[Rd] hang-up with log="x" and segments (PR#1030)

[Peter Dalgaard BSA]

sc@paracelsus.fdm.uni-freiburg.de writes:

> I experienced the following problem with R 1.3.0 which is probably a
> bug. The program hangs-up if 1.) a coordinate of segments is outside the
> ploting region and 2.) the option log="x" is used.
> 
> ##
> ## works fine
> ##
> plot(1,1, xlim=c(0.5, 2), ylim=c(0.5, 2))
> segments(0.5 , 1.2, 1, 0.6)
> segments(0.25, 1.2, 1, 0.6)
> segments(1   , 1.2, 1, 0.6)
> 
> ##
> ## hang-up
> ##
> plot(1,1, xlim=c(0.5, 2), ylim=c(0.5, 2), log="x")
> segments(0.5 , 1.2, 1, 0.6)
> segments(0.25, 1.2, 1, 0.6)
> segments(1   , 1.2, 1, 0.6)

Confirmed on Linux, but seems to have disappeared in the patched
version. Not sure what caused the fix, though... My guess would be
that it is this change in CSclipline:

@@ -2464,6 +2466,7 @@
     yb = cr->yb;
     yt = cr->yt;
     if (dd->gp.xlog || dd->gp.ylog) {
+       double temp;
 
        GConvert(x1, y1, coords, NDC, dd);
        GConvert(x2, y2, coords, NDC, dd);
@@ -2475,6 +2478,17 @@
        cr2.yb = yb;
        cr2.yt = yt;
 
+        if (cr2.xr < cr2.xl) {
+            temp = cr2.xl;
+            cr2.xl = cr2.xr;
+            cr2.xr = temp;
+        }
+        if (cr2.yt < cr2.yb) {
+            temp = cr2.yb;
+            cr2.yb = cr2.yt;
+            cr2.yt = temp;
+        }
+
        x = xl;         /* keep -Wall happy */
        y = yb;         /* keep -Wall happy */
        while( c1 || c2 ) {


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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