make dragmode and hovermode attribute of each scenes:

- Use layout.dragmode and layout.hovermode as default
  for layout.scene?.dragmode and layout.scene?.hovermode
  if plot has only GL3D (backward compat) and if valid

Author: etpinard

src/plots/cartesian/graph_interact.js

@@ -26,6 +26,7 @@ fx.layoutAttributes = {
         valType: 'enumerated',
         role: 'info',
         values: ['zoom', 'pan', 'select', 'lasso', 'orbit', 'turntable'],
+        dflt: 'zoom',
         description: [
             'Determines the mode of drag interactions.',
             '*select* and *lasso* apply only to scatter traces with',
@@ -50,7 +51,7 @@ fx.supplyLayoutDefaults = function(layoutIn, layoutOut, fullData) {
                                  attr, dflt);
     }
 
-    coerce('dragmode', layoutOut._hasGL3D ? 'turntable' : 'zoom');
+    coerce('dragmode');
 
     if(layoutOut._hasCartesian) {
         // flag for 'horizontal' plots:

src/plots/gl3d/layout/defaults.js

@@ -29,8 +29,25 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
         return Lib.coerce(sceneLayoutIn, sceneLayoutOut, layoutAttributes, attr, dflt);
     }
 
+    // some layout-wide attribute are used in all scenes
+    // if 3D is the only visible plot type
+    function getDfltFromLayout(attr) {
+        var isOnlyGL3D = !(
+            layoutOut._hasCartesian ||
+            layoutOut._hasGeo ||
+            layoutOut._hasGL2D ||
+            layoutOut._hasPie
+        );
+
+        var isValid = layoutAttributes[attr].values.indexOf(layoutIn[attr]) !== -1;
+
+        var dflt;
+        if(isOnlyGL3D && isValid) return layoutIn[attr];
+    }
+
     for(var i = 0; i < scenesLength; i++) {
         var scene = scenes[i];
+
         /*
          * Scene numbering proceeds as follows
          * scene
@@ -85,18 +102,21 @@ module.exports = function supplyLayoutDefaults(layoutIn, layoutOut, fullData) {
             if(aspectMode === 'manual') sceneLayoutOut.aspectmode = 'auto';
         }
 
-         /*
-          * scene arrangements need to be implemented: For now just splice
-          * along the horizontal direction. ie.
-          * x:[0,1] -> x:[0,0.5], x:[0.5,1] ->
-          *     x:[0, 0.333] x:[0.333,0.666] x:[0.666, 1]
-          */
+        /*
+         * scene arrangements need to be implemented: For now just splice
+         * along the horizontal direction. ie.
+         * x:[0,1] -> x:[0,0.5], x:[0.5,1] ->
+         *     x:[0, 0.333] x:[0.333,0.666] x:[0.666, 1]
+         */
         supplyGl3dAxisLayoutDefaults(sceneLayoutIn, sceneLayoutOut, {
             font: layoutOut.font,
             scene: scene,
             data: fullData
         });
 
+        coerce('dragmode', getDfltFromLayout('dragmode'));
+        coerce('hovermode', getDfltFromLayout('hovermode'));
+
         layoutOut[scene] = sceneLayoutOut;
     }
 };

src/plots/gl3d/layout/layout_attributes.js

@@ -139,6 +139,25 @@ module.exports = {
     yaxis: gl3dAxisAttrs,
     zaxis: gl3dAxisAttrs,
 
+    dragmode: {
+        valType: 'enumerated',
+        role: 'info',
+        values: ['orbit', 'turntable', 'zoom', 'pan'],
+        dflt: 'turntable',
+        description: [
+            'Determines the mode of drag interactions for this scene.'
+        ].join(' ')
+    },
+    hovermode: {
+        valType: 'enumerated',
+        role: 'info',
+        values: ['closest', false],
+        dflt: 'closest',
+        description: [
+            'Determines the mode of hover interactions for this scene.'
+        ].join(' ')
+    },
+
     _deprecated: {
         cameraposition: {
             valType: 'info_array',