image: smart default layout to constrain y axis to domain

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
         });
     }
 

test/jasmine/tests/image_test.js

@@ -123,6 +123,14 @@ describe('image smart layout defaults', function() {
         expect(gd._fullLayout.yaxis.autorange).not.toBe('reversed');
     });
 
+    it('should NOT reverse yaxis if it\'s already defined', function() {
+        gd = {};
+        gd.data = [{type: 'image', z: [[[255, 0, 0]]]}];
+        gd.layout = {yaxis: {autorange: false}};
+        supplyAllDefaults(gd);
+        expect(gd._fullLayout.yaxis.autorange).toBe(false);
+    });
+
     it('should set scaleanchor to make square pixels if only images are present', function() {
         gd = {};
         gd.data = [{type: 'image', z: [[[255, 0, 0]]]}];
@@ -138,11 +146,32 @@ describe('image smart layout defaults', function() {
     });
 
     it('should NOT set scaleanchor if it\'s already defined', function() {
-        gd.data = [{type: 'image', z: [[[255, 0, 0]]]}, {type: 'scatter', y: [5, 3, 2]}];
+        gd.data = [{type: 'image', z: [[[255, 0, 0]]]}];
         gd.layout = {yaxis: {scaleanchor: 'x3'}};
         supplyAllDefaults(gd);
         expect(gd._fullLayout.yaxis.scaleanchor).toBe(undefined);
     });
+
+    it('should constrain axes to domain if only images are present', function() {
+        gd = {};
+        gd.data = [{type: 'image', z: [[[255, 0, 0]]]}];
+        supplyAllDefaults(gd);
+        expect(gd._fullLayout.yaxis.constrain).toBe('domain');
+    });
+
+    it('should NOT constrain axes to domain if another trace is present', function() {
+        gd = {};
+        gd.data = [{type: 'image', z: [[[255, 0, 0]]]}, {type: 'scatter', y: [5, 3, 2]}];
+        supplyAllDefaults(gd);
+        expect(gd._fullLayout.yaxis.constrain).toBe(undefined);
+    });
+
+    it('should NOT constrain axes to domain if it\'s already defined', function() {
+        gd.data = [{type: 'image', z: [[[255, 0, 0]]]}];
+        gd.layout = {yaxis: {constrain: false}};
+        supplyAllDefaults(gd);
+        expect(gd._fullLayout.yaxis.constrain).toBe(undefined);
+    });
 });
 
 describe('image plot', function() {
@@ -489,7 +518,7 @@ describe('image hover:', function() {
                 zmax: [1, 1, 1],
                 text: [['A', 'B', 'C'], ['D', 'E', 'F']],
                 hovertemplate: '%{text}<extra></extra>'
-            }], layout: {width: 400, height: 400}};
+            }], layout: {width: 400, height: 400, yaxis: {constrain: 'range'}}};
 
             Plotly.newPlot(gd, mockCopy)
             .then(function() {_hover(140, 180);})