nc_files: add a pyqt5 based 'filter program' test program

While testing qtvcp I needed a test program.
This also can be a frame work for a new filter.

nc_files/filtertest-gui.py

@@ -0,0 +1,63 @@
+import sys
+from PyQt5.QtWidgets import (QApplication, QDialog, QDialogButtonBox,
+                            QVBoxLayout,QDialogButtonBox)
+from PyQt5.QtCore import QTimer, Qt
+
+class CustomDialog(QDialog):
+
+    def __init__(self, *args, **kwargs):
+        super(CustomDialog, self).__init__(*args, **kwargs)
+
+        self.setWindowFlags(self.windowFlags() | Qt.WindowStaysOnTopHint)
+        self.setWindowTitle("Filter-with-GUI Test")
+
+        QBtn = QDialogButtonBox.Cancel
+
+        self.buttonBox = QDialogButtonBox(QBtn)
+        self.buttonBox.rejected.connect(self.reject)
+
+        self.layout = QVBoxLayout()
+        self.layout.addWidget(self.buttonBox)
+        self.setLayout(self.layout)
+
+        self._percentDone = 0
+
+        self._timer = QTimer()
+        self._timer.timeout.connect(self.process)
+        self._timer.start(100)
+
+    def reject(self):
+        # This provides an error message
+        print >>sys.stderr, 'You asked to cancel before finished.'
+        raise SystemExit(1)
+
+    def process(self):
+        try:
+            # output a line of gcode
+            print >>sys.stdout, '(MSG, made line of code : {})'.format(self._percentDone)
+
+            # keep track of progress
+            self._percentDone +=1
+
+            # update progress
+            print >>sys.stderr, 'FILTER_PROGRESS={}'.format(self._percentDone)
+
+            # if done end with no error/error message
+            if self._percentDone == 100:
+                raise SystemExit(0)
+
+        except Exception as e:
+            # This provides an error message
+            print >>sys.stderr, 'Something bad happened:',e
+            # this signals the error message should be shown
+            raise SystemExit(1)
+
+
+
+if __name__ == "__main__":
+
+    app = QApplication(sys.argv)
+    w = CustomDialog()
+    w.show()
+    sys.exit( app.exec_() )
+