gallium: new 'draw' stage for line stipple

Stippled lines are converted into a series of shorter line segments

src/mesa/pipe/draw/draw_context.c

@@ -49,6 +49,7 @@ struct draw_context *draw_create( void )
 
    /* create pipeline stages */
    draw->pipeline.wide      = draw_wide_stage( draw );
+   draw->pipeline.stipple   = draw_stipple_stage( draw );
    draw->pipeline.unfilled  = draw_unfilled_stage( draw );
    draw->pipeline.twoside   = draw_twoside_stage( draw );
    draw->pipeline.offset    = draw_offset_stage( draw );
@@ -93,6 +94,7 @@ struct draw_context *draw_create( void )
 void draw_destroy( struct draw_context *draw )
 {
    draw->pipeline.wide->destroy( draw->pipeline.wide );
+   draw->pipeline.stipple->destroy( draw->pipeline.stipple );
    draw->pipeline.unfilled->destroy( draw->pipeline.unfilled );
    draw->pipeline.twoside->destroy( draw->pipeline.twoside );
    draw->pipeline.offset->destroy( draw->pipeline.offset );

src/mesa/pipe/draw/draw_private.h

@@ -158,6 +158,7 @@ struct draw_context
       struct draw_stage *twoside;
       struct draw_stage *offset;
       struct draw_stage *unfilled;
+      struct draw_stage *stipple;
       struct draw_stage *wide;
       struct draw_stage *rasterize;
    } pipeline;
@@ -248,6 +249,7 @@ extern struct draw_stage *draw_offset_stage( struct draw_context *context );
 extern struct draw_stage *draw_clip_stage( struct draw_context *context );
 extern struct draw_stage *draw_flatshade_stage( struct draw_context *context );
 extern struct draw_stage *draw_cull_stage( struct draw_context *context );
+extern struct draw_stage *draw_stipple_stage( struct draw_context *context );
 extern struct draw_stage *draw_wide_stage( struct draw_context *context );
 extern struct draw_stage *draw_validate_stage( struct draw_context *context );
 

