[Mesa-dev] [PATCH] draw: fix splitting of line loops (v2)

[Brian Paul]

When the draw module splits long line loops, the sections are emitted
as line strips.  But the primitive type wasn't set correctly so each
section was being drawn as a loop, introducing extra line segments.

To fix this, we pass a new DRAW_LINE_LOOP_AS_STRIP flag to the run()
function.  The linear/elt_run() functions have to check for this flag
and set their primitive type accordingly.

No piglit regressions.  Fixes piglit's lineloop with -count 4097 or
higher.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81174
---
 src/gallium/auxiliary/draw/draw_private.h                |  5 +++--
 .../auxiliary/draw/draw_pt_fetch_shade_pipeline.c        | 16 +++++++++++++---
 .../auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c   | 16 +++++++++++++---
 src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h          |  3 +++
 4 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/gallium/auxiliary/draw/draw_private.h b/src/gallium/auxiliary/draw/draw_private.h
index 0ad94bb..5584c4a 100644
--- a/src/gallium/auxiliary/draw/draw_private.h
+++ b/src/gallium/auxiliary/draw/draw_private.h
@@ -355,8 +355,9 @@ struct draw_vertex_info {
 };
 
 /* these flags are set if the primitive is a segment of a larger one */
-#define DRAW_SPLIT_BEFORE 0x1
-#define DRAW_SPLIT_AFTER  0x2
+#define DRAW_SPLIT_BEFORE        0x1
+#define DRAW_SPLIT_AFTER         0x2
+#define DRAW_LINE_LOOP_AS_STRIP  0x4
 
 struct draw_prim_info {
    boolean linear;
diff --git a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
index ffec863..aa20b91 100644
--- a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
+++ b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
@@ -359,6 +359,16 @@ fetch_pipeline_generic(struct draw_pt_middle_end *middle,
 }
 
 
+static inline unsigned
+prim_type(unsigned prim, unsigned flags)
+{
+   if (flags & DRAW_LINE_LOOP_AS_STRIP)
+      return PIPE_PRIM_LINE_STRIP;
+   else
+      return prim;
+}
+
+
 static void
 fetch_pipeline_run(struct draw_pt_middle_end *middle,
                    const unsigned *fetch_elts,
@@ -380,7 +390,7 @@ fetch_pipeline_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
@@ -408,7 +418,7 @@ fetch_pipeline_linear_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = count;
    prim_info.elts = NULL;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &count;
@@ -439,7 +449,7 @@ fetch_pipeline_linear_run_elts(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
diff --git a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
index e42c4af..2d7569b 100644
--- a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
+++ b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
@@ -473,6 +473,16 @@ llvm_pipeline_generic(struct draw_pt_middle_end *middle,
 }
 
 
+static inline unsigned
+prim_type(unsigned prim, unsigned flags)
+{
+   if (flags & DRAW_LINE_LOOP_AS_STRIP)
+      return PIPE_PRIM_LINE_STRIP;
+   else
+      return prim;
+}
+
+
 static void
 llvm_middle_end_run(struct draw_pt_middle_end *middle,
                     const unsigned *fetch_elts,
@@ -494,7 +504,7 @@ llvm_middle_end_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
@@ -522,7 +532,7 @@ llvm_middle_end_linear_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = count;
    prim_info.elts = NULL;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &count;
@@ -552,7 +562,7 @@ llvm_middle_end_linear_run_elts(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
diff --git a/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h b/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
index 0afabb0..6da79b9 100644
--- a/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
+++ b/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
@@ -249,6 +249,9 @@ vsplit_segment_loop_linear(struct vsplit_frontend *vsplit, unsigned flags,
 
    assert(icount + !!close_loop <= vsplit->segment_size);
 
+   /* need to draw the sections of the line loop as line strips */
+   flags |= DRAW_LINE_LOOP_AS_STRIP;
+
    if (close_loop) {
       for (nr = 0; nr < icount; nr++)
          vsplit->fetch_elts[nr] = istart + nr;
-- 
1.9.1