objc: implement ability to create Protocols at runtime

examples/protocol-dumper/main_darwin.go

@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2025 The Ebitengine Authors
+
+package main
+
+// #cgo CFLAGS: -x objective-c
+// #cgo LDFLAGS: -framework AppKit
+//
+// #import <AppKit/AppKit.h>
+//
+// __attribute__((used))
+// static void __force_protocol_load() {
+//	id o = NULL;
+//	o = @protocol(NSAccessibility);
+//	o = @protocol(NSApplicationDelegate);
+// }
+import "C"
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+	"text/template"
+
+	"github.com/ebitengine/purego/objc"
+)
+
+var protocols = []string{
+	"NSAccessibility",
+	"NSApplicationDelegate",
+}
+
+type ProtocolImpl struct {
+	Name string
+
+	RequiredInstanceMethods []objc.MethodDescription
+	RequiredClassMethods    []objc.MethodDescription
+	OptionalInstanceMethods []objc.MethodDescription
+	OptionalClassMethods    []objc.MethodDescription
+
+	AdoptedProtocols []*objc.Protocol
+
+	RequiredInstanceProperties []objc.Property
+	RequiredClassProperties    []objc.Property
+	OptionalInstanceProperties []objc.Property
+	OptionalClassProperties    []objc.Property
+}
+
+func readProtocols(names []string) (imps []ProtocolImpl, err error) {
+	for _, name := range names {
+		p := objc.GetProtocol(name)
+		if p == nil {
+			return nil, fmt.Errorf("protocol '%s' does not exist", name)
+		}
+		imp := ProtocolImpl{}
+		imp.Name = name
+		imp.RequiredInstanceMethods = p.CopyMethodDescriptionList(true, true)
+		imp.RequiredClassMethods = p.CopyMethodDescriptionList(true, false)
+		imp.OptionalInstanceMethods = p.CopyMethodDescriptionList(false, true)
+		imp.OptionalClassMethods = p.CopyMethodDescriptionList(false, false)
+
+		imp.AdoptedProtocols = p.CopyProtocolList()
+
+		imp.RequiredInstanceProperties = p.CopyPropertyList(true, true)
+		imp.RequiredClassProperties = p.CopyPropertyList(true, false)
+		imp.OptionalInstanceProperties = p.CopyPropertyList(false, true)
+		imp.OptionalClassProperties = p.CopyPropertyList(false, false)
+		imps = append(imps, imp)
+	}
+	return imps, nil
+}
+
+const templ = `// Code generated by protocol-dumper; DO NOT EDIT.
+
+package main
+
+import (
+	"log"
+
+	"github.com/ebitengine/purego/objc"
+)
+
+func init() {
+	var p *objc.Protocol
+	{{- range . }}
+	{{- $protocolName := .Name }}
+	if p = objc.AllocateProtocol("{{$protocolName}}"); p != nil {
+		{{- range .RequiredInstanceMethods }}
+		p.AddMethodDescription(objc.RegisterName("{{ .Name }}"), "{{ .Types }}", true, true)
+		{{- end }}
+
+		{{- range .RequiredClassMethods }}
+		p.AddMethodDescription(objc.RegisterName("{{ .Name }}"), "{{ .Types }}", true, false)
+		{{- end }}
+
+		{{- range .OptionalInstanceMethods }}
+		p.AddMethodDescription(objc.RegisterName("{{ .Name }}"), "{{ .Types }}", false, true)
+		{{- end }}
+
+		{{- range .OptionalClassMethods }}
+		p.AddMethodDescription(objc.RegisterName("{{ .Name }}"), "{{ .Types }}", false, false)
+		{{- end }}
+		var adoptedProtocol *objc.Protocol
+		{{- range .AdoptedProtocols }}
+		adoptedProtocol = objc.GetProtocol("{{ .Name }}")
+		if adoptedProtocol == nil {
+			log.Fatalln("protocol '{{ .Name }}' does not exist")
+		}
+		p.AddProtocol(adoptedProtocol)
+		{{- end }}
+
+		{{- range .RequiredInstanceProperties }}
+		p.AddProperty("{{ .Name }}", {{ attributeToStructString . }}, true, true)
+		{{- end }}
+
+
+		{{- range .RequiredClassProperties }}
+		p.AddProperty("{{ .Name }}", {{ attributeToStructString . }}, true, false)
+		{{- end }}
+
+		{{- range .OptionalInstanceProperties }}
+		p.AddProperty("{{ .Name }}", {{ attributeToStructString . }}, false, true)
+		{{- end }}
+
+		{{- range .OptionalClassProperties }}
+		p.AddProperty("{{ .Name }}", {{ attributeToStructString . }}, false, false)
+		{{- end }}
+		p.Register()
+	} // Finished protocol: {{$protocolName}}
+	{{- end }}
+}
+`
+
+func printProtocols(impls []ProtocolImpl, w io.Writer) error {
+	tmpl, err := template.New("protocol.tmpl").Funcs(template.FuncMap{
+		"attributeToStructString": attributeToStructString,
+	}).Parse(templ)
+	if err != nil {
+		return err
+	}
+	err = tmpl.Execute(w, impls)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func attributeToStructString(p objc.Property) string {
+	attribs := strings.Split(p.Attributes(), ",")
+	var b strings.Builder
+	b.WriteString("[]objc.PropertyAttribute{")
+	for i, attrib := range attribs {
+		b.WriteString(fmt.Sprintf(`{Name: &[]byte("%s\x00")[0], Value: &[]byte(%s)[0]}`, string(attrib[0]), strconv.Quote(attrib[1:]+"\x00")))
+		if i != len(attribs)-1 {
+			b.WriteString(", ")
+		}
+	}
+	b.WriteString("}")
+	return b.String()
+}
+
+// This program prints out the Go code to generate the OBJC protocols list.
+// To use it add the @protocol(name) to the C import section and then add it to the protocols list.
+// You'll want to run it as amd64 and arm64 since the types are slightly different for each architecture.
+func main() {
+	var imps []ProtocolImpl
+	var err error
+	if imps, err = readProtocols(protocols); err != nil {
+		panic(err)
+	}
+	if err = printProtocols(imps, os.Stdout); err != nil {
+		panic(err)
+	}
+}