implementation of setMouseCallback

callback.go

@@ -0,0 +1,38 @@
+package gocv
+
+import (
+	"sync"
+)
+
+var CGOCallback = callback{
+	fns: make(map[int]func(...interface{})),
+}
+
+type callback struct {
+	mu    sync.Mutex
+	index int
+	fns   map[int]func(...interface{})
+}
+
+func (n *callback) Register(fn func(args ...interface{})) int {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	n.index++
+	for n.fns[n.index] != nil {
+		n.index++
+	}
+	n.fns[n.index] = fn
+	return n.index
+}
+
+func (n *callback) Lookup(i int) func(...interface{}) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	return n.fns[i]
+}
+
+func (n *callback) Unregister(i int) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	delete(n.fns, i)
+}

go.mod

@@ -1,3 +1,3 @@
 module gocv.io/x/gocv
 
-go 1.13
+go 1.13

highgui.cpp

@@ -57,6 +57,11 @@ struct Rects Window_SelectROIs(const char* winname, Mat img) {
     return ret;
 }
 
+// MouseCallback
+void Window_SetMouseCallback(const char* winname, mouse_callback callback, void* userdata) {
+   cv::setMouseCallback(winname, callback, userdata);
+}
+
 // Trackbar
 void Trackbar_Create(const char* winname, const char* trackname, int max) {
     cv::createTrackbar(trackname, winname, NULL, max);

highgui.go

@@ -194,6 +194,31 @@ func (w *Window) ResizeWindow(width, height int) {
 	C.Window_Resize(cName, C.int(width), C.int(height))
 }
 
+//export go_MouseCallback
+func go_MouseCallback(event C.int, x C.int, y C.int, flags C.int, userdata unsafe.Pointer) {
+	CGOCallback.Lookup(int(*(*C.int)(userdata)))(event, x, y, flags)
+}
+
+// Sets mouse handler for the specified window.
+//
+// For further details, please see:
+// https://docs.opencv.org/4.2.0/d7/dfc/group__highgui.html#ga89e7806b0a616f6f1d502bd8c183ad3e
+//
+func (w *Window) SetMouseCallback(onMouse MouseCallback) {
+	cName := C.CString(w.name)
+	defer C.free(unsafe.Pointer(cName))
+
+	fn := C.int(CGOCallback.Register(func(args ...interface{}) {
+		onMouse(
+			MouseEventType(args[0].(C.int)),
+			int(args[1].(C.int)),
+			int(args[2].(C.int)),
+			MouseEventFlag(args[3].(C.int)),
+		)
+	}))
+	C.Window_SetMouseCallback(cName, (C.mouse_callback)(C.go_MouseCallback), unsafe.Pointer(&fn))
+}
+
 // SelectROI selects a Region Of Interest (ROI) on the given image.
 // It creates a window and allows user to select a ROI using mouse.
 //
@@ -321,3 +346,33 @@ func (t *Trackbar) SetMax(pos int) {
 
 	C.Trackbar_SetMax(cName, tName, C.int(pos))
 }
+
+type MouseCallback func(event MouseEventType, x, y int, flags MouseEventFlag)
+
+type MouseEventType int
+
+const (
+	MouseEventMove MouseEventType = iota
+	MouseEventLeftButtonDown
+	MouseEventRightButtonDown
+	MouseEventMiddleButtonDown
+	MouseEventLeftButtonUp
+	MouseEventRightButtonUp
+	MouseEventMiddleButtonUp
+	MouseEventLeftButtonDoubleClick
+	MouseEventRightButtonDoubleClick
+	MouseEventMiddleButtonDoubleClick
+	MouseEventMouseWheel
+	MouseEventHorizontalMouseWheel
+)
+
+type MouseEventFlag int
+
+const (
+	MouseEventFlagLeftButton MouseEventFlag = 1 << iota
+	MouseEventFlagRightButton
+	MouseEventFlagMiddleButton
+	MouseEventFlagCtrlKey
+	MouseEventFlagShiftKey
+	MouseEventFlagAltKey
+)

highgui_gocv.h

@@ -28,6 +28,12 @@ void Trackbar_SetPos(const char* winname, const char* trackname, int pos);
 void Trackbar_SetMin(const char* winname, const char* trackname, int pos);
 void Trackbar_SetMax(const char* winname, const char* trackname, int pos);
 
+// MouseCallback
+typedef void (*mouse_callback)(int event, int x, int y, int flags, void* userdata);
+void Window_SetMouseCallback(const char* winname, mouse_callback callback, void* userdata);
+extern void go_MouseCallback(int event, int x, int y, int flags, void* userdata);
+
+
 #ifdef __cplusplus
 }
 #endif

highgui_test.go

@@ -94,3 +94,10 @@ func TestTrackbar(t *testing.T) {
 		t.Error("Trackbar pos should have been 50")
 	}
 }
+
+func TestSetMouseCallback(t *testing.T) {
+	window := NewWindow("mouse callback")
+	defer window.Close()
+
+	window.SetMouseCallback(func(event MouseEventType, x, y int, flags MouseEventFlag) {})
+}