Add Text overaly tutorial

docs/tutorials/text_overlay.rst

@@ -0,0 +1,47 @@
+Add Text to VTKOverlayWindow
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Classes are provided that can add persistent text to a VTKOverlayWindow as:
+
+* Corner annotations
+* Large centered text
+* Generic text anywhere in the window
+
+.. image:: text_overlay.png
+
+First, we need to import relevant modules, setup a Qt Application, and create a VTKOverlayWindow.
+
+.. literalinclude:: ../../tests/tutorials/test_text_overlay_tutorial.py
+    :language: python
+    :start-after: #Tutorial-start
+    :end-before: #Tutorial-section1
+
+We can now create a corner annotations:
+
+.. literalinclude:: ../../tests/tutorials/test_text_overlay_tutorial.py
+    :language: python
+    :start-after: #Tutorial-section1
+    :end-before: #Tutorial-section2
+
+centred text:
+
+.. literalinclude:: ../../tests/tutorials/test_text_overlay_tutorial.py
+    :language: python
+    :start-after: #Tutorial-section2
+    :end-before: #Tutorial-section3
+
+and place some text at given co-ordinates in the window:
+
+.. literalinclude:: ../../tests/tutorials/test_text_overlay_tutorial.py
+    :language: python
+    :start-after: #Tutorial-section3
+    :end-before: #Tutorial-end
+
+`layer=2` is typically used for text overlay (layer 0 is the background image and layer 1 is used for VTK models).
+Finally, we execute the Qt app to show the window:
+
+.. code-block:: python
+
+   overlay_window.show()
+   sys.exit(app.exec_())
+

tests/tutorials/test_text_overlay_tutorial.py

@@ -1,30 +1,32 @@
+#Tutorial-start
 import sys
 import cv2
 from PySide2 import QtWidgets
 from sksurgeryvtk.widgets import vtk_overlay_window
 from sksurgeryvtk.text import text_overlay
 
-def test_text():
-    app = QtWidgets.QApplication([])
-
-    background = cv2.imread('tests/data/rendering/background-960-x-540.png')
-    overlay_window = vtk_overlay_window.VTKOverlayWindow()
-    overlay_window.set_video_image(background)
-
-    corner_annotation = text_overlay.VTKCornerAnnotation()
-    corner_annotation.set_text(["1", "2", "3", "4"])
-    overlay_window.add_vtk_actor(corner_annotation.text_actor, layer=2)
-
-    large_text = text_overlay.VTKLargeTextCentreOfScreen("Central Text")
-    large_text.set_colour(1.0, 0.0, 0.0)
-    large_text.set_parent_window(overlay_window)
-    overlay_window.add_vtk_actor(large_text.text_actor, layer=2)
-
-    more_text = text_overlay.VTKText("More text", x=50, y=100)
-    more_text.set_colour(0.0, 1.0, 0.0)
-    overlay_window.add_vtk_actor(more_text.text_actor, layer=2)
-
-    overlay_window.show()
-    #sys.exit(app.exec_())
+app = QtWidgets.QApplication([])
+
+background = cv2.imread('tests/data/rendering/background-960-x-540.png')
+overlay_window = vtk_overlay_window.VTKOverlayWindow()
+overlay_window.set_video_image(background)
+#Tutorial-section1
+corner_annotation = text_overlay.VTKCornerAnnotation()
+corner_annotation.set_text(["1", "2", "3", "4"])
+overlay_window.add_vtk_actor(corner_annotation.text_actor, layer=2)
+#Tutorial-section2
+arge_text = text_overlay.VTKLargeTextCentreOfScreen("Central Text")
+large_text.set_colour(1.0, 0.0, 0.0)
+large_text.set_parent_window(overlay_window)
+overlay_window.add_vtk_actor(large_text.text_actor, layer=2)
+#Tutorial-section3
+more_text = text_overlay.VTKText("More text", x=50, y=100)
+more_text.set_colour(0.0, 1.0, 0.0)
+overlay_window.add_vtk_actor(more_text.text_actor, layer=2)
+#Tutorial-end
+
+overlay_window.show()
+
+#sys.exit(app.exec_())