Exact reason is POI uses TextLayout to find the width, for which,
layout.getBounds().getWidth() return same value for "A", " A", "A ".

layout = new TextLayout("A", font, frc);   "A" width = 0.26875
layout = new TextLayout(" A", font, frc);  " A" width = 0.26875
layout = new TextLayout("A ", font, frc);  "A " width = 0.26875
layout = new TextLayout("AA", font, frc);  "AA" width = 0.535546875

Created attachment 23539 [details]
sample output which does not exhibit the problem

Created attachment 23540 [details]
screenshot from Excel 2007 - row3 is resized correctly

Works fine to me. See attached output and a screenshot. 

Try the latest trunk. Daily builds can be downloaded from http://encore.torchbox.com/poi-svn-build/

Yegor

I have tried with poi-3.5-beta6-20090424.jar and still able to reproduce the issue.
May I know which version of java you are using. I tried with java 1.5.

java version "1.5.0_16"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_16-b02)
Java HotSpot(TM) Client VM (build 1.5.0_16-b02, mixed mode, sharing)

Muhammed

Looks like working fine with java 1.6.

java version "1.6.0_04"
Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)

Any chance to get a fix for POI 3.2, where we are using it with java 1.4.2

Thanks
Muhammed

(In reply to comment #6)
> Looks like working fine with java 1.6.
> 
> java version "1.6.0_04"
> Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
> Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)
> 
> Any chance to get a fix for POI 3.2, where we are using it with java 1.4.2
> 
> Thanks
> Muhammed

(In reply to comment #6)
> Looks like working fine with java 1.6.
> 
> java version "1.6.0_04"
> Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
> Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)
> 
> Any chance to get a fix for POI 3.2, where we are using it with java 1.4.2
> 
> Thanks
> Muhammed

It might be a jdkspecific bug,  your  code works with java 1.5.13 and java 1.6.13. Try a different version of Java. I don't think there will be a special fix for JDK 1.5.0_16.

Yegor

I have a workaround for this. If I replace all whitespaces with some character(say ‘I’ – the one which take least width), autoSize seems to be working fine. 

For those who uses jdk 1.4 & 1.5, is it possible to provide a patch like this?

See the line below -  txt = txt.replaceAll(" ", "i");

    public void autoSizeColumn(short column, boolean useMergedCells) {
        AttributedString str;
        TextLayout layout;
        /**
         * Excel measures columns in units of 1/256th of a character width
         * but the docs say nothing about what particular character is used.
         * '0' looks to be a good choice.
         */
        char defaultChar = '0';
       
        /**
         * This is the multiple that the font height is scaled by when determining the
         * boundary of rotated text.
         */
        double fontHeightMultiple = 2.0;
       
        FontRenderContext frc = new FontRenderContext(null, true, true);

        HSSFWorkbook wb = new HSSFWorkbook(book);
        HSSFFont defaultFont = wb.getFontAt((short) 0);

        str = new AttributedString("" + defaultChar);
        copyAttributes(defaultFont, str, 0, 1);
        layout = new TextLayout(str.getIterator(), frc);
        int defaultCharWidth = (int)layout.getAdvance();

        double width = -1;
        rows:
        for (Iterator it = rowIterator(); it.hasNext();) {
            HSSFRow row = (HSSFRow) it.next();
            HSSFCell cell = row.getCell(column);

            if (cell == null) {
                continue;
            }
            int colspan = 1;
            for (int i = 0 ; i < getNumMergedRegions(); i++) {
                CellRangeAddress region = getMergedRegion(i);
                if (containsCell(region, row.getRowNum(), column)) {
                                                                                                    if (!useMergedCells) {
                                                                                                                        // If we're not using merged cells, skip this one and move on to the next. 
                        continue rows;
                    }
                                                                                cell = row.getCell(region.getFirstColumn());
                    colspan = 1 + region.getLastColumn() - region.getFirstColumn();
                                                                                
                }
            }

            HSSFCellStyle style = cell.getCellStyle();
            HSSFFont font = wb.getFontAt(style.getFontIndex());

            if (cell.getCellType() == HSSFCell.CELL_TYPE_STRING) {
                HSSFRichTextString rt = cell.getRichStringCellValue();
                String[] lines = rt.getString().split("\\n");
                for (int i = 0; i < lines.length; i++) {
                    String txt = lines[i] + defaultChar;
                txt = txt.replaceAll(" ", "i");
                    ...
                    ...

I'm closing it as "wontfix". 
The issue with leading white spaces is JDK-specific. Users of JDK 1.5.0_16 are advised to upgrade to a newer version. 

Yegor