push trace module into fullLayout._modules even if visible:false

- so that gl-based trace can call their plot methods w/ an
  empty array of traces and just work.
- update and improve scatterlg visibility tests to reflect
  that `restyle(gd,visible,false)` no longer clear the context

Author: etpinard

src/plots/cartesian/index.js

@@ -216,7 +216,7 @@ function plotOne(gd, plotinfo, cdSubplot, transitionOpts, makeOnCompleteCallback
             var className = (_module.layerName || name + 'layer');
             var plotMethod = _module.plot;
 
-            // plot all traces of this type on this subplot at once
+            // plot all visible traces of this type on this subplot at once
             cdModuleAndOthers = getModuleCalcData(cdSubplot, plotMethod);
             cdModule = cdModuleAndOthers[0];
             // don't need to search the found traces again - in fact we need to NOT

src/plots/get_data.js

@@ -69,6 +69,7 @@ exports.getModuleCalcData = function(calcdata, arg1) {
     for(var i = 0; i < calcdata.length; i++) {
         var cd = calcdata[i];
         var trace = cd[0].trace;
+        // N.B. 'legendonly' traces do not make it pass here
         if(trace.visible !== true) continue;
 
         // group calcdata trace not by 'module' (as the name of this function

src/plots/plots.js

@@ -696,7 +696,7 @@ plots._hasPlotType = function(category) {
         if(basePlotModules[i].name === category) return true;
     }
 
-    // check trace modules
+    // check trace modules (including non-visible:true)
     var modules = this._modules || [];
     for(i = 0; i < modules.length; i++) {
         var name = modules[i].name;
@@ -912,7 +912,7 @@ plots.supplyDataDefaults = function(dataIn, dataOut, layout, fullLayout) {
         var _module = fullTrace._module;
         if(!_module) return;
 
-        if(fullTrace.visible === true) Lib.pushUnique(modules, _module);
+        Lib.pushUnique(modules, _module);
         Lib.pushUnique(basePlotModules, fullTrace._module.basePlotModule);
 
         cnt++;

test/jasmine/tests/cartesian_test.js

@@ -197,7 +197,7 @@ describe('restyle', function() {
                 return Plotly.restyle(gd, {visible: 'legendonly'}, 1);
             })
             .then(function() {
-                expect(!!gd._fullLayout._plots.x2y2._scene).toBe(false);
+                expect(!!gd._fullLayout._plots.x2y2._scene).toBe(true);
                 return Plotly.restyle(gd, {visible: true}, 1);
             })
             .then(function() {

test/jasmine/tests/gl2d_plot_interact_test.js

@@ -358,27 +358,38 @@ describe('@gl Test gl2d plots', function() {
         var _mock = Lib.extendDeep({}, mock);
         _mock.data[0].line.width = 5;
 
+        function assertDrawCall(msg, exp) {
+            var draw = gd._fullLayout._plots.xy._scene.scatter2d.draw;
+            expect(draw).toHaveBeenCalledTimes(exp, msg);
+            draw.calls.reset();
+        }
+
         Plotly.plot(gd, _mock)
         .then(delay(30))
         .then(function() {
+            spyOn(gd._fullLayout._plots.xy._scene.scatter2d, 'draw');
             return Plotly.restyle(gd, 'visible', 'legendonly');
         })
         .then(function() {
-            expect(gd.querySelector('.gl-canvas-context')).toBe(null);
+            expect(readPixel(gd.querySelector('.gl-canvas-context'), 108, 100)[0]).toBe(0);
+            assertDrawCall('legendonly', 0);
 
             return Plotly.restyle(gd, 'visible', true);
         })
         .then(function() {
             expect(readPixel(gd.querySelector('.gl-canvas-context'), 108, 100)[0]).not.toBe(0);
+            assertDrawCall('back to visible', 1);
 
             return Plotly.restyle(gd, 'visible', false);
         })
         .then(function() {
-            expect(gd.querySelector('.gl-canvas-context')).toBe(null);
+            expect(readPixel(gd.querySelector('.gl-canvas-context'), 108, 100)[0]).toBe(0);
+            assertDrawCall('visible false', 0);
 
             return Plotly.restyle(gd, 'visible', true);
         })
         .then(function() {
+            assertDrawCall('back up', 1);
             expect(readPixel(gd.querySelector('.gl-canvas-context'), 108, 100)[0]).not.toBe(0);
         })
         .catch(failTest)