Fix - better interactive zooming in color palette

Author: linev

changes.md

@@ -1,5 +1,9 @@
 # JSROOT changelog
 
+## Changes in 5.9.x
+1. Fix zooming in color palette
+
+
 ## Changes in 5.9.0
 1. Support RX and RY drawing option together with COL of TH2
 2. Add support of #overline, #underline, #strike into TLatex parsing (#196)

scripts/JSRootPainter.hist.js

@@ -952,9 +952,9 @@
          d3.event.preventDefault();
          var m = d3.mouse(evnt);
 
-         if (m[1] < sel1) sel1 = m[1]; else sel2 = m[1];
+         sel2 = Math.min(Math.max(m[1], 0), s_height);
 
-         zoom_rect.attr("y", sel1)
+         zoom_rect.attr("y", Math.min(sel1,sel2))
                   .attr("height", Math.abs(sel2-sel1));
       }
 
@@ -993,7 +993,7 @@
                 .attr("x", "0")
                 .attr("width", s_width)
                 .attr("y", sel1)
-                .attr("height", 5);
+                .attr("height", 1);
 
          d3.select(window).on("mousemove.colzoomRect", moveRectSel)
                           .on("mouseup.colzoomRect", endRectSel, true);