Fixed bug with Line (sdlui.Renderer).

- Drop addon is based on WM_DROPFILES, dragdrop addon is based on the OLE IDragDrop interface and thus can registerer more interactions.
- The allg5ui implementation will try to fall back on the drop addon (because the dragdrop addon wouldn't work properly).
- Drop addon is refactored to use the same interface as the dragdrop addon.

addons/dragdrop/dragdrop_windows.c

@@ -0,0 +1,176 @@
+#include <Windows.h>
+#include <oleidl.h>
+#include <stdio.h>
+
+#include "vector.h"
+#include "_cgo_export.h"
+
+#define STDULONGMETHODIMP STDMETHODIMP_(ULONG)
+#define DRAGDROP_MAXFILEPATHSIZE 32767
+
+typedef struct
+{
+    IDropTargetVtbl *_vtbl;
+    long _refCount;
+
+    uint32_t _handle;
+    HWND _windowHandle;
+} DragDropHandler;
+
+static void screenToClient(HWND windowHandle, POINTL *point)
+{
+    ScreenToClient(windowHandle, (LPPOINT)point);
+}
+
+static STDMETHODIMP QueryInterface(IDropTarget *this, REFIID riid, LPVOID *ppvObj)
+{
+    // Always set out parameter to NULL, validating it first.
+    if (!ppvObj)
+        return E_INVALIDARG;
+    *ppvObj = NULL;
+    if (IsEqualIID(riid, &IID_IUnknown) || IsEqualIID(riid, &IID_IDropTarget))
+    {
+        // Increment the reference count and return the pointer.
+        *ppvObj = (LPVOID)this;
+        ((DragDropHandler *)this)->_vtbl->AddRef(this);
+        return NOERROR;
+    }
+    return E_NOINTERFACE;
+}
+
+static STDULONGMETHODIMP AddRef(IDropTarget *this)
+{
+    InterlockedIncrement(&((DragDropHandler *)this)->_refCount);
+    return ((DragDropHandler *)this)->_refCount;
+}
+
+static STDULONGMETHODIMP Release(IDropTarget *this)
+{
+    // Decrement the object's internal counter.
+    ULONG ulRefCount = InterlockedDecrement(&((DragDropHandler *)this)->_refCount);
+    if (0 == ((DragDropHandler *)this)->_refCount)
+    {
+        GlobalFree(this);
+    }
+    return ulRefCount;
+}
+
+static STDMETHODIMP DragEnter(IDropTarget *this, __RPC__in_opt IDataObject *pDataObj, DWORD grfKeyState, POINTL pt, __RPC__inout DWORD *pdwEffect)
+{
+    *pdwEffect = DROPEFFECT_COPY;
+
+    wchar_t filePath[DRAGDROP_MAXFILEPATHSIZE];
+
+    FORMATETC format;
+    format.cfFormat = CF_HDROP;
+    format.ptd = NULL;
+    format.dwAspect = DVASPECT_CONTENT;
+    format.lindex = -1;
+    format.tymed = TYMED_HGLOBAL;
+
+    STGMEDIUM medium;
+
+    HRESULT result = pDataObj->lpVtbl->GetData(pDataObj, &format, &medium);
+    if (result != S_OK)
+        return E_UNEXPECTED;
+    HDROP drop = (HDROP)GlobalLock(medium.hGlobal);
+
+    clearFiles(((DragDropHandler *)this)->_handle);
+    UINT numberOfFiles = DragQueryFile(drop, 0xFFFFFFFF, NULL, 0);
+    for (UINT fileIndex = 0; fileIndex < numberOfFiles; fileIndex++)
+    {
+        UINT length = DragQueryFileW(drop, fileIndex, filePath, DRAGDROP_MAXFILEPATHSIZE);
+        addFile(((DragDropHandler *)this)->_handle, &filePath[0], length);
+    }
+
+    GlobalUnlock(medium.hGlobal);
+    if (medium.pUnkForRelease != NULL)
+        medium.pUnkForRelease->lpVtbl->Release(medium.pUnkForRelease);
+
+    screenToClient(((DragDropHandler *)this)->_windowHandle, &pt);
+    onDragEnter(((DragDropHandler *)this)->_handle, pt.x, pt.y);
+
+    return S_OK;
+}
+
+static STDMETHODIMP DragOver(IDropTarget *this, DWORD grfKeyState, POINTL pt, __RPC__inout DWORD *pdwEffect)
+{
+    *pdwEffect = DROPEFFECT_COPY;
+    screenToClient(((DragDropHandler *)this)->_windowHandle, &pt);
+    onDragOver(((DragDropHandler *)this)->_handle, pt.x, pt.y);
+    return S_OK;
+}
+
+static STDMETHODIMP DragLeave(IDropTarget *this)
+{
+    onDragLeave(((DragDropHandler *)this)->_handle);
+    return S_OK;
+}
+
+static STDMETHODIMP Drop(IDropTarget *this, __RPC__in_opt IDataObject *pDataObj, DWORD grfKeyState, POINTL pt, __RPC__inout DWORD *pdwEffect)
+{
+    *pdwEffect = DROPEFFECT_COPY;
+    screenToClient(((DragDropHandler *)this)->_windowHandle, &pt);
+    onDrop(((DragDropHandler *)this)->_handle, pt.x, pt.y);
+    return S_OK;
+}
+
+static const IDropTargetVtbl DragDropHandlerVtbl = {
+    QueryInterface,
+    AddRef,
+    Release,
+    DragEnter,
+    DragOver,
+    DragLeave,
+    Drop,
+};
+
+static DragDropHandler *newDragDropHandler(HWND windowHandle, uint32_t handle)
+{
+    DragDropHandler *handler = malloc(sizeof(DragDropHandler));
+    handler->_vtbl = (IDropTargetVtbl *)&DragDropHandlerVtbl;
+    handler->_refCount = 0;
+    handler->_windowHandle = windowHandle;
+    handler->_handle = handle;
+    return handler;
+}
+
+BOOL dragDropInitialized = FALSE;
+typedef vector(DragDropHandler *) DragDropHandlers;
+DragDropHandlers handlers;
+
+static void VerifyResult(CHAR *component, HRESULT result)
+{
+    if (result == S_OK)
+        return;
+    printf("%s failed (error code: %d)\n", component, result);
+}
+
+static void initDragDrop(void)
+{
+    if (dragDropInitialized == TRUE)
+        return;
+
+    HRESULT result = OleInitialize(NULL);
+    VerifyResult("OleInitialize", result);
+
+    vector_init(handlers);
+
+    dragDropInitialized = TRUE;
+}
+
+uint32_t RegisterHandler(void *window)
+{
+    initDragDrop();
+
+    size_t handle = handlers.count + 1;
+    HWND windowHandle = (HWND)window;
+    DragDropHandler *handler = newDragDropHandler(windowHandle, handle);
+    vector_append(DragDropHandler *, handlers, handler);
+
+    DragAcceptFiles(windowHandle, TRUE);
+    HRESULT result = RegisterDragDrop(windowHandle, (IDropTarget *)handler);
+    VerifyResult("RegisterDragDrop", result);
+
+    return (uint32_t)handle;
+}

