remove autorange duplication for matching axes

Author: alexcjohnson

src/plot_api/subroutines.js

@@ -670,10 +670,28 @@ exports.doAutoRangeAndConstraints = function(gd) {
     var axList = Axes.list(gd, '', true);
     var ax;
 
+    var autoRangeDone = {};
+
     for(var i = 0; i < axList.length; i++) {
         ax = axList[i];
-        cleanAxisConstraints(gd, ax);
-        doAutoRange(gd, ax);
+        if(!autoRangeDone[ax._id]) {
+            autoRangeDone[ax._id] = 1;
+            cleanAxisConstraints(gd, ax);
+            doAutoRange(gd, ax);
+
+            // For matching axes, just propagate this autorange to the group.
+            // The extra arg to doAutoRange avoids recalculating the range,
+            // since doAutoRange by itself accounts for all matching axes. but
+            // there are other side-effects of doAutoRange that we still want.
+            var matchGroup = ax._matchGroup;
+            if(matchGroup) {
+                for(var id2 in matchGroup) {
+                    var ax2 = Axes.getFromId(gd, id2);
+                    doAutoRange(gd, ax2, ax.range);
+                    autoRangeDone[id2] = 1;
+                }
+            }
+        }
     }
 
     enforceAxisConstraints(gd);

src/plots/cartesian/autorange.js

@@ -245,8 +245,6 @@ function concatExtremes(gd, ax, noMatch) {
     _concat(fullLayout.shapes || [], ax._shapeIndices || []);
 
     // Include the extremes from other matched axes with this one
-    // TODO: find a way to only do this calculation once, rather than
-    // repeating it for every axis in the matched group
     if(ax._matchGroup && !noMatch) {
         for(var axId2 in ax._matchGroup) {
             if(axId2 !== ax._id) {
@@ -269,11 +267,11 @@ function concatExtremes(gd, ax, noMatch) {
     return {min: minArray, max: maxArray};
 }
 
-function doAutoRange(gd, ax) {
+function doAutoRange(gd, ax, presetRange) {
     ax.setScale();
 
     if(ax.autorange) {
-        ax.range = getAutoRange(gd, ax);
+        ax.range = presetRange ? presetRange.slice() : getAutoRange(gd, ax);
 
         ax._r = ax.range.slice();
         ax._rl = Lib.simpleMap(ax._r, ax.r2l);