User interface toolkit for Go with support for SDL2 and HTML Canvas render targets.
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// +build !js
package ui
import (
"fmt"
"time"
"git.kirsle.net/go/render"
"git.kirsle.net/go/render/event"
"git.kirsle.net/go/render/sdl"
)
// Target frames per second for the MainWindow to render at.
var (
FPS = 60
)
// Default width and height for MainWindow.
var (
DefaultWidth = 640
DefaultHeight = 480
)
// MainWindow is the parent window of a UI application.
type MainWindow struct {
Engine render.Engine
supervisor *Supervisor
frame *Frame
loopCallbacks []func(*event.State)
w int
h int
}
// NewMainWindow initializes the MainWindow. You should probably only have one
// of these per application. Dimensions are the width and height of the window.
//
// Example: NewMainWindow("Title Bar") // default 640x480 window
// NewMainWindow("Title", 800, 600) // both required
func NewMainWindow(title string, dimensions ...int) (*MainWindow, error) {
var (
width = DefaultWidth
height = DefaultHeight
)
if len(dimensions) > 0 {
if len(dimensions) != 2 {
return nil, fmt.Errorf("provide width and height dimensions, like NewMainWindow(title, 800, 600)")
}
width, height = dimensions[0], dimensions[1]
}
mw := &MainWindow{
w: width,
h: height,
supervisor: NewSupervisor(),
loopCallbacks: []func(*event.State){},
}
mw.Engine = sdl.New(
title,
mw.w,
mw.h,
)
if err := mw.Engine.Setup(); err != nil {
return nil, err
}
// Add a default frame to the window.
mw.frame = NewFrame("MainWindow Body")
mw.frame.SetBackground(render.RGBA(0, 153, 255, 100))
// Compute initial window size.
mw.resized()
return mw, nil
}
// SetTitle changes the title of the window.
func (mw *MainWindow) SetTitle(title string) {
mw.Engine.SetTitle(title)
}
// Add a child widget to the window's supervisor. This alone does not make the
// child widget render each frame; use Pack, Place or Attach for that.
func (mw *MainWindow) Add(w Widget) {
mw.supervisor.Add(w)
}
// Pack a child widget into the window's default frame.
func (mw *MainWindow) Pack(w Widget, pack Pack) {
mw.Add(w)
mw.frame.Pack(w, pack)
}
// Place a child widget into the window's default frame.
func (mw *MainWindow) Place(w Widget, config Place) {
mw.Add(w)
mw.frame.Place(w, config)
}
// Attach a child widget to the window without its position managed. The
// widget's Present() method will be called each time the window Presents, but
// the positioning of the child widget must be handled manually by the caller.
//
// Pack and Place are usually the methods you want to use to put a child widget
// into the window. One example use case for Attach is when you want to create
// child Window widgets which can be dragged by their title bars; their dynamic
// drag-drop positioning is best managed manually, and Pack or Place would
// interfere with their positioning otherwise.
//
// This also calls .Add() to add the widget to the MainWindow's Supervisor.
//
// Implementation details:
// - Adds the widget to the MainWindow's Supervisor.
// - Calls Frame.Add(w) so it will Present each time the main frame Presents.
// - Calls w.Compute() on your widget so it can calculate its initial size.
func (mw *MainWindow) Attach(w Widget) {
mw.Add(w)
mw.frame.Add(w)
w.Compute(mw.Engine)
}
// Frame returns the window's main frame, if needed.
func (mw *MainWindow) Frame() *Frame {
return mw.frame
}
// Supervisor returns the window's Supervisor instance.
func (mw *MainWindow) Supervisor() *Supervisor {
return mw.supervisor
}
// resized handles the window being resized.
func (mw *MainWindow) resized() {
mw.frame.Resize(render.Rect{
W: mw.w,
H: mw.h,
})
}
// SetBackground changes the window's frame's background color.
func (mw *MainWindow) SetBackground(color render.Color) {
mw.frame.SetBackground(color)
}
// OnLoop registers a function to be called on every loop of the main window.
// This enables your application to register global event handlers or whatnot.
// The function is called between the event polling and the updating of any UI
// elements.
func (mw *MainWindow) OnLoop(callback func(*event.State)) {
mw.loopCallbacks = append(mw.loopCallbacks, callback)
}
// MainLoop starts the main event loop and blocks until there's an error.
func (mw *MainWindow) MainLoop() error {
for true {
if err := mw.Loop(); err != nil {
return err
}
}
return nil
}
// Loop does one loop of the UI.
func (mw *MainWindow) Loop() error {
mw.Engine.Clear(render.White)
// Record how long this loop took.
start := time.Now()
// Poll for events.
ev, err := mw.Engine.Poll()
if err != nil {
return fmt.Errorf("event poll error: %s", err)
}
if ev.WindowResized {
w, h := mw.Engine.WindowSize()
if w != mw.w || h != mw.h {
mw.w = w
mw.h = h
mw.resized()
}
}
// Ping any loop callbacks.
for _, cb := range mw.loopCallbacks {
cb(ev)
}
mw.frame.Compute(mw.Engine)
// Render the child widgets.
mw.supervisor.Loop(ev)
mw.frame.Present(mw.Engine, mw.frame.Point())
mw.supervisor.Present(mw.Engine)
mw.Engine.Present()
// Delay to maintain target frames per second.
var delay uint32
var targetFPS = 1000 / FPS
elapsed := time.Now().Sub(start) / time.Millisecond
if targetFPS-int(elapsed) > 0 {
delay = uint32(targetFPS - int(elapsed))
}
mw.Engine.Delay(delay)
return nil
}