add basic parametric arrow drawing

/**

 * This file is part of the "fviz" project

 *   Copyright (c) 2018 Paul Asmuth

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include "arrows.h"

using namespace std::placeholders;

namespace fviz {

ReturnCode arrow_draw_default(

    const Point& from,

    const Point& to,

    const Measure& size,

    const Color& color,

    Layer* layer) {

  auto direction = vec2_normalize(vec2_sub(to, from));

  auto ortho = vec2{direction.y, direction.x * -1};

  double head_width_factor = 2;

  double head_length_factor = 4;

  Path head_path;

  head_path.moveTo(vec2_add(to, vec2_mul(ortho, size * head_width_factor)));

  head_path.lineTo(vec2_sub(to, vec2_mul(ortho, size * head_width_factor)));

  head_path.lineTo(vec2_add(to, vec2_mul(direction, size * head_length_factor)));

  head_path.closePath();

  StrokeStyle line_style;

  line_style.color = color;

  line_style.line_width = size;

  strokeLine(layer, from, to, line_style);

  FillStyle head_style;

  head_style.color = color;

  fillPath(layer, head_path, head_style);

  return OK;

}

Arrow arrow_create_default() {

  return bind(&arrow_draw_default, _1, _2, _3, _4, _5);

}

} // namespace fviz

/**

 * This file is part of the "fviz" project

 *   Copyright (c) 2018 Paul Asmuth

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#pragma once

#include <unordered_map>

#include <optional>

#include "graphics/color.h"

#include "graphics/layer.h"

#include "graphics/geometry.h"

#include "return_code.h"

#include "sexpr.h"

namespace fviz {

using Arrow = std::function<

    ReturnCode (

        const Point& from,

        const Point& to,

        const Measure& size,

        const Color& color,

        Layer* layer)>;

Arrow arrow_create_default();

} // namespace fviz