Any way to get rid of PolyFillArc artifacts?

Sam Varshavchik mrsam at
Fri Jun 19 05:56:35 PDT 2015

I am creating a pixmap of a certain size, and sending a PolyFillArc request  
from (0, 0), sized (width, height).

x11trace log, when using a pixmap sized (61, 61):

00:<:042e: 16: Request(53): CreatePixmap depth=0x01 pid=0x03e000e8  
00002d5 width=61 height=61

[ … ]

000:<:0434: 16: Request(55): CreateGC cid=0x03e000eb drawable=0x03e000e8  

[ … ]

000:<:043b: 88: Request(56): ChangeGC gc=0x03e000eb  
values={function=Set(0x0f) plane-mask=0xffffffff foreground=0x00000000  
background=0x00000001 line-width=0 line-style=Solid(0x00) cap- 
style=Butt(0x01) join-style=Miter(0x00) fill-style=Solid(0x00) fill- 
rule=EvenOdd(0x00) tile-stipple-x-origin=0 tile-stipple-y-origin=0 subwindow- 
mode=ClipByChildren(0x00) graphics-exposures=true(0x01) clip-x-origin=0 clip- 
y-origin=0 clip-mask=None(0x00000000) dash-offset=0 arc-mode=PieSlice(0x01)}
000:<:043c: 24: Request(71): PolyFillArc drawable=0x03e000e8 gc=0x03e000eb  
arcs={x=0 y=0 w=61 h=61 angle1=0 angle2=23040};

The results from this is an arc that touches nicely on the right and the  
bottom side, but doesn't touch the top and the left borders at all, it's one  
pixel off. Row 0 and column 0 are unchanged, and the circle approaches and  
rounds on the second row and column.

Now, if I make the size of the arc even, if I change the pixmap to be 60x60,  
I get a slightly different result. The circle still touches the bottom and  
the right borders nicely, and on the top and the left border, there appears  
to be a single pixel at the center point. It looks something like this:


I'm using xorg 7.7 with the noveau driver. Any tips on drawing circles that  
touch all four boundary corners nicely? Artificially expanding the size of  
the circle boundaries, and using a clip mask, depending on whether the  
dimensions are odd or even, sounds hackish.

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