Allow creating TextBox or SuggestionPopup when extending VFilterSelect (#12491)

This patch adds two methods, that one can override when extending VFilterSelect.
By doing so, the developer can for example change the behavior of setting text,
or performing clicks in the suggestion popup.
This change is backwards compatible, as it just offers two new methods to
override.

Change-Id: Icc8fd154ef1abaed96e6af742af77c3225db3fe4

client/src/com/vaadin/client/ui/VFilterSelect.java

@@ -916,6 +916,27 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
         }
     }
 
+    /**
+     * TextBox variant used as input element for filter selects, which prevents
+     * selecting text when disabled.
+     * 
+     * @since 7.1.5
+     */
+    public class FilterSelectTextBox extends TextBox {
+
+        /**
+         * Overridden to avoid selecting text when text input is disabled
+         */
+        @Override
+        public void setSelectionRange(int pos, int length) {
+            if (textInputEnabled) {
+                super.setSelectionRange(pos, length);
+            } else {
+                super.setSelectionRange(getValue().length(), 0);
+            }
+        }
+    }
+
     @Deprecated
     public static final FilteringMode FILTERINGMODE_OFF = FilteringMode.OFF;
     @Deprecated
@@ -938,21 +959,10 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
      * <p>
      * For internal use only. May be removed or replaced in the future.
      */
-    public final TextBox tb = new TextBox() {
-
-        // Overridden to avoid selecting text when text input is disabled
-        @Override
-        public void setSelectionRange(int pos, int length) {
-            if (textInputEnabled) {
-                super.setSelectionRange(pos, length);
-            } else {
-                super.setSelectionRange(getValue().length(), 0);
-            }
-        };
-    };
+    public final TextBox tb;
 
     /** For internal use only. May be removed or replaced in the future. */
-    public final SuggestionPopup suggestionPopup = new SuggestionPopup();
+    public final SuggestionPopup suggestionPopup;
 
     /**
      * Used when measuring the width of the popup
@@ -1096,9 +1106,12 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
     private boolean textInputEnabled = true;
 
     /**
-     * Default constructor
+     * Default constructor.
      */
     public VFilterSelect() {
+        tb = createTextBox();
+        suggestionPopup = createSuggestionPopup();
+
         selectedItemIcon.setStyleName("v-icon");
         selectedItemIcon.addLoadHandler(new LoadHandler() {
 
@@ -1136,6 +1149,32 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
         setStyleName(CLASSNAME);
     }
 
+    /**
+     * This method will create the TextBox used by the VFilterSelect instance.
+     * It is invoked during the Constructor and should only be overridden if a
+     * custom TextBox shall be used. The overriding method cannot use any
+     * instance variables.
+     * 
+     * @since 7.1.5
+     * @return TextBox instance used by this VFilterSelect
+     */
+    protected TextBox createTextBox() {
+        return new FilterSelectTextBox();
+    }
+
+    /**
+     * This method will create the SuggestionPopup used by the VFilterSelect
+     * instance. It is invoked during the Constructor and should only be
+     * overridden if a custom SuggestionPopup shall be used. The overriding
+     * method cannot use any instance variables.
+     * 
+     * @since 7.1.5
+     * @return SuggestionPopup instance used by this VFilterSelect
+     */
+    protected SuggestionPopup createSuggestionPopup() {
+        return new SuggestionPopup();
+    }
+
     @Override
     public void setStyleName(String style) {
         super.setStyleName(style);