[Waba-spec] Bug in Graphics.drawRect (!!) and graphics issues

[Sean L. <se...@cs...>]

I've identified a bug in Waba's Graphics.drawRect, and maybe also 
SuperWaba's implementation of other graphics primitives.  Presently, 
Waba draws rectangles with one less pixel in width and one less pixel in 
height than java.awt.Graphics does. This is a nasty bug because drawRect 
is used *everywhere* in the Waba system, and fixing this bug may cause 
quite a number of apps to draw one-off.  What should we do here?

This is going to crop up again and again if we don't decide on a 
strategy here: what about drawRoundRect? drawOval? drawArc?  All of 
these are correctly implemented by assuming a rectangle 1 larger and 1 
higher than actually requested.

For example, the corrected code is:

public void drawRect(int x, int y, int width, int height)
	{
	int x2 = x + width; // got rid of a -1
	int y2 = y + height; // got rid of a -1
	drawLine(x, y, x2 - 1, y);
	drawLine(x2, y, x2, y2 - 1);
	drawLine(x2, y2, x + 1, y2);
	drawLine(x, y2, x, y + 1);
	}

In Java, the here are the actual boundaries.  <=X means the X coordinate 
of the leftmost pixel.  >=X means the X coordinate of the rightmost 
pixel.  Etc.

Object					<=X	<=Y	>=X			>=Y
drawLine(x,y,x2,y2)		x	y	x2			y2
drawRect(x,y,width,height)	x	y	x+width		y+height
	OOPS! Waba draws >=X as x+width-1, and >=Y as y+height-1
fillRect(x,y,width,height)	x	y	x+width-1		y+height-1

Other ones fyi:

drawRoundRect(x,y,width,	
	height,awidth,aheight)	x	y	x+width		y+height
fillRoundRect(x,y,width,	
	height,awidth,aheight)	x	y	x+width		y+height
drawOval(x,y,width,height)	x	y	x+width		y+height
fillOval(x,y,width,height)	x+1	y+1	x+width-2		y+height-2
	OOPS! This is *different* from drawRoundRect -- thus if you're using
	drawRoundRect to do drawOval (in SuperWaba say), you're probably 
off by one.

drawArc and fillArc perform similarly to drawOval/fillOval, though there 
are some oddities with drawing the leftmost ray in Java (it doesn't get 
filled, very weird).