com.google.dart.tools.ui.internal.cleanup.preference.ModifyDialogTabPage.java Source code

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/*
 * Copyright (c) 2011, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
 * 
 * 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.google.dart.tools.ui.internal.cleanup.preference;

import com.google.dart.tools.ui.DartToolsPlugin;
import com.google.dart.tools.ui.DartUI;
import com.google.dart.tools.ui.Messages;
import com.google.dart.tools.ui.internal.util.SWTUtil;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.jface.dialogs.IDialogConstants;
import org.eclipse.jface.dialogs.IDialogSettings;
import org.eclipse.jface.dialogs.IInputValidator;
import org.eclipse.jface.layout.PixelConverter;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.SashForm;
import org.eclipse.swt.custom.ScrolledComposite;
import org.eclipse.swt.events.ControlEvent;
import org.eclipse.swt.events.ControlListener;
import org.eclipse.swt.events.FocusAdapter;
import org.eclipse.swt.events.FocusEvent;
import org.eclipse.swt.events.FocusListener;
import org.eclipse.swt.events.ModifyEvent;
import org.eclipse.swt.events.ModifyListener;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Layout;
import org.eclipse.swt.widgets.Text;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Observable;
import java.util.Observer;

public abstract class ModifyDialogTabPage implements IModifyDialogTabPage {

    /**
     * Wrapper around a checkbox and a label.
     */
    protected class ButtonPreference extends Preference {
        private final String[] fValues;
        private final Button fCheckbox;

        /**
         * Create a new CheckboxPreference.
         * 
         * @param composite The composite on which the SWT widgets are added.
         * @param numColumns The number of columns in the composite's GridLayout.
         * @param preferences The map to store the values.
         * @param key The key to store the values.
         * @param values An array of two elements indicating the values to store on unchecked/checked.
         * @param text The label text for this Preference.
         * @param style SWT style flag for the button
         */
        public ButtonPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
                String[] values, String text, int style) {
            super(preferences, key);
            if (values == null || text == null) {
                throw new IllegalArgumentException(
                        FormatterMessages.ModifyDialogTabPage_error_msg_values_text_unassigned);
            }
            fValues = values;

            fCheckbox = new Button(composite, style);
            fCheckbox.setText(text);
            fCheckbox.setLayoutData(createGridData(numColumns, GridData.FILL_HORIZONTAL, SWT.DEFAULT));
            fCheckbox.setFont(composite.getFont());

            updateWidget();

            fCheckbox.addSelectionListener(new SelectionAdapter() {
                @Override
                public void widgetSelected(SelectionEvent e) {
                    checkboxChecked(((Button) e.widget).getSelection());
                }
            });
        }

        public boolean getChecked() {
            return fValues[1].equals(getPreferences().get(getKey()));
        }

        @Override
        public Control getControl() {
            return fCheckbox;
        }

        public void setChecked(boolean checked) {
            getPreferences().put(getKey(), checked ? fValues[1] : fValues[0]);
            updateWidget();
            checkboxChecked(checked);
        }

        protected void checkboxChecked(boolean state) {
            getPreferences().put(getKey(), state ? fValues[1] : fValues[0]);
            setChanged();
            notifyObservers();
        }

        @Override
        protected void updateWidget() {
            if (getKey() != null) {
                fCheckbox.setEnabled(getEnabled());
                fCheckbox.setSelection(getChecked());
            } else {
                fCheckbox.setSelection(false);
                fCheckbox.setEnabled(false);
            }
        }
    }

    protected final class CheckboxPreference extends ButtonPreference {
        public CheckboxPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
                String[] values, String text) {
            super(composite, numColumns, preferences, key, values, text, SWT.CHECK);
        }
    }

    /**
     * Wrapper around a Combo box.
     */
    protected final class ComboPreference extends Preference {
        private final String[] fItems;
        private final String[] fValues;
        private final Combo fCombo;

