The same fix Marius implemented for gen6 (commit a9b04d8a) and
gen7 (commit 24ecf37a).
---
src/mesa/drivers/dri/i965/gen8_sf_state.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
Ken, I don't have gen8 hardware available to test this so it would
be nice if someone else verifies that this fixes the piglit tests you
mentioned.
diff --git a/src/mesa/drivers/dri/i965/gen8_sf_state.c
b/src/mesa/drivers/dri/i965/gen8_sf_state.c
index 83ef62b..22c1c4a 100644
--- a/src/mesa/drivers/dri/i965/gen8_sf_state.c
+++ b/src/mesa/drivers/dri/i965/gen8_sf_state.c
@@ -156,8 +156,26 @@ upload_sf(struct brw_context *brw)
/* _NEW_LINE */
float line_width = brw_get_line_width(brw);
uint32_t line_width_u3_7 = U_FIXED(line_width, 7);
- if (line_width_u3_7 == 0)
- line_width_u3_7 = 1;
+
+ /* Line width of 0 is not allowed when MSAA enabled */
+ if (ctx->Multisample._Enabled) {
+ if (line_width_u3_7 == 0)
+ line_width_u3_7 = 1;
+ } else if (ctx->Line.SmoothFlag && ctx->Line.Width < 1.5) {
+ /* For 1 pixel line thickness or less, the general
+ * anti-aliasing algorithm gives up, and a garbage line is
+ * generated. Setting a Line Width of 0.0 specifies the
+ * rasterization of the "thinnest" (one-pixel-wide),
+ * non-antialiased lines.
+ *
+ * Lines rendered with zero Line Width are rasterized using
+ * Grid Intersection Quantization rules as specified by
+ * bspec section 6.3.12.1 Zero-Width (Cosmetic) Line
+ * Rasterization.
+ */
+ line_width_u3_7 = 0;
+ }
+
if (brw->gen >= 9 || brw->is_cherryview) {
dw1 |= line_width_u3_7 << GEN9_SF_LINE_WIDTH_SHIFT;
} else {
--
1.9.1
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