src/mesa/pipe/draw/draw_stipple.c

@@ -0,0 +1,242 @@
+/**************************************************************************
+ * 
+ * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ * 
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ * 
+ **************************************************************************/
+
+/* Authors:  Keith Whitwell <keith@tungstengraphics.com>
+ */
+
+/* Implement line stipple by cutting lines up into smaller lines.
+ * There are hundreds of ways to implement line stipple, this is one
+ * choice that should work in all situations, requires no state
+ * manipulations, but with a penalty in terms of large amounts of
+ * generated geometry.
+ */
+
+
+#include "pipe/p_util.h"
+#include "pipe/p_defines.h"
+#include "pipe/p_shader_tokens.h"
+#include "draw_private.h"
+
+
+/** Subclass of draw_stage */
+struct stipple_stage {
+   struct draw_stage stage;
+   float counter;
+   uint pattern;
+   uint factor;
+};
+
+
+static INLINE struct stipple_stage *
+stipple_stage(struct draw_stage *stage)
+{
+   return (struct stipple_stage *) stage;
+}
+
+
+/**
+ * Compute interpolated vertex attributes for 'dst' at position 't' 
+ * between 'v0' and 'v1'.
+ */
+static void
+screen_interp( struct draw_context *draw,
+               struct vertex_header *dst,
+               float t,
+               const struct vertex_header *v0, 
+               const struct vertex_header *v1 )
+{
+   uint attr;
+   for (attr = 0; attr < draw->vertex_info.num_attribs; attr++) {
+      switch (draw->vertex_info.interp_mode[attr]) {
+      case INTERP_NONE:
+      case INTERP_CONSTANT:
+         COPY_4FV(dst->data[attr], v0->data[attr]);
+         break;
+      case INTERP_PERSPECTIVE:
+         /* Fall-through */
+         /* XXX special-case perspective? */
+      case INTERP_LINEAR:
+         {
+            const float *val0 = v0->data[attr];
+            const float *val1 = v1->data[attr];
+            float *newv = dst->data[attr];
+            uint i;
+            for (i = 0; i < 4; i++) {
+               newv[i] = val0[i] + t * (val1[i] - val0[i]);
+            }
+         }
+         break;
+      default:
+         abort();
+      }
+   }
+}
+
+
+static void
+emit_segment(struct draw_stage *stage, struct prim_header *header,
+             float t0, float t1)
+{
+   struct vertex_header *v0new = dup_vert(stage, header->v[0], 0);
+   struct vertex_header *v1new = dup_vert(stage, header->v[1], 1);
+   struct prim_header newprim = *header;
+
+   if (t0 > 0.0) {
+      screen_interp( stage->draw, v0new, t0, header->v[0], header->v[1] );
+      newprim.v[0] = v0new;
+   }
+
+   if (t1 < 1.0) {
+      screen_interp( stage->draw, v1new, t1, header->v[0], header->v[1] );
+      newprim.v[1] = v1new;
+   }
+
+   stage->next->line( stage->next, &newprim );
+}
+
+
+static INLINE unsigned
+stipple_test(int counter, ushort pattern, int factor)
+{
+   int b = (counter / factor) & 0xf;
+   return (1 << b) & pattern;
+}
+
+
+static void
+stipple_line(struct draw_stage *stage, struct prim_header *header)
+{
+   struct stipple_stage *stipple = stipple_stage(stage);
+   struct vertex_header *v0 = header->v[0];
+   struct vertex_header *v1 = header->v[1];
+   const float *pos0 = v0->data[0];
+   const float *pos1 = v1->data[0];
+   float start = 0;
+   int state = 0;
+
+   float x0 = pos0[0];
+   float x1 = pos1[0];
+   float y0 = pos0[1];
+   float y1 = pos1[1];
+
+   float dx = x0 > x1 ? x0 - x1 : x1 - x0;
+   float dy = y0 > y1 ? y0 - y1 : y1 - y0;
+
+   float length = MAX2(dx, dy);
+   int i;
+
+   /* XXX ToDo: intead of iterating pixel-by-pixel, use a look-up table.
+    */
+   for (i = 0; i < length; i++) {
+      int result = stipple_test( stipple->counter+i,
+                                 stipple->pattern, stipple->factor );
+      if (result != state) {
+         /* changing from "off" to "on" or vice versa */
+	 if (state) {
+	    if (start != i) {
+               /* finishing an "on" segment */
+	       emit_segment( stage, header, start / length, i / length );
+            }
+	 }
+	 else {
+            /* starting an "on" segment */
+	    start = i;
+	 }
+	 state = result;	   
+      }
+   }
+
+   if (state && start < length)
+      emit_segment( stage, header, start / length, 1.0 );
+
+   stipple->counter += length;
+}
+
+
+static void
+reset_stipple_counter(struct draw_stage *stage)
+{
+   struct stipple_stage *stipple = stipple_stage(stage);
+   stipple->counter = 0;
+   stage->next->reset_stipple_counter( stage->next );
+}
+
+
+static void
+stipple_begin(struct draw_stage *stage)
+{
+   struct stipple_stage *stipple = stipple_stage(stage);
+   struct draw_context *draw = stage->draw;
+
+   stipple->pattern = draw->rasterizer->line_stipple_pattern;
+   stipple->factor = draw->rasterizer->line_stipple_factor + 1;
+
+   stage->next->begin( stage->next );
+}
+
+
+static void
+stipple_end(struct draw_stage *stage)
+{
+   stage->next->end( stage->next );
+}
+
+
+static void
+passthrough_point(struct draw_stage *stage, struct prim_header *header)
+{
+   stage->next->point( stage->next, header );
+}
+
+
+static void
+passthrough_tri(struct draw_stage *stage, struct prim_header *header)
+{
+   stage->next->tri(stage->next, header);
+}
+
+
+/**
+ * Create line stippler stage
+ */
+struct draw_stage *draw_stipple_stage( struct draw_context *draw )
+{
+   struct stipple_stage *stipple = CALLOC_STRUCT(stipple_stage);
+
+   draw_alloc_tmps( &stipple->stage, 2 );
+
+   stipple->stage.draw = draw;
+   stipple->stage.next = NULL;
+   stipple->stage.begin = stipple_begin;
+   stipple->stage.point = passthrough_point;
+   stipple->stage.line = stipple_line;
+   stipple->stage.tri = passthrough_tri;
+   stipple->stage.reset_stipple_counter = reset_stipple_counter;
+   stipple->stage.end = stipple_end;
+
+   return &stipple->stage;
+}

src/mesa/pipe/draw/draw_validate.c

@@ -58,6 +58,11 @@ static void validate_begin( struct draw_stage *stage )
       next = draw->pipeline.wide;
    }
 
+   if (draw->rasterizer->line_stipple_enable) {
+      draw->pipeline.stipple->next = next;
+      next = draw->pipeline.stipple;
+   }
+
    if (draw->rasterizer->fill_cw != PIPE_POLYGON_MODE_FILL ||
        draw->rasterizer->fill_ccw != PIPE_POLYGON_MODE_FILL) {
       draw->pipeline.unfilled->next = next;

src/mesa/sources

@@ -165,6 +165,7 @@ DRAW_SOURCES = \
 	pipe/draw/draw_flatshade.c \
 	pipe/draw/draw_offset.c \
 	pipe/draw/draw_prim.c \
+	pipe/draw/draw_stipple.c \
 	pipe/draw/draw_twoside.c \
 	pipe/draw/draw_unfilled.c \
 	pipe/draw/draw_validate.c \