introduce redrawReglTraces subroutine

- which (re)-draw scattergl, scatterpolargl, splom traces as well as
  splom regl grid line in one go, always in the correct order
- packaging these gl draw calls in one subroutine is especially
  useful for drag and selections, where buffers of targeted traces/scene
  are updated, but *all* traces need to be redraw following clearGlCanvases

Author: etpinard

src/plot_api/subroutines.js

@@ -600,6 +600,8 @@ exports.drawData = function(gd) {
         basePlotModules[i].plot(gd);
     }
 
+    exports.redrawReglTraces(gd);
+
     // styling separate from drawing
     Plots.style(gd);
 
@@ -613,6 +615,61 @@ exports.drawData = function(gd) {
     return Plots.previousPromises(gd);
 };
 
+// Draw (or redraw) all traces in one go,
+// useful during drag and selection where buffers of targeted traces are updated,
+// but all traces need to be redrawn following clearGlCanvases.
+//
+// Note that _module.plot for regl trace does NOT draw things
+// on the canvas, they only update the buffers.
+// Drawing is perform here.
+//
+// TODO try adding per-subplot option using gl.SCISSOR_TEST for
+// non-overlaying, disjoint subplots.
+//
+// TODO try to include parcoords in here.
+exports.redrawReglTraces = function(gd) {
+    var fullLayout = gd._fullLayout;
+
+    if(fullLayout._has('regl')) {
+        var fullData = gd._fullData;
+        var cartesianIds = [];
+        var polarIds = [];
+        var i, sp;
+
+        if(fullLayout._hasOnlyLargeSploms) {
+            fullLayout._splomGrid.draw();
+        }
+
+        // N.B.
+        // - Loop over fullData (not _splomScenes) to preserve splom trace-to-trace ordering
+        // - Fill list if subplot ids (instead of fullLayout._subplots) to handle cases where all traces
+        //   of a given module are `visible !== true`
+        for(i = 0; i < fullData.length; i++) {
+            var trace = fullData[i];
+
+            if(trace.visible === true) {
+                if(trace.type === 'splom') {
+                    fullLayout._splomScenes[trace.uid].draw();
+                } else if(trace.type === 'scattergl') {
+                    Lib.pushUnique(cartesianIds, trace.xaxis + trace.yaxis);
+                } else if(trace.type === 'scatterpolargl') {
+                    Lib.pushUnique(polarIds, trace.subplot);
+                }
+            }
+        }
+
+        for(i = 0; i < cartesianIds.length; i++) {
+            sp = fullLayout._plots[cartesianIds[i]];
+            if(sp._scene) sp._scene.draw();
+        }
+
+        for(i = 0; i < polarIds.length; i++) {
+            sp = fullLayout[polarIds[i]]._subplot;
+            if(sp._scene) sp._scene.draw();
+        }
+    }
+};
+
 exports.doAutoRangeAndConstraints = function(gd) {
     var axList = Axes.list(gd, '', true);
 

src/traces/scattergl/index.js

@@ -640,8 +640,6 @@ function plot(gd, subplot, cdata) {
     if(scene.glText) {
         scene.glText.forEach(function(text) { text.update(vpRange0); });
     }
-
-    scene.draw();
 }
 
 

src/traces/splom/base_plot.js

@@ -28,7 +28,7 @@ function plot(gd) {
     if(!success) return;
 
     if(fullLayout._hasOnlyLargeSploms) {
-        drawGrid(gd);
+        updateGrid(gd);
     }
 
     _module.plot(gd, {}, splomCalcData);
@@ -84,17 +84,15 @@ function dragOne(gd, trace, scene) {
     }
 }
 
-function drawGrid(gd) {
+function updateGrid(gd) {
     var fullLayout = gd._fullLayout;
     var regl = fullLayout._glcanvas.data()[0].regl;
     var splomGrid = fullLayout._splomGrid;
 
     if(!splomGrid) {
         splomGrid = fullLayout._splomGrid = createLine(regl);
     }
-
     splomGrid.update(makeGridData(gd));
-    splomGrid.draw();
 }
 
 function makeGridData(gd) {

src/traces/splom/index.js

@@ -302,8 +302,6 @@ function plotOne(gd, cd0) {
         scene.matrix.update(opts, null);
         stash.xpx = stash.ypx = null;
     }
-
-    scene.draw();
 }
 
 function editStyle(gd, cd0) {

test/jasmine/tests/gl2d_plot_interact_test.js

@@ -1182,7 +1182,10 @@ describe('Test scattergl autorange:', function() {
 
     describe('should return the approximative values for ~big~ data', function() {
         beforeEach(function() {
-            spyOn(ScatterGl, 'plot');
+            // to avoid expansive draw calls (which could be problematic on CI)
+            spyOn(ScatterGl, 'plot').and.callFake(function(gd) {
+                gd._fullLayout._plots.xy._scene.scatter2d = {draw: function() {}};
+            });
         });
 
         // threshold for 'fast' axis expansion routine