Re: line corners with terminals for vector graphics

[<br...@ph...>]

Ethan A Merritt wrote:
> On Wednesday 01 February 2006 06:22 pm, Mojca Miklavec wrote:

>>One thing can be (has to be) fixed in the terminal itself however:
>>when MetaPost draws a rectangular frame, it uses continuous line from
>>4 line segments, but the beginning of the first line and the end of
>>the last line are "not properly connected" (the curve is not closed).

> But it's not obvious to me why the line would not be closed.

Well, the terminal driver API currently has no way for the core to tell
the driver the difference between a polyline that just happens to byte
its own tail (i.e. end == start), and one that is actually meant to be
a (non-filled) polygon.  In the context of Postscript, that shows by the 
fact that PS_FLUSH_PATH never emits a "closepath" command in front of 
the "stroke".  Only the point symbols, PS_polygon() and the filled-box 
operators emit closepath.

Without the closepath, one of the corners of the graph box will not have 
neither a mitre, nor a round or any other join.  As an example, look 
what this plot comes out as, in PostScript:

	set border 31 lt -1 lw 10
	plot x

and examine the lower left corner of the graph box.

> Or are you saying that it meets up properly, but the line-join
> at that corner is not consisent with the other line-joins?

The problem is that at the tail-byting corner, there is no line join at 
all --- just two lines ends that happen to be in the same place.