import org.eclipse.swt.widgets.ScrollBar;

	 * Container for cached widget infos.

	 * 

	 * @since 3.7

	 */

	static class WidgetInfos {

		/**

		 * the text widget line count

		 */

		int maxLines;

		/**

		 * the height of the vertical scrollbar thumb

		 */

		int thumbHeight;

		/**

		 * the visible lines of the text widget

		 */

		double visibleLines;

		/**

		 * the invisible lines of the text widget

		 */

		double invisibleLines;

		/**

		 * the bounds of {@link OverviewRuler#fCanvas}

		 */

		Rectangle bounds;

		/**

		 * the writable area in the text widget (height of all lines in pixels)

		 */

		int writable;

		/**

		 * Initializes the widget infos.

		 * 

		 * @param textWidget the text widget

		 * @param canvas the overview ruler canvas

		 */

		public WidgetInfos(StyledText textWidget, Canvas canvas) {

			maxLines= textWidget.getLineCount();

			bounds= canvas.getBounds();

			writable= JFaceTextUtil.computeLineHeight(textWidget, 0, maxLines, maxLines);

			ScrollBar verticalBar= textWidget.getVerticalBar();

			thumbHeight= verticalBar != null ? Math.max(Math.min(bounds.height, verticalBar.getThumbBounds().height), 0) : 0;

	        int partialTopIndex= JFaceTextUtil.getPartialTopIndex(textWidget);

	        int topLineHeight= textWidget.getLineHeight(textWidget.getOffsetAtLine(partialTopIndex));

	        int topLinePixel= textWidget.getLinePixel(partialTopIndex);

	        double topIndex= partialTopIndex - (double) topLinePixel / topLineHeight;

	        int partialBottomIndex= JFaceTextUtil.getPartialBottomIndex(textWidget);

	        int bottomLineHeight= textWidget.getLineHeight(textWidget.getOffsetAtLine(partialBottomIndex));

	        int bottomLinePixel= textWidget.getLinePixel(partialBottomIndex);

	        double bottomIndex= partialBottomIndex - ((double) bottomLinePixel - textWidget.getClientArea().height) / bottomLineHeight;

	        visibleLines= bottomIndex - topIndex;

	        invisibleLines= maxLines - visibleLines;

		}

	}

	private static final boolean DEBUG_DRAW= false;

	private static final boolean DEBUG_COMPUTE_Y= false;

	private static final boolean DEBUG_TO_DOCUMENT_LINE_NUMBER= false;

	/**

					if (infos == null) {

						infos= new WidgetInfos(textWidget, fCanvas);

						r.x= INSET;

						r.width= infos.bounds.width - (2 * INSET);

					}

						int startOffset= visible != null ? annotationOffset - visible.getOffset() : widgetRegion.getOffset();

						int startLine= textWidget.getLineAtOffset(startOffset);

						yy= computeY(startLine, infos);

		if (DEBUG_DRAW) {

			// draw debugging guides (boundaries):

			if (infos == null)

				infos= new WidgetInfos(textWidget, fCanvas);

			gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_DARK_MAGENTA));

			yy= infos.thumbHeight / 2;

			gc.drawLine(0, yy, infos.bounds.x/2, yy);

			yy= infos.bounds.height - infos.thumbHeight / 2;

			gc.drawLine(0, yy, infos.bounds.x/2, yy);

			gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_BLUE));

			yy= 0;

			gc.drawLine(0, yy, infos.bounds.x/2, yy);

			yy= infos.bounds.height - 1;

			gc.drawLine(0, yy, infos.bounds.x/2, yy);

		}

	}

	/**

	 * Computes and returns the y location of the given startLine.

