Print position of selected cross in status bar

command_box.py

@@ -2,7 +2,10 @@ from kivy.uix.label import Label
 
 class Command_box(Label):
     
-    def __init__(self,**kwargs):
+    def __init__(self,app,**kwargs):
+        # app is used to share information between widgets
+        self.app=app
+
         # init Label
         super(Command_box,self).__init__(**kwargs)
 

cross.py

@@ -208,7 +208,7 @@ def cross_polar(t):
 # cross painter
 class Cross_painter(Widget):
 
-    def __init__(self,**kwargs):
+    def __init__(self,app,**kwargs):
 
         # list of crosses
         self.crosses=[]
@@ -216,6 +216,9 @@ class Cross_painter(Widget):
         # selected cross
         self.selected=None
 
+        # app is used to share information between widgets
+        self.app=app
+
         # init Widget
         super(Cross_painter,self).__init__(**kwargs)
 
@@ -262,6 +265,8 @@ class Cross_painter(Widget):
                 # redraw
                 self.canvas.clear()
                 self.draw()
+                # report position in status bar
+                self.app.status_bar.set_position(" {:05.2f} , {:05.2f}".format(self.selected.pos.x,self.selected.pos.y))
 
 
     # find the cross at position pos

jam.kv

@@ -1,7 +1,7 @@
 #: kivy 2.0.0
 
 <Status_bar>:
-  canvas:
+  canvas.before:
     Color:
       rgb: 1,1,1
     Rectangle:
@@ -9,9 +9,13 @@
       size: self.size
   size_hint_y: None
   height: 20
+  text_size: self.size
+  markup: True
+  color: (0,0,0,1)
+
 
 <Command_box>:
-  canvas:
+  canvas.before:
     Color:
       rgb: 0,0,0
     Rectangle:
@@ -19,4 +23,5 @@
       size: self.size
   size_hint_y: None
   height: 20
+  text_size: self.size
   

main.py

@@ -14,12 +14,12 @@ class Jam_app(App):
 
     def build(self):
         layout=BoxLayout(orientation="vertical")
-        painter=Cross_painter()
-        status=Status_bar()
-        command=Command_box()
-        layout.add_widget(painter)
-        layout.add_widget(status)
-        layout.add_widget(command)
+        self.painter=Cross_painter(self)
+        self.status_bar=Status_bar(self)
+        self.command_box=Command_box(self)
+        layout.add_widget(self.painter)
+        layout.add_widget(self.status_bar)
+        layout.add_widget(self.command_box)
         return layout
 
 

status_bar.py

@@ -1,8 +1,15 @@
 from kivy.uix.label import Label
 from kivy.graphics import Color,Rectangle
+from kivy.utils import escape_markup
 
 class Status_bar(Label):
 
-    def __init__(self,**kwargs):
+    def __init__(self,app,**kwargs):
+        # app is used to share information between widgets
+        self.app=app
+
         # init Label
         super(Status_bar,self).__init__(**kwargs)
+
+    def set_position(self,string):
+        self.text=escape_markup(string)