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//! A rectangular viewport and associated 2D and 3D cameras.

use ::{std, glium};

use ::{graphics, Camera2d, Camera3d};

/// A viewport defined by a `glium::Rect` structure, with associated 2D and 3D
/// cameras
pub struct Viewport {
  /// Describes the viewport position and size.
  ///
  /// `left` and `bottom` are the number of pixels between the left and bottom
  /// of the screen with the left and bottom borders of the viewport rectangle.
  pub rect                : glium::Rect,
  pub camera2d            : Camera2d,
  pub camera3d            : Camera3d
}

pub struct Builder {
  rect            : glium::Rect,
  /// Set 3D camera projection to orthographic with the given zoom
  orthographic_3d : Option <f32>,
  pose_3d         : Option <graphics::Pose3d <f32>>,
  zoom_2d         : Option <f32>
}

impl Viewport {
  /// Create a new viewport with the given `Rect`
  ///
  /// # Panics
  ///
  /// Width or height are zero:
  ///
  /// ```should_panic
  /// # extern crate gl_utils;
  /// # extern crate cgmath;
  /// # extern crate glium;
  /// # fn main () {
  /// # use gl_utils::render::Viewport;
  /// let mut viewport = Viewport::new (glium::Rect {
  ///   left: 0, bottom: 0, width: 0, height: 0
  /// });
  /// # }
  /// ```
  ///
  /// Width or height are greater than `u16::MAX` (65535):
  ///
  /// ```should_panic
  /// # extern crate gl_utils;
  /// # extern crate cgmath;
  /// # extern crate glium;
  /// # fn main () {
  /// # use gl_utils::render::Viewport;
  /// let mut viewport = Viewport::new (glium::Rect {
  ///   left: 0, bottom: 0, width: 65536, height: 65536
  /// });
  /// # }
  /// ```
  pub fn new (rect : glium::Rect) -> Self {
    assert!(rect.width  <= std::u16::MAX as u32);
    assert!(rect.height <= std::u16::MAX as u32);
    Viewport {
      rect,
      camera2d: Camera2d::new (rect.width as u16, rect.height as u16),
      camera3d: Camera3d::new (rect.width as u16, rect.height as u16)
    }
  }

  /// Also initializes `self.camera3d` with position and orientation
  pub fn with_pose_3d (
    rect : glium::Rect,
    pose : graphics::Pose3d <f32>
  ) -> Self {
    assert!(rect.width  <= std::u16::MAX as u32);
    assert!(rect.height <= std::u16::MAX as u32);
    Viewport {
      rect,
      camera2d: Camera2d::new (rect.width as u16, rect.height as u16),
      camera3d: Camera3d::with_pose (
        rect.width as u16, rect.height as u16,
        pose
      )
    }
  }

  /// Should be called when screen resolution changes.
  ///
  /// # Panics
  ///
  /// Width and height must be less than or equal to `u16::MAX` (65535):
  ///
  /// ```should_panic
  /// # extern crate gl_utils;
  /// # extern crate cgmath;
  /// # extern crate glium;
  /// # fn main () {
  /// # use gl_utils::render::Viewport;
  /// # let mut viewport = Viewport::new (glium::Rect {
  /// #   left: 0, bottom: 0, width: 320, height: 240
  /// # });
  /// viewport.set_rect (glium::Rect {
  ///   left:   0,       bottom: 0,
  ///   width:  100_000, height: 100_000 // panics
  /// });
  /// # }
  /// ```
  ///
  /// Width or height are zero:
  ///
  /// ```should_panic
  /// # extern crate gl_utils;
  /// # extern crate cgmath;
  /// # extern crate glium;
  /// # fn main () {
  /// # use gl_utils::render::Viewport;
  /// # let mut viewport = Viewport::new (glium::Rect {
  /// #   left: 0, bottom: 0, width: 320, height: 240
  /// # });
  /// viewport.set_rect (glium::Rect {
  ///   left:   0, bottom: 0,
  ///   width:  0, height: 0 // panics
  /// });
  /// # }
  /// ```
  pub fn set_rect (&mut self, rect : glium::Rect) {
    assert!(rect.width  <= std::u16::MAX as u32);
    assert!(rect.height <= std::u16::MAX as u32);
    self.rect = rect;
    self.camera2d
      .set_viewport_dimensions (rect.width as u16, rect.height as u16);
    self.camera3d
      .set_viewport_dimensions (rect.width as u16, rect.height as u16);
  }
}

impl Builder {
  #[inline]
  pub fn new (rect : glium::Rect) -> Self {
    Builder {
      rect,
      orthographic_3d: None,
      pose_3d:         None,
      zoom_2d:         None
    }
  }
  pub fn with_zoom_2d (self, zoom : f32) -> Self {
    Builder { zoom_2d: Some (zoom), .. self }
  }
  /// Changes the 3D camera projection from perspective (default) to orthographic
  pub fn orthographic_3d (self, zoom : f32) -> Self {
    Builder { orthographic_3d: Some (zoom), .. self }
  }
  pub fn with_pose_3d (self, pose_3d : graphics::Pose3d <f32>) -> Self {
    Builder { pose_3d: Some (pose_3d), .. self }
  }
  #[inline]
  pub fn build (self) -> Viewport {
    let mut viewport = if let Some (pose_3d) = self.pose_3d {
      Viewport::with_pose_3d (self.rect, pose_3d)
    } else {
      Viewport::new (self.rect)
    };
    if let Some (zoom) = self.orthographic_3d {
      viewport.camera3d.projection3d.to_orthographic (zoom);
    }
    if let Some (zoom) = self.zoom_2d {
      viewport.camera2d.set_zoom (zoom);
    }
    viewport
  }
}