacity of the given canvas and returns the previous value.

`(canvas-fill-mode [canvas canvas?]) → symbol?`

Retrieves the current polygon fill mode of the given canvas. Possible values are

'even-odd
'winding

`(canvas-fill-mode-set! [canvas canvas?] [fill-mode symbol?]) → symbol? (set! (canvas-fill-mode [canvas canvas?]) [fill-mode symbol?]) → symbol?`

Sets the current polygon fill mode of the given canvas and returns the previous value.

`(canvas-interior-style [canvas canvas?]) → (or/c symbol? list?)`

Retrieves the current interior style of the given canvas. Possible values are

'solid
'(hatch horizontal)
'(hatch vertical)
'(hatch forward-diagonal)
'(hatch backward-diagonal)
'(hatch cross)
'(hatch diagonal-cross)
(list 'stipple [width integer?] [height integer?] [data blob?])
(list 'pattern/rgb [width integer?] [height integer?] [data blob?])
(list 'pattern/rgba [width integer?] [height integer?] [data blob?])
#f

`(canvas-interior-style-set! [canvas canvas?] [interior-style (or/c symbol? list?)]) → void? (set! (canvas-interior-style [canvas canvas?]) [interior-style (or/c symbol? list?)]) → void?`

Sets the current interior style of the given canvas and returns the previous value.

Text

`(canvas-text! [canvas canvas?] [x real?] [y real?] [text string?]) → void?`

Draws a string of text on the given canvas.

`(canvas-font [canvas canvas?]) → string?`

Retrieves the current font of the given canvas.

`(canvas-font-set! [canvas canvas?] [font string?]) → void? (set! (canvas-font [canvas canvas?]) [font string?]) → void?`

Sets the current font of the given canvas and returns the previous value.

`(canvas-text-alignment [canvas canvas?]) → symbol?`

Retrieves the current text alignment of the given canvas. Possible values are

'north
'south
'east
'west
'north-east
'north-west
'south-east
'south-west
'center
'base-left
'base-center
'base-right

`(canvas-text-alignment-set! [canvas canvas?] [text-alignment symbol?]) → void? (set! (canvas-text-alignment [canvas canvas?]) [text-alignment symbol?]) → void?`

Sets the current text alignment of the given canvas and returns the previous value.

`(canvas-text-orientation [canvas canvas?]) → real?`

Retrieves the current text orientation of the given canvas.

`(canvas-text-orientation-set! [canvas canvas?] [orientation real?]) → void? (set! (canvas-text-orientation [canvas canvas?]) [orientation real?]) → void?`

Sets the current text orientation of the given canvas and returns the previous value.

`(canvas-font-dimensions [canvas canvas?]) → (values integer? integer? integer? integer?)`

Returns the maximum width, height, ascent and descent of the current font of the given canvas.

`(canvas-text-size [canvas canvas?] [text string?]) → (values integer? integer?)`

Computes the width and height of the given text when drawn on the given canvas.

`(canvas-text-box [canvas canvas?] [x integer?] [y integer?] [text string?]) → (values integer? integer? integer? integer?)`

Computes the bounding box of the given text when drawn on the given canvas. Returns the minimum and maximum x and y coordinates.

Vertices

`(call-with-canvas-in-mode [canvas canvas?] [mode symbol?] [proc (-> canvas? any)]) → any`

Calls proc with the given canvas and ready to receive vertex data in the given mode. Returns whatever proc returns.

Possible modes are

'open-lines
'closed-lines
'fill
'clip
'bezier
'region
'path

`(canvas-path-set! [canvas canvas?] [path-action symbol?]) → void?`

Configures the action between sequences of vertex data sent to the given canvas. Possible actions are

'new
'move-to
'line-to
'arc
'curve-to
'close
'fill
'stroke
'fill+stroke
'clip

`(canvas-vertex! [canvas canvas?] [x real?] [y real?]) → void?`

Sends a vertex to the given canvas.

Canvas Draw