Configtool: add ability to cancel upload.

In case communications to the bootloader doesn't work as expected,
avrdude often takes many many minutes to recognize this, so it's
very convenient to be able to abort these fruitless attempts.

This should solve issue #131.

configtool/build.py

@@ -74,6 +74,7 @@ class ScriptThread:
         wx.PostEvent(self.win, evt)
         p.kill()
         self.running = False
+        p.wait()
         return
 
       rc = p.wait()
@@ -310,6 +311,7 @@ class Upload(wx.Dialog):
     self.cpu = cpu
     self.baud = self.settings.uploadspeed
     self.Bind(wx.EVT_CLOSE, self.onExit)
+    self.cancelPending = False
 
     hsz = wx.BoxSizer(wx.HORIZONTAL)
     hsz.AddSpacer((10, 10))
@@ -338,9 +340,9 @@ class Upload(wx.Dialog):
       self.active = False
     else:
       self.Bind(EVT_SCRIPT_UPDATE, self.uploadUpdate)
-      t = ScriptThread(self, self.script)
+      self.t = ScriptThread(self, self.script)
       self.active = True
-      t.Start()
+      self.t.Start()
 
   def generateUploadScript(self):
     self.script = []
@@ -362,15 +364,31 @@ class Upload(wx.Dialog):
 
     if evt.state == SCRIPT_RUNNING:
       pass
+
     if evt.state == SCRIPT_CANCELLED:
-      self.log.AppendText("Upload terminated abnormally.\n")
       self.active = False
+
+      if self.cancelPending:
+        self.EndModal(wx.ID_OK)
+
+      self.log.AppendText("Upload terminated abnormally.\n")
+
     if evt.state == SCRIPT_FINISHED:
       self.log.AppendText("Upload completed normally.\n")
       self.active = False
 
   def onExit(self, evt):
     if self.active:
+      dlg = wx.MessageDialog(self, "Are you sure you want to cancel upload?",
+                             "Upload active",
+                             wx.YES_NO | wx.NO_DEFAULT | wx.ICON_INFORMATION)
+      rc = dlg.ShowModal()
+      dlg.Destroy()
+
+      if rc == wx.ID_YES:
+        self.cancelPending = True
+        self.log.AppendText("Cancelling...\n")
+        self.t.Stop()
       return
 
     self.EndModal(wx.ID_OK)