        /**
         * Create a new ComboPreference.
         * 
         * @param composite The composite on which the SWT widgets are added.
         * @param numColumns The number of columns in the composite's GridLayout.
         * @param preferences The map to store the values.
         * @param key The key to store the values.
         * @param values An array of n elements indicating the values to store for each selection.
         * @param text The label text for this Preference.
         * @param items An array of n elements indicating the text to be written in the combo box.
         */
        public ComboPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
                String[] values, String text, String[] items) {
            super(preferences, key);
            if (values == null || items == null || text == null) {
                throw new IllegalArgumentException(
                        FormatterMessages.ModifyDialogTabPage_error_msg_values_items_text_unassigned);
            }
            fValues = values;
            fItems = items;
            createLabel(numColumns - 1, composite, text);
            fCombo = new Combo(composite, SWT.SINGLE | SWT.READ_ONLY);
            fCombo.setFont(composite.getFont());
            SWTUtil.setDefaultVisibleItemCount(fCombo);
            fCombo.setItems(items);

            int max = 0;
            for (int i = 0; i < items.length; i++) {
                if (items[i].length() > max) {
                    max = items[i].length();
                }
            }

            fCombo.setLayoutData(createGridData(1, GridData.HORIZONTAL_ALIGN_FILL,
                    fCombo.computeSize(SWT.DEFAULT, SWT.DEFAULT).x));

            updateWidget();

            fCombo.addSelectionListener(new SelectionAdapter() {
                @Override
                public void widgetSelected(SelectionEvent e) {
                    comboSelected(((Combo) e.widget).getSelectionIndex());
                }
            });
        }

        @Override
        public Control getControl() {
            return fCombo;
        }

        public String getSelectedItem() {
            final String selected = getPreferences().get(getKey());
            for (int i = 0; i < fValues.length; i++) {
                if (fValues[i].equals(selected)) {
                    return fItems[i];
                }
            }
            return ""; //$NON-NLS-1$
        }

        public boolean hasValue(String value) {
            return value.equals(getPreferences().get(getKey()));
        }

        protected void comboSelected(int index) {
            getPreferences().put(getKey(), fValues[index]);
            setChanged();
            notifyObservers(fValues[index]);
        }

        @Override
        protected void updateWidget() {
            if (getKey() != null) {
                fCombo.setEnabled(getEnabled());
                fCombo.setText(getSelectedItem());
            } else {
                fCombo.setText(""); //$NON-NLS-1$
                fCombo.setEnabled(false);
            }
        }
    }

    /**
     * This class provides the default way to preserve and re-establish the focus over multiple modify
     * sessions. Each ModifyDialogTabPage has its own instance, and it should add all relevant
     * controls upon creation, always in the same sequence. This established a mapping of controls to
     * indexes, which allows to restore the focus in a later session. The index is saved in the dialog
     * settings, and there is only one common preference for all tab pages. It is always the currently
     * active tab page which stores its focus index.
     */
    protected final static class DefaultFocusManager extends FocusAdapter {

        private final static String PREF_LAST_FOCUS_INDEX = DartUI.ID_PLUGIN
                + "formatter_page.modify_dialog_tab_page.last_focus_index"; //$NON-NLS-1$

        private final IDialogSettings fDialogSettings;

        private final Map<Control, Integer> fItemMap;
        private final List<Control> fItemList;

        private int fIndex;

        public DefaultFocusManager() {
            fDialogSettings = DartToolsPlugin.getDefault().getDialogSettings();
            fItemMap = new HashMap<Control, Integer>();
            fItemList = new ArrayList<Control>();
            fIndex = 0;
        }

        public void add(Control control) {
            control.addFocusListener(this);
            fItemList.add(fIndex, control);
            fItemMap.put(control, new Integer(fIndex++));
        }

        public void add(Preference preference) {
            final Control control = preference.getControl();
            if (control != null) {
                add(control);
            }
        }

        @Override
        public void focusGained(FocusEvent e) {
            fDialogSettings.put(PREF_LAST_FOCUS_INDEX, fItemMap.get(e.widget).intValue());
        }

        public boolean isUsed() {
            return fIndex != 0;
        }

        public void resetFocus() {
            fDialogSettings.put(PREF_LAST_FOCUS_INDEX, -1);
        }

        public void restoreFocus() {
            int index = 0;
            try {
                index = fDialogSettings.getInt(PREF_LAST_FOCUS_INDEX);
                // make sure the value is within the range
                if ((index >= 0) && (index <= fItemList.size() - 1)) {
                    fItemList.get(index).setFocus();
                }
            } catch (NumberFormatException ex) {
                // this is the first time
            }
        }
    }

