Allow grid columns to optionally shrink to be narrower than contents

Fixes #8548

client/src/main/java/com/vaadin/client/connectors/grid/ColumnConnector.java

         column.setMinimumWidth(getState().minWidth);
     }
 
+    @OnStateChange("minimumWidthFromContent")
+    void updateMinimumWidthFromContent() {
+        column.setMinimumWidthFromContent(getState().minimumWidthFromContent);
+    }
+
     @OnStateChange("maxWidth")
     void updateMaxWidth() {
         column.setMaximumWidth(getState().maxWidth);

client/src/main/java/com/vaadin/client/widgets/Grid.java

                 final int expandRatio = defaultExpandRatios ? 1
                         : column.getExpandRatio();
                 final double maxWidth = getMaxWidth(column);
-                final double newWidth = Math.min(maxWidth,
-                        column.getWidthActual());
+                double newWidth;
+                if (column.isMinimumWidthFromContent()) {
+                    newWidth = Math.min(maxWidth, column.getWidthActual());
+                } else {
+                    newWidth = 0;
+                }
+
                 boolean shouldExpand = newWidth < maxWidth && expandRatio > 0
                         && column != selectionColumn;
                 if (shouldExpand) {
      * @param <T>
      *            the row type
      */
-    public static abstract class Column<C, T> {
+    public abstract static class Column<C, T> {
 
         /**
          * Default renderer for GridColumns. Renders everything into text
         private double minimumWidthPx = GridConstants.DEFAULT_MIN_WIDTH;
         private double maximumWidthPx = GridConstants.DEFAULT_MAX_WIDTH;
         private int expandRatio = GridConstants.DEFAULT_EXPAND_RATIO;
+        private boolean minimumWidthFromContent = true;
 
         /**
          * Constructs a new column with a simple TextRenderer.
             return this;
         }
 
+        /**
+         * Sets whether the width of the contents in the column should be
+         * considered minimum width for this column.
+         * <p>
+         * If this is set to <code>true</code> (default for backwards
+         * compatibility), then a column will not shrink to smaller than the
+         * width required to show the contents available when calculating the
+         * widths (first N rows).
+         * <p>
+         * If this is set to <code>false</code>, then a column will shrink if
+         * necessary to the minimum width defined by
+         * {@link #setMinimumWidth(double)} <em>when it is set to expand</em>.
+         *
+         * @param minimumWidthFromContent
+         *            <code>true</code> to reserve space for all contents,
+         *            <code>false</code> to allow the column to shrink smaller
+         *            than the contents
+         * @since
+         */
+        public void setMinimumWidthFromContent(
+                boolean minimumWidthFromContent) {
+            this.minimumWidthFromContent = minimumWidthFromContent;
+        }
+
+        /**
+         * Gets whether the width of the contents in the column should be
+         * considered minimum width for this column.
+         *
+         * @return <code>true</code> to reserve space for all contents,
+         *         <code>false</code> to allow the column to shrink smaller than
+         *         the contents
+         * @since
+         */
+        public boolean isMinimumWidthFromContent() {
+            return minimumWidthFromContent;
+        }
+
         /**
          * Sets the maximum width for this column.
          * <p>
         protected void setDefaultHeaderContent(HeaderCell cell) {
             cell.setText(headerCaption);
         }
+
     }
 
     protected class BodyUpdater implements EscalatorUpdater {

documentation/components/components-grid.asciidoc

 [methodname]#setExpandRatio()#.
 
 When using expand ratios, the columns with a non-zero expand ratio use the extra
-space remaining from other columns, in proportion to the defined ratios.
+space remaining from other columns, in proportion to the defined ratios. Do note
+that the minimum width of an expanded column by default is based on the contents
+of the column (the initially rendered rows). To allow the column to become
+narrower than this, use [methodname]#setMinimumWidthFromContent(false)#
+(introduced in 8.1).
 
 You can specify minimum and maximum widths for the expanding columns with
 [methodname]#setMinimumWidth()# and [methodname]#setMaximumWidth()#,

server/src/main/java/com/vaadin/ui/Grid.java

          * This defines the minimum guaranteed pixel width of the column
          * <em>when it is set to expand</em>.
          *
+         * @param pixels
+         *            the minimum width for the column
          * @throws IllegalStateException
          *             if the column is no longer attached to any grid
          * @see #setExpandRatio(int)
+         * @return the column itself
          */
         public Column<T, V> setMinimumWidth(double pixels)
                 throws IllegalStateException {
             return getState(false).minWidth;
         }
 
