[PATCH xserver 2/2] Eliminate coordinate mode in PolyPoint, PolyLines and FillPolygon ops

[Adam Jackson]

On Fri, 2016-09-23 at 01:15 +0300, Keith Packard wrote:

> +static void
> +FixCoordModePrevious(int npt, xPoint *ppt)
> +{
> +    int x, y;
> +
> +    x = ppt->x;
> +    y = ppt->y;
> +    npt--;
> +    while (npt--) {
> +        ppt++;
> +        x = (ppt->x += x);
> +        y = (ppt->y += y);
> +    }
> +}

You want to make this non-static, so in the xinerama case you can do
this translation once at the top level.

> @@ -1785,9 +1800,12 @@ ProcPolyPoint(ClientPtr client)
>      }
>      VALIDATE_DRAWABLE_AND_GC(stuff->drawable, pDraw, DixWriteAccess);
>      npoint = bytes_to_int32((client->req_len << 2) - sizeof(xPolyPointReq));
> -    if (npoint)
> -        (*pGC->ops->PolyPoint) (pDraw, pGC, stuff->coordMode, npoint,
> +    if (npoint) {
> +        if (stuff->coordMode == CoordModePrevious)
> +            FixCoordModePrevious(npoint, (xPoint *) &stuff[1]);
> +        (*pGC->ops->PolyPoint) (pDraw, pGC, npoint,
>                                  (xPoint *) &stuff[1]);
> +    }
>      return Success;
>  }

You're not correcting stuff->coordMode in place, which means under
xinerama you'll mutate geometry once per screen, which ain't right.

- ajax