+struct gl_context;
+struct gl_renderbuffer;
+
+
+/**
+ * \defgroup SpanFlags
+ * Special bitflags to describe span data.
+ *
+ * In general, the point/line/triangle functions interpolate/emit the
+ * attributes specified by swrast->_ActiveAttribs (i.e. FRAT_BIT_* values).
+ * Some things don't fit into that, though, so we have these flags.
+ */
+/*@{*/
+#define SPAN_RGBA 0x01 /**< interpMask and arrayMask */
+#define SPAN_Z 0x02 /**< interpMask and arrayMask */
+#define SPAN_FLAT 0x04 /**< interpMask: flat shading? */
+#define SPAN_XY 0x08 /**< array.x[], y[] valid? */
+#define SPAN_MASK 0x10 /**< was array.mask[] filled in by caller? */
+#define SPAN_LAMBDA 0x20 /**< array.lambda[] valid? */
+#define SPAN_COVERAGE 0x40 /**< array.coverage[] valid? */
+/*@}*/
+
+
+/**
+ * \sw_span_arrays
+ * \brief Arrays of fragment values.
+ *
+ * These will either be computed from the span x/xStep values or
+ * filled in by glDraw/CopyPixels, etc.
+ * These arrays are separated out of sw_span to conserve memory.
+ */
+typedef struct sw_span_arrays
+{
+ /** Per-fragment attributes (indexed by VARYING_SLOT_* tokens) */
+ /* XXX someday look at transposing first two indexes for better memory
+ * access pattern.
+ */
+ GLfloat attribs[VARYING_SLOT_MAX][SWRAST_MAX_WIDTH][4];
+
+ /** This mask indicates which fragments are alive or culled */
+ GLubyte mask[SWRAST_MAX_WIDTH];
+
+ GLenum ChanType; /**< Color channel type, GL_UNSIGNED_BYTE, GL_FLOAT */
+
+ /** Attribute arrays that don't fit into attribs[] array above */
+ /*@{*/
+ GLubyte rgba8[SWRAST_MAX_WIDTH][4];
+ GLushort rgba16[SWRAST_MAX_WIDTH][4];
+ GLchan (*rgba)[4]; /** either == rgba8 or rgba16 */
+ GLint x[SWRAST_MAX_WIDTH]; /**< fragment X coords */
+ GLint y[SWRAST_MAX_WIDTH]; /**< fragment Y coords */
+ GLuint z[SWRAST_MAX_WIDTH]; /**< fragment Z coords */
+ GLuint index[SWRAST_MAX_WIDTH]; /**< Color indexes */
+ GLfloat lambda[MAX_TEXTURE_COORD_UNITS][SWRAST_MAX_WIDTH]; /**< Texture LOD */
+ GLfloat coverage[SWRAST_MAX_WIDTH]; /**< Fragment coverage for AA/smoothing */
+ /*@}*/
+} SWspanarrays;
+
+
+/**
+ * The SWspan structure describes the colors, Z, fogcoord, texcoords,
+ * etc for either a horizontal run or an array of independent pixels.
+ * We can either specify a base/step to indicate interpolated values, or
+ * fill in explicit arrays of values. The interpMask and arrayMask bitfields
+ * indicate which attributes are active interpolants or arrays, respectively.
+ *
+ * It would be interesting to experiment with multiprocessor rasterization
+ * with this structure. The triangle rasterizer could simply emit a
+ * stream of these structures which would be consumed by one or more
+ * span-processing threads which could run in parallel.
+ */
+typedef struct sw_span
+{
+ /** Coord of first fragment in horizontal span/run */
+ GLint x, y;
+
+ /** Number of fragments in the span */
+ GLuint end;
+
+ /** for clipping left edge of spans */
+ GLuint leftClip;
+
+ /** This flag indicates that mask[] array is effectively filled with ones */
+ GLboolean writeAll;
+
+ /** either GL_POLYGON, GL_LINE, GL_POLYGON, GL_BITMAP */
+ GLenum primitive;
+
+ /** 0 = front-facing span, 1 = back-facing span (for two-sided stencil) */
+ GLuint facing;
+
+ /**
+ * This bitmask (of \link SpanFlags SPAN_* flags\endlink) indicates
+ * which of the attrStart/StepX/StepY variables are relevant.
+ */
+ GLbitfield interpMask;
+
+ /** Fragment attribute interpolants */
+ GLfloat attrStart[VARYING_SLOT_MAX][4]; /**< initial value */
+ GLfloat attrStepX[VARYING_SLOT_MAX][4]; /**< dvalue/dx */
+ GLfloat attrStepY[VARYING_SLOT_MAX][4]; /**< dvalue/dy */
+
+ /* XXX the rest of these will go away eventually... */
+
+ /* For horizontal spans, step is the partial derivative wrt X.
+ * For lines, step is the delta from one fragment to the next.
+ */
+ GLfixed red, redStep;
+ GLfixed green, greenStep;
+ GLfixed blue, blueStep;
+ GLfixed alpha, alphaStep;
+ GLfixed index, indexStep;
+ GLfixed z, zStep; /**< XXX z should probably be GLuint */
+ GLfixed intTex[2], intTexStep[2]; /**< (s,t) for unit[0] only */
+
+ /**
+ * This bitmask (of \link SpanFlags SPAN_* flags\endlink) indicates
+ * which of the fragment arrays in the span_arrays struct are relevant.
+ */
+ GLbitfield arrayMask;
+
+ /** Mask of VARYING_BIT_x bits */
+ GLbitfield64 arrayAttribs;
+
+ /**
+ * We store the arrays of fragment values in a separate struct so
+ * that we can allocate sw_span structs on the stack without using
+ * a lot of memory. The span_arrays struct is about 1.4MB while the
+ * sw_span struct is only about 512 bytes.
+ */
+ SWspanarrays *array;
+} SWspan;
+
+
+
+#define INIT_SPAN(S, PRIMITIVE) \
+do { \
+ (S).primitive = (PRIMITIVE); \
+ (S).interpMask = 0x0; \
+ (S).arrayMask = 0x0; \
+ (S).arrayAttribs = 0x0; \
+ (S).end = 0; \
+ (S).leftClip = 0; \
+ (S).facing = 0; \
+ (S).array = SWRAST_CONTEXT(ctx)->SpanArrays; \
+} while (0)