Enable multiple component selection using shift key presses (#1891)

* Enable multiple component selection using shift key presses
* Add highlight to select components and show number of components selected
* Make selected component properties default when there is no full intersection
* Allow unselection of already selected components

appinventor/appengine/src/com/google/appinventor/client/editor/simple/components/MockForm.java

@@ -10,6 +10,7 @@ import static com.google.appinventor.client.Ode.MESSAGES;
 
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 
 import com.google.appinventor.client.editor.simple.SimpleEditor;
@@ -915,14 +916,25 @@ public final class MockForm extends MockContainer {
     if (newSelectedComponent == null) {
       throw new IllegalArgumentException("at least one component must always be selected");
     }
-    if (newSelectedComponent == oldSelectedComponent) {
+    YaFormEditor formEditor = (YaFormEditor) editor;
+    boolean shouldSelectMultipleComponents = formEditor.getShouldSelectMultipleComponents();
+    List<MockComponent> selectedComponents = formEditor.getSelectedComponents();
+    if (shouldSelectMultipleComponents && selectedComponents.size() > 1 && formEditor.isSelectedComponent(newSelectedComponent)) {
+      int index = selectedComponents.indexOf(newSelectedComponent);
+      selectedComponent = selectedComponents.get((index == 0) ? 1 : index - 1);
+      newSelectedComponent.onSelectedChange(false);
       return;
     }
 
     selectedComponent = newSelectedComponent;
+    Map<String, MockComponent> componentsMap = formEditor.getComponents();
 
-    if (oldSelectedComponent != null) {     // Can be null initially
-      oldSelectedComponent.onSelectedChange(false);
+    if (oldSelectedComponent != null && !shouldSelectMultipleComponents) {     // Can be null initially
+      for (MockComponent component : componentsMap.values()) {
+        if (component.getName() != selectedComponent.getName()) {
+          component.onSelectedChange(false);
+        }
+      }
     }
     newSelectedComponent.onSelectedChange(true);
   }

appinventor/appengine/src/com/google/appinventor/client/editor/simple/palette/AbstractPaletteItemWidget.java

@@ -4,7 +4,6 @@
 // http://www.apache.org/licenses/LICENSE-2.0
 
 package com.google.appinventor.client.editor.simple.palette;
-
 import com.google.gwt.event.dom.client.ClickEvent;
 import com.google.gwt.event.dom.client.ClickHandler;
 import com.google.gwt.event.dom.client.TouchEndEvent;

appinventor/appengine/src/com/google/appinventor/client/widgets/properties/EditableProperty.java

@@ -146,7 +146,7 @@ public final class EditableProperty extends Property {
    *
    * @return  property caption
    */
-  String getCaption() {
+  public String getCaption() {
     return caption;
   }