Add some comments to explain things, code clarifications.

Also, add quad.facing field for front/back facing.  See comments for details.

3 files changed, 72 insertions, 36 deletions

diff --git a/src/mesa/softpipe/generic/g_headers.h b/src/mesa/softpipe/generic/g_headers.h
index 1db325a4ab6..96ff52a453b 100644
--- a/src/mesa/softpipe/generic/g_headers.h
+++ b/src/mesa/softpipe/generic/g_headers.h
@@ -93,6 +93,7 @@ struct quad_header {
    GLint x0;
    GLint y0;
    GLuint mask;
+   GLuint facing;   /**< Front or back facing? */
 
    struct {
       GLfloat color[4][QUAD_SIZE];	/* rrrr, gggg, bbbb, aaaa */
diff --git a/src/mesa/softpipe/generic/g_prim_setup.c b/src/mesa/softpipe/generic/g_prim_setup.c
index 3e9639f7bc1..ce93c0a6f96 100644
--- a/src/mesa/softpipe/generic/g_prim_setup.c
+++ b/src/mesa/softpipe/generic/g_prim_setup.c
@@ -68,35 +68,30 @@ struct setup_stage {
    struct quad_header quad; 
 
    struct {
-      GLint left[2];
+      GLint left[2];   /**< [0] = row0, [1] = row1 */
       GLint right[2];
       GLint y;
       GLuint y_flags;
-      GLuint mask;
+      GLuint mask;     /**< mask of MASK_BOTTOM/TOP_LEFT/RIGHT bits */
    } span;
 
 };
 
 
 
-
+/**
+ * Basically a cast wrapper.
+ */
 static inline struct setup_stage *setup_stage( struct prim_stage *stage )
 {
    return (struct setup_stage *)stage;
 }
 
 
-
-static inline GLint _min(GLint x, GLint y) 
-{
-   return x < y ? x : y;
-}
-
-static inline GLint _max(GLint x, GLint y) 
-{
-   return x > y ? x : y;
-}
-
+/**
+ * Given an X or Y coordinate, return the block/quad coordinate that it
+ * belongs to.
+ */
 static inline GLint block( GLint x )
 {
    return x & ~1;
@@ -110,7 +105,9 @@ static void setup_begin( struct prim_stage *stage )
 }
 
 
-
+/**
+ * Run shader on a quad/block.
+ */
 static void run_shader_block( struct setup_stage *setup, 
 			      GLint x, GLint y, GLuint mask )
 {
@@ -122,7 +119,11 @@ static void run_shader_block( struct setup_stage *setup,
 }
 
 
-/* this is pretty nasty...  may need to rework flush_spans again to
+/**
+ * Compute mask which indicates which pixels in the 2x2 quad are actually inside
+ * the triangle's bounds.
+ *
+ * this is pretty nasty...  may need to rework flush_spans again to
  * fix it, if possible.
  */
 static GLuint calculate_mask( struct setup_stage *setup,
@@ -146,6 +147,9 @@ static GLuint calculate_mask( struct setup_stage *setup,
 }
 
 
+/**
+ * Render a horizontal span of quads
+ */
 static void flush_spans( struct setup_stage *setup )
 {
    GLint minleft, maxright;
@@ -153,10 +157,8 @@ static void flush_spans( struct setup_stage *setup )
 
    switch (setup->span.y_flags) {      
    case 3:
-      minleft = _min(setup->span.left[0],
-		    setup->span.left[1]);
-      maxright = _max(setup->span.right[0],
-		     setup->span.right[1]);
+      minleft = MIN2(setup->span.left[0], setup->span.left[1]);
+      maxright = MAX2(setup->span.right[0], setup->span.right[1]);
       break;
 
    case 1:
@@ -188,8 +190,10 @@ static void flush_spans( struct setup_stage *setup )
    setup->span.right[1] = 0;
 }
 
-
      
+/**
+ * Do setup for point rasterization, then render the point.
+ */
 static void
 setup_point( struct prim_stage *stage, 
 	     struct prim_header *header )
@@ -197,6 +201,9 @@ setup_point( struct prim_stage *stage,
 }
 
 
+/**
+ * Do setup for line rasterization, then render the line.
+ */
 static void
 setup_line( struct prim_stage *stage,
 	    struct prim_header *header )
@@ -204,10 +211,6 @@ setup_line( struct prim_stage *stage,
 }
 
 
-
-
-
-
 static GLboolean setup_sort_vertices( struct setup_stage *setup,
 				      const struct prim_header *prim )
 {
@@ -288,6 +291,11 @@ static GLboolean setup_sort_vertices( struct setup_stage *setup,
       setup->oneoverarea = 1.0 / area;
    }
 
+   /* XXX need to know if this is a front or back-facing triangle:
+    *  - the GLSL gl_FrontFacing fragment attribute (bool)
+    *  - two-sided stencil test
+    */
+   setup->quad.facing = 0;
 
    _mesa_printf("%s one-over-area %f\n", __FUNCTION__, setup->oneoverarea );
 
@@ -296,6 +304,9 @@ static GLboolean setup_sort_vertices( struct setup_stage *setup,
 }
 
