refactor: layout manager to viewer (#1026)

* docs: formatting

* Prefer numRows and numColumns to percentage width/height for layout

* fix: LayoutManager --> ViewportGrid (get out of UI component library)

* docs: remove outdated docs

* Don't expose ExampleDropTarget

* Revert thumnail entry drag source removal

* Update screaming tests

* fix drag-n-drop

* fix vtk mpr2d CC: @jamesapetts

* remove setSingleLayoutData

* remove vtk qualifier

extensions/vtk/src/utils/setMPRLayout.js

@@ -1,60 +1,43 @@
 import setLayoutAndViewportData from './setLayoutAndViewportData.js';
-import setSingleLayoutData from './setSingleLayoutData.js';
 
 export default function setMPRLayout(displaySet) {
   return new Promise((resolve, reject) => {
-    let viewports = [];
-    const rows = 1;
-    const columns = 3;
-    const numViewports = rows * columns;
+    const viewports = [];
+    const numRows = 1;
+    const numColumns = 3;
+    const numViewports = numRows * numColumns;
     const viewportSpecificData = {};
-    for (let i = 0; i < numViewports; i++) {
-      viewports.push({
-        height: `${100 / rows}%`,
-        width: `${100 / columns}%`,
-      });
 
+    for (let i = 0; i < numViewports; i++) {
+      viewports.push({});
       viewportSpecificData[i] = displaySet;
       viewportSpecificData[i].plugin = 'vtk';
     }
-    const layout = {
-      viewports,
-    };
-
-    const viewportIndices = [0, 1, 2];
-    let updatedViewports = layout.viewports;
 
     const apis = [];
-    viewportIndices.forEach(viewportIndex => {
-      apis[viewportIndex] = null;
-      /*const currentData = layout.viewports[viewportIndex];
-      if (currentData && currentData.plugin === 'vtk') {
-        reject(new Error('Should not have reached this point??'));
-      }*/
-
-      const data = {
+    viewports.forEach((viewport, index) => {
+      apis[index] = null;
+      viewports[index] = Object.assign({}, viewports[index], {
         // plugin: 'vtk',
         vtk: {
           mode: 'mpr', // TODO: not used
           afterCreation: api => {
-            apis[viewportIndex] = api;
+            apis[index] = api;
 
             if (apis.every(a => !!a)) {
               resolve(apis);
             }
           },
         },
-      };
-
-      updatedViewports = setSingleLayoutData(
-        updatedViewports,
-        viewportIndex,
-        data
-      );
+      });
     });
 
     setLayoutAndViewportData(
-      { viewports: updatedViewports },
+      {
+        numRows,
+        numColumns,
+        viewports,
+      },
       viewportSpecificData
     );
   });