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* Mesa 3-D graphics library
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* Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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#include "swrast/s_aaline.h"
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#include "swrast/s_context.h"
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#include "swrast/s_span.h"
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#include "swrast/swrast.h"
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* Info about the AA line we're rendering
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GLfloat x0, y0; /* start */
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GLfloat x1, y1; /* end */
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GLfloat dx, dy; /* direction vector */
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GLfloat len; /* length */
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GLfloat halfWidth; /* half of line width */
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GLfloat xAdj, yAdj; /* X and Y adjustment for quad corners around line */
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/* for coverage computation */
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GLfloat qx0, qy0; /* quad vertices */
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GLfloat ex0, ey0; /* quad edge vectors */
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GLfloat rPlane[4], gPlane[4], bPlane[4], aPlane[4];
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GLfloat srPlane[4], sgPlane[4], sbPlane[4];
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GLfloat sPlane[FRAG_ATTRIB_MAX][4];
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GLfloat tPlane[FRAG_ATTRIB_MAX][4];
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GLfloat uPlane[FRAG_ATTRIB_MAX][4];
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GLfloat vPlane[FRAG_ATTRIB_MAX][4];
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GLfloat lambda[FRAG_ATTRIB_MAX];
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GLfloat texWidth[FRAG_ATTRIB_MAX];
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GLfloat texHeight[FRAG_ATTRIB_MAX];
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* Compute the equation of a plane used to interpolate line fragment data
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* such as color, Z, texture coords, etc.
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* Input: (x0, y0) and (x1,y1) are the endpoints of the line.
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* z0, and z1 are the end point values to interpolate.
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* Output: plane - the plane equation.
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* Note: we don't really have enough parameters to specify a plane.
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* We take the endpoints of the line and compute a plane such that
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* the cross product of the line vector and the plane normal is
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* parallel to the projection plane.
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compute_plane(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
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GLfloat z0, GLfloat z1, GLfloat plane[4])
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const GLfloat px = x1 - x0;
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const GLfloat py = y1 - y0;
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const GLfloat pz = z1 - z0;
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const GLfloat qx = -py;
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const GLfloat qy = px;
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const GLfloat qz = 0;
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const GLfloat a = py * qz - pz * qy;
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const GLfloat b = pz * qx - px * qz;
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const GLfloat c = px * qy - py * qx;
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const GLfloat d = -(a * x0 + b * y0 + c * z0);
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const GLfloat px = x1 - x0;
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const GLfloat py = y1 - y0;
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const GLfloat pz = z0 - z1;
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const GLfloat a = pz * px;
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const GLfloat b = pz * py;
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const GLfloat c = px * px + py * py;
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const GLfloat d = -(a * x0 + b * y0 + c * z0);
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if (a == 0.0 && b == 0.0 && c == 0.0 && d == 0.0) {
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constant_plane(GLfloat value, GLfloat plane[4])
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static INLINE GLfloat
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solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4])
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const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
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#define SOLVE_PLANE(X, Y, PLANE) \
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((PLANE[3] + PLANE[0] * (X) + PLANE[1] * (Y)) / -PLANE[2])
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* Return 1 / solve_plane().
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static INLINE GLfloat
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solve_plane_recip(GLfloat x, GLfloat y, const GLfloat plane[4])
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const GLfloat denom = plane[3] + plane[0] * x + plane[1] * y;
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return -plane[2] / denom;
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* Solve plane and return clamped GLchan value.
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solve_plane_chan(GLfloat x, GLfloat y, const GLfloat plane[4])
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const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2];
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#if CHAN_TYPE == GL_FLOAT
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return CLAMP(z, 0.0F, CHAN_MAXF);
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else if (z > CHAN_MAX)
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return (GLchan) IROUND_POS(z);
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* Compute mipmap level of detail.
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static INLINE GLfloat
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compute_lambda(const GLfloat sPlane[4], const GLfloat tPlane[4],
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GLfloat invQ, GLfloat width, GLfloat height)
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GLfloat dudx = sPlane[0] / sPlane[2] * invQ * width;
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GLfloat dudy = sPlane[1] / sPlane[2] * invQ * width;
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GLfloat dvdx = tPlane[0] / tPlane[2] * invQ * height;
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GLfloat dvdy = tPlane[1] / tPlane[2] * invQ * height;
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GLfloat r1 = dudx * dudx + dudy * dudy;
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GLfloat r2 = dvdx * dvdx + dvdy * dvdy;
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GLfloat rho2 = r1 + r2;
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/* return log base 2 of rho */
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return (GLfloat) (LOGF(rho2) * 1.442695 * 0.5);/* 1.442695 = 1/log(2) */
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* Fill in the samples[] array with the (x,y) subpixel positions of
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* xSamples * ySamples sample positions.
