142 lines
3.5 KiB
Go
142 lines
3.5 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// An app that draws a green triangle on a red background.
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//
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// Note: This demo is an early preview of Go 1.5. In order to build this
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// program as an Android APK using the gomobile tool.
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//
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// See http://godoc.org/golang.org/x/mobile/cmd/gomobile to install gomobile.
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//
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// Get the basic example and use gomobile to build or install it on your device.
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//
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// $ go get -d golang.org/x/mobile/example/basic
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// $ gomobile build golang.org/x/mobile/example/basic # will build an APK
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//
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// # plug your Android device to your computer or start an Android emulator.
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// # if you have adb installed on your machine, use gomobile install to
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// # build and deploy the APK to an Android target.
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// $ gomobile install golang.org/x/mobile/example/basic
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//
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// Switch to your device or emulator to start the Basic application from
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// the launcher.
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// You can also run the application on your desktop by running the command
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// below. (Note: It currently doesn't work on Windows.)
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// $ go install golang.org/x/mobile/example/basic && basic
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package main
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import (
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"encoding/binary"
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"log"
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"golang.org/x/mobile/app"
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"golang.org/x/mobile/app/debug"
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"golang.org/x/mobile/event"
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"golang.org/x/mobile/f32"
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"golang.org/x/mobile/geom"
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"golang.org/x/mobile/gl"
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"golang.org/x/mobile/gl/glutil"
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)
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var (
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program gl.Program
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position gl.Attrib
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offset gl.Uniform
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color gl.Uniform
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buf gl.Buffer
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green float32
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touchLoc geom.Point
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)
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func main() {
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app.Run(app.Callbacks{
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Start: start,
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Stop: stop,
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Draw: draw,
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Touch: touch,
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})
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}
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func start() {
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var err error
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program, err = glutil.CreateProgram(vertexShader, fragmentShader)
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if err != nil {
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log.Printf("error creating GL program: %v", err)
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return
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}
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buf = gl.CreateBuffer()
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gl.BindBuffer(gl.ARRAY_BUFFER, buf)
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gl.BufferData(gl.ARRAY_BUFFER, triangleData, gl.STATIC_DRAW)
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position = gl.GetAttribLocation(program, "position")
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color = gl.GetUniformLocation(program, "color")
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offset = gl.GetUniformLocation(program, "offset")
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touchLoc = geom.Point{geom.Width / 2, geom.Height / 2}
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// TODO(crawshaw): the debug package needs to put GL state init here
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}
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func stop() {
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gl.DeleteProgram(program)
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gl.DeleteBuffer(buf)
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}
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func touch(t event.Touch) {
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touchLoc = t.Loc
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}
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func draw() {
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gl.ClearColor(1, 0, 0, 1)
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gl.Clear(gl.COLOR_BUFFER_BIT)
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gl.UseProgram(program)
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green += 0.01
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if green > 1 {
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green = 0
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}
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gl.Uniform4f(color, 0, green, 0, 1)
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gl.Uniform2f(offset, float32(touchLoc.X/geom.Width), float32(touchLoc.Y/geom.Height))
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gl.BindBuffer(gl.ARRAY_BUFFER, buf)
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gl.EnableVertexAttribArray(position)
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gl.VertexAttribPointer(position, coordsPerVertex, gl.FLOAT, false, 0, 0)
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gl.DrawArrays(gl.TRIANGLES, 0, vertexCount)
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gl.DisableVertexAttribArray(position)
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debug.DrawFPS()
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}
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var triangleData = f32.Bytes(binary.LittleEndian,
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0.0, 0.4, 0.0, // top left
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0.0, 0.0, 0.0, // bottom left
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0.4, 0.0, 0.0, // bottom right
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)
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const (
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coordsPerVertex = 3
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vertexCount = 3
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)
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const vertexShader = `#version 100
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uniform vec2 offset;
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attribute vec4 position;
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void main() {
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// offset comes in with x/y values between 0 and 1.
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// position bounds are -1 to 1.
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vec4 offset4 = vec4(2.0*offset.x-1.0, 1.0-2.0*offset.y, 0, 0);
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gl_Position = position + offset4;
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}`
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const fragmentShader = `#version 100
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precision mediump float;
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uniform vec4 color;
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void main() {
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gl_FragColor = color;
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}`
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