initviz: use finer scale steps for smoother zoom control

Change timeline expansion/contraction zoom factor from 1.5× to 1.1×
for smoother, more precise control when adjusting the time scale.

Adapted from xrmx/bootchart#42 (PATCH 004/182)

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

Author: troglobit

initviz/gui.py

@@ -171,10 +171,10 @@ def set_xscale(self, xscale):
             self.zoom_to_best_fit(allocation)
 
     def on_expand(self, action):
-        self.set_xscale (self.xscale * 1.5)
+        self.set_xscale (self.xscale * 1.1)
 
     def on_contract(self, action):
-        self.set_xscale (self.xscale / 1.5)
+        self.set_xscale (self.xscale / 1.1)
 
     def on_zoom_in(self, action):
         self.zoom_image(self.zoom_ratio * self.ZOOM_INCREMENT)