screen

type Buffer interface {
	// Release releases the Buffer's resources, after all pending uploads and
	// draws resolve.
	//
	// The behavior of the Buffer after Release, whether calling its methods or
	// passing it as an argument, is undefined.
	Release()

	// Size returns the size of the Buffer's image.
	Size() image.Point

	// Bounds returns the bounds of the Buffer's image. It is equal to
	// image.Rectangle{Max: b.Size()}.
	Bounds() image.Rectangle

	// RGBA returns the pixel buffer as an *image.RGBA.
	//
	// Its contents should not be accessed while the Buffer is uploading.
	//
	// The contents of the returned *image.RGBA's Pix field (of type []byte)
	// can be modified at other times, but that Pix slice itself (i.e. its
	// underlying pointer, length and capacity) should not be modified at any
	// time.
	//
	// The following is valid:
	//	m := buffer.RGBA()
	//	if len(m.Pix) >= 4 {
	//		m.Pix[0] = 0xff
	//		m.Pix[1] = 0x00
	//		m.Pix[2] = 0x00
	//		m.Pix[3] = 0xff
	//	}
	// or, equivalently:
	//	m := buffer.RGBA()
	//	m.SetRGBA(m.Rect.Min.X, m.Rect.Min.Y, color.RGBA{0xff, 0x00, 0x00, 0xff})
	// and using the standard library's image/draw package is also valid:
	//	dst := buffer.RGBA()
	//	draw.Draw(dst, dst.Bounds(), etc)
	// but the following is invalid:
	//	m := buffer.RGBA()
	//	m.Pix = anotherByteSlice
	// and so is this:
	//	*buffer.RGBA() = anotherImageRGBA
	RGBA() *image.RGBA
}

type DrawOptions struct {
}

type Drawer interface {
	// Draw draws the sub-Texture defined by src and sr to the destination (the
	// method receiver). src2dst defines how to transform src coordinates to
	// dst coordinates. For example, if src2dst is the matrix
	//
	// m00 m01 m02
	// m10 m11 m12
	//
	// then the src-space point (sx, sy) maps to the dst-space point
	// (m00*sx + m01*sy + m02, m10*sx + m11*sy + m12).
	Draw(src2dst f64.Aff3, src Texture, sr image.Rectangle, op draw.Op, opts *DrawOptions)

	// DrawUniform is like Draw except that the src is a uniform color instead
	// of a Texture.
	DrawUniform(src2dst f64.Aff3, src color.Color, sr image.Rectangle, op draw.Op, opts *DrawOptions)

	// Copy copies the sub-Texture defined by src and sr to the destination
	// (the method receiver), such that sr.Min in src-space aligns with dp in
	// dst-space.
	Copy(dp image.Point, src Texture, sr image.Rectangle, op draw.Op, opts *DrawOptions)

	// Scale scales the sub-Texture defined by src and sr to the destination
	// (the method receiver), such that sr in src-space is mapped to dr in
	// dst-space.
	Scale(dr image.Rectangle, src Texture, sr image.Rectangle, op draw.Op, opts *DrawOptions)
}

type EventDeque interface {
	// Send adds an event to the end of the deque. They are returned by
	// NextEvent in FIFO order.
	Send(event interface{})

	// SendFirst adds an event to the start of the deque. They are returned by
	// NextEvent in LIFO order, and have priority over events sent via Send.
	SendFirst(event interface{})

	// NextEvent returns the next event in the deque. It blocks until such an
	// event has been sent.
	//
	// Typical event types include:
	//	- lifecycle.Event
	//	- size.Event
	//	- paint.Event
	//	- key.Event
	//	- mouse.Event
	//	- touch.Event
	// from the golang.org/x/mobile/event/... packages. Other packages may send
	// events, of those types above or of other types, via Send or SendFirst.
	NextEvent() interface{}
}

type NewWindowOptions struct {
	// Width and Height specify the dimensions of the new window. If Width
	// or Height are zero, a driver-dependent default will be used for each
	// zero value dimension.
	Width, Height int

	// Title specifies the window title.
	Title string
}

type PublishResult struct {
	// BackBufferPreserved is whether the contents of the back buffer was
	// preserved. If false, the contents are undefined.
	BackBufferPreserved bool
}

type Screen interface {
	// NewBuffer returns a new Buffer for this screen.
	NewBuffer(size image.Point) (Buffer, error)

	// NewTexture returns a new Texture for this screen.
	NewTexture(size image.Point) (Texture, error)

	// NewWindow returns a new Window for this screen.
	//
	// A nil opts is valid and means to use the default option values.
	NewWindow(opts *NewWindowOptions) (Window, error)
}

type Texture interface {
	// Release releases the Texture's resources, after all pending uploads and
	// draws resolve.
	//
	// The behavior of the Texture after Release, whether calling its methods
	// or passing it as an argument, is undefined.
	Release()

	// Size returns the size of the Texture's image.
	Size() image.Point

	// Bounds returns the bounds of the Texture's image. It is equal to
	// image.Rectangle{Max: t.Size()}.
	Bounds() image.Rectangle

	Uploader
}

type Uploader interface {
	// Upload uploads the sub-Buffer defined by src and sr to the destination
	// (the method receiver), such that sr.Min in src-space aligns with dp in
	// dst-space. The destination's contents are overwritten; the draw operator
	// is implicitly draw.Src.
	//
	// It is valid to upload a Buffer while another upload of the same Buffer
	// is in progress, but a Buffer's image.RGBA pixel contents should not be
	// accessed while it is uploading. A Buffer is re-usable, in that its pixel
	// contents can be further modified, once all outstanding calls to Upload
	// have returned.
	//
	// TODO: make it optional that a Buffer's contents is preserved after
	// Upload? Undoing a swizzle is a non-trivial amount of work, and can be
	// redundant if the next paint cycle starts by clearing the buffer.
	//
	// When uploading to a Window, there will not be any visible effect until
	// Publish is called.
	Upload(dp image.Point, src Buffer, sr image.Rectangle)

	// Fill fills that part of the destination (the method receiver) defined by
	// dr with the given color.
	//
	// When filling a Window, there will not be any visible effect until
	// Publish is called.
	Fill(dr image.Rectangle, src color.Color, op draw.Op)
}

type Window interface {
	// Release closes the window.
	//
	// The behavior of the Window after Release, whether calling its methods or
	// passing it as an argument, is undefined.
	Release()

	EventDeque

	Uploader

	Drawer

	// Publish flushes any pending Upload and Draw calls to the window, and
	// swaps the back buffer to the front.
	Publish() PublishResult
}