new docs for htdch
svn: r2760
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Matthias Felleisen
parent
770e6aa288
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d7d55e05b4
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{ (define LIBNAME "A Functional Drawing Library (HtDC)")
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(include "head.tinc") }
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This `draw' package provides classes and methods for a visual
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This <code>draw</code> package provides classes and methods for a visual
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world. Here is its class diagram of public fields and methods:
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<pre>
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<code>
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@ -11,9 +11,9 @@ world. Here is its class diagram of public fields and methods:
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| Canvas theCanvas |------>| Canvas |
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+-----------------------------------+ +---------------------------------------+
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| boolean bigBang(int,int,double) | +---------------------------------------+
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| boolean endOfTime() | | boolean start(int,int) |
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| boolean endOfWorld() | | boolean stop() |
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| World lastWorld() | | boolean drawCircle(Posn,int,Color) |
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| boolean endOfTime() | | boolean show() |
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| World endOfWorld() | | boolean close() |
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| | | boolean drawCircle(Posn,int,Color) |
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| | | boolean drawDisk(Posn,int,Color) |
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| abstract World onTick() | | boolean drawRect(Posn,int,int,Color) |
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| abstract World onKeyEvent(String) | | boolean drawLine(Posn,Posn,Color) |
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@ -46,4 +46,125 @@ world. Here is its class diagram of public fields and methods:
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</code>
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</pre>
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<a name="world" />
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<p>The abstract <code>World</code> class exports the following methods:
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<ul>
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<li><code>bigBang(width,height,speed)</code>, which initializes the world,
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associates it with a <code>width</code> x <code>height</code> <a
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href="#canvas"><code>Canvas</code></a>, displays
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this canvas, and finally starts the clock at a rate of one tick per
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<code>speed</code> seconds. If it succeeds with all of its actions, the method
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produces <code>true</code>.
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<p>A <code>World</code> is associated with one default <code>Canvas</code>,
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called <code>theCanvas</code>. If a <code>World</code> needs additional
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canvases for its graphical presentation, its concrete subclasses must add
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those.</p>
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</li>
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<li><code>endOfTime</code>, stops the clock and, if it succeeds, produces
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<code>true</code>.
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</li>
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<li><code>endOfWorld</code>, stops the clock and, if it succeeds, produces the
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last <code>World</code>.
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</li>
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</ul>
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The methods may fail due to the unavailability of the physical devices,
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inappropriate uses, etc. In those cases, they fail with an exception.</p>
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<p>A derived concrete class must supply definitions for the following methods:
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<ul>
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<li><code>onTick()</code>, which is invoked for every tick of the clock. Its
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purpose is to create a <code>World</code> whose differences with
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<code>this</code> one represent what happened during the amount of time it takes
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the clock to tick.
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</li>
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<li><code>onKeyEvent(key)</code>, which is invoked for every keyboard event. Its
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purposes is to create a <code>World</code> whose differences with
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<code>this</code> one represent what happens due to the user's use of the
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keyboard. The latter is represented with the string-valued argument
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<code>key</code>.
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</li>
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<li><code>draw()</code>, which is invoked <em>after</em> one of the two event
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handlers has been called. Its purpose is to present <code>this World </code>
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graphically on its canvas. If it succeeds, its result is <code>true.</code>
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</li>
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<li><code>erase()</code>, which is invoked <em>after</em> one of the two event
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handlers has been called. Its purpose is to erase <code>this World</code>'s
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canvas, as much as needed. If it succeeds, its result is <code>true.</code>
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</li>
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</ul>
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A program may, in principle, start several instances of (subclasses of)
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<code>World</code>. If it does, the event handlers are called in a unpredictable
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order. </p>
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<a name="canvas" />
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<p>To create an instance of the <code>Canvas</code> class, a program must supply
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two <code>int</code> values: one for the width of the canvas and one for its
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height. The canvas is a rectangle, whose borders are parallel to the computer
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screen's borders. A program can use the following methods on instances of
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<code>Canvas:</code>
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<ul>
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<li><code>show()</code>, which displays the canvas.
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If it succeeds, it produces <code>true</code>.</li>
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<li><code>close()</code>, which destroys the canvas.
