VB与API学习笔记（4）消息传递
windows是以消息为基础的。
学一个SendMessage传送消息（命令）的API
Option Explicit
'发送消息命令
'hwnd接收消息的句柄,wMsg消息的编号（类型）
'wParam消息的第一参数
'IParam消息的第二参数，此参数是传址，为了传值，前须加byval
Private Declare Function SendMessage _
Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const WM_SYSCOMMAND = &H112
Private Const SC_MAXIMIZE = &HF030&
Private Const WM_SETTEXT = &HC
Private Const WM_GETTEXT = &HD
Private Sub Command1_Click()
Dim s As String
SendMessage Me.hwnd, WM_SYSCOMMAND, SC_MAXIMIZE, ByVal 0& '最大化
SendMessage Me.hwnd, WM_SETTEXT, 0, ByVal "新的标题" '设置窗体标题
'为返回值做准备
s = String(80, Chr(0))
SendMessage Me.hwnd, WM_GETTEXT, Len(s), ByVal s '返回窗体标题
s = Left$(s, InStr(s, Chr(0)) - 1)
Print s
End Sub
'可以看到第二参数情况：
'传数据0 byval 0&
'字符串常数 byval "新的标题"
'字符串变量 byval s 这是取回返回值时
上面可以看到消息种类有:WM_GETTEXT,WM_SETTEXT,WM_SYSCOMMAND
最后一种还有几个参数：SC_MINIMIZE,SC_RESTORE,SC_CLOSE和窗体的几个状态命令等同
注： WM即：windows message
SC即：system command
一、TEXTBOX
对应VB有的：
事件：
En_Change change
En_KillFocus LostFocus
EN_SetFocus GotFocus
属性：
EM_GetPasswordChar PasswordChar
EM_GetSel SelText,SelStart,SelLength
EM_LimitText MaxLength
EM_ReplaceSel SelText
EM_SetLimitText MaxLength
EM_SetPasswordChar PasswordChar
EM_SetReadOnly Locked
VB中没有的类型：
EM_LineScroll 以行为单位，卷动TextBox
EM_Scroll 以行或页为单位卷动
EM_GetLineCount 计算总行数
EM_GetLine 读取某一行的字符串
EM_LineIndex 读取某一行第一个字母在TextBox中的索引
EM_LineLength 读取某一字母所在行次的“行字符数” （即这一行的字符数）
EM_CharFromPos 读取鼠标所在位置的字符索引
EM_SetSel 设置选择区域
视觉上的滚动如下：
Private Declare Function SendMessage _
Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const EM_LINESCROLL = &HB6
Private Sub Command1_Click() '注意卷动受“视察”限制，最后刚好满足视窗时，不再上卷，同理左右卷。同时加上滚动条，可看出效果。
' SendMessage Text1.hwnd, EM_LINESCROLL, 0, ByVal 9 '下卷3行
' SendMessage Text1.hwnd, EM_LINESCROLL, 0, ByVal -1 '上卷1行
' SendMessage Text1.hwnd, EM_LINESCROLL, 1, ByVal 0 '右卷1行
' SendMessage Text1.hwnd, EM_LINESCROLL, -1, ByVal 0 '左卷1行
SendMessage Text1.hwnd, EM_LINESCROLL, 1, ByVal 1 '同时向下向右卷一行
End Sub
Private Sub Form_Load()
Text1.Text = "第一行.........................." & vbCrLf & _
"第二行.........................." & vbCrLf & _
"第三行.........................." & vbCrLf & _
"第四行.........................." & vbCrLf & _
"第五行.........................." & vbCrLf & _
"第六行.........................." & vbCrLf & _
"第七行.........................." & vbCrLf & _
"第八行.........................." & vbCrLf & _
"第九行.........................." & vbCrLf & _
"第十行.........................." & vbCrLf
End Sub
InStr
注意：第一参数wParam是水平卷动，向下为正，向上为负
第二参数IParam是垂直卷动，向右为正，向左为负。 这两个受视窗限制。到“底”后不会再卷动
另一个卷动类型：EM_Scroll 是以行或页，由wParam具体指出：
wParam: SB_LineUp 向上一行
SB_LineDown 向下。。
SB_PageUp 向上一页
SB_PageDown 向下一页
SB：傻B，傻瓜式的：）
此时IParam无作用，用byval 0&
SentMessage Text1.hwnd,EM_Scroll,SB_PageDown,byval 0& '向下翻一页
获取总行数：EM_GetLineCount
LineCount=SendMessage(text1.hwnd,em_getlineCount,0,byval 0&) '后两参数无作用，用0
读取某行字串：EM_GetLine
Option Explicit
Private Declare Sub RtlMoveMemory _
Lib "kernel32" (Dest As Any, _
Src As Any, _
ByVal Length As Long)
Private Declare Function SendMessage _
Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const EM_LINESCROLL = &HB6
Private Const EM_GETLINECOUNT = &HBA
Private Const EM_LINEINDEX = &HBB
Private Const EM_LINELENGTH = &HC1
Private Const EM_GETLINE = &HC4 '取得某行串，返回值在最后一参数中
Private Sub Command1_Click()
Dim a As Long
a = SendMessage(Text1.hwnd, EM_GETLINECOUNT, 0, ByVal 0&)
Print a '显示11行，为什么？因为最后有一个回车换行，将计算为第11行。注意行索引是从0开始的
End Sub
Private Sub Command2_Click()
Dim s As String
Dim pos As Long
Dim Length As Integer
'先取出该行的长度
pos = SendMessage(Text1.hwnd, EM_LINEINDEX, 3, ByVal 0&) '3行首字母索引
