| /* |
| * Copyright 2023 Google LLC |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| #include "src/base/SkQuads.h" |
| |
| #include "include/private/base/SkFloatingPoint.h" |
| |
| #include <cmath> |
| |
| // Solve 0 = M * x + B. If M is 0, there are no solutions, unless B is also 0, |
| // in which case there are infinite solutions, so we just return 1 of them. |
| static int solve_linear(const double M, const double B, double solution[2]) { |
| if (sk_double_nearly_zero(M)) { |
| solution[0] = 0; |
| if (sk_double_nearly_zero(B)) { |
| return 1; |
| } |
| return 0; |
| } |
| solution[0] = -B / M; |
| return 1; |
| } |
| |
| int SkQuads::RootsReal(const double A, const double B, const double C, double solution[2]) { |
| if (!A) { |
| return solve_linear(B, C, solution); |
| } |
| const double p = B / (2 * A); |
| const double q = C / A; |
| if (sk_double_nearly_zero(A)) { |
| return solve_linear(B, C, solution); |
| } |
| /* normal form: x^2 + px + q = 0 */ |
| const double p2 = p * p; |
| if (!sk_doubles_nearly_equal_ulps(p2, q) && p2 < q) { |
| return 0; |
| } |
| double sqrt_D = 0; |
| if (p2 > q) { |
| sqrt_D = sqrt(p2 - q); |
| } |
| solution[0] = sqrt_D - p; |
| solution[1] = -sqrt_D - p; |
| if (sk_doubles_nearly_equal_ulps(solution[0], solution[1])) { |
| return 1; |
| } |
| return 2; |
| } |