+        /**
+         * Sets whether the width of the contents in the column should be
+         * considered minimum width for this column.
+         * <p>
+         * If this is set to <code>true</code> (default for backwards
+         * compatibility), then a column will not shrink to smaller than the
+         * width required to show the contents available when calculating the
+         * widths (only the widths of the initially rendered rows are
+         * considered).
+         * <p>
+         * If this is set to <code>false</code> and the column has been set to
+         * expand using #setExpandRatio(int), then the contents of the column
+         * will be ignored when calculating the width, and the column will thus
+         * shrink down to the minimum width defined by #setMinimumWidth(double)
+         * if necessary.
+         *
+         * @param minimumWidthFromContent
+         *            <code>true</code> to reserve space for all contents,
+         *            <code>false</code> to allow the column to shrink smaller
+         *            than the contents
+         * @return the column itself
+         * @throws IllegalStateException
+         *             if the column is no longer attached to any grid
+         * @see #setMinimumWidth(double)
+         * @since
+         */
+        public Column<T, V> setMinimumWidthFromContent(
+                boolean minimumWidthFromContent) throws IllegalStateException {
+            checkColumnIsAttached();
+
+            if (isMinimumWidthFromContent() != minimumWidthFromContent) {
+                getState().minimumWidthFromContent = minimumWidthFromContent;
+                getGrid().markAsDirty();
+            }
+            return this;
+        }
+
+        /**
+         * Gets whether the width of the contents in the column should be
+         * considered minimum width for this column.
+         *
+         * @return <code>true</code> to reserve space for all contents,
+         *         <code>false</code> to allow the column to shrink smaller than
+         *         the contents
+         * @see #setMinimumWidthFromContent(boolean)
+         * @since
+         */
+        public boolean isMinimumWidthFromContent() {
+            return getState(false).minimumWidthFromContent;
+        }
+
         /**
          * Sets the maximum width for this column.
          * <p>

shared/src/main/java/com/vaadin/shared/ui/grid/ColumnState.java

     public boolean resizable = true;
 
     public Connector renderer;
+    /**
+     * Whether the contents define the minimum width for this column.
+     */
+    public boolean minimumWidthFromContent = true;
 
 }

uitest/src/main/java/com/vaadin/tests/components/grid/GridColumnShrinkSmallerThanContents.java

+/*
+ * Copyright 2000-2016 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.tests.components.grid;
+
+import com.vaadin.annotations.Widgetset;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Component;
+import com.vaadin.ui.Grid;
+
+@Widgetset("com.vaadin.DefaultWidgetSet")
+public class GridColumnShrinkSmallerThanContents extends AbstractTestUI {
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        addComponent(createGrid(true));
+        addComponent(createGrid(false));
+    }
+
+    private Component createGrid(boolean minimumWidthFromContent) {
+        Grid<Object> grid = new Grid<>();
+        grid.addColumn(item -> "Contents in column 1");
+        grid.addColumn(
+                item -> "Contents in column 2. Contents in column 2. Contents in column 2. Contents in column 2. Contents in column 2.")
+                .setExpandRatio(1)
+                .setMinimumWidthFromContent(minimumWidthFromContent);
+        grid.setItems(new Object(), new Object());
+        grid.setWidth("500px");
+        return grid;
+    }
+
+}

uitest/src/test/java/com/vaadin/tests/components/grid/GridColumnShrinkSmallerThanContentsTest.java

+/*
+ * Copyright 2000-2016 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.tests.components.grid;
+
+import org.junit.Test;
+
+import com.vaadin.testbench.elements.GridElement;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+
+public class GridColumnShrinkSmallerThanContentsTest extends SingleBrowserTest {
+
+    @Test
+    public void scrollbarAndNoScrollbar() {
+        openTestURL();
+        GridElement noshrinkColumnGrid = $(GridElement.class).get(0);
+        GridElement shrinkColumnGrid = $(GridElement.class).get(1);
+        assertHorizontalScrollbar(noshrinkColumnGrid.getHorizontalScroller(),
+                "Should have a horizontal scrollbar as column 2 should be wide");
+        assertNoHorizontalScrollbar(shrinkColumnGrid.getHorizontalScroller(),
+                "Should not have a horizontal scrollbar as column 2 should be narrow");
+    }
+}

uitest/src/test/java/com/vaadin/tests/tb3/AbstractTB3Test.java

 
     protected void assertNoHorizontalScrollbar(WebElement element,
             String errorMessage) {
+        assertHasHorizontalScrollbar(element, errorMessage, false);
+    }
+
+    protected void assertHorizontalScrollbar(WebElement element,
+            String errorMessage) {
+        assertHasHorizontalScrollbar(element, errorMessage, true);
+    }
+
+    private void assertHasHorizontalScrollbar(WebElement element,
+            String errorMessage, boolean expected) {
         // IE rounds clientWidth/clientHeight down and scrollHeight/scrollWidth
         // up, so using clientWidth/clientHeight will fail if the element height
         // is not an integer
         int clientWidth = getClientWidth(element);
         int scrollWidth = getScrollWidth(element);
         boolean hasScrollbar = scrollWidth > clientWidth;
-
-        Assert.assertFalse(
-                "The element should not have a horizontal scrollbar (scrollWidth: "
-                        + scrollWidth + ", clientWidth: " + clientWidth + "): "
-                        + errorMessage,
-                hasScrollbar);
+        String message = "The element should";
+        if (!expected) {
+            message += " not";
+        }
+        message += " have a horizontal scrollbar (scrollWidth: " + scrollWidth
+                + ", clientWidth: " + clientWidth + "): " + errorMessage;
+        Assert.assertEquals(message, expected, hasScrollbar);
     }
 
     protected void assertNoVerticalScrollbar(WebElement element,