NF: Builder self-screenshot: initial commit

motivation: might be useful for automating some Builder tests, fun for users (?)

status: builder.BuilderFrame.getSelfie() can get and save a png image of the BuilderFrame
needs work:
- compensate for toolbar (?) height on Mac, linux
- set the image name + path
- ability to trigger: bind to a camera icon on toolbar?

psychopy/app/builder/builder.py

@@ -4593,6 +4593,27 @@ def generateScript(self, experimentPath):
             return None
         return script
 
+    def getSelfie(self, event=None):
+        """Returns path to a bitmap snapshot of self, as it appears in the UI at this moment.
+        """
+        # http://wxpython-users.1045709.n5.nabble.com/Screen-capture-via-wxPython-td2348994.html
+        offset = 0
+        htReduction = 0  # see link for ideas on how to set this
+        dc = wx.ClientDC(self)
+        rect = self.GetRect()
+        bmp = wx.EmptyBitmap(rect.width, rect.height - htReduction)
+        memdc = wx.MemoryDC()
+        memdc.SelectObject(bmp)
+
+        memdc.Blit(0, 0, rect.width, rect.height, dc, 0, offset)
+        memdc.SelectObject(wx.NullBitmap)
+
+        img = bmp.ConvertToImage()
+        fileName = "BuilderFrame_selfie.png"
+        img.SaveFile(fileName, wx.BITMAP_TYPE_PNG)
+
+        return os.path.abspath(fileName)
+
 
 class ReadmeFrame(wx.Frame):
     def __init__(self, parent):