NS_IMETHODIMP
nsCanvasRenderingContext2D::SetTextStyle(const nsAString& style)
{
    if (style.IsEmpty())
        return NS_ERROR_INVALID_ARG;

    nsAutoString fontStr(NS_LITERAL_STRING("font: "));
    fontStr.Append(style);

    nsresult rv;

    nsCOMPtr<nsICSSStyleRule> styleRule;
    rv = mCSSParser->ParseStyleAttribute(fontStr,
                                         nsnull,
                                         nsnull,
                                         getter_AddRefs(styleRule));
    if (NS_FAILED(rv))
        return rv;

    nsCSSDeclaration *decl = styleRule->GetDeclaration();
    if (!decl)
        return NS_ERROR_FAILURE;

    nsRuleData rule(eStyleStruct_Font, nsnull, nsnull);
    nsAutoPtr<nsRuleDataFont> fontData(new nsRuleDataFont);

    rule.mFontData = fontData;
    rv = decl->MapRuleInfoInto(&rule);
    if (NS_FAILED(rv))
        return rv;

    nsAutoString fontFamily;
    float size = 12.0;
    if (rule.mFontData->mFamily.GetUnit() != eCSSUnit_Null)
        rule.mFontData->mFamily.GetStringValue(fontFamily);

    if (rule.mFontData->mSize.GetUnit() != eCSSUnit_Null)
        size = rule.mFontData->mSize.GetFloatValue();

    rule.mFontData = nsnull;

...