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* Note that the four corner samples are put into the first four
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* positions of the array. This allows us to optimize for the common
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* case of all samples being inside the polygon.
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make_sample_table(GLint xSamples, GLint ySamples, GLfloat samples[][2])
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const GLfloat dx = 1.0F / (GLfloat) xSamples;
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const GLfloat dy = 1.0F / (GLfloat) ySamples;
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for (x = 0; x < xSamples; x++) {
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for (y = 0; y < ySamples; y++) {
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if (x == 0 && y == 0) {
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else if (x == xSamples - 1 && y == 0) {
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else if (x == 0 && y == ySamples - 1) {
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else if (x == xSamples - 1 && y == ySamples - 1) {
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samples[j][0] = x * dx + 0.5F * dx;
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samples[j][1] = y * dy + 0.5F * dy;
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* Compute how much of the given pixel's area is inside the rectangle
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* defined by vertices v0, v1, v2, v3.
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* Vertices MUST be specified in counter-clockwise order.
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* Return: coverage in [0, 1].
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compute_coveragef(const struct LineInfo *info,
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GLint winx, GLint winy)
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static GLfloat samples[SUB_PIXEL * SUB_PIXEL][2];
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static GLboolean haveSamples = GL_FALSE;
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const GLfloat x = (GLfloat) winx;
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const GLfloat y = (GLfloat) winy;
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GLfloat insideCount = SUB_PIXEL * SUB_PIXEL;
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make_sample_table(SUB_PIXEL, SUB_PIXEL, samples);
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haveSamples = GL_TRUE;
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const GLfloat area = dx0 * dy1 - dx1 * dy0;
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for (i = 0; i < stop; i++) {
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const GLfloat sx = x + samples[i][0];
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const GLfloat sy = y + samples[i][1];
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const GLfloat fx0 = sx - info->qx0;
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const GLfloat fy0 = sy - info->qy0;
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const GLfloat fx1 = sx - info->qx1;
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const GLfloat fy1 = sy - info->qy1;
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const GLfloat fx2 = sx - info->qx2;
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const GLfloat fy2 = sy - info->qy2;
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const GLfloat fx3 = sx - info->qx3;
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const GLfloat fy3 = sy - info->qy3;
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/* cross product determines if sample is inside or outside each edge */
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GLfloat cross0 = (info->ex0 * fy0 - info->ey0 * fx0);
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GLfloat cross1 = (info->ex1 * fy1 - info->ey1 * fx1);
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GLfloat cross2 = (info->ex2 * fy2 - info->ey2 * fx2);
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GLfloat cross3 = (info->ex3 * fy3 - info->ey3 * fx3);
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/* Check if the sample is exactly on an edge. If so, let cross be a
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* positive or negative value depending on the direction of the edge.
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cross0 = info->ex0 + info->ey0;
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cross1 = info->ex1 + info->ey1;
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cross2 = info->ex2 + info->ey2;
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cross3 = info->ex3 + info->ey3;
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if (cross0 < 0.0F || cross1 < 0.0F || cross2 < 0.0F || cross3 < 0.0F) {
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/* point is outside quadrilateral */
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stop = SUB_PIXEL * SUB_PIXEL;
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return insideCount * (1.0F / (SUB_PIXEL * SUB_PIXEL));
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* Compute coverage value for color index mode.
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* XXX this may not be quite correct.
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* \return coverage in [0,15].
