/
screen.go
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/
screen.go
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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package screen provides interfaces for portable two-dimensional graphics and
// input events.
//
// Screens are not created directly. Instead, driver packages provide access to
// the screen through a Main function that is designed to be called by the
// program's main function. The golang.org/x/exp/shiny/driver package provides
// the default driver for the system, such as the X11 driver for desktop Linux,
// but other drivers, such as the OpenGL driver, can be explicitly invoked by
// calling that driver's Main function. To use the default driver:
//
// package main
//
// import (
// "golang.org/x/exp/shiny/driver"
// "golang.org/x/exp/shiny/screen"
// )
//
// func main() {
// driver.Main(func(s screen.Screen) {
// w, err := s.NewWindow(nil)
// if err != nil {
// handleError(err)
// return
// }
// for e := range w.Events() {
// handleEvent(e)
// }
// })
// }
package screen
import (
"image"
"image/color"
"image/draw"
"golang.org/x/image/math/f64"
)
// TODO: specify image format (Alpha or Gray, not just RGBA) for NewBuffer
// and/or NewTexture?
// Screen creates Buffers, Textures and Windows.
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.
NewWindow(opts *NewWindowOptions) (Window, error)
}
// TODO: rename Buffer to Image, to be less confusing with a Window's back and
// front buffers.
// Buffer is an in-memory pixel buffer. Its pixels can be modified by any Go
// code that takes an *image.RGBA, such as the standard library's image/draw
// package.
//
// To see a Buffer's contents on a screen, upload it to a Texture (and then
// draw the Texture on a Window) or upload it directly to a Window.
//
// When specifying a sub-Buffer via Upload, a Buffer's top-left pixel is always
// (0, 0) in its own coordinate space.
type Buffer interface {
// Release releases the Buffer's resources, after all pending uploads and
// draws resolve. The behavior of the Buffer after Release 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.
RGBA() *image.RGBA
}
// Texture is a pixel buffer, but not one that is directly accessible as a
// []byte. Conceptually, it could live on a GPU, in another process or even be
// across a network, instead of on a CPU in this process.
//
// Buffers can be uploaded to Textures, and Textures can be drawn on Windows.
//
// When specifying a sub-Texture via Draw, a Texture's top-left pixel is always
// (0, 0) in its own coordinate space.
type Texture interface {
// Release releases the Texture's resources, after all pending uploads and
// draws resolve. The behavior of the Texture after Release 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
// TODO: also implement Drawer? If so, merge the Uploader and Drawer
// interfaces??
}
// Window is a top-level, double-buffered GUI window.
type Window interface {
// Release closes the window and its event channel.
Release()
// Events returns the window's event channel, which carries key, mouse,
// paint and other events.
//
// TODO: define and describe these events.
Events() <-chan interface{}
// Send sends an event to the window.
Send(event interface{})
Uploader
Drawer
// Publish flushes any pending Upload and Draw calls to the window, and
// swaps the back buffer to the front.
Publish() PublishResult
}
// PublishResult is the result of an Window.Publish call.
type PublishResult struct {
// BackBufferPreserved is whether the contents of the back buffer was
// preserved. If false, the contents are undefined.
BackBufferPreserved bool
}
// NewWindowOptions are optional arguments to NewWindow.
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
// TODO: fullscreen, title, icon, cursorHidden?
}
// Uploader is something you can upload a Buffer to.
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.
//
// 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)
}
// TODO: have a Downloader interface? Not every graphical app needs to be
// interactive or involve a window. You could use the GPU for hardware-
// accelerated image manipulation: upload a buffer, do some texture ops, then
// download the result.
// Drawer is something you can draw Textures on.
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).
//
// When drawing on a Window, there will not be any visible effect until
// Publish is called.
Draw(src2dst f64.Aff3, src Texture, sr image.Rectangle, op draw.Op, opts *DrawOptions)
}
// Copy copies the sub-Texture defined by src and sr to dst, such that sr.Min
// in src-space aligns with dp in dst-space.
//
// When drawing on a Window, there will not be any visible effect until Publish
// is called.
func Copy(dst Drawer, dp image.Point, src Texture, sr image.Rectangle, op draw.Op, opts *DrawOptions) {
dst.Draw(f64.Aff3{
1, 0, float64(dp.X - sr.Min.X),
0, 1, float64(dp.Y - sr.Min.Y),
}, src, sr, op, opts)
}
// Scale scales the sub-Texture defined by src and sr to dst, such that sr in
// src-space is mapped to dr in dst-space.
//
// When drawing on a Window, there will not be any visible effect until Publish
// is called.
func Scale(dst Drawer, dr image.Rectangle, src Texture, sr image.Rectangle, op draw.Op, opts *DrawOptions) {
rx := float64(dr.Dx()) / float64(sr.Dx())
ry := float64(dr.Dy()) / float64(sr.Dy())
dst.Draw(f64.Aff3{
rx, 0, float64(dr.Min.X) - rx*float64(sr.Min.X),
0, ry, float64(dr.Min.Y) - ry*float64(sr.Min.Y),
}, src, sr, op, opts)
}
// These draw.Op constants are provided so that users of this package don't
// have to explicitly import "image/draw".
const (
Over = draw.Over
Src = draw.Src
)
// DrawOptions are optional arguments to Draw.
type DrawOptions struct {
// TODO: transparency in [0x0000, 0xffff]?
// TODO: scaler (nearest neighbor vs linear)?
}