    /**
     * Wrapper around a textfied which requests an integer input of a given range.
     */
    protected final class NumberPreference extends Preference {

        private final int fMinValue, fMaxValue;
        private final Label fNumberLabel;
        private final Text fNumberText;

        protected int fSelected;
        protected int fOldSelected;

        /**
         * Create a new NumberPreference.
         * 
         * @param composite The composite on which the SWT widgets are added.
         * @param numColumns The number of columns in the composite's GridLayout.
         * @param preferences The map to store the values.
         * @param key The key to store the values.
         * @param minValue The minimum value which is valid input.
         * @param maxValue The maximum value which is valid input.
         * @param text The label text for this Preference.
         */
        public NumberPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
                int minValue, int maxValue, String text) {
            super(preferences, key);

            fNumberLabel = createLabel(numColumns - 1, composite, text, GridData.FILL_HORIZONTAL);
            fNumberText = new Text(composite, SWT.SINGLE | SWT.BORDER | SWT.RIGHT);
            fNumberText.setFont(composite.getFont());

            final int length = Integer.toString(maxValue).length() + 3;
            fNumberText.setLayoutData(createGridData(1, GridData.HORIZONTAL_ALIGN_END,
                    fPixelConverter.convertWidthInCharsToPixels(length)));

            fMinValue = minValue;
            fMaxValue = maxValue;

            updateWidget();

            fNumberText.addFocusListener(new FocusListener() {
                @Override
                public void focusGained(FocusEvent e) {
                    NumberPreference.this.focusGained();
                }

                @Override
                public void focusLost(FocusEvent e) {
                    NumberPreference.this.focusLost();
                }
            });

            fNumberText.addModifyListener(new ModifyListener() {
                @Override
                public void modifyText(ModifyEvent e) {
                    fieldModified();
                }
            });
        }

        @Override
        public Control getControl() {
            return fNumberText;
        }

        protected void fieldModified() {
            final String trimInput = fNumberText.getText().trim();
            final boolean valid = validInput(trimInput);

            updateStatus(valid ? null : createErrorStatus());

            if (valid) {
                final int number = Integer.parseInt(trimInput);
                if (fSelected != number) {
                    fSelected = number;
                    saveSelected();
                }
            }
        }

        protected void focusGained() {
            fOldSelected = fSelected;
            fNumberText.setSelection(0, fNumberText.getCharCount());
        }

        protected void focusLost() {
            updateStatus(null);
            final String input = fNumberText.getText();
            if (!validInput(input)) {
                fSelected = fOldSelected;
            } else {
                fSelected = Integer.parseInt(input);
            }
            if (fSelected != fOldSelected) {
                saveSelected();
                fNumberText.setText(Integer.toString(fSelected));
            }
        }

        @Override
        protected void updateWidget() {
            final boolean hasKey = getKey() != null;

            fNumberLabel.setEnabled(hasKey && getEnabled());
            fNumberText.setEnabled(hasKey && getEnabled());

            if (hasKey) {
                String s = getPreferences().get(getKey());
                try {
                    fSelected = Integer.parseInt(s);
                } catch (NumberFormatException e) {
                    final String message = Messages.format(
                            FormatterMessages.ModifyDialogTabPage_NumberPreference_error_invalid_key, getKey());
                    DartToolsPlugin
                            .log(new Status(IStatus.ERROR, DartToolsPlugin.getPluginId(), IStatus.OK, message, e));
                    s = ""; //$NON-NLS-1$
                }
                fNumberText.setText(s);
            } else {
                fNumberText.setText(""); //$NON-NLS-1$
            }
        }

        private IStatus createErrorStatus() {
            return new Status(IStatus.ERROR, DartToolsPlugin.getPluginId(), 0,
                    Messages.format(FormatterMessages.ModifyDialogTabPage_NumberPreference_error_invalid_value,
                            new String[] { Integer.toString(fMinValue), Integer.toString(fMaxValue) }),
                    null);

