canvas.h

// Copyright 2018 The Darwin Neuroevolution Framework Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// 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 <QFrame>
#include <QPointF>
#include <QRectF>
#include <QTransform>

namespace core_ui {

class Canvas : public QFrame {
 public:
  explicit Canvas(QWidget* parent);

  int borderSize() const { return border_size_; }
  
  void setBorderSize(int border_size);

  const QRectF& viewport() const { return viewport_rect_; }
  
  void setViewport(const QRectF& viewport_rect);
  
  void setViewport(const QPointF& top_left, const QPointF& bottom_right);

  const QTransform& transformFromViewport() const;
  
  const QTransform& transformToViewport() const;

  double scale() const;

 protected:
  void resizeEvent(QResizeEvent* event) override;

 private:
  void updateTransformations() const;

 private:
  // fixed border around the viewport, in pixels
  int border_size_ = 0;

  // logical viewport coordinates
  QRectF viewport_rect_{ 0, 0, 1, 1 };

  // cached, lazy evaluated transformations
  mutable bool valid_transformations_ = false;
  mutable QTransform transform_from_viewport_;
  mutable QTransform transform_to_viewport_;
  mutable double scale_ = 0;
};

}  // namespace core_ui