+ ASSERT(dx >= 0);
+ ASSERT(dy >= 0);
+
+ numPixels = MAX2(dx, dy);
+
+ /*
+ * Span setup: compute start and step values for all interpolated values.
+ */
+ interpFlags |= SPAN_RGBA;
+ if (ctx->Light.ShadeModel == GL_SMOOTH) {
+ span.red = ChanToFixed(vert0->color[0]);
+ span.green = ChanToFixed(vert0->color[1]);
+ span.blue = ChanToFixed(vert0->color[2]);
+ span.alpha = ChanToFixed(vert0->color[3]);
+ span.redStep = (ChanToFixed(vert1->color[0]) - span.red ) / numPixels;
+ span.greenStep = (ChanToFixed(vert1->color[1]) - span.green) / numPixels;
+ span.blueStep = (ChanToFixed(vert1->color[2]) - span.blue ) / numPixels;
+ span.alphaStep = (ChanToFixed(vert1->color[3]) - span.alpha) / numPixels;
+ }
+ else {
+ span.red = ChanToFixed(vert1->color[0]);
+ span.green = ChanToFixed(vert1->color[1]);
+ span.blue = ChanToFixed(vert1->color[2]);
+ span.alpha = ChanToFixed(vert1->color[3]);
+ span.redStep = 0;
+ span.greenStep = 0;
+ span.blueStep = 0;
+ span.alphaStep = 0;
+ }
+#if defined(INTERP_Z) || defined(DEPTH_TYPE)
+ interpFlags |= SPAN_Z;
+ {
+ if (depthBits <= 16) {
+ span.z = FloatToFixed(vert0->attrib[FRAG_ATTRIB_WPOS][2]) + FIXED_HALF;
+ span.zStep = FloatToFixed( vert1->attrib[FRAG_ATTRIB_WPOS][2]
+ - vert0->attrib[FRAG_ATTRIB_WPOS][2]) / numPixels;
+ }
+ else {
+ /* don't use fixed point */
+ span.z = (GLuint) vert0->attrib[FRAG_ATTRIB_WPOS][2];
+ span.zStep = (GLint) (( vert1->attrib[FRAG_ATTRIB_WPOS][2]
+ - vert0->attrib[FRAG_ATTRIB_WPOS][2]) / numPixels);
+ }
+ }
+#endif
+#if defined(INTERP_ATTRIBS)
+ {
+ const GLfloat invLen = 1.0F / numPixels;
+ const GLfloat invw0 = vert0->attrib[FRAG_ATTRIB_WPOS][3];
+ const GLfloat invw1 = vert1->attrib[FRAG_ATTRIB_WPOS][3];
+
+ span.attrStart[FRAG_ATTRIB_WPOS][3] = invw0;
+ span.attrStepX[FRAG_ATTRIB_WPOS][3] = (invw1 - invw0) * invLen;
+ span.attrStepY[FRAG_ATTRIB_WPOS][3] = 0.0;
+
+ ATTRIB_LOOP_BEGIN
+ if (swrast->_InterpMode[attr] == GL_FLAT) {
+ COPY_4V(span.attrStart[attr], vert1->attrib[attr]);
+ ASSIGN_4V(span.attrStepX[attr], 0.0, 0.0, 0.0, 0.0);
+ }
+ else {
+ GLuint c;
+ for (c = 0; c < 4; c++) {
+ float da;
+ span.attrStart[attr][c] = invw0 * vert0->attrib[attr][c];
+ da = (invw1 * vert1->attrib[attr][c]) - span.attrStart[attr][c];
+ span.attrStepX[attr][c] = da * invLen;
+ }
+ }
+ ASSIGN_4V(span.attrStepY[attr], 0.0, 0.0, 0.0, 0.0);
+ ATTRIB_LOOP_END
+ }
+#endif
+
+ INIT_SPAN(span, GL_LINE);
+ span.end = numPixels;
+ span.interpMask = interpFlags;
+ span.arrayMask = SPAN_XY;
+
+ span.facing = swrast->PointLineFacing;
+
+