        }

        private void saveSelected() {
            getPreferences().put(getKey(), Integer.toString(fSelected));
            setChanged();
            notifyObservers();
        }

        private boolean validInput(String trimInput) {
            int number;

            try {
                number = Integer.parseInt(trimInput);
            } catch (NumberFormatException x) {
                return false;
            }

            if (number < fMinValue) {
                return false;
            }
            if (number > fMaxValue) {
                return false;
            }
            return true;
        }
    }

    /**
     * The base class of all Preference classes. A preference class provides a wrapper around one or
     * more SWT widgets and handles the input of values for some key. On each change, the new value is
     * written to the map and the listeners are notified.
     */
    protected abstract class Preference extends Observable {
        private final Map<String, String> fPreferences;
        private boolean fEnabled;
        private String fKey;

        /**
         * Create a new Preference.
         * 
         * @param preferences The map where the value is written.
         * @param key The key for which a value is managed.
         */
        public Preference(Map<String, String> preferences, String key) {
            fPreferences = preferences;
            fEnabled = true;
            fKey = key;
        }

        /**
         * Returns the main control of a preference, which is mainly used to manage the focus. This may
         * be <code>null</code> if the preference doesn't have a control which is able to have the
         * focus.
         * 
         * @return The main control
         */
        public abstract Control getControl();

        /**
         * @return Gets the enabled state of all SWT widgets of this Preference.
         */
        public final boolean getEnabled() {
            return fEnabled;
        }

        /**
         * @return Gets the currently used key which is used to store the value.
         */
        public final String getKey() {
            return fKey;
        }

        /**
         * Set the enabled state of all SWT widgets of this preference.
         * 
         * @param enabled new value
         */
        public final void setEnabled(boolean enabled) {
            fEnabled = enabled;
            updateWidget();
        }

        /**
         * Set the key which is used to store the value.
         * 
         * @param key New value
         */
        public final void setKey(String key) {
            if (key == null || !fKey.equals(key)) {
                fKey = key;
                updateWidget();
            }
        }

        /**
         * @return Gets the map of this Preference.
         */
        protected final Map<String, String> getPreferences() {
            return fPreferences;
        }

        /**
         * To be implemented in subclasses. Update the SWT widgets when the state of this object has
         * changed (enabled, key, ...).
         */
        protected abstract void updateWidget();
    }

    protected final class RadioPreference extends ButtonPreference {
        public RadioPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
                String[] values, String text) {
            super(composite, numColumns, preferences, key, values, text, SWT.RADIO);
        }
    }

    /**
     * Wrapper around a text field which requests a string input.
     * 
     * @since 3.6
     */
    protected final class StringPreference extends Preference {

        /**
         * Validates the input.
         * <p>
         * The default implementation declares all non-<code>null</code> values as valid.
         * </p>
         * 
         * @since 3.6
         */
        protected class Validator {
            boolean isValid(String input) {
                return input != null;
            }
        }

        private final Label fLabel;

        private final Text fText;

        private IInputValidator fInputValidator;

        protected String fSelected;

        protected String fOldSelected;

        /**
         * Creates a new <code>StringPreference</code>.
         * 
         * @param composite the composite on which the SWT widgets are added.
         * @param numColumns the number of columns in the composite's {@link GridLayout}
         * @param preferences the map to store the values.
         * @param key the key to store the values.
         * @param text the label text for this Preference.
         * @param inputValidator the input validator or <code>null</code> if none
         */
        public StringPreference(Composite composite, int numColumns, Map<String, String> preferences, String key,
                String text, IInputValidator inputValidator) {
            super(preferences, key);

            fInputValidator = inputValidator;

            fLabel = new Label(composite, SWT.NONE);
            fLabel.setFont(composite.getFont());
            fLabel.setText(text);

            fLabel.setLayoutData(createGridData(numColumns - 1, GridData.HORIZONTAL_ALIGN_BEGINNING, SWT.DEFAULT));

            fText = new Text(composite, SWT.SINGLE | SWT.BORDER);
            fText.setFont(composite.getFont());

            final int length = 30;
            fText.setLayoutData(createGridData(1, GridData.HORIZONTAL_ALIGN_BEGINNING,
                    fPixelConverter.convertWidthInCharsToPixels(length)));

            updateWidget();

            fText.addFocusListener(new FocusListener() {
                @Override
                public void focusGained(FocusEvent e) {
                    StringPreference.this.focusGained();
                }

