Some updates in Horizon fixing some issues for upcoming release

dipy/viz/gmem.py

@@ -0,0 +1,39 @@
+class GlobalHorizon(object):
+    def __init__(self):
+        # window level sharing
+        self.window_timer_cnt = 0
+
+        # slicer level sharing
+        self.slicer_opacity = 1
+        self.slicer_colormap = 'gray'
+        self.slicer_colormaps = ['gray', 'magma', 'viridis', 'jet', 'Pastel1', 'disting']
+        self.slicer_colormap_cnt = 0
+        self.slicer_axes = ['x', 'y', 'z']
+
+        self.slicer_curr_x = None
+        self.slicer_curr_y = None
+        self.slicer_curr_z = None
+
+        self.slicer_curr_actor_x = None
+        self.slicer_curr_actor_y = None
+        self.slicer_curr_actor_z = None
+
+        self.slicer_orig_shape = None
+        self.slicer_resliced_shape = None
+
+        self.slicer_vol_idx = None
+        self.slicer_vol = None
+
+        self.slicer_peaks_actor_z = None
+        self.slicer_rgb = False
+
+        self.slicer_grid = False
+
+        # tractogram level sharing
+        self.cluster_thr = 15
+        self.streamline_actors = []
+        self.centroid_actors = []
+        self.cluster_actors = []
+
+
+HORIMEM = GlobalHorizon()