macOS: external drag and drop support

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)

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);

io/router/pointer.go

@@ -801,6 +801,14 @@ func (q *pointerQueue) deliverEnterLeaveEvents(p *pointerInfo, events *handlerEv
 	p.entered = append(p.entered[:0], hits...)
 }
 
+func (q *pointerQueue) notifyPotentialTargets(src *pointerHandler, events *handlerEvents, event event.Event) {
+	for k, tgt := range q.handlers {
+		if _, ok := firstMimeMatch(src, tgt); ok {
+			events.Add(k, event)
+		}
+	}
+}
+
 func (q *pointerQueue) deliverDragEvent(p *pointerInfo, events *handlerEvents) {
 	if p.dataSource != nil {
 		return
@@ -814,11 +822,7 @@ func (q *pointerQueue) deliverDragEvent(p *pointerInfo, events *handlerEvents) {
 		// One data source handler per pointer.
 		p.dataSource = k
 		// Notify all potential targets.
-		for k, tgt := range q.handlers {
-			if _, ok := firstMimeMatch(src, tgt); ok {
-				events.Add(k, transfer.InitiateEvent{})
-			}
-		}
+		q.notifyPotentialTargets(src, events, transfer.InitiateEvent{})
 		break
 	}
 }
@@ -858,9 +862,9 @@ 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)

io/router/router.go

@@ -182,6 +182,8 @@ func (q *Router) Queue(events ...event.Event) bool {
 			}
 		case clipboard.Event:
 			q.cqueue.Push(e, &q.handlers)
+		case transfer.DataEvent:
+			q.pointer.queue.notifyPotentialTargets(&pointerHandler{sourceMimes: []string{e.Type}}, &q.handlers, e)
 		}
 	}
 	return q.handlers.HadEvents()

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() {}