Merge pull request #9137 from jcalbert/discrete_slider

WeatherGod · web-flow · commit ffc20d40b99c · 2017-10-17T17:12:31.000-04:00
Adds option for Slider to snap to discrete values
diff --git a/doc/users/next_whats_new/2017-08-31_discrete-sliders.rst b/doc/users/next_whats_new/2017-08-31_discrete-sliders.rst
@@ -0,0 +1,8 @@
+Slider UI widget can snap to discrete values
+--------------------------------------------
+
+The slider UI widget can take the optional argument *valstep*.  Doing so
+forces the slider to take on only discrete values, starting from *valmin* and
+counting up to *valmax* with steps of size *valstep*.
+
+If *closedmax==True*, then the slider will snap to *valmax* as well.  
diff --git a/examples/widgets/slider_demo.py b/examples/widgets/slider_demo.py
@@ -13,6 +13,7 @@
 t = np.arange(0.0, 1.0, 0.001)
 a0 = 5
 f0 = 3
+delta_f = 5.0
 s = a0*np.sin(2*np.pi*f0*t)
 l, = plt.plot(t, s, lw=2, color='red')
 plt.axis([0, 1, -10, 10])
@@ -21,7 +22,7 @@
 axfreq = plt.axes([0.25, 0.1, 0.65, 0.03], facecolor=axcolor)
 axamp = plt.axes([0.25, 0.15, 0.65, 0.03], facecolor=axcolor)
 
-sfreq = Slider(axfreq, 'Freq', 0.1, 30.0, valinit=f0)
+sfreq = Slider(axfreq, 'Freq', 0.1, 30.0, valinit=f0, valstep=delta_f)
 samp = Slider(axamp, 'Amp', 0.1, 10.0, valinit=a0)
 
 
diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
@@ -273,7 +273,7 @@ class Slider(AxesWidget):
     """
     def __init__(self, ax, label, valmin, valmax, valinit=0.5, valfmt='%1.2f',
                  closedmin=True, closedmax=True, slidermin=None,
-                 slidermax=None, dragging=True, **kwargs):
+                 slidermax=None, dragging=True, valstep=None, **kwargs):
         """
         Parameters
         ----------
@@ -312,6 +312,9 @@ def __init__(self, ax, label, valmin, valmax, valinit=0.5, valfmt='%1.2f',
         dragging : bool, optional, default: True
             If True the slider can be dragged by the mouse.
 
+        valstep : float, optional, default: None
+            If given, the slider will snap to multiples of `valstep`.
+
         Notes
         -----
         Additional kwargs are passed on to ``self.poly`` which is the
@@ -334,6 +337,7 @@ def __init__(self, ax, label, valmin, valmax, valinit=0.5, valfmt='%1.2f',
         self.drag_active = False
         self.valmin = valmin
         self.valmax = valmax
+        self.valstep = valstep
         valinit = self._value_in_bounds(valinit)
         if valinit is None:
             valinit = valmin
@@ -368,6 +372,10 @@ def __init__(self, ax, label, valmin, valmax, valinit=0.5, valfmt='%1.2f',
 
     def _value_in_bounds(self, val):
         """ Makes sure self.val is with given bounds."""
+        if self.valstep:
+            val = np.round((val - self.valmin)/self.valstep)*self.valstep
+            val += self.valmin
+
         if val <= self.valmin:
             if not self.closedmin:
                 return
@@ -410,7 +418,7 @@ def _update(self, event):
             event.canvas.release_mouse(self.ax)
             return
         val = self._value_in_bounds(event.xdata)
-        if val is not None:
+        if (val is not None) and (val != self.val):
             self.set_val(val)
 
     def set_val(self, val):