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If it succeeds, it produces <code>true</code>.</li>
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<li><code>drawCircle(p,r,c)</code>, which draws a circle on <code>this
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Canvas</code> at <code>p</code> with radius <code>r</code> and color
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<code>c</code>. If it succeeds, it produces <code>true</code>.</li>
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<li><code>drawDisk(p,r,c)</code>, which draws a disk on
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<code>this Canvas</code> at <code>p</code> with radius <code>r</code> and color
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<code>c</code>. If it succeeds, it produces <code>true</code>.</li>
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<li><code>drawRect(p,w,h, c)</code>, which draws a solid rectangle on <code>this
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Canvas</code> at <code>p</code> with width <code>w</code>, height
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<code>h</code>, and color <code>c</code>. The rectangle's lines are parallel to
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the canvas's borders. If it succeeds, it produces <code>true</code>.</li>
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<li><code>drawLine(p0,p1,c)</code>, which draws a line on <code>this
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Canvas</code> from <code>p0</code> to <code>p1</code> using color
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<code>c</code>. If it succeeds, it produces <code>true</code>.</li>
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<li><code>drawString(p,s)</code>, which draws the string <code>s</code> at
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<code>p</code> on <code>this Canvas</code>. If it succeeds, it produces
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<code>true</code>.</li>
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<li><code>clearCircle(p,r,c)</code>, which erases a circle from <code>this
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Canvas</code> at <code>p</code> with radius <code>r</code> and color
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<code>c</code>. If it succeeds, it produces <code>true</code>.</li>
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<li><code>clearDisk(p,r,c)</code>, which erases a disk from
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<code>this Canvas</code> at <code>p</code> with radius <code>r</code> and color
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<code>c</code>. If it succeeds, it produces <code>true</code>.</li>
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<li><code>clearRect(p,w,w,c)</code>, which draws a solid rectangle from <code>this
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Canvas</code> at <code>p</code> with width <code>w</code>, height
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<code>h</code>, and color <code>c</code>. The rectangle's lines are parallel to
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the canvas's borders. If it succeeds, it produces <code>true</code>.</li>
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<li><code>clearLine(Posn p0, Posn p1, Color c)</code>, which erases a line from <code>this
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Canvas</code> from <code>p0</code> to <code>p1</code> using color
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<code>c</code>. If it succeeds, it produces <code>true</code>.</li>
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</ul>
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The methods may fail due to the unavailability of the physical devices,
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inappropriate uses, etc. In those cases, they fail with an exception.</p>
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</p>
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<p>To create an instance of the <code>Posn</code> class, a program must supply
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two <code>int</code> values: one for its x coordinate of the canvas and the
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second for its y coordinate. </p>
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<p>The <code>Color</code> class is abstract. Its variants (subclasses) are
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created with no arguments.
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</p>
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{(include "foot.tinc")}
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@ -2,11 +2,14 @@
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(include "head.tinc") }
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This `idraw' package provides classes and imperative methods for
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a visual world. Here is its class diagram of public fields and methods:
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This <code>idraw</code> package provides stateful classes and imperative methods
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for a visual world. Here is its class diagram of public fields and methods:
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<pre>
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<code>
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import draw.Color;
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import draw.Posn;
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+---------------------------------+
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| abstract World |
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+---------------------------------+ +------------------------------------+
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@ -25,28 +28,18 @@ a visual world. Here is its class diagram of public fields and methods:
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| void clearRect(Posn,int,int,Color) |
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| void clearLine(Posn,Posn,Color) |
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+------------------------------------+
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+----------+
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| Posn |
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+----------+
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| int x |
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| int y |
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+----------+
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+-------+
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| Color |
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+-------+
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/ \
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---
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------------------------------------------
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| | | | |
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+-------+ +-------+ +-------+ +-------+ +-------+
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| Blue | | Green | | Red | | White | | Yellow|
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+-------+ +-------+ +-------+ +-------+ +-------+
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</code>
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</pre>
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<p>The abstract <code>World</code> class in <code>idraw</code> provides the same
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methods as the <code>World</code> class in <a href="./draw.html#world">the
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<code>draw</code> library</a>. Their return values are usually <code>void</code>,
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however, except for <code>endOfTime</code> and <code>endOfWorld</code>, which
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continue to return the last world.</p>
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<p>In an analogous manner, the methods in the <code>Canvas</code> class export
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the same methods as the <code>Canvas</code> class in <a
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href="./draw.html#canvas">the <code>draw</code> package</a>. Their return values,
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however, are <code>void</code>. </p>
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{(include "foot.tinc")}
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