addons/dragdrop/dragdrop_windows.go

@@ -0,0 +1,96 @@
+// +build windows
+
+package dragdrop
+
+import (
+	"unsafe"
+
+	"golang.org/x/text/encoding/unicode"
+	"opslag.de/schobers/geom"
+	"opslag.de/schobers/zntg/ui"
+)
+
+/*
+#cgo LDFLAGS: -lole32 -luuid
+
+#include <Windows.h>
+#include <oleidl.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+extern uint32_t RegisterHandler(void* windowHandle);
+*/
+import "C"
+
+//export clearFiles
+func clearFiles(handle uint32) {
+	handler := handlers[handle]
+	handler.Files = nil
+	handlers[handle] = handler
+}
+
+//export addFile
+func addFile(handle uint32, pathNative *C.wchar_t, pathNativeLength C.UINT) {
+	pathBytes := C.GoBytes(unsafe.Pointer(pathNative), C.int(pathNativeLength)*C.sizeof_wchar_t)
+	decoder := unicode.UTF16(unicode.LittleEndian, unicode.UseBOM).NewDecoder()
+	path, err := decoder.Bytes(pathBytes)
+	if err != nil {
+		return
+	}
+	handler := handlers[handle]
+	handler.Files = append(handler.Files, string(path))
+	handlers[handle] = handler
+}
+
+//export onDragEnter
+func onDragEnter(handle uint32, x, y C.LONG) {
+	invokeHandler(handle, func(target ui.DragDropEventTarget, files []string) {
+		target.DragEnter(pos(x, y), files)
+	})
+}
+
+//export onDragOver
+func onDragOver(handle uint32, x, y C.LONG) {
+	invokeHandler(handle, func(target ui.DragDropEventTarget, _ []string) {
+		target.DragMove(pos(x, y))
+	})
+}
+
+//export onDragLeave
+func onDragLeave(handle uint32) {
+	invokeHandler(handle, func(target ui.DragDropEventTarget, _ []string) {
+		target.DragLeave()
+	})
+}
+
+//export onDrop
+func onDrop(handle uint32, x, y C.LONG) {
+	invokeHandler(handle, func(target ui.DragDropEventTarget, files []string) {
+		target.Drop(pos(x, y), files)
+	})
+}
+
+type handler struct {
+	Target ui.DragDropEventTarget
+	Files  []string
+}
+
+var handlers map[uint32]handler = map[uint32]handler{}
+
+func invokeHandler(handle uint32, invoke func(ui.DragDropEventTarget, []string)) {
+	handler := handlers[handle]
+	invoke(handler.Target, handler.Files)
+}
+
+func pos(x, y C.LONG) geom.PointF32 { return geom.Pt(int(x), int(y)).ToF32() }
+
+type provider struct{}
+
+func (p provider) Register(windowHandle uintptr, target ui.DragDropEventTarget) {
+	handle := C.RegisterHandler(unsafe.Pointer(windowHandle))
+	handlers[uint32(handle)] = handler{target, nil}
+}
+
+func init() {
+	ui.DefaultDragDropProvider = provider{}
+}

