pretransition event

closes #806

spec/base-mixin-spec.js

@@ -27,17 +27,20 @@ describe("dc.baseMixin", function () {
     });
 
     describe('renderlets', function () {
-        var firstRenderlet, secondRenderlet, thirdRenderlet;
+        var firstRenderlet, secondRenderlet, thirdRenderlet,
+            pretransition;
         beforeEach(function () {
             var expectedCallbackSignature = function (callbackChart) {
                 expect(callbackChart).toBe(chart);
             };
             firstRenderlet = jasmine.createSpy().and.callFake(expectedCallbackSignature);
             secondRenderlet = jasmine.createSpy().and.callFake(expectedCallbackSignature);
             thirdRenderlet = jasmine.createSpy().and.callFake(expectedCallbackSignature);
+            pretransition = jasmine.createSpy().and.callFake(expectedCallbackSignature);
             chart.renderlet(firstRenderlet); // still testing renderlet event-namespace generation here
             chart.renderlet(secondRenderlet);
             chart.on('renderlet.third', thirdRenderlet);
+            chart.on('pretransition.pret', pretransition);
         });
 
         it('should not execute a renderlet until after the render transitions', function() {
@@ -54,6 +57,18 @@ describe("dc.baseMixin", function () {
             expect(firstRenderlet).toHaveBeenCalled();
         });
 
+        it('should execute pretransition event before the render transitions', function() {
+            chart.render();
+            expect(pretransition).toHaveBeenCalled();
+            flushAllD3Transitions();
+        });
+
+        it('should execute pretransition event before the redraw transitions', function() {
+            chart.redraw();
+            expect(pretransition).toHaveBeenCalled();
+            flushAllD3Transitions();
+        });
+
         it('should execute each renderlet after a render', function () {
             chart.render();
             flushAllD3Transitions();

src/base-mixin.js

@@ -58,7 +58,8 @@ dc.baseMixin = function (_chart) {
         'postRedraw',
         'filtered',
         'zoomed',
-        'renderlet');
+        'renderlet',
+        'pretransition');
 
     var _legend;
 
@@ -476,6 +477,7 @@ dc.baseMixin = function (_chart) {
     };
 
     _chart._activateRenderlets = function (event) {
+        _listeners.pretransition(_chart);
         if (_chart.transitionDuration() > 0 && _svg) {
             _svg.transition().duration(_chart.transitionDuration())
                 .each('end', function () {
@@ -1107,6 +1109,9 @@ dc.baseMixin = function (_chart) {
     This listener function will be invoked after transitions after redraw and render. Replaces the
     deprecated `.renderlet()` method.
 
+    #### .on('pretransition', function(chart, filter){...})
+    Like `.on('renderlet', ...)` but the event is fired before transitions start.
+
     #### .on('preRender', function(chart){...})
     This listener function will be invoked before chart rendering.
 

web/docs/api-latest.md

@@ -546,6 +546,9 @@ All dc chart instance supports the following listeners.
 This listener function will be invoked after transitions after redraw and render. Replaces the
 deprecated `.renderlet()` method.
 
+#### .on('pretransition', function(chart, filter){...})
+Like `.on('renderlet', ...)` but the event is fired before transitions start.
+
 #### .on('preRender', function(chart){...})
 This listener function will be invoked before chart rendering.
 

web/docs/index.html

@@ -552,6 +552,8 @@ <h4 id="-options-optionsobject-">.options(optionsObject)</h4>
 <h4 id="-on-renderlet-function-chart-filter-">.on(‘renderlet’, function(chart, filter){…})</h4>
 <p>This listener function will be invoked after transitions after redraw and render. Replaces the
 deprecated <code>.renderlet()</code> method.</p>
+<h4 id="-on-pretransition-function-chart-filter-">.on(‘pretransition’, function(chart, filter){…})</h4>
+<p>Like <code>.on(&#39;renderlet&#39;, ...)</code> but the event is fired before transitions start.</p>
 <h4 id="-on-prerender-function-chart-">.on(‘preRender’, function(chart){…})</h4>
 <p>This listener function will be invoked before chart rendering.</p>
 <h4 id="-on-postrender-function-chart-">.on(‘postRender’, function(chart){…})</h4>