                @Override
                public void focusLost(FocusEvent e) {
                    StringPreference.this.focusLost();
                }
            });

            fText.addModifyListener(new ModifyListener() {
                @Override
                public void modifyText(ModifyEvent e) {
                    fieldModified();
                }
            });
        }

        @Override
        public Control getControl() {
            return fText;
        }

        protected void fieldModified() {
            final String text = fText.getText();
            final String errorText = fInputValidator != null ? fInputValidator.isValid(text) : null;
            if (errorText == null) {
                updateStatus(null);
                if (fSelected != text) {
                    fSelected = text;
                    saveSelected();
                }
            } else {
                updateStatus(createErrorStatus(errorText));
            }
        }

        protected void focusGained() {
            fOldSelected = fSelected;
            fText.setSelection(0, fText.getCharCount());
        }

        protected void focusLost() {
            updateStatus(null);
            final String input = fText.getText();
            if (fInputValidator != null && fInputValidator.isValid(input) != null) {
                fSelected = fOldSelected;
            } else {
                fSelected = input;
            }
            if (fSelected != fOldSelected) {
                saveSelected();
                fText.setText(fSelected);
            }
        }

        @Override
        protected void updateWidget() {
            final boolean hasKey = getKey() != null;

            fLabel.setEnabled(hasKey && getEnabled());
            fText.setEnabled(hasKey && getEnabled());

            if (hasKey) {
                fSelected = getPreferences().get(getKey());
                fText.setText(fSelected);
            } else {
                fText.setText(""); //$NON-NLS-1$
            }
        }

        private IStatus createErrorStatus(String errorText) {
            return new Status(IStatus.ERROR, DartToolsPlugin.getPluginId(), 0, errorText, null);

        }

        private void saveSelected() {
            getPreferences().put(getKey(), fSelected);
            setChanged();
            notifyObservers();
        }
    }

    /**
     * Layout used for the settings part. Makes sure to show scrollbars if necessary. The settings
     * part needs to be layouted on resize.
     */
    private static class PageLayout extends Layout {

        private final ScrolledComposite fContainer;
        private final int fMinimalWidth;
        private final int fMinimalHight;

        private PageLayout(ScrolledComposite container, int minimalWidth, int minimalHight) {
            fContainer = container;
            fMinimalWidth = minimalWidth;
            fMinimalHight = minimalHight;
        }

        @Override
        public Point computeSize(Composite composite, int wHint, int hHint, boolean force) {
            if (wHint != SWT.DEFAULT && hHint != SWT.DEFAULT) {
                return new Point(wHint, hHint);
            }

            int x = fMinimalWidth;
            int y = fMinimalHight;
            Control[] children = composite.getChildren();
            for (int i = 0; i < children.length; i++) {
                Point size = children[i].computeSize(SWT.DEFAULT, SWT.DEFAULT, force);
                x = Math.max(x, size.x);
                y = Math.max(y, size.y);
            }

            Rectangle area = fContainer.getClientArea();
            if (area.width > x) {
                fContainer.setExpandHorizontal(true);
            } else {
                fContainer.setExpandHorizontal(false);
            }

            if (area.height > y) {
                fContainer.setExpandVertical(true);
            } else {
                fContainer.setExpandVertical(false);
            }

            if (wHint != SWT.DEFAULT) {
                x = wHint;
            }
            if (hHint != SWT.DEFAULT) {
                y = hHint;
            }

            return new Point(x, y);
        }

        @Override
        public void layout(Composite composite, boolean force) {
            Rectangle rect = composite.getClientArea();
            Control[] children = composite.getChildren();
            for (int i = 0; i < children.length; i++) {
                children[i].setSize(rect.width, rect.height);
            }
        }
    }