Length = SendMessage(Text1.hwnd, EM_LINELENGTH, pos, ByVal 0&) '该索引所在行的长度
'初始化返回字串
s = String$(Length, Chr(0)) '行串长度初始化
RtlMoveMemory ByVal s, Length, 2 '前两字节指定字串总长，不指定取不出字串
SendMessage Text1.hwnd, EM_GETLINE, 3, ByVal s
Print s '显示第4行，因为行索引是从0开始的。
End Sub
Private Sub Form_Load()
Text1.Text = "第一行..........................1" & vbCrLf & _
"第二行..........................2" & vbCrLf & _
"第三行..........................3" & vbCrLf & _
"第四行..........................4" & vbCrLf & _
"第五行..........................5" & vbCrLf & _
"第六行..........................6" & vbCrLf & _
"第七行..........................7" & vbCrLf & _
"第八行..........................8" & vbCrLf & _
"第九行..........................9" & vbCrLf & _
"第十行..........................10" & vbCrLf
End Sub
读取字符串位置:EM_CharFromPos=&HD7& '在win32api.txt中没有，手动添加
CharPos = SendMessage(txtText1.hwnd, EM_CharFromPos, 0, ByVal pos)
wParam：无用，用0
IParam: Long， 传入相对于TextBox左上角的像素位置，&H11223344,高位两字节是Y坐标，低两字节是X坐标。
即：Y*65536+X. 注意是像素，若为Twip要转换
返回值： Long, &H11223344,高两字节是行数，低两字节是字符位置。CharPos\65536即行，CharPos mod 65536即字符位置。
Private Declare Function SendMessage _
Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
lParam As Any) As Long
Private Const EM_CharFromPos As Long = &HD7&
Private Sub txtText1_MouseDown(Button As Integer, _
Shift As Integer, _
X As Single, _
Y As Single)
Dim pos As Long '传入位置
Dim CharPos As Long '传出位置
pos = Y / Screen.TwipsPerPixelY * 65536 + X / Screen.TwipsPerPixelY
CharPos = SendMessage(txtText1.hwnd, EM_CharFromPos, 0, ByVal pos) '转入，获取行，位置
Print "第" & CharPos \ 65536 & "行" '提取高两字节
Print "第" & CharPos Mod 65536 & "个字符" '提取低两字节
End Sub
再次可以看到，行索引是从0开始，字符位置是从最开始算起的（注意上面因为回车与换行算两个字符，所以位置是9）
获取鼠标所在位置的单词：
思路：
1、取得鼠标的位置
2、从鼠标位置分别向前和向后循环检查分隔符的位置，以确定整个单词的起点和终点。
3、根据起点和终点提取单词。
Private Declare Function SendMessage _
Lib "user32" _
Alias "SendMessageA" (ByVal hwnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
lParam As Any) As Long
Private Const EM_CharFromPos As Long = &HD7&
Private Sub txtText1_MouseDown(Button As Integer, _
Shift As Integer, _
X As Single, _
Y As Single)
Dim pos As Long '传入位置
Dim CharPos As Long '传出位置
Dim i As Integer '字符位置
pos = Y / Screen.TwipsPerPixelY * 65536 + X / Screen.TwipsPerPixelY
CharPos = SendMessage(txtText1.hwnd, EM_CharFromPos, 0, ByVal pos) '转入，获取行，位置
i = CharPos Mod 65536
Print GetWord(txtText1, i)
End Sub
Private Function IsDelimiter(ByVal char As Byte) As Boolean '判断是否是分隔号
Dim s As String
s = Chr(char)
IsDelimiter = False
If s = " " Or s = "." Or s = "?" Or s = vbCr Or s = vbLf Then '分隔符自定
IsDelimiter = True
End If
End Function
Private Function GetWord(txtBox As TextBox, pos As Integer) As String '取得鼠标所在单词
Dim pos1 As Integer, pos2 As Integer
Dim b() As Byte, i As Integer
b = StrConv(txtBox, vbFromUnicode)
pos1 = 0
pos2 = UBound(b)
'分别取得鼠标位置的前后分隔符位置，为下一步取单词作准备
For i = pos To 0 Step -1 '鼠标位置的前一个分隔符位置
If IsDelimiter(b(i)) Then
pos1 = i + 1
Exit For
End If
Next
For i = pos To pos2 '鼠标位置的后一个分隔符位置
If IsDelimiter(b(i)) Then
pos2 = i - 1
Exit For
End If
Next
If pos2 > pos1 Then
ReDim b2(pos2 - pos1) As Byte '变量上下限定义时，用ReDim
For i = pos1 To pos2
b2(i - pos1) = b(i)
Next
GetWord = StrConv(b2, vbUnicode)
Else
GetWord = ""
End If
End Function
看到这个程序不由得再次感叹，为啥要用vbformunicode，因为API是外国用的，不适用中国的双字节字符。为了适合中文（比如上面是
中英文混合字符），就得全转到字节方式，取得单词后，再回到unicode状态。所以上面的pos1,pos2是字节状态的位置，和字符的位置
是不同的。
因此若根据pos1,pos2来用：
text1.selstart=pos1
text1.sellength=pos2-pos1+1
来选择这个单词将会出错。
若要选择这个单词，再次用API: EM_SetSel
sendMessage txt.hwnd,Em_SetSel,pos1,byval cLng(pos2+1)
wParam: 起始位置
Iparam: 终点位置+1
二、listBox,Combo 这个两个的API感到用处不大。略过。