98 lines
2.7 KiB
Java
98 lines
2.7 KiB
Java
package draw;
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import geometry.*;
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import colors.*;
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public class Canvas {
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private int width = 0;
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private int height = 0;
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/**
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*@author Matthias Felleisen, Kathy Gray
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*@param width positive int, the width of the visible canvas
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*@param height positive int, the height of the visible canvas
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*/
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public Canvas(int width, int height) {
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this.width = width;
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this.height = height;
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}
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// these two are cheats:
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protected native boolean copy();
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protected native boolean stop();
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// I need to figure out how to accomplish these two things, especially stop,
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// directly at the Scheme level w/o going thru the Java layer.
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private boolean showing = false;
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/**
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*@return true, if it can display a white canvas
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*The method initializes the canvas to a white area,
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*enables the drawing methods, and finally displays the canvas. If it
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*succeeds, it produces <code>true</code>. Invoking the method a second
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*time without calling <code>close</code> before has no effect.
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*/
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public boolean show() {
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if (!showing) {
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xshow();
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showing = true;
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}
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return true;
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}
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/**
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*@return true, if it can hide the canvas
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*The method hides the canvas and erases the current content.
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*/
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public boolean close() {
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xclose();
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showing = false;
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return true;
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}
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public native boolean xshow();
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public native boolean xclose();
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/**
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*@param p the center of the circle
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*@param r its radius
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*@param c its outline color
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*@return true, if it can draw the circle into this canvas
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*/
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public native boolean drawCircle(Posn p, int r, IColor c);
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/**
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*@param p the center of the disk
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*@param r its radius
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*@param c its fill and outline color
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*@return true, if it can draw the disk into this canvas
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*/
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public native boolean drawDisk(Posn p, int r, IColor c);
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/**
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*@param p the upper left of the rectangle
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*@param width positive int
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*@param height positive int
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*@param c its outline color
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*@return true, if it can draw the rectangle into this canvas
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*/
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public native boolean drawRect(Posn p, int width, int height, IColor c);
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/**
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*@param p0 the first point on the line
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*@param p1 the second point on the line
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*@param c its color
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*@return true, if it can draw the line into this canvas
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*/
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public native boolean drawLine(Posn p0, Posn p1, IColor c);
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/**
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*@param p the position of the baseline of the string
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*@param s the message to be drawn
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*@return true, if it can draw the string into this canvas
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*/
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public native boolean drawString(Posn p, String s);
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}
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