add globalTransforms config argument

- transform options can be specified using the config arg
  or globally using Plotly.setPlotConfig()
- global transforms are applied to all traces
  and are supplied before all other trace transforms.

Author: etpinard

src/plot_api/plot_config.js

@@ -94,7 +94,11 @@ module.exports = {
 
     // Turn all console logging on or off (errors will be thrown)
     // This should ONLY be set via Plotly.setPlotConfig
-    logging: false
+    logging: false,
+
+    // Set global transform to be applied to all traces with no
+    // specification needed
+    globalTransforms: []
 };
 
 // where and how the background gets set can be overridden by context

src/plots/plots.js

@@ -472,6 +472,7 @@ plots.supplyDefaults = function(gd) {
     newFullLayout._dataLength = newData.length;
 
     // then do the data
+    newFullLayout._globalTransforms = gd._context.globalTransforms;
     plots.supplyDataDefaults(newData, newFullData, newFullLayout);
 
     // attach helper method to check whether a plot type is present on graph
@@ -750,13 +751,16 @@ plots.supplyTraceDefaults = function(traceIn, traceIndex, layout) {
 };
 
 function supplyTransformDefaults(traceIn, traceOut, layout) {
-    if(!Array.isArray(traceIn.transforms)) return;
+    var globalTransforms = layout._globalTransforms || [];
 
-    var containerIn = traceIn.transforms,
+    if(!Array.isArray(traceIn.transforms) && globalTransforms.length === 0) return;
+
+    var containerIn = traceIn.transforms || [],
+        transformList = globalTransforms.concat(containerIn),
         containerOut = traceOut.transforms = [];
 
-    for(var i = 0; i < containerIn.length; i++) {
-        var transformIn = containerIn[i],
+    for(var i = 0; i < transformList.length; i++) {
+        var transformIn = transformList[i],
             type = transformIn.type,
             _module = transformsRegistry[type],
             transformOut;

test/jasmine/tests/transforms_test.js

@@ -63,6 +63,40 @@ describe('one-to-one transforms:', function() {
         expect(traceOut.y).toBe(traceIn.y);
     });
 
+    it('supplyTraceDefaults should honored global transforms', function() {
+        var traceIn = {
+            y: [2, 1, 2],
+            transforms: [{
+                type: 'filter',
+                operation: '>',
+                value: '0',
+                filtersrc: 'x'
+            }]
+        };
+
+        var layout = {
+            _globalTransforms: [{
+                type: 'filter'
+            }]
+        };
+
+        var traceOut = Plots.supplyTraceDefaults(traceIn, 0, layout);
+
+        expect(traceOut.transforms[0]).toEqual({
+            type: 'filter',
+            operation: '=',
+            value: 0,
+            filtersrc: 'x'
+        }, '- global first');
+
+        expect(traceOut.transforms[1]).toEqual({
+            type: 'filter',
+            operation: '>',
+            value: 0,
+            filtersrc: 'x'
+        }, '- trace second');
+    });
+
     it('supplyDataDefaults should apply the transform while', function() {
         var dataIn = [{
             x: [-2, -2, 1, 2, 3],