added window pollkey function (#1198)

highgui.cpp

@@ -33,6 +33,10 @@ int Window_WaitKeyEx(int delay = 0) {
     return cv::waitKeyEx(delay);
 }
 
+int Window_PollKey(void) {
+    return cv::pollKey();
+}
+
 void Window_Move(const char* winname, int x, int y) {
     cv::moveWindow(winname, x, y);
 }

highgui.go

@@ -172,6 +172,25 @@ func (w *Window) WaitKeyEx(delay int) int {
 	return int(C.Window_WaitKey(C.int(delay)))
 }
 
+// PollKey polls for a pressed key.
+// The function pollKey polls for a key event without waiting.
+// It returns the code of the pressed key or -1 if no key was pressed since
+// the last invocation. To wait until a key was pressed, use waitKey.
+//
+// The functions waitKey and pollKey are the only methods in HighGUI that can
+// fetch and handle GUI events, so one of them needs to be called periodically
+// for normal event processing unless HighGUI is used within an environment that
+// takes care of event processing.
+// The function only works if there is at least one HighGUI window created and
+// the window is active. If there are several HighGUI windows, any of them can
+// be active.
+//
+// For further details, please see:
+// https://docs.opencv.org/4.x/d7/dfc/group__highgui.html#ga6d20fbd3100ec3badc1eaa653aff99d7
+func (w *Window) PollKey() int {
+	return int(C.Window_PollKey())
+}
+
 // MoveWindow moves window to the specified position.
 //
 // For further details, please see:

highgui_gocv.h

@@ -17,6 +17,7 @@ void Window_SetProperty(const char* winname, int flag, double value);
 void Window_SetTitle(const char* winname, const char* title);
 int Window_WaitKey(int);
 int Window_WaitKeyEx(int);
+int Window_PollKey(void);
 void Window_Move(const char* winname, int x, int y);
 void Window_Resize(const char* winname, int width, int height);
 struct Rect Window_SelectROI(const char* winname, Mat img);

highgui_test.go

@@ -113,6 +113,16 @@ func TestTrackbarWithValue(t *testing.T) {
 	}
 }
 
+func TestPollKey(t *testing.T) {
+
+	w := NewWindow("polly")
+	defer w.Close()
+
+	if v := w.PollKey(); v != -1 {
+		t.Errorf("got %d want -1", v)
+	}
+}
+
 func TestWaitKeyEx(t *testing.T) {
 
 	w := NewWindow("wait")