[Mesa-dev] [PATCH] draw: fix line stippling

[sroland at vmware.com]

From: Roland Scheidegger <sroland at vmware.com>

The logic was comparing actual ints, not true/false values.
This meant that it was emitting always multiple line segments instead of just
one even if the stipple test had the same result, which looks inefficient, and
the segments also overlapped thus breaking line aa as well.
(In practice, with the no-op default line stipple pattern, for a 10-pixel
long line from 0-9 it was emitting 10 segments, with the individual segments
ranging from 0-1, 0-2, 0-3 and so on.)

This fixes https://bugs.freedesktop.org/show_bug.cgi?id=94193

CC: <mesa-stable at lists.freedesktop.org>
---
 src/gallium/auxiliary/draw/draw_pipe_stipple.c | 30 +++++++++++++-------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/gallium/auxiliary/draw/draw_pipe_stipple.c b/src/gallium/auxiliary/draw/draw_pipe_stipple.c
index dcf05aa..04854ad 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_stipple.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_stipple.c
@@ -108,11 +108,11 @@ emit_segment(struct draw_stage *stage, struct prim_header *header,
 }
 
 
-static inline unsigned
+static inline boolean
 stipple_test(int counter, ushort pattern, int factor)
 {
    int b = (counter / factor) & 0xf;
-   return (1 << b) & pattern;
+   return !!((1 << b) & pattern);
 }
 
 
@@ -126,7 +126,7 @@ stipple_line(struct draw_stage *stage, struct prim_header *header)
    const float *pos0 = v0->data[pos];
    const float *pos1 = v1->data[pos];
    float start = 0;
-   int state = 0;
+   boolean state = 0;
 
    float x0 = pos0[0];
    float x1 = pos1[0];
@@ -143,29 +143,29 @@ stipple_line(struct draw_stage *stage, struct prim_header *header)
       stipple->counter = 0;
 
 
-   /* XXX ToDo: intead of iterating pixel-by-pixel, use a look-up table.
+   /* XXX ToDo: instead of iterating pixel-by-pixel, use a look-up table.
     */
    for (i = 0; i < length; i++) {
-      int result = stipple_test( (int) stipple->counter+i,
-                                 (ushort) stipple->pattern, stipple->factor );
+      boolean result = stipple_test((int)stipple->counter + i,
+                                    (ushort)stipple->pattern, stipple->factor);
       if (result != state) {
          /* changing from "off" to "on" or vice versa */
-	 if (state) {
-	    if (start != i) {
+         if (state) {
+            if (start != i) {
                /* finishing an "on" segment */
-	       emit_segment( stage, header, start / length, i / length );
+               emit_segment(stage, header, start / length, i / length);
             }
-	 }
-	 else {
+         }
+         else {
             /* starting an "on" segment */
-	    start = (float) i;
-	 }
-	 state = result;	   
+            start = (float)i;
+         }
+         state = result;
       }
    }
 
    if (state && start < length)
-      emit_segment( stage, header, start / length, 1.0 );
+      emit_segment(stage, header, start / length, 1.0);
 
    stipple->counter += length;
 }
-- 
2.1.4