	 * 

	 * @param startLine the start line

	 * @param infos the cached widget infos

	 * @return the vertical position of the given startLine in the overview ruler

	 * @since 3.7

	 */

	private int computeY(int startLine, WidgetInfos infos) {

		// this is the inverse of #toLineNumbers(int)

		int yy;

		if (infos.bounds.height > infos.writable || infos.invisibleLines <= 0) { // too few lines for relative positions: align annotations with textWidget lines

			yy = Math.max(0, (2 * startLine + 1) * infos.writable / (infos.maxLines * 2) - infos.bounds.y);

			if (DEBUG_COMPUTE_Y)

				System.out.println("static: " + yy); //$NON-NLS-1$

		} else if (startLine + 1 < infos.visibleLines / 2) { // before middle of first page: map to area from 0 to thumbHeight/2

			yy= (int) (startLine * infos.thumbHeight / infos.visibleLines); // == startLine * (thumbHeight / 2) / (visibleLines / 2);

			if (DEBUG_COMPUTE_Y)

				System.out.println("start:  " + yy); //$NON-NLS-1$

		} else if (infos.maxLines - infos.visibleLines / 2 <= startLine) { // after middle of last page: map to area from canvasHeight-1 - thumbHeight/2 to canvasHeight-1

			yy= (int) (infos.bounds.height-1 - (double)infos.thumbHeight / 2 + (startLine - (infos.maxLines - infos.visibleLines / 2) + 1) * infos.thumbHeight / infos.visibleLines);

			if (DEBUG_COMPUTE_Y)

				System.out.println("end:    " + yy); //$NON-NLS-1$

		} else {

			yy= (int) ((double)infos.thumbHeight/2 + (startLine + 1 - infos.visibleLines / 2) * (infos.bounds.height - infos.thumbHeight) / infos.invisibleLines);

			if (DEBUG_COMPUTE_Y)

				System.out.println("middle: " + yy); //$NON-NLS-1$

		}

		// center of rectangle should be at the calculated position:

		yy-= ANNOTATION_HEIGHT / 2;

		// cap at start/end:

		yy= Math.max(0, Math.min(yy, infos.bounds.height-1 - ANNOTATION_HEIGHT));

		return yy;

		if (y_coordinate < ANNOTATION_HEIGHT && y_coordinate < infos.bounds.y)

			lines[0]= 0;

		if (lines[0] < 0)

			lines[0]= 0;

		if (lines[1] > infos.maxLines)

			lines[1]= infos.maxLines;

		if (DEBUG_TO_DOCUMENT_LINE_NUMBER)

			System.out.println("result: [" + lines[0] + ", " + lines[1] + "]"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$

				/*

				 * Goal: Center of thumb should align with center of line mark in overview ruler. 

				 */

//				//TODO: should move this into the painter in OverviewRuler

//				

//				ScrollBar verticalBar= textWidget.getVerticalBar();

//				double thumbTrackHeight= verticalBar.getThumbTrackBounds().height;

//				double thumbHeight= verticalBar.getThumbBounds().height;

//				double textLineCount= Math.max(1, textWidget.getLineCount());

//				int topIndex= textWidget.getTopIndex();

//				Rectangle clientArea= textWidget.getClientArea();

//				int bottomIndex= textWidget.getLineIndex(clientArea.y + clientArea.height);

//				double visibleLineCount= bottomIndex - topIndex + 1;

//				// (thumbHeight-additionalThumbHeight)/thumbTrackHeight == visibleLineCount/textLineCount:

//				double additionalThumbHeight= Math.max(0, thumbHeight - visibleLineCount/textLineCount*thumbTrackHeight);

//				

//				//TODO:

////				System.out.println(additionalThumbHeight);

////				fOverviewRuler.getControl().setBackground(fOverviewRuler.getControl().getDisplay().getSystemColor(SWT.COLOR_GREEN));

//				

//				int overviewRulerX= clArea.x + clArea.width - overviewRulerWidth - 1;

//				int overviewRulerY= (int)(clArea.y + arrowHeights[0] + additionalThumbHeight/2d);

//				int overviewRulerHeight= (int)(clArea.height - arrowHeights[0] - arrowHeights[1] - additionalThumbHeight - scrollbarHeight);

//				fOverviewRuler.getControl().setBounds(overviewRulerX, overviewRulerY, overviewRulerWidth, overviewRulerHeight);