darwin-external-dragndrop: implement external drag n' drop for darwin

app/os_macos.go

@@ -8,7 +8,11 @@ package app
 import (
 	"errors"
 	"image"
+	"io"
+	"mime"
+	"path/filepath"
 	"runtime"
+	"strings"
 	"time"
 	"unicode"
 	"unicode/utf8"
@@ -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 {
+			return io.NopCloser(strings.NewReader(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; // NSDragOperationGeneric
+}
+- (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/router.go

@@ -182,6 +182,14 @@ func (q *Router) Queue(events ...event.Event) bool {
 			}
 		case clipboard.Event:
 			q.cqueue.Push(e, &q.handlers)
+		case transfer.DataEvent:
+			for tag, handler := range q.pointer.queue.handlers {
+				for _, mimeType := range (*handler).targetMimes {
+					if mimeType == e.Type {
+						q.handlers.Add(tag, e)
+					}
+				}
+			}
 		}
 	}
 	return q.handlers.HadEvents()