 
+/**
+ * Compute a0 for a constant-valued coefficient (GL_FLAT shading).
+ */
 static void const_coeff( struct setup_stage *setup,
 			 GLuint slot,
 			 GLuint i )
@@ -309,6 +320,9 @@ static void const_coeff( struct setup_stage *setup,
 }
 
 
+/**
+ * Compute a0, dadx and dady for a linearly interpolated coefficient.
+ */
 static void linear_coeff( struct setup_stage *setup,
 			  GLuint slot,
 			  GLuint i)
@@ -345,6 +359,9 @@ static void linear_coeff( struct setup_stage *setup,
 }
 
 
+/**
+ * Compute a0, dadx and dady for a perspective-corrected interpolant.
+ */
 static void persp_coeff( struct setup_stage *setup,
 			 GLuint slot,
 			 GLuint i )
@@ -430,10 +447,10 @@ static void setup_edges( struct setup_stage *setup )
 }
 
 
-
-
-
-
+/**
+ * Render the upper or lower half of a triangle.
+ * Scissoring is applied here too.
+ */
 static void subtriangle( struct setup_stage *setup,
 			 struct edge *eleft,
 			 struct edge *eright,
@@ -511,6 +528,9 @@ static void subtriangle( struct setup_stage *setup,
 }
 
 
+/**
+ * Do setup for triangle rasterization, then render the triangle.
+ */
 static void setup_tri( struct prim_stage *stage,
 		       struct prim_header *prim )
 {
diff --git a/src/mesa/softpipe/generic/g_tile_fs.c b/src/mesa/softpipe/generic/g_tile_fs.c
index 35e1ab63dea..8473a9b5f19 100644
--- a/src/mesa/softpipe/generic/g_tile_fs.c
+++ b/src/mesa/softpipe/generic/g_tile_fs.c
@@ -44,6 +44,9 @@ struct exec_machine {
 };
 
 
+/**
+ * Compute quad's attributes values, as constants (GL_FLAT shading).
+ */
 static void INLINE cinterp( struct exec_machine *exec,
 			    GLuint attrib,
 			    GLuint i )
@@ -56,7 +59,10 @@ static void INLINE cinterp( struct exec_machine *exec,
 }
 
 
-/* Push into the fp:
+/**
+ * Compute quad's attribute values by linear interpolation.
+ *
+ * Push into the fp:
  * 
  *   INPUT[attr] = MAD COEF_A0[attr], COEF_DADX[attr], INPUT_WPOS.xxxx
  *   INPUT[attr] = MAD INPUT[attr],   COEF_DADY[attr], INPUT_WPOS.yyyy
@@ -68,14 +74,20 @@ static INLINE void linterp( struct exec_machine *exec,
    GLuint j;
 
    for (j = 0; j < QUAD_SIZE; j++) {
+      const GLfloat x = exec->attr[FRAG_ATTRIB_WPOS][0][j];
+      const GLfloat y = exec->attr[FRAG_ATTRIB_WPOS][1][j];
       exec->attr[attrib][i][j] = (exec->coef[attrib].a0[i] +
-				  exec->coef[attrib].dadx[i] * exec->attr[0][0][j] + 
-				  exec->coef[attrib].dady[i] * exec->attr[0][1][j]);
+				  exec->coef[attrib].dadx[i] * x + 
+				  exec->coef[attrib].dady[i] * y);
    }
 }
 
 
-/* Push into the fp:
+/**
+ * Compute quad's attribute values by linear interpolation with
+ * perspective correction.
+ *
+ * Push into the fp:
  * 
  *   INPUT[attr] = MAD COEF_A0[attr], COEF_DADX[attr], INPUT_WPOS.xxxx
  *   INPUT[attr] = MAD INPUT[attr],   COEF_DADY[attr], INPUT_WPOS.yyyy
@@ -90,10 +102,12 @@ static INLINE void pinterp( struct exec_machine *exec,
    GLuint j;
 
    for (j = 0; j < QUAD_SIZE; j++) {
+      const GLfloat x = exec->attr[FRAG_ATTRIB_WPOS][0][j];
+      const GLfloat y = exec->attr[FRAG_ATTRIB_WPOS][1][j];
+      const GLfloat invW = exec->attr[FRAG_ATTRIB_WPOS][3][j];
       exec->attr[attrib][i][j] = ((exec->coef[attrib].a0[i] +
-				   exec->coef[attrib].dadx[i] * exec->attr[0][0][j] + 
-				   exec->coef[attrib].dady[i] * exec->attr[0][1][j]) *
-				  exec->attr[0][3][j]);
+				   exec->coef[attrib].dadx[i] * x + 
+				   exec->coef[attrib].dady[i] * y) * invW);
    }
 }
 
@@ -125,6 +139,7 @@ void quad_shade( struct generic_context *generic,
    exec.attr[FRAG_ATTRIB_WPOS][1][3] = fy + 1.0;
 
    /* Z and W are done by linear interpolation:
+    * XXX we'll probably have to use integers for Z
     */
    if (generic->need_z) {
       linterp(&exec, 0, 2);