addons/dragdrop/vector.h

@@ -0,0 +1,26 @@
+#ifndef __VECTOR_H__
+#define __VECTOR_H__
+
+#define vector(type)  \
+    struct            \
+    {                 \
+        type *items;  \
+        size_t count; \
+    }
+
+#define vector_init(v) \
+    do                 \
+    {                  \
+        (v).items = 0; \
+        (v).count = 0; \
+    } while (0);
+
+#define vector_append(type, v, i)                                         \
+    do                                                                    \
+    {                                                                     \
+        (v).count++;                                                      \
+        (v).items = (type *)realloc((v).items, sizeof(type) * (v).count); \
+        (v).items[(v).count - 1] = i;                                     \
+    } while (0);
+
+#endif // __VECTOR_H__

addons/drop/drop_windows.c

@@ -7,8 +7,8 @@
 
 #define droppedFilePathSize 32767
 
+BOOL dropHookInitialized = FALSE;
 HHOOK nextHook;
-uint32_t nextDropID = 0;
 
 LRESULT CALLBACK DragAndDropHook(
     _In_ int nCode,
@@ -24,29 +24,40 @@ LRESULT CALLBACK DragAndDropHook(
     case WM_DROPFILES:
     {
         wchar_t droppedFilePath[droppedFilePathSize];
-        uint32_t dropID = nextDropID++;
 
+        clearDrop();
         HDROP drop = (HDROP)message->wParam;
-        POINT position;
-        DragQueryPoint(drop, &position);
-        droppedFilesPosition(dropID, position.x, position.y);
         UINT numberOfFiles = DragQueryFile(drop, 0xFFFFFFFF, NULL, 0);
         for (UINT fileIndex = 0; fileIndex < numberOfFiles; fileIndex++)
         {
             UINT length = DragQueryFileW(drop, fileIndex, droppedFilePath, droppedFilePathSize);
-            droppedFilesFile(dropID, &droppedFilePath[0], length);
+            addDroppedFile(&droppedFilePath[0], length);
         }
-        droppedFilesDrop(dropID);
+        POINT position;
+        DragQueryPoint(drop, &position);
+
+        dropFinished(position.x, position.y);
     }
     break;
     }
     return CallNextHookEx(nextHook, nCode, wParam, lParam);
 }
 
+void initDropHook(HWND windowHandle)
+{
+    if (dropHookInitialized == TRUE)
+        return;
+
+    DWORD threadId = GetWindowThreadProcessId(windowHandle, NULL);
+    nextHook = SetWindowsHookEx(WH_GETMESSAGE, DragAndDropHook, NULL, threadId);
+
+    dropHookInitialized = TRUE;
+}
+
 void SetDragAndDropHook(void *window)
 {
     HWND windowHandle = (HWND)window;
+    initDropHook(windowHandle);
+
     DragAcceptFiles(windowHandle, TRUE);
-    DWORD threadId = GetWindowThreadProcessId(windowHandle, NULL);
-    nextHook = SetWindowsHookEx(WH_GETMESSAGE, DragAndDropHook, NULL, threadId);
 }

addons/drop/drop_windows.go

@@ -3,11 +3,11 @@
 package drop
 
 import (
-	"errors"
 	"unsafe"
 