    /*
     * Convenience method to create a GridData.
     */
    protected static GridData createGridData(int numColumns, int style, int widthHint) {
        final GridData gd = new GridData(style);
        gd.horizontalSpan = numColumns;
        gd.widthHint = widthHint;
        return gd;
    }

    /*
     * Convenience method to create a label.
     */
    protected static Label createLabel(int numColumns, Composite parent, String text) {
        return createLabel(numColumns, parent, text, GridData.FILL_HORIZONTAL);
    }

    /*
     * Convenience method to create a label
     */
    protected static Label createLabel(int numColumns, Composite parent, String text, int gridDataStyle) {
        final Label label = new Label(parent, SWT.WRAP);
        label.setFont(parent.getFont());
        label.setText(text);

        PixelConverter pixelConverter = new PixelConverter(parent);
        label.setLayoutData(
                createGridData(numColumns, gridDataStyle, pixelConverter.convertHorizontalDLUsToPixels(150)));
        return label;
    }

    /*
     * Create a nice javadoc comment for some string.
     */
    protected static String createPreviewHeader(String title) {
        return "/**\n* " + title + "\n*/\n"; //$NON-NLS-1$ //$NON-NLS-2$
    }

    /**
     * This is the default listener for any of the Preference classes. It is added by the respective
     * factory methods and updates the page's preview on each change.
     */
    protected final Observer fUpdater = new Observer() {
        @Override
        public void update(Observable o, Object arg) {
            doUpdatePreview();
            notifyValuesModified();
        }
    };

    /**
     * The default focus manager. This widget knows all widgets which can have the focus and listens
     * for focusGained events, on which it stores the index of the current focus holder. When the
     * dialog is restarted, <code>restoreFocus()</code> sets the focus to the last control which had
     * it. The standard Preference object are managed by this focus manager if they are created using
     * the respective factory methods. Other SWT widgets can be added in subclasses when they are
     * created.
     */
    protected final DefaultFocusManager fDefaultFocusManager;

    /**
     * A pixel converter for layout calculations
     */
    protected PixelConverter fPixelConverter;

    /**
     * The map where the current settings are stored.
     */
    protected Map<String, String> fWorkingValues;

    /**
     * The modify dialog where we can display status messages.
     */
    private IModifyDialogTabPage.IModificationListener fModifyListener;

    public ModifyDialogTabPage() {
        fDefaultFocusManager = new DefaultFocusManager();
    }

    /*
     * Create a new <code>ModifyDialogTabPage</code>
     */
    public ModifyDialogTabPage(IModifyDialogTabPage.IModificationListener modifyListener,
            Map<String, String> workingValues) {
        fWorkingValues = workingValues;
        fModifyListener = modifyListener;
        fDefaultFocusManager = new DefaultFocusManager();
    }

    /**
     * Create the contents of this tab page.
     * <p>
     * Subclasses should implement <code>doCreatePreferences</code> and <code>doCreatePreview</code>
     * may also be overridden as necessary.
     * </p>
     * 
     * @param parent The parent composite
     * @return Created content control
     */
    @Override
    public Composite createContents(Composite parent) {
        final int numColumns = 4;

        if (fPixelConverter == null) {
            fPixelConverter = new PixelConverter(parent);
        }

        final SashForm sashForm = new SashForm(parent, SWT.HORIZONTAL);
        sashForm.setFont(parent.getFont());

        Composite scrollContainer = new Composite(sashForm, SWT.NONE);

        GridData gridData = new GridData(SWT.FILL, SWT.FILL, true, true);
        scrollContainer.setLayoutData(gridData);

        GridLayout layout = new GridLayout(2, false);
        layout.marginHeight = 0;
        layout.marginWidth = 0;
        layout.horizontalSpacing = 0;
        layout.verticalSpacing = 0;
        scrollContainer.setLayout(layout);

