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在VB中建立可旋转的文本特效

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长沙 陈锐

在VB中利用Windows的API函数可以实现很多的VB无法实现的扩展功能,下面的程序介绍的是如何通过调用Windows中的API函数实现文本旋转显示的特级效果。
  首先建立一个工程文件,然后选菜单中的Project | Add Class Module 加入一个新的类文件,并将这个类的Name属性改变为APIFont,然后在类的代码窗口中加入以下的代码:
  Option Explicit
  
  Private Declare Function SelectClipRgn Lib “gdi32”(ByVal hdc As Long, ByVal hRgn As _
  Long) As Long
  Private Declare Function CreateRectRgn Lib “gdi32”(ByVal X1 As Long, ByVal Y1 As _
  Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
  Private Declare Function SetTextColor Lib “gdi32”(ByVal hdc As Long, ByVal crColor As _
  Long) As Long
  Private Declare Function DeleteObject Lib “gdi32”(ByVal hObject As Long) As Long
  Private Declare Function CreateFontIndirect Lib “gdi32” Alias “CreateFontIndirectA” _
  (lpLogFont As LOGFONT) As Long
  Private Declare Function SelectObject Lib “gdi32”(ByVal hdc As Long, ByVal hObject As _
  Long) As Long
  Private Declare Function TextOut Lib “gdi32” Alias “TextOutA” (ByVal hdc As Long, _
  ByVal X As Long, ByVal Y As Long, ByVal lpString As String, ByVal nCount As _
  Long) As Long
  Private Declare Function SetTextAlign Lib “gdi32”(ByVal hdc As Long, ByVal wFlags _
  As Long) As Long
  
  Private Type RECT
   Left As Long
   Top As Long
   Right As Long
   Bottom As Long
  End Type
  
  Private Const TA_LEFT = 0
  Private Const TA_RIGHT = 2
  Private Const TA_CENTER = 6
  Private Const TA_TOP = 0
  Private Const TA_BOTTOM = 8
  Private Const TA_BASELINE = 24
  
  Private Type LOGFONT
   lfHeight As Long
   lfWidth As Long
   lfEscapement As Long
   lfOrientation As Long
   lfWeight As Long
   lfItalic As Byte
   lfUnderline As Byte
   lfStrikeOut As Byte
   lfCharSet As Byte
   lfOutPrecision As Byte
   lfClipPrecision As Byte
   lfQuality As Byte
   lfPitchAndFamily As Byte
   lfFaceName As String * 50
  End Type
  
  Private m_LF As LOGFONT
  Private NewFont As Long
  Private OrgFont As Long
  Public Sub CharPlace(o As Object, txt$, X, Y)
   Dim Throw As Long
   Dim hregion As Long
   Dim R As RECT
  
   R.Left = X
   R.Right = X + o.TextWidth(txt$) * 2
   R.Top = Y
   R.Bottom = Y + o.TextHeight(txt$) * 2
  
   hregion = CreateRectRgn(R.Left, R.Top, R.Right, R.Bottom)
   Throw = SelectClipRgn(o.hdc, hregion)
   Throw = TextOut(o.hdc, X, Y, txt$, Len(txt$))
   DeleteObject (hregion)
  End Sub
  Public Sub SetAlign(o As Object, Top, BaseLine, Bottom, Left, Center, Right)
   Dim Vert As Long
   Dim Horz As Long
  
   If Top = True Then Vert = TA_TOP
   If BaseLine = True Then Vert = TA_BASELINE
   If Bottom = True Then Vert = TA_BOTTOM
   If Left = True Then Horz = TA_LEFT
   If Center = True Then Horz = TA_CENTER
   If Right = True Then Horz = TA_RIGHT
   SetTextAlign o.hdc, Vert Or Horz
  End Sub
  Public Sub setcolor(o As Object, CValue As Long)
   Dim Throw As Long
  
   Throw = SetTextColor(o.hdc, CValue)
  End Sub
  Public Sub SelectOrg(o As Object)
   Dim Throw As Long
  
   NewFont = SelectObject(o.hdc, OrgFont)
   Throw = DeleteObject(NewFont)
  End Sub
  Public Sub SelectFont(o As Object)
   NewFont = CreateFontIndirect(m_LF)
   OrgFont = SelectObject(o.hdc, NewFont)
  End Sub
  Public Sub FontOut(text$, o As Control, XX, YY)
   Dim Throw As Long
  