 	"golang.org/x/text/encoding/unicode"
 	"opslag.de/schobers/geom"
+	"opslag.de/schobers/zntg/ui"
 )
 
 /*
@@ -18,53 +18,48 @@ void SetDragAndDropHook(void* window);
 */
 import "C"
 
-var handler Dropper = nil
-var drops map[uint32]droppedFiles = map[uint32]droppedFiles{}
-
-type droppedFiles struct {
-	X, Y  int
-	Files []string
+type handler struct {
+	Target ui.DragDropEventTarget
+	Files  []string
 }
 
-//export droppedFilesPosition
-func droppedFilesPosition(id C.uint32_t, x, y C.INT) {
-	files := drops[uint32(id)]
-	files.X = int(x)
-	files.Y = int(y)
-	drops[uint32(id)] = files
+var targets map[ui.DragDropEventTarget]struct{} = map[ui.DragDropEventTarget]struct{}{}
+var droppedFiles []string
+
+//export clearDrop
+func clearDrop() {
+	droppedFiles = nil
 }
 
-//export droppedFilesFile
-func droppedFilesFile(id C.uint32_t, filePath *C.wchar_t, filePathLength C.UINT) {
-	files := drops[uint32(id)]
+//export dropFinished
+func dropFinished(x, y C.INT) {
+	for target := range targets {
+		target.Drop(geom.PtF32(float32(x), float32(y)), droppedFiles)
+	}
+}
+
+//export addDroppedFile
+func addDroppedFile(filePath *C.wchar_t, filePathLength C.UINT) {
 	pathBytes := C.GoBytes(unsafe.Pointer(filePath), C.int(filePathLength)*C.sizeof_wchar_t)
 	decoder := unicode.UTF16(unicode.LittleEndian, unicode.UseBOM).NewDecoder()
 	path, err := decoder.Bytes(pathBytes)
 	if err != nil {
 		return
 	}
-	files.Files = append(files.Files, string(path))
-	drops[uint32(id)] = files
+	droppedFiles = append(droppedFiles, string(path))
 }
 
-//export droppedFilesDrop
-func droppedFilesDrop(id C.uint32_t) {
-	h := handler
-	if h == nil {
-		return
-	}
-	drop, ok := drops[uint32(id)]
-	if !ok {
-		return
-	}
-	h.FilesDropped(geom.Pt(drop.X, drop.Y).ToF32(), drop.Files)
+func RegisterAsDefaultProvider() {
+	ui.DefaultDragDropProvider = &provider{}
 }
 
-func Register(dropper Dropper) error {
-	if handler != nil {
-		return errors.New(`can only register single dropper`)
-	}
-	handler = dropper
-	C.SetDragAndDropHook(unsafe.Pointer(dropper.WindowHandle()))
-	return nil
+type provider struct{}
+
+func (p provider) Register(windowHandle uintptr, target ui.DragDropEventTarget) {
+	C.SetDragAndDropHook(unsafe.Pointer(windowHandle))
+	targets[target] = struct{}{}
+}
+
+func init() {
+	ui.DefaultDragDropProvider = provider{}
 }

addons/drop/dropper.go

@@ -1,9 +0,0 @@
-package drop
-
-import "opslag.de/schobers/geom"
-
-type Dropper interface {
-	WindowHandle() uintptr
-
-	FilesDropped(geom.PointF32, []string)
-}

allg5ui/renderer.go

@@ -10,6 +10,7 @@ import (
 
 	"opslag.de/schobers/allg5"
 	"opslag.de/schobers/geom"
+	"opslag.de/schobers/zntg/addons/drop"
 	"opslag.de/schobers/zntg/ui"
 )
 
@@ -47,6 +48,11 @@ func NewRenderer(w, h int, opts allg5.NewDisplayOptions) (*Renderer, error) {
 	})
 	clean = nil
 
+	if ui.DefaultDragDropProvider != nil {
+		// make sure we fall back on simple drop (OLE implementation doesn't seem to work, reason unknown yet).
+		drop.RegisterAsDefaultProvider()
+	}
+
 	return &Renderer{disp, eq, nil, user, &ui.OSResources{}, dispPos(disp), ui.KeyState{}, ui.KeyModifierNone, ui.MouseCursorDefault}, nil
 }
 
