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node.go
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node.go
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package app
import (
"context"
"fmt"
"io"
"net/url"
"reflect"
"github.com/maxence-charriere/go-app/v7/pkg/errors"
)
// UI is the interface that describes a user interface element such as
// components and HTML elements.
type UI interface {
// Kind represents the specific kind of a UI element.
Kind() Kind
// JSValue returns the javascript value linked to the element.
JSValue() Value
// Reports whether the element is mounted.
Mounted() bool
name() string
self() UI
setSelf(UI)
context() context.Context
attributes() map[string]string
eventHandlers() map[string]eventHandler
parent() UI
setParent(UI)
children() []UI
mount() error
dismount()
update(UI) error
onNav(*url.URL)
}
// Kind represents the specific kind of a user interface element.
type Kind uint
func (k Kind) String() string {
switch k {
case SimpleText:
return "text"
case HTML:
return "html"
case Component:
return "component"
case Selector:
return "selector"
case RawHTML:
return "raw"
default:
return "undefined"
}
}
const (
// UndefinedElem represents an undefined UI element.
UndefinedElem Kind = iota
// SimpleText represents a simple text element.
SimpleText
// HTML represents an HTML element.
HTML
// Component represents a customized, independent and reusable UI element.
Component
// Selector represents an element that is used to select a subset of
// elements within a given list.
Selector
// RawHTML represents an HTML element obtained from a raw HTML code snippet.
RawHTML
)
// FilterUIElems returns a filtered version of the given UI elements where
// selector elements such as If and Range are interpreted and removed. It also
// remove nil elements.
//
// It should be used only when implementing components that can accept content
// with variadic arguments like HTML elements Body method.
func FilterUIElems(uis ...UI) []UI {
if len(uis) == 0 {
return nil
}
elems := make([]UI, 0, len(uis))
for _, n := range uis {
// Ignore nil elements:
if v := reflect.ValueOf(n); n == nil ||
v.Kind() == reflect.Ptr && v.IsNil() {
continue
}
switch n.Kind() {
case SimpleText, HTML, Component, RawHTML:
elems = append(elems, n)
case Selector:
elems = append(elems, n.children()...)
default:
panic(errors.New("filtering ui elements failed").
Tag("reason", "unexpected element type found").
Tag("kind", n.Kind()).
Tag("name", n.name()),
)
}
}
return elems
}
// EventHandler represents a function that can handle HTML events. They are
// always called on the UI goroutine.
type EventHandler func(ctx Context, e Event)
type eventHandler struct {
event string
jsvalue Func
value EventHandler
}
func (h eventHandler) equal(o eventHandler) bool {
return h.event == o.event &&
fmt.Sprintf("%p", h.value) == fmt.Sprintf("%p", o.value)
}
func makeJsEventHandler(src UI, h EventHandler) Func {
return FuncOf(func(this Value, args []Value) interface{} {
dispatch(func() {
if !src.Mounted() {
return
}
ctx := Context{
Context: src.context(),
Src: src,
JSSrc: src.JSValue(),
}
event := Event{
Value: args[0],
}
trackMousePosition(event)
h(ctx, event)
})
return nil
})
}
func trackMousePosition(e Event) {
x := e.Get("clientX")
if !x.Truthy() {
return
}
y := e.Get("clientY")
if !y.Truthy() {
return
}
Window().setCursorPosition(x.Int(), y.Int())
}
func isErrReplace(err error) bool {
_, replace := errors.Tag(err, "replace")
return replace
}
func mount(n UI) error {
n.setSelf(n)
return n.mount()
}
func dismount(n UI) {
n.dismount()
n.setSelf(nil)
}
func update(a, b UI) error {
a.setSelf(a)
b.setSelf(b)
return a.update(b)
}
type writableNode interface {
html(w io.Writer)
htmlWithIndent(w io.Writer, indent int)
}