   Throw = TextOut(o.hdc, XX, YY, text$, Len(text$))
  End Sub
  
  Public Property Get Width() As Long
   Width = m_LF.lfWidth
  End Property
  
  Public Property Let Width(ByVal W As Long)
   m_LF.lfWidth = W
  End Property
  
  Public Property Get Height() As Long
   Height = m_LF.lfHeight
  End Property
  
  Public Property Let Height(ByVal vNewValue As Long)
   m_LF.lfHeight = vNewValue
  End Property
  
  Public Property Get Escapement() As Long
   Escapement = m_LF.lfEscapement
  End Property
  
  Public Property Let Escapement(ByVal vNewValue As Long)
   m_LF.lfEscapement = vNewValue
  End Property
  
  Public Property Get Weight() As Long
   Weight = m_LF.lfWeight
  End Property
  
  Public Property Let Weight(ByVal vNewValue As Long)
   m_LF.lfWeight = vNewValue
  End Property
  
  Public Property Get Italic() As Byte
   Italic = m_LF.lfItalic
  End Property
  
  Public Property Let Italic(ByVal vNewValue As Byte)
   m_LF.lfItalic = vNewValue
  End Property
  
  Public Property Get UnderLine() As Byte
   UnderLine = m_LF.lfUnderline
  End Property
  
  Public Property Let UnderLine(ByVal vNewValue As Byte)
   m_LF.lfUnderline = vNewValue
  End Property
  
  Public Property Get StrikeOut() As Byte
   StrikeOut = m_LF.lfStrikeOut
  End Property
  
  Public Property Let StrikeOut(ByVal vNewValue As Byte)
   m_LF.lfStrikeOut = vNewValue
  End Property
  
  Public Property Get FaceName() As String
   FaceName = m_LF.lfFaceName
  End Property
  
  Public Property Let FaceName(ByVal vNewValue As String)
   m_LF.lfFaceName = vNewValue
  End Property
  
  Private Sub Class_Initialize()
   m_LF.lfHeight = 30
   m_LF.lfWidth = 10
   m_LF.lfEscapement = 0
   m_LF.lfWeight = 400
   m_LF.lfItalic = 0
   m_LF.lfUnderline = 0
   m_LF.lfStrikeOut = 0
   m_LF.lfOutPrecision = 0
   m_LF.lfClipPrecision = 0
   m_LF.lfQuality = 0
   m_LF.lfPitchAndFamily = 0
   m_LF.lfCharSet = 0
   m_LF.lfFaceName = "Arial" + Chr(0)
  End Sub
  在工程文件的Form1中加入一个PictureBox和一个CommandButton控件,然后在Form1的代码窗口中加入以下的代码:
  Option Explicit
  
  Dim AF As APIFont
  Dim X, Y As Integer
  
  Private Sub Command1_Click()
   Dim i As Integer
  
   Set AF = Nothing
   Set AF = New APIFont
   Picture2.Cls
   For i = 0 To 3600 Step 360
   AF.Escapement = i
   AF.SelectFont Picture2
   X = Picture2.ScaleWidth / 2
   Y = Picture2.ScaleHeight / 2
   '在字符串后面要加入7个空格
   AF.FontOut “电脑商情报第42期 ”, Picture2, X, Y
   AF.SelectOrg Picture2
   Next i
  End Sub
  
  Private Sub Form_Load()
   Picture2.ScaleMode = 3
  End Sub
  运行程序,点击Form上的Command1按钮,在窗口的图片框就会出现旋转的文本显示,程序的效果如图所示:
  值得注意的问题是,由于Windows的动态连接库的中英文版本的关系,在一些系统中显示中文可能会有一些问题,大家可能看到,上面程序中的语句:AF.FontOut “脑商情报第42期”,Picture2, X, Y中的字符串后面有7个空格,这是对于“电脑商情报第42期”中的7个中文字符,中文系统计算的是7个字符,但是实际它们占据的是14个字节的空间,所以在输出时要在后面添加7个空格做“替身”。上面的程序在中文Win98,VB6下运行通过。

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