From 21026bf7cdfcd2adecb656ca66359f0fac4edb7c Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.alekhin@intel.com>
Date: Thu, 19 Apr 2018 18:42:01 +0300
Subject: [PATCH] python: fix support of UI callbacks

---
 modules/python/src2/cv2.cpp | 58 +++++++++++++++++++++++++------------
 1 file changed, 40 insertions(+), 18 deletions(-)

diff --git a/modules/python/src2/cv2.cpp b/modules/python/src2/cv2.cpp
index 7d55513315..2c2e9ecf61 100644
--- a/modules/python/src2/cv2.cpp
+++ b/modules/python/src2/cv2.cpp
@@ -27,6 +27,7 @@
 
 #include "pycompat.hpp"
 
+#include <map>
 
 static PyObject* opencv_error = 0;
 
@@ -1621,13 +1622,19 @@ static PyObject *pycvSetMouseCallback(PyObject*, PyObject *args, PyObject *kw)
     if (param == NULL) {
         param = Py_None;
     }
-    static PyObject* last_param = NULL;
-    if (last_param) {
-        Py_DECREF(last_param);
-        last_param = NULL;
+    PyObject* py_callback_info = Py_BuildValue("OO", on_mouse, param);
+    static std::map<std::string, PyObject*> registered_callbacks;
+    std::map<std::string, PyObject*>::iterator i = registered_callbacks.find(name);
+    if (i != registered_callbacks.end())
+    {
+        Py_DECREF(i->second);
+        i->second = py_callback_info;
+    }
+    else
+    {
+        registered_callbacks.insert(std::pair<std::string, PyObject*>(std::string(name), py_callback_info));
     }
-    last_param = Py_BuildValue("OO", on_mouse, param);
-    ERRWRAP2(setMouseCallback(name, OnMouse, last_param));
+    ERRWRAP2(setMouseCallback(name, OnMouse, py_callback_info));
     Py_RETURN_NONE;
 }
 #endif
@@ -1663,13 +1670,20 @@ static PyObject *pycvCreateTrackbar(PyObject*, PyObject *args)
         PyErr_SetString(PyExc_TypeError, "on_change must be callable");
         return NULL;
     }
-    static PyObject* last_param = NULL;
-    if (last_param) {
-        Py_DECREF(last_param);
-        last_param = NULL;
+    PyObject* py_callback_info = Py_BuildValue("OO", on_change, Py_None);
+    std::string name = std::string(window_name) + ":" + std::string(trackbar_name);
+    static std::map<std::string, PyObject*> registered_callbacks;
+    std::map<std::string, PyObject*>::iterator i = registered_callbacks.find(name);
+    if (i != registered_callbacks.end())
+    {
+        Py_DECREF(i->second);
+        i->second = py_callback_info;
     }
-    last_param = Py_BuildValue("OO", on_change, Py_None);
-    ERRWRAP2(createTrackbar(trackbar_name, window_name, value, count, OnChange, last_param));
+    else
+    {
+        registered_callbacks.insert(std::pair<std::string, PyObject*>(name, py_callback_info));
+    }
+    ERRWRAP2(createTrackbar(trackbar_name, window_name, value, count, OnChange, py_callback_info));
     Py_RETURN_NONE;
 }
 
@@ -1717,13 +1731,21 @@ static PyObject *pycvCreateButton(PyObject*, PyObject *args, PyObject *kw)
         userdata = Py_None;
     }
 
-    static PyObject* last_param = NULL;
-    if (last_param) {
-        Py_DECREF(last_param);
-        last_param = NULL;
+    PyObject* py_callback_info = Py_BuildValue("OO", on_change, userdata);
+    std::string name(button_name);
+
+    static std::map<std::string, PyObject*> registered_callbacks;
+    std::map<std::string, PyObject*>::iterator i = registered_callbacks.find(name);
+    if (i != registered_callbacks.end())
+    {
+        Py_DECREF(i->second);
+        i->second = py_callback_info;
+    }
+    else
+    {
+        registered_callbacks.insert(std::pair<std::string, PyObject*>(name, py_callback_info));
     }
-    last_param = Py_BuildValue("OO", on_change, userdata);
-    ERRWRAP2(createButton(button_name, OnButtonChange, last_param, button_type, initial_button_state != 0));
+    ERRWRAP2(createButton(button_name, OnButtonChange, py_callback_info, button_type, initial_button_state != 0));
     Py_RETURN_NONE;
 }
 #endif