Mesa (7.9): llvmpipe: fix flatshading in new line code

[Keith Whitwell]

Module: Mesa
Branch: 7.9
Commit: 141dbbfc7856d8e33cf6d628758ef3ef2654de93
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=141dbbfc7856d8e33cf6d628758ef3ef2654de93

Author: Keith Whitwell <keithw at vmware.com>
Date:   Tue Sep 21 14:28:51 2010 +0100

llvmpipe: fix flatshading in new line code

Calculate interpolants before rearranging the vertices.

---

 src/gallium/drivers/llvmpipe/lp_setup_line.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/gallium/drivers/llvmpipe/lp_setup_line.c b/src/gallium/drivers/llvmpipe/lp_setup_line.c
index 9f090d1..829eb8a 100644
--- a/src/gallium/drivers/llvmpipe/lp_setup_line.c
+++ b/src/gallium/drivers/llvmpipe/lp_setup_line.c
@@ -292,6 +292,7 @@ try_setup_line( struct lp_setup_context *setup,
    float x2diff;
    float y2diff;
    float dx, dy;
+   float area;
 
    boolean draw_start;
    boolean draw_end;
@@ -311,6 +312,18 @@ try_setup_line( struct lp_setup_context *setup,
 
    dx = v1[0][0] - v2[0][0];
    dy = v1[0][1] - v2[0][1];
+   area = (dx * dx  + dy * dy);
+   if (area == 0) {
+      LP_COUNT(nr_culled_tris);
+      return TRUE;
+   }
+
+   info.oneoverarea = 1.0f / area;
+   info.dx = dx;
+   info.dy = dy;
+   info.v1 = v1;
+   info.v2 = v2;
+
   
    /* X-MAJOR LINE */
    if (fabsf(dx) >= fabsf(dy)) {
@@ -573,12 +586,6 @@ try_setup_line( struct lp_setup_context *setup,
    line->plane[3].dcdx = y[3] - y[0];
 
 
-   info.oneoverarea = 1.0f / (dx * dx  + dy * dy);    
-   info.dx = dx;
-   info.dy = dy;
-   info.v1 = v1;
-   info.v2 = v2;
-
    /* Setup parameter interpolants:
     */
    setup_line_coefficients( setup, line, &info);