Fix bug in serial plotter for negative values

Fix arduino#4365
Fix arduino#4292

Author: cmaglie

app/src/processing/app/SerialPlotter.java

@@ -87,12 +87,17 @@ private Ticks computeBounds() {
       minY = Double.POSITIVE_INFINITY;
       maxY = Double.NEGATIVE_INFINITY;
       for(Graph g : graphs) {
-        double bMin = g.buffer.min() / 2.0;
-        double bMax = g.buffer.max() * 2.0;
-        minY = bMin < minY ? bMin : minY;
-        maxY = bMax > maxY ? bMax : maxY;
+        minY = Math.min(g.buffer.min(), minY);
+        maxY = Math.max(g.buffer.max(), maxY);
       }
-      
+
+      final double MIN_DELTA = 10.0;
+      if (maxY - minY < MIN_DELTA) {
+        double mid = (maxY + minY) / 2;
+        maxY = mid + MIN_DELTA / 2;
+        minY = mid - MIN_DELTA / 2;
+      }
+
       Ticks ticks = new Ticks(minY, maxY, 3);
       minY = Math.min(minY, ticks.getTick(0));
       maxY = Math.max(maxY, ticks.getTick(ticks.getTickCount() - 1));

build/shared/revisions.txt

@@ -5,6 +5,7 @@ ARDUINO 1.6.8
 * Fixed incorrect key bindings handling for changing tab. Thanks @matthijskooijman
 * MacOSX: Fixed handling of add indent/remove indent shortcuts (CMD+[ and CMD+])
 * Fixed incorrect update of available libraries in Library Manager. Thanks @vicnevicne
+* Serial plotter now correctly resize graphs with negative values. Thanks @vicnevicne
 
 [core]
 * avr: fixed USB_SendControl(...) for buffer with len > 64. Thanks @NicoHood