interrupts-graph.py: conditionally update domain

Do not update domain if looking at a previous part, or if the new line
fits in the current graph. This makes it easier to look at older data
while updating the plot.

1 files changed, 9 insertions, 2 deletions

diff --git a/rare/interrupts-graph.py b/rare/interrupts-graph.py
index 76006cd..1a26cce 100755
--- a/rare/interrupts-graph.py
+++ b/rare/interrupts-graph.py
@@ -234,10 +234,11 @@ def refresh_data():
     return updated
 
 smooth = {}
+last_min_x = 0
 @synchronized(data_lock)
 def update():
     """Reads new data and updates the line values."""
-    global update_legend
+    global update_legend, last_min_x
     # Update lines
     for name in names:
         ys = yvalues[name]
@@ -298,7 +299,13 @@ def update():
 
     # The first XRANGE items fit in the screen
     min_x = max(start_time - XRANGE, 0)
-    plt.xlim(min_x, min_x + XRANGE)
+    cur_min_x, _ = plt.xlim()
+    # If the current range is equal or further than the previously recorded
+    # range, consider it sticky and update the xlim with the new range.
+    if cur_min_x >= last_min_x:
+        last_min_x = min_x
+        if cur_min_x <= min_x:
+            plt.xlim(min_x, min_x + XRANGE)
 
 def do_draw():
     """Actually draw the graph, updating the legend if necessary."""