@@ -152,6 +158,10 @@ func (r *Renderer) Refresh() {
 	r.user.EmitEvent()
 }
 
+func (r *Renderer) Stamp() float64 {
+	return allg5.GetTime()
+}
+
 // Renderer implementation (lifetime)
 
 func (r *Renderer) Destroy() error {

sdlui/renderer.go

@@ -205,6 +205,10 @@ func (r *Renderer) Refresh() {
 	sdl.PushEvent(e)
 }
 
+func (r *Renderer) Stamp() float64 {
+	return .001 * float64(sdl.GetTicks())
+}
+
 // Lifetime
 
 func (r *Renderer) Destroy() error {
@@ -363,7 +367,7 @@ func (r *Renderer) FillRectangle(rect geom.RectangleF32, c color.Color) {
 
 func (r *Renderer) Line(p, q geom.PointF32, color color.Color, thickness float32) {
 	r.SetDrawColorGo(color)
-	r.renderer.DrawLineF(p.X, p.Y, p.X, p.Y)
+	r.renderer.DrawLineF(p.X, p.Y, q.X, q.Y)
 }
 
 func (r *Renderer) Rectangle(rect geom.RectangleF32, c color.Color, thickness float32) {

ui/dragdrop.go

@@ -0,0 +1,46 @@
+package ui
+
+import "opslag.de/schobers/geom"
+
+type DragDropEventTarget interface {
+	DragEnter(geom.PointF32, []string)
+	DragMove(geom.PointF32)
+	DragLeave()
+	Drop(geom.PointF32, []string)
+}
+
+type DragDropProvider interface {
+	Register(windowHandle uintptr, target DragDropEventTarget)
+}
+
+var DefaultDragDropProvider DragDropProvider = nil
+
+type dragDropEventTarget struct {
+	renderer Renderer
+	events   []Event
+}
+
+func (t *dragDropEventTarget) eventBase() EventBase {
+	return EventBase{StampInSeconds: t.renderer.Stamp()}
+}
+
+func (t *dragDropEventTarget) pushEvent(e Event) {
+	t.events = append(t.events, e)
+	t.renderer.Refresh()
+}
+
+func (t *dragDropEventTarget) DragEnter(pos geom.PointF32, files []string) {
+	t.pushEvent(&DisplayDragEnterEvent{EventBase: t.eventBase(), X: pos.X, Y: pos.Y, Files: files})
+}
+
+func (t *dragDropEventTarget) DragMove(pos geom.PointF32) {
+	t.pushEvent(&DisplayDragMoveEnter{EventBase: t.eventBase(), X: pos.X, Y: pos.Y})
+}
+
+func (t *dragDropEventTarget) DragLeave() {
+	t.pushEvent(&DisplayDragLeaveEvent{EventBase: t.eventBase()})
+}
+
+func (t *dragDropEventTarget) Drop(pos geom.PointF32, files []string) {
+	t.pushEvent(&DisplayDropEvent{EventBase: t.eventBase(), X: pos.X, Y: pos.Y, Files: files})
+}

ui/event.go

@@ -6,6 +6,31 @@ type DisplayCloseEvent struct {
 	EventBase
 }
 
+type DisplayDragEnterEvent struct {
+	EventBase
+	X, Y  float32
+	Files []string
+}
+
+type DisplayDragLeaveEvent struct {
+	EventBase
+}
+
+type DisplayDragMoveEnter struct {
+	EventBase
+	X, Y float32
+}
+
+type DisplayDropEvent struct {
+	EventBase
+	X, Y  float32
+	Files []string
+}
+
+func (e DisplayDropEvent) Pos() geom.PointF32 {
+	return geom.PtF32(e.X, e.Y)
+}
+
 type DisplayMoveEvent struct {
 	EventBase
 	Bounds geom.RectangleF32

