[graph] correctly make screenshot of multiple canvases in sigma

src/Gargantext/Components/GraphExplorer/Button.purs

@@ -55,7 +55,6 @@ cameraButton session id sigmaRef = simpleButton {
       let sigma = R.readRef sigmaRef
       Sigmax.dependOnSigma sigma "[cameraButton] sigma: Nothing" $ \s -> do
         screen <- Sigma.takeScreenshot s
-        log2 "[cameraButton] screenshot" screen
         launchAff_ $ do
           uploadArbitraryDataURL session id (Just "screenshot.png") screen
   , text: "Screenshot"

src/Gargantext/Hooks/Sigmax/Sigma.js

@@ -191,7 +191,13 @@ function bindMouseSelectorPlugin(left, right, sig) {
 function bind(sigma, event, handler) { sigma.bind(event, handler); }
 
 function takeScreenshot(sigma) {
-  return sigma.renderers[0].container.lastChild.toDataURL();
+  let c = sigma.renderers[0].container;
+  let edges = c.getElementsByClassName('sigma-edges')[0];
+  let scene = c.getElementsByClassName('sigma-scene')[0];
+  let sceneCtx = scene.getContext('2d');
+  sceneCtx.globalAlpha = 1;
+  sceneCtx.drawImage(edges, 0, 0);
+  return scene.toDataURL('image/png');
 }
 
 exports._sigma = _sigma;