svn: r6898

collects/htdch/draw/Canvas.java

@@ -7,6 +7,11 @@ public class Canvas {
     private int width = 0; 
     private int height = 0; 
 
+    /** 
+     *@author Matthias Felleisen, Kathy Gray 
+     *@param width positive int, the width of the visible canvas 
+     *@param height positive int, the height of the visible canvas 
+     */ 
     public Canvas(int width, int height) { 
 	this.width = width; 
 	this.height = height; 
@@ -19,6 +24,14 @@ public class Canvas {
     // directly at the Scheme level w/o going thru the Java layer.
      
     private boolean showing = false; 
+
+    /** 
+     *@return  true, if it can display a white canvas 
+     *The method initializes the canvas to a white area, 
+     *enables the drawing methods, and finally displays the canvas. If it
+     *succeeds, it produces <code>true</code>. Invoking the method a second
+     *time without calling <code>close</code> before has no effect.  
+     */
     public boolean show() { 
 	if (!showing) {
 	    xshow();
@@ -26,6 +39,12 @@ public class Canvas {
 	}
 	return true; 
     }
+
+    
+    /** 
+     *@return  true, if it can hide the canvas 
+     *The method hides the canvas and erases the current content. 
+     */
     public boolean close() { 
 	xclose(); 
 	showing = false; 
@@ -34,13 +53,64 @@ public class Canvas {
 	    
     public native boolean xshow();
     public native boolean xclose();
+
+    /** 
+     *@param p the center of the circle 
+     *@param r its radius
+     *@param c its outline color 
+     *@return true, if it can draw the circle into this canvas 
+     */
     public native boolean drawCircle(Posn p, int r, AColor c);
+
+    /** 
+     *@param p the center of the disk 
+     *@param r its radius
+     *@param c its fill and outline color 
+     *@return true, if it can draw the disk into this canvas 
+     */
     public native boolean drawDisk(Posn p, int r, AColor c);
+
+    /** 
+     *@param p the upper left of the rectangle 
+     *@param width positive int 
+     *@param height positive int 
+     *@param c its outline color 
+     *@return true, if it can draw the rectangle into this canvas 
+     */
     public native boolean drawRect(Posn p, int width, int height, AColor c);
+
+    /** 
+     *@param p0 the first point on the line 
+     *@param p1 the second point on the line 
+     *@param c its color 
+     *@return true, if it can draw the line into this canvas 
+     */
     public native boolean drawLine(Posn p0, Posn p1, AColor c);
+
+    /** 
+     *@param p the position of the baseline of the string 
+     *@param s the message to be drawn 
+     *@return true, if it can draw the string into this canvas 
+     */
     public native boolean drawString(Posn p, String s);
+
+    /** 
+     *@return true, if it can erase the specified circle from this canvas 
+     */
     public native boolean clearCircle(Posn p, int r, AColor c);
+
+    /** 
+     *@return true, if it can erase the specified disk from this canvas 
+     */
     public native boolean clearDisk(Posn p, int r, AColor c);
+
+    /** 
+     *@return true, if it can erase the specified rectangle from this canvas 
+     */
     public native boolean clearRect(Posn p, int width, int height, AColor c);
+
+    /** 
+     *@return true, if it can erase the specified string from this canvas 
+     */
     public native boolean clearLine(Posn p0, Posn p1, AColor c);
 }