Package org.guvnor.m2repo.client.widgets

Source Code of org.guvnor.m2repo.client.widgets.ResizableHeader$HeaderCell

package org.guvnor.m2repo.client.widgets;

import com.google.gwt.cell.client.AbstractCell;
import com.google.gwt.cell.client.Cell;
import com.google.gwt.cell.client.Cell.Context;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.dom.client.Style.Cursor;
import com.google.gwt.dom.client.Style.Position;
import com.google.gwt.dom.client.Style.Unit;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.safehtml.shared.SafeHtmlUtils;
import com.google.gwt.user.cellview.client.AbstractCellTable;
import com.google.gwt.user.cellview.client.Column;
import com.google.gwt.user.cellview.client.Header;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Event.NativePreviewEvent;
import com.google.gwt.user.client.Event.NativePreviewHandler;

public class ResizableHeader<T> extends Header<String> {

    private Column<T, ?> column = null;
    private AbstractCellTable<T> cellTable;
    private String title = "";
    private static final int width = 20;

    public ResizableHeader( String title,
                            AbstractCellTable<T> cellTable,
                            Column<T, ?> column ) {
        super( new HeaderCell() );
        this.title = title;
        this.cellTable = cellTable;
        this.column = column;
    }

    @Override
    public String getValue() {
        return title;
    }

    @Override
    public void onBrowserEvent( Context context,
                                Element target,
                                NativeEvent event ) {
        String eventType = event.getType();
        if ( eventType.equals( "mousemove" ) ) {
            new ColumnResizeHelper<T>( cellTable, column, target );
        } else {
            return;
        }
    }

    private void setCursor( Element element,
                            Cursor cursor ) {
        element.getStyle().setCursor( cursor );
    }

    class ColumnResizeHelper<E> implements NativePreviewHandler {

        private HandlerRegistration handler;
        private AbstractCellTable<E> table;
        private Column<E, ?> col;
        private Element el;
        private boolean mousedown;
        private Element measuringElement;

        public ColumnResizeHelper( AbstractCellTable<E> table,
                                   Column<E, ?> col,
                                   Element el ) {
            this.el = el;
            this.table = table;
            this.col = col;
            handler = Event.addNativePreviewHandler( this );
        }

        @SuppressWarnings("unchecked")
        @Override
        public void onPreviewNativeEvent( NativePreviewEvent event ) {
            NativeEvent nativeEvent = event.getNativeEvent();
            nativeEvent.preventDefault();
            nativeEvent.stopPropagation();

            String eventType = nativeEvent.getType();
            int clientX = nativeEvent.getClientX();
            if ( eventType.equals( "mousemove" ) && mousedown ) {
                int absoluteLeft = el.getAbsoluteLeft();
                int newWidth = clientX - absoluteLeft;
                newWidth = newWidth < width ? width : newWidth;
                table.setColumnWidth( col, newWidth + "px" );
                return;
            }

            if ( eventType.equals( "mousemove" ) || eventType.equals( "mousedown" ) ) {
                Element eventTargetEl = nativeEvent.getEventTarget().cast();
                int absoluteLeft = eventTargetEl.getAbsoluteLeft();
                int offsetWidth = eventTargetEl.getOffsetWidth();
                if ( clientX > absoluteLeft + offsetWidth - width ) {
                    if ( eventType.equals( "mousedown" ) ) {
                        mousedown = true;
                    } else {
                        setCursor( el, Cursor.COL_RESIZE );
                    }
                } else {
                    removeHandler();
                    return;
                }
            } else if ( eventType.equals( "mouseup" ) ) {
                mousedown = false;
            } else if ( eventType.equals( "mouseout" ) && !mousedown ) {
                removeHandler();
                return;
            }

            if ( eventType.equals( "dblclick" ) ) {
                // Get column
                nativeEvent.preventDefault();
                nativeEvent.stopPropagation();
                double max = 0;
                startMeasuring();
                for ( E t : table.getVisibleItems() ) {
                    Object value = col.getValue( t );
                    SafeHtmlBuilder sb = new SafeHtmlBuilder();
                    Cell<Object> cell = (Cell<Object>) col.getCell();
                    cell.render( null, value, sb );
                    max = Math.max( measureText( sb.toSafeHtml().asString() ), max );
                }
                finishMeasuring();
                table.setColumnWidth( col, ( max + width ) + "px" );
                removeHandler();
            }
        }

        private void removeHandler() {
            handler.removeHandler();
            setCursor( el, Cursor.DEFAULT );
        }

        private void startMeasuring() {
            Document document = Document.get();
            measuringElement = document.createElement( "div" );
            measuringElement.getStyle().setPosition( Position.ABSOLUTE );
            measuringElement.getStyle().setLeft( -1000, Unit.PX );
            measuringElement.getStyle().setTop( -1000, Unit.PX );
            document.getBody().appendChild( measuringElement );
        }

        private double measureText( String text ) {
            measuringElement.setInnerHTML( text );
            return measuringElement.getOffsetWidth();
        }

        private void finishMeasuring() {
            Document.get().getBody().removeChild( measuringElement );
        }
    }

    static class HeaderCell extends AbstractCell<String> {

        public HeaderCell() {
            super( "click", "mousedown", "mousemove", "dblclick" );
        }

        @Override
        public void render( Context context,
                            String value,
                            SafeHtmlBuilder sb ) {
            sb.append( SafeHtmlUtils.fromString( value ) );
        }

    }

}
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