fix incorrect colors in Lefty postscript output

This code intended to print color data to its output file in postscript (PS)
format. However it miscalculated the low nibble of each non-zero byte as 1 due
to an incorrect operator. This may have not been noticed in the resulting image
due to low precision. This was exposed by the compiler flag -Wlogical-op. Fixes
#1927.

At first glance, it looks like this could be written without shifting and
masking at all by simply printing the byte padded to width 2, but maybe I am
missing some subtlety.

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc50ca5964d10e87eac4c1eac81183c2f0cb3e49..0dfb7920b672ef8d3d43d3328ea8b5c3d4554add 100644 (file)
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- typos in gpcanvas.c #1927
+
 ## [2.46.0] - 2021-02-13
 
 ### Added

diff --git a/cmd/lefty/ws/x11/gpcanvas.c b/cmd/lefty/ws/x11/gpcanvas.c
index 355457b34fbe4239d70e0f56394cceaa2d3a4650..00229e8c7cc4a9e10d3d3a4e13bdf714d33d704b 100644 (file)
--- a/cmd/lefty/ws/x11/gpcanvas.c
+++ b/cmd/lefty/ws/x11/gpcanvas.c
@@ -699,11 +699,11 @@ int GPbitblt (
             bitmap->u.bits + 3 * ((int) bitmap->size.x * (br.o.y + y) + br.o.x)
         );
         for (x = 0; x < bs.x; x++) {
-            hi = (*s >> 4) & 15, lo = *s++ && 15;
+            hi = (*s >> 4) & 15, lo = *s++ & 15;
             fprintf (FP, "%x%x", hi, lo);
-            hi = (*s >> 4) & 15, lo = *s++ && 15;
+            hi = (*s >> 4) & 15, lo = *s++ & 15;
             fprintf (FP, "%x%x", hi, lo);
-            hi = (*s >> 4) & 15, lo = *s++ && 15;
+            hi = (*s >> 4) & 15, lo = *s++ & 15;
             fprintf (FP, "%x%x", hi, lo);
         }
         fprintf (FP, "\n");