TextBox模拟拖曳选取文字

　　我们知道Rich text或Word 或VB的程式撰写环境，可以将Mouse移到Select起来的文字按Mouse左键做拖曳移动的功能，後来想，TextBox能不能做呢？这可真的吃了不少苦头，这个程式模拟其做法，但主要的精神是在於对TextBox的了解。

　　首先，TextBox中当选取一段文字之後，我们只要按Mosue，便使Select的区域失效，且可能进入另外的一个Select域，故第一件事是如何在有Select的区域时，使这动作失效的作法是在MouseUp时Check一下有没有选取文字，如果有，就使用SubClass的技术，拦截Mouse的左键，所以当我们按左键时，不会再有选取文字又不见了的情况。

　　第二，我们没有按下Mouse，那如何得知Mouse所在的地方到底是TextBox的哪个字呢，所幸有EM_CHARFROMPOS这个讯息可Send给textBox，其传回值的HiWord 得该字元是在第几行0为base，LowWord是该字元在TextBox中的位置(含换行与LineFeed)，因而我们可以单

　　由MouseMove便得知何时Mouse要是箭号，何时是内定I形的Mouse。当然想得知Mouse所在可以透过Mouse Event的X, Y座标，但是它们是以Twips为单位，而另外也可以用GetCursorPos()来得知Mouse的位置，但这是相对於萤幕者，EMCHARFROMPOS的讯息需要的是相对於TextBox

　　的座标，有许多种方法可以完成这转换，但我选ScreenToClient()这个API，比较直接。

　　第叁，Caret如何隐藏呢？使用HideCaret可完成，但这个Function只能呼叫一次，以便下回 ShowCaret()时可以将Caret Show出来，这是因为呼叫2次的HideCaret时，也要呼叫2次的ShowCaret才能使Caret出现。另设定Caret的SetCaretPos() API只是令Caret出现在什麽地，但如果您KeyIn任何字时，仍出现在原来之地方，而不是方才设定之处，而要用EM_SETSEL的Message才能设定KeyIn的位置是Caret的位置。

　　另有一个取得textbox中第charindex个字元，在textbox中Mouse的位置(textbox的左上角为原点)

　　pos = SendMessage(hwnd, EM_POSFROMCHAR, charindex, 0)

