image: smart default layout to constrain y axis to domain

Author: antoinerg

src/plots/cartesian/constraints.js

@@ -21,6 +21,7 @@ exports.handleConstraintDefaults = function(containerIn, containerOut, coerce, o
     var allAxisIds = opts.allAxisIds;
     var layoutOut = opts.layoutOut;
     var scaleanchorDflt = opts.scaleanchorDflt;
+    var constrainDflt = opts.constrainDflt;
     var constraintGroups = layoutOut._axisConstraintGroups;
     var matchGroups = layoutOut._axisMatchGroups;
     var axId = containerOut._id;
@@ -31,7 +32,7 @@ exports.handleConstraintDefaults = function(containerIn, containerOut, coerce, o
 
     // coerce the constraint mechanics even if this axis has no scaleanchor
     // because it may be the anchor of another axis.
-    var constrain = coerce('constrain');
+    var constrain = coerce('constrain', constrainDflt);
     Lib.coerce(containerIn, containerOut, {
         constraintoward: {
             valType: 'enumerated',

src/plots/cartesian/layout_defaults.js

@@ -43,6 +43,8 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
     var yaMayReverse = {};
     var yaMustNotScaleanchor = {};
     var yaMayScaleanchor = {};
+    var yaMustNotConstrainDomain = {};
+    var yaMayConstrainDomain = {};
     var outerTicks = {};
     var noGrids = {};
     var i, j;
@@ -81,16 +83,19 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
                 if(yaName) yaMayHide[yaName] = true;
             }
             yaMustNotScaleanchor[yaName] = true;
+            yaMustNotConstrainDomain[yaName] = true;
         } else if(trace.type === 'image') {
             if(yaName) {
                 yaMayReverse[yaName] = true;
                 yaMayScaleanchor[yaName] = true;
+                yaMayConstrainDomain[yaName] = true;
             }
         } else {
             if(yaName) {
                 yaMustDisplay[yaName] = true;
                 yaMustNotReverse[yaName] = true;
                 yaMustNotScaleanchor[yaName] = true;
+                yaMustNotConstrainDomain[yaName] = true;
             }
 
             if(!traceIs(trace, 'carpet') || (trace.type === 'carpet' && !trace._cheater)) {
@@ -309,10 +314,18 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
         ) {
             scaleanchorDflt = axLayoutOut.anchor;
         }
+
+        var constrainDflt = null;
+        if(axLetter === 'y' && !axLayoutIn.hasOwnProperty('constrain') &&
+              !yaMustNotConstrainDomain[axName] && yaMayConstrainDomain[axName]
+        ) {
+            constrainDflt = 'domain';
+        }
         handleConstraintDefaults(axLayoutIn, axLayoutOut, coerce, {
             allAxisIds: allAxisIds,
             layoutOut: layoutOut,
-            scaleanchorDflt: scaleanchorDflt
+            scaleanchorDflt: scaleanchorDflt,
+            constrainDflt: constrainDflt
         });
     }