BF: Add depth parameter to Slider writeInitCode

Add depth parameter to Slider writeInitCode and writeInitCodeJS
methods so sliders are rendered in the same order they are displayed
in the routine canvas.

psychopy/experiment/components/slider/__init__.py

@@ -177,13 +177,15 @@ def writeInitCode(self, buff):
         if inits['units'].val == 'from exp settings':
             inits['units'].val = None
 
+        inits['depth'] = -self.getPosInRoutine()
+
         # build up an initialization string for Slider():
         initStr = ("{name} = visual.Slider(win=win, name='{name}',\n"
                    "    size={size}, pos={pos}, units={units},\n"
                    "    labels={labels}, ticks={ticks},\n"
                    "    granularity={granularity}, style={styles},\n"
                    "    color={color}, font={font},\n"
-                   "    flip={flip})\n"
+                   "    flip={flip}, depth={depth})\n"
                    .format(**inits))
         buff.writeIndented(initStr)
 
@@ -222,14 +224,16 @@ def writeInitCodeJS(self, buff):
         inits['styles'].val += ','
         inits['styles'].val = py2js.expression2js(inits['styles'].val)
 
+        inits['depth'] = -self.getPosInRoutine()
+
         # build up an initialization string for Slider():
         initStr = ("{name} = new visual.Slider({{\n"
                    "  win: psychoJS.window, name: '{name}',\n"
                    "  size: {size}, pos: {pos}, units: {units},\n"
                    "  labels: {labels}, ticks: {ticks},\n"
                    "  granularity: {granularity}, style: {styles},\n"
                    "  color: new util.Color({color}), \n"
-                   "  fontFamily: {font}, bold: true, italic: false, \n"
+                   "  fontFamily: {font}, bold: true, italic: false, depth: {depth}, \n"
                    ).format(**inits)
         initStr += ("  flip: {flip},\n"
                     "}});\n\n").format(flip=boolConverter[inits['flip'].val])