　　my = pos 2 ^ 16 'Y座标

　　mx = pos Mod 2 ^ 16 'X座标

　　这个程式的重点便是上面所写的，其他是苦功

　　'以下在.Bas

　　'注:本程式之所以要用一个变数来存Caret是否被隐藏，原因是：当HideCaret()呼叫N次

　　'便得呼叫N次 ShowCaret()来复原，反之亦然，所以程式中，用一个变数来确认Hide/Show

　　'的动作只做一次

Option ExplicitDeclare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _　(ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As LongDeclare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _　(ByVal hwnd As Long, ByVal nIndex As Long) As LongDeclare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" _　(ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, _　 ByVal wParam As Long, ByVal lParam As Long) As LongPublic Const GWL_WNDPROC = (-4)Public Const WM_MOUSEMOVE = &H200Public Const WM_RBUTTONDOWN = &H204Public Const WM_LBUTTONDOWN = &H201Public Const WM_CUT = &H300Public Const WM_PASTE = &H302Public Const EM_POSFROMCHAR = 214Public Const EM_CHARFROMPOS = 215Public Const EM_SETSEL = &HB1Public Const EM_GETSEL = &HB0Public Const EM_SCROLL = &HB5Public Const EM_LINEFROMCHAR = &HC9Public Const EM_LINEINDEX = &HBBPublic Const EM_LINESCROLL = &HB6Public Const SB_LINEDOWN = 1Public Const SB_LINEUP = 0Type POINTAPI　　　　X As Long　　　　Y As LongEnd TypeType RECT　　　　Left As Long　　　　Top As Long　　　　Right As Long　　　　Bottom As LongEnd TypeDeclare Function GetWindowRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As LongDeclare Function GetClientRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As LongDeclare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As LongDeclare Function HideCaret Lib "user32" (ByVal hwnd As Long) As LongDeclare Function ShowCaret Lib "user32" (ByVal hwnd As Long) As LongDeclare Function SetCaretPos Lib "user32" (ByVal X As Long, ByVal Y As Long) As LongDeclare Function GetCursorPos Lib "user32" (lpPoint As POINTAPI) As LongDeclare Function ScreenToClient Lib "user32" (ByVal hwnd As Long, lpPoint As POINTAPI) As LongPrivate SelEnd As Long '存TextBox Mark起来的起点Private SelST As Long　'存textBix Mark起来的终点Private CaretHide As Boolean '存Caret是否被隐藏Private CanPaste As Boolean '存是否处於可以Paste的状态Public preWinProc As Long'取得Mouse所在的字元在TextBox中的位置Public Function GetCharIndex(ByVal hwnd As Long, Optional CharLineNo As Long) As LongDim mx As Integer, my As IntegerDim wParam As Long, lParam As LongDim i As LongDim pos As Long, pt As POINTAPICall GetCursorPos(pt)　'取得相对Screen的Mouse之位置i = ScreenToClient(hwnd, pt) '将Mouse位置转换成相对於TextBox的位置mx = pt.Xmy = pt.YIf mx  0 Then mx = 0If my  0 Then my = 0lParam = mx + 2 ^ 16 * mywParam = 0i = SendMessage(hwnd, EM_CHARFROMPOS, 0, lParam)If Not IsMissing(CharLineNo) Then　 CharLineNo = i  2 ^ 16 '取得该字元是在第几行,0为baseEnd IfGetCharIndex = i Mod 2 ^ 16 '传回该字元是在textBox中的第几个字,0为baseEnd FunctionPublic Sub SetCaretPosition(ByVal hwnd As Long)　 Dim mx As Long, my As Long, pos As Long　 Dim charindex As Long　 Dim pt As POINTAPI, i As Long　 Dim rect5 As RECT, rect6 As RECT　 charindex = GetCharIndex(hwnd)　 '取得textbox中第charindex个字元，在textbox中Mouse的位置(textbox的左上角为点　 pos = SendMessage(hwnd, EM_POSFROMCHAR, charindex, 0)　 my = pos  2 ^ 16　 mx = pos Mod 2 ^ 16　 '设定Caret出现的位置，但只是显示的位置，实际keyin进去的字出现的地方没因而更动　 Call SetCaretPos(mx, my)　 '取得Mouse所在之座标(Screen左上角为原点)　 Call GetCursorPos(pt)　 '取得TextBox的萤幕座标(Screen左上角为原点)　 Call GetWindowRect(hwnd, rect6)　 '取得TextBox可keyin字的区域大小(textBox左上角为原点)　 Call GetClientRect(hwnd, rect5)　 '取得textbox Client区域相对Screen的座标　 rect5.Left = rect6.Left　 rect5.Right = rect5.Right + rect6.Left　 rect5.Top = rect6.Top　 rect5.Bottom = rect5.Bottom + rect6.Top　 'Mouse移到四个边时，自动scroll，就算不必Scroll时也可呼叫，只是不会有作用　 If pt.Y = rect5.Top + 3 Then　　　i = SendMessage(hwnd, EM_SCROLL, SB_LINEUP, 0)　 End If　 If pt.Y = rect5.Bottom - 3 Then　　　Call SendMessage(hwnd, EM_SCROLL, SB_LINEDOWN, 0)　 End If　 If pt.X = rect5.Left + 3 Then　　　 i = SendMessage(hwnd, EM_LINESCROLL, -1, 0)　 End If　 If pt.X = rect5.Right - 3 Then　　　 Call SendMessage(hwnd, EM_LINESCROLL, 1, 0)　 End IfEnd Sub'设定Mouse的形状Public Sub SetMouseShap(hwnd As Long, ByVal Button As Integer)Dim charindex As LongDim i As LongIf preWinProc  0 Then　 If Button = 1 Then　　　Screen.ActiveControl.MousePointer = 99　　　Screen.ActiveControl.MouseIcon = LoadPicture("dragmove.cur")　　　'请自行设定dragmove.cur的位置　　　Call SetCaretPosition(hwnd)　　　Exit Sub　 End If　charindex = GetCharIndex(hwnd)　'设定Mouse移过mark的区块时，Mouse变箭号　If charindex = SelST And charindex = SelEnd Then　　 If Button = 0 Then　　　　Screen.ActiveControl.MousePointer = 1　　 End If　Else　　 Screen.ActiveControl.MousePointer = 0　End IfEnd IfEnd SubPublic Function wndproc(ByVal hwnd As Long, ByVal Msg As Long, _　　　　　　　　　　　　 ByVal wParam As Long, ByVal lParam As Long) As Long

