518抽奖软件源码之：GDI+上下左右中对齐

在开发“518抽奖软件”的时候，需要用到GDI+的写文字功能。 GDI+在对齐方面比原来的GDI复杂些，主要是 StringFormat 的参数设置和行高的测定问题，详情参考下面的源码。

GDIPLUS(gdi+)对齐处理的函数源码

 
//单行文本，rc内对齐，align是水平对齐，valign是垂直对齐
//
void Tapp::paint_str(HDC hDc, const WCHAR* str, LOGFONT& lf, COLORREF color, RECT& rc, WORD align, WORD valign)
{
    if (!str) return;
    if (rc.right - rc.left <= 1 || rc.bottom - rc.top <= 1) return;

    StringFormat fmt;
    fmt.SetFormatFlags(StringFormatFlagsNoWrap | StringFormatFlagsNoClip | StringFormatFlagsMeasureTrailingSpaces);

    if (align == ALIGN_NEAR) fmt.SetAlignment(StringAlignmentNear);
    else if (align == ALIGN_CENTER) fmt.SetAlignment(StringAlignmentCenter);
    else fmt.SetAlignment(StringAlignmentFar);
    fmt.SetLineAlignment(StringAlignmentNear);

    RectF rcF;
    rcF.X = rc.left;
    rcF.Y = rc.top;
    rcF.Width = rc.right - rc.left;
    rcF.Height = rc.bottom - rc.top;

    FontFamily ff(lf.lfFaceName);
    Font gfont(hDc, &lf);
    SolidBrush  bru(Color(GetRValue(color), GetGValue(color), GetBValue(color)));
    Graphics g(hDc);

    int style = FontStyleRegular;
    if (lf.lfItalic) style = FontStyleItalic;
    if (lf.lfWeight == FW_BOLD) style = FontStyleBold;
    if (lf.lfItalic && lf.lfWeight == FW_BOLD) style = FontStyleBoldItalic;
    double r = (double)(ff.GetCellAscent(style) + ff.GetCellDescent(style)) / (double)ff.GetLineSpacing(style);

    if (align == ALIGN_NEAR) rcF.Width += 500.0;
    else if (align == ALIGN_FAR) { rcF.X -= 500.0; rcF.Width += 500.0; }
    else { rcF.X -= 500.0; rcF.Width += 1000.0; }

    if (valign == ALIGN_NEAR) rcF.Height += 500.0;
    else if (valign == ALIGN_CENTER) {
        rcF.Y -= 500.0;
        rcF.Height += 1000.0;
        rcF.Y += ((rcF.Height - gfont.GetHeight(&g)*r) / 2.0);
    }
    else {
        rcF.Y -= 500.0;
        rcF.Height += 500.0;
        rcF.Y += (rcF.Height - gfont.GetHeight(&g)*r);
    }

    SetTextRenderingHint(TextRenderingHintAntiAlias);
    g.DrawString(str, -1, &gfont, rcF, &fmt, &bru);
}