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compute_coveragei(const struct LineInfo *info,
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GLint winx, GLint winy)
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return compute_coveragef(info, winx, winy) * 15.0F;
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typedef void (*plot_func)(GLcontext *ctx, struct LineInfo *line,
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* Draw an AA line segment (called many times per line when stippling)
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segment(GLcontext *ctx,
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struct LineInfo *line,
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GLfloat t0, GLfloat t1)
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const GLfloat absDx = (line->dx < 0.0F) ? -line->dx : line->dx;
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const GLfloat absDy = (line->dy < 0.0F) ? -line->dy : line->dy;
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/* compute the actual segment's endpoints */
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const GLfloat x0 = line->x0 + t0 * line->dx;
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const GLfloat y0 = line->y0 + t0 * line->dy;
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const GLfloat x1 = line->x0 + t1 * line->dx;
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const GLfloat y1 = line->y0 + t1 * line->dy;
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/* compute vertices of the line-aligned quadrilateral */
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line->qx0 = x0 - line->yAdj;
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line->qy0 = y0 + line->xAdj;
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line->qx1 = x0 + line->yAdj;
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line->qy1 = y0 - line->xAdj;
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line->qx2 = x1 + line->yAdj;
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line->qy2 = y1 - line->xAdj;
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line->qx3 = x1 - line->yAdj;
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line->qy3 = y1 + line->xAdj;
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/* compute the quad's edge vectors (for coverage calc) */
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line->ex0 = line->qx1 - line->qx0;
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line->ey0 = line->qy1 - line->qy0;
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line->ex1 = line->qx2 - line->qx1;
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line->ey1 = line->qy2 - line->qy1;
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line->ex2 = line->qx3 - line->qx2;
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line->ey2 = line->qy3 - line->qy2;
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line->ex3 = line->qx0 - line->qx3;
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line->ey3 = line->qy0 - line->qy3;
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GLfloat dydx = line->dy / line->dx;
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GLfloat xLeft, xRight, yBot, yTop;
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xLeft = x0 - line->halfWidth;
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xRight = x1 + line->halfWidth;
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if (line->dy >= 0.0) {
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yBot = y0 - 3.0F * line->halfWidth;
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yTop = y0 + line->halfWidth;
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yBot = y0 - line->halfWidth;
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yTop = y0 + 3.0F * line->halfWidth;
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xLeft = x1 - line->halfWidth;
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xRight = x0 + line->halfWidth;
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if (line->dy <= 0.0) {
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yBot = y1 - 3.0F * line->halfWidth;
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yTop = y1 + line->halfWidth;
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yBot = y1 - line->halfWidth;
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yTop = y1 + 3.0F * line->halfWidth;
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/* scan along the line, left-to-right */
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ixRight = (GLint) (xRight + 1.0F);
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/*printf("avg span height: %g\n", yTop - yBot);*/
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for (ix = (GLint) xLeft; ix < ixRight; ix++) {
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const GLint iyBot = (GLint) yBot;
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const GLint iyTop = (GLint) (yTop + 1.0F);
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/* scan across the line, bottom-to-top */
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for (iy = iyBot; iy < iyTop; iy++) {
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(*plot)(ctx, line, ix, iy);
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GLfloat dxdy = line->dx / line->dy;
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GLfloat yBot, yTop, xLeft, xRight;
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yBot = y0 - line->halfWidth;
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yTop = y1 + line->halfWidth;
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if (line->dx >= 0.0) {
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xLeft = x0 - 3.0F * line->halfWidth;
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xRight = x0 + line->halfWidth;
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xLeft = x0 - line->halfWidth;
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xRight = x0 + 3.0F * line->halfWidth;
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yBot = y1 - line->halfWidth;
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yTop = y0 + line->halfWidth;
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if (line->dx <= 0.0) {
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xLeft = x1 - 3.0F * line->halfWidth;
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xRight = x1 + line->halfWidth;
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xLeft = x1 - line->halfWidth;
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xRight = x1 + 3.0F * line->halfWidth;
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/* scan along the line, bottom-to-top */
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iyTop = (GLint) (yTop + 1.0F);
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/*printf("avg span width: %g\n", xRight - xLeft);*/
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for (iy = (GLint) yBot; iy < iyTop; iy++) {
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const GLint ixLeft = (GLint) xLeft;
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const GLint ixRight = (GLint) (xRight + 1.0F);
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/* scan across the line, left-to-right */
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for (ix = ixLeft; ix < ixRight; ix++) {
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(*plot)(ctx, line, ix, iy);
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#define NAME(x) aa_ci_##x
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#include "s_aalinetemp.h"
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#define NAME(x) aa_rgba_##x
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#include "s_aalinetemp.h"
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#define NAME(x) aa_tex_rgba_##x
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#include "s_aalinetemp.h"
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#define NAME(x) aa_multitex_spec_##x
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#include "s_aalinetemp.h"
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_swrast_choose_aa_line_function(GLcontext *ctx)
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SWcontext *swrast = SWRAST_CONTEXT(ctx);
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ASSERT(ctx->Line.SmoothFlag);
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if (ctx->Visual.rgbMode) {
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if (ctx->Texture._EnabledCoordUnits != 0
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|| ctx->FragmentProgram._Current) {
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if (ctx->Light.Model.ColorControl==GL_SEPARATE_SPECULAR_COLOR ||
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ctx->Fog.ColorSumEnabled)
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swrast->Line = aa_multitex_spec_line;
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swrast->Line = aa_tex_rgba_line;
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swrast->Line = aa_rgba_line;
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swrast->Line = aa_ci_line;