        ScrolledComposite scroll = new ScrolledComposite(scrollContainer, SWT.V_SCROLL | SWT.H_SCROLL);
        scroll.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        scroll.setExpandHorizontal(true);
        scroll.setExpandVertical(true);

        final Composite settingsContainer = new Composite(scroll, SWT.NONE);
        settingsContainer.setFont(sashForm.getFont());

        scroll.setContent(settingsContainer);

        settingsContainer.setLayout(new PageLayout(scroll, 400, 400));
        settingsContainer.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

        Composite settingsPane = new Composite(settingsContainer, SWT.NONE);
        settingsPane.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

        layout = new GridLayout(numColumns, false);
        layout.verticalSpacing = (int) (1.5
                * fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING));
        layout.horizontalSpacing = fPixelConverter
                .convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_SPACING);
        layout.marginHeight = fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
        layout.marginWidth = fPixelConverter.convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
        settingsPane.setLayout(layout);
        doCreatePreferences(settingsPane, numColumns);

        settingsContainer.setSize(settingsContainer.computeSize(SWT.DEFAULT, SWT.DEFAULT));

        scroll.addControlListener(new ControlListener() {

            @Override
            public void controlMoved(ControlEvent e) {
            }

            @Override
            public void controlResized(ControlEvent e) {
                settingsContainer.setSize(settingsContainer.computeSize(SWT.DEFAULT, SWT.DEFAULT));
            }
        });

        Label sashHandle = new Label(scrollContainer, SWT.SEPARATOR | SWT.VERTICAL);
        gridData = new GridData(SWT.RIGHT, SWT.FILL, false, true);
        sashHandle.setLayoutData(gridData);

        final Composite previewPane = new Composite(sashForm, SWT.NONE);
        previewPane.setLayout(createGridLayout(numColumns, true));
        previewPane.setFont(sashForm.getFont());
        doCreatePreviewPane(previewPane, numColumns);

        initializePage();

        sashForm.setWeights(new int[] { 3, 3 });
        return sashForm;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public final void makeVisible() {
        fDefaultFocusManager.resetFocus();
        doUpdatePreview();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setInitialFocus() {
        if (fDefaultFocusManager.isUsed()) {
            fDefaultFocusManager.restoreFocus();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setModifyListener(IModifyDialogTabPage.IModificationListener modifyListener) {
        fModifyListener = modifyListener;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setWorkingValues(Map<String, String> workingValues) {
        fWorkingValues = workingValues;
    }

    /*
     * Convenience method to create a CheckboxPreference. The widget is registered as a potential
     * focus holder, and the default updater is added.
     */
    protected CheckboxPreference createCheckboxPref(Composite composite, int numColumns, String name, String key,
            String[] values) {
        final CheckboxPreference pref = new CheckboxPreference(composite, numColumns, fWorkingValues, key, values,
                name);
        fDefaultFocusManager.add(pref);
        pref.addObserver(fUpdater);
        return pref;
    }

    /*
     * Convenience method to create a ComboPreference. The widget is registered as a potential focus
     * holder, and the default updater is added.
     */
    protected ComboPreference createComboPref(Composite composite, int numColumns, String name, String key,
            String[] values, String[] items) {
        final ComboPreference pref = new ComboPreference(composite, numColumns, fWorkingValues, key, values, name,
                items);
        fDefaultFocusManager.add(pref);
        pref.addObserver(fUpdater);
        return pref;
    }

    /*
     * Create a GridLayout with the default margin and spacing settings, as well as the specified
     * number of columns.
     */
    protected GridLayout createGridLayout(int numColumns, boolean margins) {
        final GridLayout layout = new GridLayout(numColumns, false);
        layout.verticalSpacing = fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING);
        layout.horizontalSpacing = fPixelConverter
                .convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_SPACING);
        if (margins) {
            layout.marginHeight = fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
            layout.marginWidth = fPixelConverter.convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
        } else {
            layout.marginHeight = 0;
            layout.marginWidth = 0;
        }
        return layout;
    }