　　'以下程式会截取mouse move，处理完後，再将之送往原来的Window Procedure

Dim charindex As LongDim i As LongIf Msg = WM_LBUTTONDOWN Then　　If CaretHide Then　　　 Call ShowCaret(hwnd)　　　 CaretHide = False　　End If　　If SelEnd - SelST  0 Then　　　 charindex = GetCharIndex(hwnd)　　　 If charindex = SelST And charindex = SelEnd Then　　　　　Call SetCaretPosition(hwnd)　　　　　Screen.ActiveControl.MousePointer = 99　　　　　Screen.ActiveControl.MouseIcon = LoadPicture("c:tmp2dragmove.cur")　　　　　CanPaste = True　　　　　Exit Function　　　 End If　　End IfEnd Ifwndproc = CallWindowProc(preWinProc, hwnd, Msg, wParam, lParam)End FunctionPublic Sub MoveText(ByVal hwnd As Long, CanFree As Boolean)Dim i As Long, sellen As Long, charindex As Longsellen = SelEnd - SelST'如果Caret落在mark起来之处则不处理charindex = GetCharIndex(hwnd)If charindex = SelST And charindex = SelEnd Then　 CanFree = False　 Exit SubEnd IfCall SendMessage(hwnd, WM_CUT, 0, 0) '将Mark起来的地方Cut掉Dim setpos As LongIf charindex  SelST Then　 setpos = charindexElse　 If charindex  SelEnd Then setpos = charindex - sellenEnd If'设定Caret新位置，此时Keyin进去的字才真的会在此位置出现，使用SetCaretPos()则不行Call SendMessage(hwnd, EM_SETSEL, setpos, setpos)Call SendMessage(hwnd, WM_PASTE, 0, 0)End SubPublic Sub SetHook(ByVal hwnd As Long, ByVal Button As Integer)Dim ret As LongDim i As LongDim charindex As LongIf Button = 1 Then　　If Screen.ActiveControl.SelLength  0 Then　　　 If preWinProc = 0 Then　　　　　'记录原本的Window Procedure的位址　　　　　preWinProc = GetWindowLong(hwnd, GWL_WNDPROC)　　　　　ret = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf wndproc)　　　　　Call HideCaret(hwnd)　　　　　CaretHide = True　　　　　CanPaste = False　　　　　'取得Mark起来的区域之Start, End之Index，之所以不用Text.SelStart　　　　　'与Text.SelLength来做的原因是：vb对之的度量是字元为单位，但API　　　　　'的其他呼叫都以Byte为单位，我如此做，省得中间的转换　　　　　i = SendMessage(hwnd, EM_GETSEL, 0, 0)　　　　　SelEnd = i  2 ^ 16　　　　　SelST = i Mod 2 ^ 16　　　 Else　　　　Dim CanFree As Boolean　　　　CanFree = True　　　　If CanPaste Then　　　　　 Call MoveText(hwnd, CanFree)　　　　End If　　　　If CanFree Then Call FreeHook(hwnd)　　　 End If　　Else　　　 If preWinProc  0 Then　　　　　Call FreeHook(hwnd)　　　 End If　　End IfEnd IfEnd SubPublic Sub FreeHook(ByVal hwnd As Long)Dim ret As LongIf preWinProc  0 Then　 ret = SetWindowLong(hwnd, GWL_WNDPROC, preWinProc)End IfpreWinProc = 0Screen.ActiveControl.MousePointer = 0If CaretHide Then　 Call ShowCaret(hwnd)　 CaretHide = FalseEnd IfEnd SubPublic Sub GetCaretPos(ByVal hwnd5 As Long, lineno As Long, colno As Long)Dim i As Long, j As LongDim lParam As Long, wParam As LongDim k As Longi = SendMessage(hwnd5, EM_GETSEL, wParam, lParam)j = i / 2 ^ 16　'取得目前Caret所在前面有多少个bytelineno = SendMessage(hwnd5, EM_LINEFROMCHAR, j, 0) '取得前面有多少行lineno = lineno + 1k = SendMessage(hwnd5, EM_LINEINDEX, -1, 0)'取得目前caret所在行前面有多少个bytecolno = j - k + 1End Sub'以下在FormPrivate Sub Text1_LostFocus()Call FreeHook(Text1.hwnd)End SubPrivate Sub Text1_KeyDown(KeyCode As Integer, Shift As Integer)Call FreeHook(Text1.hwnd)End SubPrivate Sub Text1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)　Call SetMouseShap(Text1.hwnd, Button)End SubPrivate Sub Text1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)　Call SetHook(Text1.hwnd, Button)End Sub