From eb440387490abbaca03dbee9b5fada248146dcfd Mon Sep 17 00:00:00 2001
From: StarHack <danielschmidth@googlemail.com>
Date: Sat, 25 Feb 2023 12:44:16 +0100
Subject: [PATCH] darwin-external-dragndrop: implement external drag n' drop
 for darwin

---
 app/os_macos.go         | 21 +++++++++++++++++++++
 app/os_macos.m          | 15 +++++++++++++++
 io/router/pointer.go    |  4 ++--
 io/router/router.go     | 13 +++++++++++++
 io/transfer/transfer.go |  2 +-
 5 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/app/os_macos.go b/app/os_macos.go
index 516157aaa..51f0bc2ba 100644
--- a/app/os_macos.go
+++ b/app/os_macos.go
@@ -8,6 +8,10 @@ package app
 import (
 	"errors"
 	"image"
+	"io"
+	"mime"
+	"os"
+	"path/filepath"
 	"runtime"
 	"time"
 	"unicode"
@@ -18,6 +22,7 @@ import (
 	"gioui.org/io/key"
 	"gioui.org/io/pointer"
 	"gioui.org/io/system"
+	"gioui.org/io/transfer"
 	"gioui.org/unit"
 
 	_ "gioui.org/internal/cocoainit"
@@ -557,6 +562,22 @@ func gio_onMouse(view, evt C.CFTypeRef, cdir C.int, cbtn C.NSInteger, x, y, dx,
 	})
 }
 
+//export gio_onExternalDrop
+func gio_onExternalDrop(view C.CFTypeRef, path *C.char) {
+	fileUrl := C.GoString(path)
+	w := mustView(view)
+
+	fileExtension := filepath.Ext(fileUrl)
+	mime := mime.TypeByExtension(fileExtension)
+
+	w.w.Event(transfer.DataEvent{
+		Type: mime,
+		Open: func() (io.ReadCloser, error) {
+			return os.Open(fileUrl)
+		},
+	})
+}
+
 //export gio_onDraw
 func gio_onDraw(view C.CFTypeRef) {
 	w := mustView(view)
diff --git a/app/os_macos.m b/app/os_macos.m
index 49964fbf1..dc62b5eaf 100644
--- a/app/os_macos.m
+++ b/app/os_macos.m
@@ -110,6 +110,20 @@ - (void)mouseMoved:(NSEvent *)event {
 - (void)mouseDragged:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_MOVE, 0, 0);
 }
+-(NSDragOperation)draggingEntered:(id < NSDraggingInfo >)sender
+{
+	return NSDragOperationCopy;
+}
+- (void)draggingEnded:(id <NSDraggingInfo>)sender
+{
+	NSPasteboard* pbrd = [sender draggingPasteboard];
+	NSArray* droppedFiles = [pbrd propertyListForType:NSFilenamesPboardType];
+
+	for (NSString* filePath in droppedFiles) {
+		NSURL* url = [NSURL fileURLWithPath:filePath];
+		gio_onExternalDrop((__bridge CFTypeRef)self, (char*)[[url path] UTF8String]);
+	}
+}
 - (void)scrollWheel:(NSEvent *)event {
 	CGFloat dx = -event.scrollingDeltaX;
 	CGFloat dy = -event.scrollingDeltaY;
@@ -366,6 +380,7 @@ CFTypeRef gio_createView(void) {
 	@autoreleasepool {
 		NSRect frame = NSMakeRect(0, 0, 0, 0);
 		GioView* view = [[GioView alloc] initWithFrame:frame];
+		[view registerForDraggedTypes: [NSArray arrayWithObjects:NSTIFFPboardType, NSFilenamesPboardType, nil]];
 		view.wantsLayer = YES;
 		view.layerContentsRedrawPolicy = NSViewLayerContentsRedrawDuringViewResize;
 		return CFBridgingRetain(view);
diff --git a/io/router/pointer.go b/io/router/pointer.go
index e95bc6e7a..4e8e8c294 100644
--- a/io/router/pointer.go
+++ b/io/router/pointer.go
@@ -858,9 +858,9 @@ func (q *pointerQueue) deliverTransferDataEvent(p *pointerInfo, events *handlerE
 	transferIdx := len(q.transfers)
 	events.Add(p.dataTarget, transfer.DataEvent{
 		Type: src.offeredMime,
-		Open: func() io.ReadCloser {
+		Open: func() (io.ReadCloser, error) {
 			q.transfers[transferIdx] = nil
-			return src.data
+			return src.data, nil
 		},
 	})
 	q.transfers = append(q.transfers, src.data)
diff --git a/io/router/router.go b/io/router/router.go
index e3b3be8d9..bc69aea95 100644
--- a/io/router/router.go
+++ b/io/router/router.go
@@ -182,6 +182,19 @@ func (q *Router) Queue(events ...event.Event) bool {
 			}
 		case clipboard.Event:
 			q.cqueue.Push(e, &q.handlers)
+		case transfer.DataEvent:
+			pq := &q.pointer.queue
+			for _, h := range pq.hitTree {
+				if h.tag != nil {
+					targetMimes := pq.handlers[h.tag].targetMimes
+					for _, mimeType := range targetMimes {
+						if mimeType == e.Type {
+							q.handlers.Add(h.tag, e)
+							break
+						}
+					}
+				}
+			}
 		}
 	}
 	return q.handlers.HadEvents()
diff --git a/io/transfer/transfer.go b/io/transfer/transfer.go
index 78e2b9005..2ec700c7c 100644
--- a/io/transfer/transfer.go
+++ b/io/transfer/transfer.go
@@ -103,7 +103,7 @@ type DataEvent struct {
 	Type string
 	// Open returns the transfer data. It is only valid to call Open in the frame
 	// the DataEvent is received. The caller must close the return value after use.
-	Open func() io.ReadCloser
+	Open func() (io.ReadCloser, error)
 }
 
 func (DataEvent) ImplementsEvent() {}