src/gallium/auxiliary/draw/draw_pipe_wide_line.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28 /* Authors:  Keith Whitwell <keith@tungstengraphics.com>
  29  */
  30
  31 #include "pipe/p_util.h"
  32 #include "pipe/p_defines.h"
  33 #include "pipe/p_shader_tokens.h"
  34 #include "draw_private.h"
  35 #include "draw_pipe.h"
  36
  37
  38 struct wideline_stage {
  39    struct draw_stage stage;
  40
  41    float half_line_width;
  42 };
  43
  44
  45
  46 static INLINE struct wideline_stage *wideline_stage( struct draw_stage *stage )
  47 {
  48    return (struct wideline_stage *)stage;
  49 }
  50
  51
  52 static void wideline_point( struct draw_stage *stage,
  53                                struct prim_header *header )
  54 {
  55    stage->next->point( stage->next, header );
  56 }
  57
  58
  59 static void wideline_tri( struct draw_stage *stage,
  60                              struct prim_header *header )
  61 {
  62    stage->next->tri(stage->next, header);
  63 }
  64
  65
  66 /**
  67  * Draw a wide line by drawing a quad (two triangles).
  68  * XXX need to disable polygon stipple.
  69  */
  70 static void wideline_line( struct draw_stage *stage,
  71                            struct prim_header *header )
  72 {
  73    /*const struct wideline_stage *wide = wideline_stage(stage);*/
  74    const float half_width = 0.5f * stage->draw->rasterizer->line_width;
  75
  76    struct prim_header tri;
  77
  78    struct vertex_header *v0 = dup_vert(stage, header->v[0], 0);
  79    struct vertex_header *v1 = dup_vert(stage, header->v[0], 1);
  80    struct vertex_header *v2 = dup_vert(stage, header->v[1], 2);
  81    struct vertex_header *v3 = dup_vert(stage, header->v[1], 3);
  82
  83    float *pos0 = v0->data[0];
  84    float *pos1 = v1->data[0];
  85    float *pos2 = v2->data[0];
  86    float *pos3 = v3->data[0];
  87
  88    const float dx = FABSF(pos0[0] - pos2[0]);
  89    const float dy = FABSF(pos0[1] - pos2[1]);
  90
  91    /* small tweak to meet GL specification */
  92    const float bias = 0.125f;
  93
  94    /*
  95     * Draw wide line as a quad (two tris) by "stretching" the line along
  96     * X or Y.
  97     * We need to tweak coords in several ways to be conformant here.
  98     */
  99
 100    if (dx > dy) {
 101       /* x-major line */
 102       pos0[1] = pos0[1] - half_width - bias;
 103       pos1[1] = pos1[1] + half_width - bias;
 104       pos2[1] = pos2[1] - half_width - bias;
 105       pos3[1] = pos3[1] + half_width - bias;
 106       if (pos0[0] < pos2[0]) {
 107          /* left to right line */
 108          pos0[0] -= 0.5f;
 109          pos1[0] -= 0.5f;
 110          pos2[0] -= 0.5f;
 111          pos3[0] -= 0.5f;
 112       }
 113       else {
 114          /* right to left line */
 115          pos0[0] += 0.5f;
 116          pos1[0] += 0.5f;
 117          pos2[0] += 0.5f;
 118          pos3[0] += 0.5f;
 119       }
 120    }
 121    else {
 122       /* y-major line */
 123       pos0[0] = pos0[0] - half_width + bias;
 124       pos1[0] = pos1[0] + half_width + bias;
 125       pos2[0] = pos2[0] - half_width + bias;
 126       pos3[0] = pos3[0] + half_width + bias;
 127       if (pos0[1] < pos2[1]) {
 128          /* top to bottom line */
 129          pos0[1] -= 0.5f;
 130          pos1[1] -= 0.5f;
 131          pos2[1] -= 0.5f;
 132          pos3[1] -= 0.5f;
 133       }
 134       else {
 135          /* bottom to top line */
 136          pos0[1] += 0.5f;
 137          pos1[1] += 0.5f;
 138          pos2[1] += 0.5f;
 139          pos3[1] += 0.5f;
 140       }
 141    }
 142
 143    tri.det = header->det;  /* only the sign matters */
 144    tri.v[0] = v0;
 145    tri.v[1] = v2;
 146    tri.v[2] = v3;
 147    stage->next->tri( stage->next, &tri );
 148
 149    tri.v[0] = v0;
 150    tri.v[1] = v3;
 151    tri.v[2] = v1;
 152    stage->next->tri( stage->next, &tri );
 153 }
 154
 155
 156 static void wideline_flush( struct draw_stage *stage, unsigned flags )
 157 {
 158    stage->next->flush( stage->next, flags );
 159 }
 160
 161
 162 static void wideline_reset_stipple_counter( struct draw_stage *stage )
 163 {
 164    stage->next->reset_stipple_counter( stage->next );
 165 }
 166
 167
 168 static void wideline_destroy( struct draw_stage *stage )
 169 {
 170    draw_free_temp_verts( stage );
 171    FREE( stage );
 172 }
 173
 174
 175 struct draw_stage *draw_wide_line_stage( struct draw_context *draw )
 176 {
 177    struct wideline_stage *wide = CALLOC_STRUCT(wideline_stage);
 178
 179    draw_alloc_temp_verts( &wide->stage, 4 );
 180
 181    wide->stage.draw = draw;
 182    wide->stage.next = NULL;
 183    wide->stage.point = wideline_point;
 184    wide->stage.line = wideline_line;
 185    wide->stage.tri = wideline_tri;
 186    wide->stage.flush = wideline_flush;
 187    wide->stage.reset_stipple_counter = wideline_reset_stipple_counter;
 188    wide->stage.destroy = wideline_destroy;
 189
 190    return &wide->stage;
 191 }