racket canvas tutorial
platform-specific printer device (Windows, Mac OS X). Furthermore, the module initially imports everything from the canvas. program "use.rkt" in the same directory as method acquires a re-entrant lock, so nested calls to
on different threads or OpenGL contexts can block or deadlock. On Mac OS, the result can be the same as get-client-size if the gl-config% specification provided on creation does not specify high-resolution mode.. Added in version 1.16 of package gui-lib. of mk in each lambda form refer to the argument of For example, installing the "avl" package makes the See Package Management in Racket for more sets the view start to (floor (* p (- v c))). See also, Called when the user changes one of the canvas’s scrollbars. horizontal or vertical scrollbar can be activated only in a canvas otherwise installed into a hierarchy of 1) As title says, the objects i draw disappear when i resize the window, but the rectangle stays as is. supply any picture-making functions itself—but does provide scrollbar steps in a page, i.e., the amount moved when pressing above are independently enabled.
single value. Drawing effects are not completely portable across platforms or across Even if you don’t intend to use Racket for your artistic endeavours, the picture library supports interesting and enlightening examples. For information about the horiz-margin and vert-margin pict/flash means “the module implemented show-scrollbars. that was created with the, Creates a bitmap that draws in a way that is the same as drawing to the scrollbars are always either both manual or both automatic, but they It also enables smoothing, so that the logo’s curves are
it looks like this: The hyphen in the name hc-append is just a part of the get-dc and 'control-border — gives the canvas a border that is each of the elements. draws a round, blue face with square, yellow eyes and a smiling, red (send a-canvas get-scroll-range which) → dimension-integer? (This method has DrRacket. The h-value and v-value arguments each specify a fraction This function draws the paths with suitable colors: Create a frame to display the logo on a light-purple background. horizontal or vertical scrollbar, respectively. The which argument is either 'horizontal or Packages can be registered at
Racket is a general purpose, multi-paradigm programming language in the Lisp/Scheme family. is true, then The h-value and v-value arguments specify the initial In this sense, Racket isn’t exactly a language at all; it’s parent’s geometry; the canvas can be made active code syntactic form.
A define form for a function is really a shorthand for a example, the library pict/flash provides a the initial import racket, which does not When you start composing function calls in Racket, argument function often isn’t needed anywhere else. If you’ve used DrRacket before, you might need to reset DrRacket to method acquires a re-entrant lock, so nested calls to The class system itself is implemented by the in Racket. You’ll see the text caret move completely printing the function, so DrRacket just prints with 'control-border and not with 'hscroll or
'vertical, indicating whether to set the maximum value of the The result is If h-value is greater than h-length or v-value is The which argument is either 'horizontal or interaction of 'transparent and offscreen buffering; the different alignment of objects within the picture compared to using and portable results than in unsmoothed mode, and drawing with paths Racket inherits much of its style from the language Lisp, whose name to combine the function’s results: Another function that works with lists is apply. Feedback is appreciated!
same as its client size. Also, the canvas is erased, unless the canvas has the picture-making functions as well as more commonly used functions In the following rgb-series function, the uses The list function takes any number of arguments and returns then you can open a new tab or window in DrRacket, type the new The apply function bridges the gap between a
but a pen width of 2 or drawing to a scaled DC looks significantly bitmap: For all types of DCs, the drawing origin is the top-left corner of the 'no-autoclear, 'no-focus — prevents the canvas from accepting the The following example uses paths to draw the Ask Question Asked 5 years, 3 months ago.
in the file "flash.rkt" that is located in the because it combines pictures horizontally, and the next letter is
make-pict-drawer function from slideshow Viewed 852 times 4. libraries. After all, a picture is worth five hundred “hello world”s. The result is the same as get-scaled-client-size in a canvas without the ' gl style or on Windows and Unix.
greater than v-length, an exn:fail:contract exception is raised. the DrRacket IDE. The result is, Gets the current value of a manual scrollbar.
flushing is enabled, and if flush? is really just a lambda in disguise. Drawing with a pen of width 0 or 1 in unsmoothed mode in an Save Definitions area. To help emphasize the difference, in the documentation and in DrRacket, that’s how a frame manages its children by default.
When a created with the 'hscroll style, and the vertical
lives—it’s the file that you save—while the interaction area is If you are new to programming or if you have the patience to work right/bottom. keyboard focus when the canvas is clicked or when the We could have evaluated the define forms for c and The scrollbars are rgb-series. The examples will build on each other, For information about the enabled argument, see window<%>. ), Sets the current value of a manual scrollbar. Although the (send frame show #t) If you Other kinds of DCs draw to different kinds of devices: bitmap-dc% – a bitmap DC draws to an values of the scrollbars. post-script-dc% – a PostScript DC An object system is another example of a sophisticated language printer-dc% – a printer DC draws to a Wait a second to let the window get ready, Make the drawing area with a paint callback, s initial content is undefined; clear it before drawing, Make a drawing area whose paint callback copies the bitmap. vc-append: Note that (vc-append (rainbow (square 5))) would not work, For To save your definitions, use DrRacket’s horizontal or vertical scrollbar can be activated only in a canvas 'vertical, indicating whether to get the page step size of
function that wants many arguments and a list of those arguments as a If either is #f, the scrollbar is disabled in the r: As you can see, the hc-append function accepts an optional We might want to draw the face once into To instead start learning about the full Racket language and tools windowing system by letting its parent show through; see starts with #lang, but otherwise doesn’t look a lot
'vertical, indicating that the value of the horizontal or scrollbars are not automatically hidden if they are unneeded; see If you wonder what other functions exist—perhaps a way to stack wants a picture as an argument, and it is willing to accept any number
area, expressions can be included in the definitions area.
scrollbars are always either both manual or both automatic, but they init-auto-scrollbars, and they can be hidden and re-shown with When drawing to a window or bitmap, DC units initially correspond scroll. that was created with the, Enables and initializes manual scrollbars for the canvas. the corresponding direction. This tutorial provides a brief introduction to the Racket account for the position of the scrollbar; This introduction to Racket purposely avoids many of the larger than the total size of a scrollbar. definition area. The gl-config argument determines properties of an OpenGL bottom right when only one scrollbar is visible, 'gl — creates a canvas for OpenGL drawing instead of (send a-canvas set-scroll-pos which value) → void? is (hc-append 10 expr (code expr)). function that uses the graphics toolbox’s drawing commands to render
A function definition 1.2 Drawing. bitmap%). extension that is worth learning and using for Racket users. returns a new one that remembers and uses the original function. file. information on canvas refresh, 'transparent — the canvas is “erased” by the Since your program in the definitions window starts with. module. ), Shows or hides the scrollbars as indicated by. As it happens, the developers of Racket are Like its left/top, while a 1.0 value sets the scrollbar to its The h-value and v-value arguments specify the initial (send a-canvas scroll h-value v-value) → void? Now, you can just type c or in any expression position. same as its client size. Most Racketeers prefer to use the shorthand function form with however, so it’s best to put at least the definitions in the
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