    /*
     * Factory methods to make GUI construction easier
     */

    /*
     * Convenience method to create a group
     */
    protected Group createGroup(int numColumns, Composite parent, String text) {
        final Group group = new Group(parent, SWT.NONE);
        group.setFont(parent.getFont());
        group.setLayoutData(createGridData(numColumns, GridData.FILL_HORIZONTAL, SWT.DEFAULT));

        final GridLayout layout = new GridLayout(numColumns, false);
        layout.verticalSpacing = fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING);
        layout.horizontalSpacing = fPixelConverter
                .convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_SPACING);
        layout.marginHeight = fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING);

        //layout.marginHeight= fPixelConverter.convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
        //layout.marginWidth= fPixelConverter.convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);

        group.setLayout(layout);//createGridLayout(numColumns, true));
        group.setText(text);
        return group;
    }

    /*
     * Convenience method to create a NumberPreference. The widget is registered as a potential focus
     * holder, and the default updater is added.
     */
    protected NumberPreference createNumberPref(Composite composite, int numColumns, String name, String key,
            int minValue, int maxValue) {
        final NumberPreference pref = new NumberPreference(composite, numColumns, fWorkingValues, key, minValue,
                maxValue, name);
        fDefaultFocusManager.add(pref);
        pref.addObserver(fUpdater);
        return pref;
    }

    protected RadioPreference createRadioPref(Composite composite, int numColumns, String name, String key,
            String[] values) {
        final RadioPreference pref = new RadioPreference(composite, numColumns, fWorkingValues, key, values, name);
        fDefaultFocusManager.add(pref);
        pref.addObserver(fUpdater);
        return pref;
    }

    /*
     * Convenience method to create a StringPreference. The widget is registered as a potential focus
     * holder, and the default updater is added.
     * 
     * @since 3.6
     */
    protected StringPreference createStringPref(Composite composite, int numColumns, String name, String key,
            IInputValidator inputValidator) {
        StringPreference pref = new StringPreference(composite, numColumns, fWorkingValues, key, name,
                inputValidator);
        fDefaultFocusManager.add(pref);
        pref.addObserver(fUpdater);
        return pref;
    }

    /**
     * To be implemented by subclasses. This method should return an instance of JavaPreview.
     * Currently, the choice is between CompilationUnitPreview which contains a valid compilation
     * unit, or a SnippetPreview which formats several independent code snippets and displays them in
     * the same window.
     * 
     * @param parent Parent composite
     * @return Created preview
     */
    protected abstract DartPreview doCreateJavaPreview(Composite parent);

    /**
     * Create the left side of the modify dialog. This is meant to be implemented by subclasses.
     * 
     * @param composite Composite to create in
     * @param numColumns Number of columns to use
     */
    protected abstract void doCreatePreferences(Composite composite, int numColumns);

    /**
     * Create the right side of the modify dialog. By default, the preview is displayed there.
     * Subclasses can override this method in order to customize the right-hand side of the dialog.
     * 
     * @param composite Composite to create in
     * @param numColumns Number of columns to use
     * @return Created composite
     */
    protected Composite doCreatePreviewPane(Composite composite, int numColumns) {

        createLabel(numColumns, composite, FormatterMessages.ModifyDialogTabPage_preview_label_text);

        final DartPreview preview = doCreateJavaPreview(composite);
        fDefaultFocusManager.add(preview.getControl());

        final GridData gd = createGridData(numColumns, GridData.FILL_BOTH, 0);
        gd.widthHint = 0;
        gd.heightHint = 0;
        preview.getControl().setLayoutData(gd);

        return composite;
    }

    /**
     * Update the preview. To be implemented by subclasses.
     */
    protected abstract void doUpdatePreview();

    /**
     * This method is called after all controls have been allocated, including the preview. It can be
     * used to set the preview text and to create listeners.
     */
    protected abstract void initializePage();

    protected void notifyValuesModified() {
        fModifyListener.valuesModified();
    }

    /**
     * Set the status field on the dialog. This can be used by tab pages to report inconsistent input.
     * The OK button is disabled if the kind is IStatus.ERROR.
     * 
     * @param status Status describing the current page error state
     */
    protected void updateStatus(IStatus status) {
        fModifyListener.updateStatus(status);
    }
}