bundles/org.eclipse.ui/Eclipse JFace Text/org/eclipse/jface/text/TextViewerHoverManager.java

package org.eclipse.jface.text;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */

import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;

import org.eclipse.jface.text.AbstractHoverInformationControlManager;
import org.eclipse.jface.text.IInformationControlCreator;

/**
 * This manager controls the layout, content, visibility, etc. of an information
 * control in reaction to mouse hover events issued by the text widget of a
 * text viewer.
 */
class TextViewerHoverManager extends AbstractHoverInformationControlManager {
	
	/** The text viewer */
	private TextViewer fTextViewer;
	
	
	/**
	 * Creates a new text viewer hover manager specific for the given text viewer.
	 * The manager uses the given information control creator.
	 *
	 * @param textViewer the viewer for which the controller is created
	 * @param creator the information control creator
	 */
	public TextViewerHoverManager(TextViewer textViewer, IInformationControlCreator creator) {
		super(creator);
		fTextViewer= textViewer;
	}
	
	/**
	 * @see AbstractHoverInformationControlManager#computeInformation
	 */
	protected void computeInformation() {
		
		Point location= getHoverEventLocation();
		int offset= computeOffsetAtLocation(location.x, location.y);
		if (offset == -1)
			return;
			
		ITextHover hover= fTextViewer.getTextHover(offset);
		if (hover == null)
			return;
			
		IRegion region= hover.getHoverRegion(fTextViewer, offset);
		if (region == null)
			return;
		
		setInformation(hover.getHoverInfo(fTextViewer, region), computeArea(region));
	}
	
	/**
	 * Computes the document offset underlying the given text widget coordinates.
	 * This method uses a linear search as it cannot make any assumption about
	 * how the document is actually presented in the widget. (Covers cases such
	 * as bidi text.)
	 *
	 * @param x the x coordinate inside the text widget
	 * @param y the y coordinate inside the text widget
	 * @return the document offset corresponding to the given point
	 */
	private int computeOffsetAtLocation(int x, int y) {
		
		IDocument document= fTextViewer.getVisibleDocument();
		StyledText styledText= fTextViewer.getTextWidget();
		
		
		int line= (y + styledText.getTopPixel()) / styledText.getLineHeight();
		int lineCount= document.getNumberOfLines();
		
		if (line > lineCount - 1)
			line= lineCount - 1;
		
		if (line < 0)
			line= 0;
		
		try {
			
			IRegion lineInfo= document.getLineInformation(line);
			int low= lineInfo.getOffset();
			int high= low + lineInfo.getLength();
			
			int lookup= styledText.getLocationAtOffset(low).x;
			int guess= low;
			int guessDelta= Math.abs(lookup - x);
			
			for (int i= low + 1; i < high; i++) {
				lookup= styledText.getLocationAtOffset(i).x;
				int delta= Math.abs(lookup - x);
				if (delta < guessDelta) {
					guess= i;
					guessDelta= delta;
				}
			}
			
			return guess + fTextViewer.getVisibleRegionOffset();
		
		} catch (BadLocationException e) {
		}
		
		return -1;
	}
	
	/**
	 * Determines graphical area covered by the given text region.
	 *
	 * @param region the region whose graphical extend must be computed
	 * @return the graphical extend of the given region
	 */
	private Rectangle computeArea(IRegion region) {
				
		StyledText styledText= fTextViewer.getTextWidget();
		
		IRegion visibleRegion= fTextViewer.getVisibleRegion();
		int start= region.getOffset() - visibleRegion.getOffset();
		int end= start + region.getLength();
		if (end > visibleRegion.getLength())
			end= visibleRegion.getLength();
		
		Point upperLeft= styledText.getLocationAtOffset(start);
		Point lowerRight= new Point(upperLeft.x, upperLeft.y);
		
		for (int i= start +1; i < end; i++) {
			
			Point p= styledText.getLocationAtOffset(i);
			
			if (upperLeft.x > p.x)
				upperLeft.x= p.x;
				
			if (upperLeft.y > p.y)
				upperLeft.y= p.y;
				
			if (lowerRight.x  < p.x)
				lowerRight.x= p.x;
				
			if (lowerRight.y < p.y)
				lowerRight.y= p.y;
		}

		lowerRight.x += fTextViewer.getAverageCharWidth();
		lowerRight.y += styledText.getLineHeight();
		
		int width= lowerRight.x - upperLeft.x;
		int height= lowerRight.y - upperLeft.y;
		return new Rectangle(upperLeft.x, upperLeft.y, width, height);
	}
	
	/*
	 * @see AbstractInformationControlManager#showInformationControl(Rectangle)
	 */
	protected void showInformationControl(Rectangle subjectArea) {
		if (fTextViewer != null && fTextViewer.requestWidgetToken(this))
			super.showInformationControl(subjectArea);
	}

	/*
	 * @see AbstractInformationControlManager#hideInformationControl()
	 */
	protected void hideInformationControl() {
		try {
			super.hideInformationControl();
		} finally {
			if (fTextViewer != null)
				fTextViewer.releaseWidgetToken(this);
		}
	}

	/*
	 * @see AbstractInformationControlManager#handleInformationControlDisposed()
	 */
	protected void handleInformationControlDisposed() {
		try {
			super.handleInformationControlDisposed();
		} finally {
			if (fTextViewer != null)
				fTextViewer.releaseWidgetToken(this);
		}
	}
}