Optimize layout performance of Table (#17947)

Adds functions for skipping child component layout measuring.
Removes unnecessary code from VScrollTable.

1. case: no components

- render time without the fix: ~105ms 
- render time with fix: ~105ms 

2. case: 2 button and 2 textfield cols

- render time without the fix: ~279ms 
- render time with fix: ~240ms (~17% faster) 

3. case: 3 button and 3 textfield cols

- render time without the fix: ~350ms 
- render time with fix: ~281ms (~20% faster) 

Change-Id: I6025f8ee2fd438d228ff3b65f43535961cf12c0b

2 files changed, 95 insertions, 1 deletions

diff --git a/server/src/com/vaadin/ui/HasChildMeasurementHint.java b/server/src/com/vaadin/ui/HasChildMeasurementHint.java
new file mode 100644
index 0000000000..dadf7d0be6
--- /dev/null
+++ b/server/src/com/vaadin/ui/HasChildMeasurementHint.java
@@ -0,0 +1,69 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.ui;
+
+/**
+ * Component with layout measuring hint. Used to improve granularity of control
+ * over child component measurements.
+ * 
+ * @since
+ * @author Vaadin Ltd
+ */
+public interface HasChildMeasurementHint extends HasComponents {
+
+    /**
+     * Specifies how you would like child components measurements to be handled.
+     * Since this is a hint, it can be ignored when deemed necessary.
+     */
+    public enum ChildMeasurementHint {
+
+        /**
+         * Always measure all child components (default).
+         */
+        MEASURE_ALWAYS,
+
+        /**
+         * Measure child component only if child component is a Layout or
+         * implements either ManagedLayout or ElementResizeListener.
+         */
+        MEASURE_IF_NEEDED,
+
+        /**
+         * Never measure child components. This can improve rendering speed of
+         * components with lots of children (e.g. Table), but can cause some
+         * child components to be rendered incorrectly (e.g. ComboBox).
+         */
+        MEASURE_NEVER
+
+    }
+
+    /**
+     * Sets desired child size measurement hint.
+     * 
+     * @param hint
+     *            desired hint. A value of null will reset value back to the
+     *            default (MEASURE_ALWAYS)
+     */
+    void setChildMeasurementHint(ChildMeasurementHint hint);
+
+    /**
+     * Returns the current child size measurement hint.
+     * 
+     * @return a child measurement hint value
+     */
+    ChildMeasurementHint getChildMeasurementHint();
+
+}
diff --git a/server/src/com/vaadin/ui/Table.java b/server/src/com/vaadin/ui/Table.java
index 69874d9947..3edfe7845f 100644
--- a/server/src/com/vaadin/ui/Table.java
+++ b/server/src/com/vaadin/ui/Table.java
@@ -100,7 +100,7 @@ import com.vaadin.util.ReflectTools;
 @SuppressWarnings({ "deprecation" })
 public class Table extends AbstractSelect implements Action.Container,
         Container.Ordered, Container.Sortable, ItemClickNotifier, DragSource,
-        DropTarget, HasComponents {
+        DropTarget, HasComponents, HasChildMeasurementHint {
 
     private transient Logger logger = null;
 
@@ -357,6 +357,11 @@ public class Table extends AbstractSelect implements Action.Container,
     private static final Object ROW_HEADER_FAKE_PROPERTY_ID = new UniqueSerializable() {
     };
 
+    /**
+     * How layout manager should behave when measuring Table's child components
+     */
+    private ChildMeasurementHint childMeasurementHint = ChildMeasurementHint.MEASURE_ALWAYS;
+
     /* Private table extensions to Select */
 
     /**
@@ -3542,6 +3547,7 @@ public class Table extends AbstractSelect implements Action.Container,
         paintTabIndex(target);
         paintDragMode(target);
         paintSelectMode(target);
+        paintTableChildLayoutMeasureMode(target);
 
         if (cacheRate != CACHE_RATE_DEFAULT) {
             target.addAttribute("cr", cacheRate);
@@ -3882,6 +3888,11 @@ public class Table extends AbstractSelect implements Action.Container,
         }
     }
 
+    private void paintTableChildLayoutMeasureMode(PaintTarget target)
+            throws PaintException {
+        target.addAttribute("measurehint", getChildMeasurementHint().ordinal());
+    }
+
     /**
      * Checks whether row headers are visible.
      * 
@@ -6467,4 +6478,18 @@ public class Table extends AbstractSelect implements Action.Container,
         }
         return logger;
     }
+
+    @Override
+    public void setChildMeasurementHint(ChildMeasurementHint hint) {
+        if (hint == null) {
+            childMeasurementHint = ChildMeasurementHint.MEASURE_ALWAYS;
+        } else {
+            childMeasurementHint = hint;
+        }
+    }
+
+    @Override
+    public ChildMeasurementHint getChildMeasurementHint() {
+        return childMeasurementHint;
+    }
 }