ui/examples/03_dragdrop/dragdrop.go

@@ -0,0 +1,122 @@
+package main
+
+import (
+	"image/color"
+	"log"
+	"strings"
+	"time"
+
+	"opslag.de/schobers/geom"
+
+	_ "opslag.de/schobers/zntg/addons/dragdrop" // import drag & drop functionality
+	_ "opslag.de/schobers/zntg/sdlui"           // import the renderer for the UI
+
+	"opslag.de/schobers/zntg/ui"
+)
+
+type dropFiles struct {
+	ui.StackPanel
+
+	ctx   ui.Context
+	files *ui.Paragraph
+	ping  *ping
+}
+
+type ping struct {
+	ui.OverlayBase
+
+	circle   ui.Texture
+	position geom.PointF32
+	over     bool
+	tick     time.Time
+}
+
+func (p *ping) Render(ctx ui.Context) {
+	elapsed := time.Since(p.tick)
+	const animationDuration = 500 * time.Millisecond
+	if elapsed > animationDuration {
+		return
+	}
+	tint := color.Gray{Y: uint8(elapsed * 255 / animationDuration)}
+	center := geom.PtF32(float32(p.circle.Width()), float32(p.circle.Height())).Mul(.5)
+	ctx.Renderer().DrawTexturePointOptions(p.circle, p.position.Sub(center), ui.DrawOptions{Tint: tint})
+	ctx.Animate()
+}
+
+func (d *dropFiles) Handle(ctx ui.Context, e ui.Event) bool {
+	switch e := e.(type) {
+	case *ui.DisplayDragMoveEnter:
+		d.ping.tick = time.Now()
+		d.ping.position = geom.PtF32(e.X, e.Y)
+		d.ping.over = true
+		d.ctx.Animate()
+		return true
+	case *ui.DisplayDropEvent:
+		d.files.Text = "Files dropped:\n" + strings.Join(e.Files, "\n")
+		d.ping.tick = time.Now()
+		d.ping.position = geom.PtF32(e.X, e.Y)
+		d.ping.over = false
+		d.ctx.Animate()
+		return true
+	}
+	return d.StackPanel.Handle(ctx, e)
+}
+
+func newCircle() ui.ImageSource {
+	const side = 16
+	center := geom.PtF32(.5*side, .5*side)
+	return &ui.AlphaPixelImageSource{
+		ImageAlphaPixelTestFn: func(p geom.PointF32) uint8 {
+			dist := p.Distance(center)
+			if dist < 7 {
+				return 255
+			} else if dist > 8 {
+				return 0
+			}
+			return uint8((8 - dist) * 255 * 0.5)
+		},
+		Size: geom.Pt(side, side),
+	}
+}
+
+func (d *dropFiles) Init(ctx ui.Context) error {
+	d.ctx = ctx
+
+	_, err := ctx.Fonts().CreateFontPath("default", "../resources/font/OpenSans-Regular.ttf", 14)
+	if err != nil {
+		return err
+	}
+
+	d.files = ui.BuildParagraph("", nil)
+
+	pingCircle, err := ctx.Renderer().CreateTexture(newCircle())
+	if err != nil {
+		return err
+	}
+	d.ping = &ping{circle: pingCircle}
+	ctx.Overlays().AddOnTop("ping", d.ping, true)
+
+	d.Background = color.White
+	d.Children = []ui.Control{
+		&ui.Label{Text: "Drop files on this window!"},
+		d.files,
+	}
+	return nil
+}
+
+func run() error {
+	var render, err = ui.NewRendererDefault("Files Drop Example", 800, 600)
+	if err != nil {
+		return err
+	}
+	defer render.Destroy()
+
+	return ui.RunWait(render, ui.DefaultStyle(), &dropFiles{}, true)
+}
+
+func main() {
+	var err = run()
+	if err != nil {
+		log.Fatal(err)
+	}
+}

ui/renderer.go

@@ -12,6 +12,7 @@ type Renderer interface {
 	// Events
 	PushEvents(t EventTarget, wait bool) bool
 	Refresh()
+	Stamp() float64 // in seconds
 
 	// Lifetime
 	Destroy() error

ui/ui.go

@@ -26,6 +26,13 @@ func RunWait(r Renderer, s *Style, view Control, wait bool) error {
 			return err
 		}
 	}
+
+	dragDropTarget := &dragDropEventTarget{renderer: r}
+	dragDrop := DefaultDragDropProvider
+	if dragDrop != nil {
+		dragDrop.Register(r.WindowHandle(), dragDropTarget)
+	}
+
 	anim := time.NewTicker(30 * time.Millisecond)
 	go func() {
 		for {
@@ -62,6 +69,12 @@ func RunWait(r Renderer, s *Style, view Control, wait bool) error {
 		} else {
 			ctx.tooltip.Text = tooltip
 		}
+
+		dragDropEvents := dragDropTarget.events
+		dragDropTarget.events = nil
+		for _, e := range dragDropEvents {
+			ctx.Handle(e)
+		}
 	}
 	return nil
 }