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Arc

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說明：
Arc 函式會在指定的裝置環境代碼(Device Context)上繪製弧線

引用函式庫：
GDI32

適用系統：
Windows NT 3.1 或 Windows 95以上

函式原型：

Declare Function Arc Lib "gdi32" Alias "Arc" ( _
    ByVal hdc As Long, _
    ByVal nLeftRect As Long, _
    ByVal nTopRect As Long, _
    ByVal nRightRect As Long, _
    ByVal nBottomRect As Long, _
    ByVal nXStartArc As Long, _
    ByVal nYStartArc As Long, _
    ByVal nXEndtArc As Long, _
    ByVal nYEndtArc As Long _
    ) As Long



參數型態及說明：
hdc：Long 要繪製弧形的裝置環境代碼(Device Context)
nLeftRect：Long 弧線形的左上方 X 座標
nTopRect：Long 弧線的左上方 Y 座標
nRightRect：Long 弧線的右下方 X 座標
nBottomRect：Long 弧線的右下方 Y 座標
nXStartArc：Long 弧線起始點的 X 座標
nYStartArc：Long 弧線起始點的 Y 座標
nXEndArc：Long 弧線終點的 X 座標
nYEndArc：Long 弧線終點的 Y 座標

回傳值：
Long 繪製成功的話，將會回傳非零的數值；若繪製失敗的話，則回傳 0

.NET Framework API：
System.Drawing.Graphics.DrawArc

VB範例：

檢視原始碼 Visual Basic
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'VB的宣告
Private Declare Function Arc Lib "gdi32" ( _
	ByVal hdc As Long, _
	ByVal nLeftRect As Long, _
	ByVal nTopRect As Long, _
	ByVal nRightRect As Long, _
	ByVal nBottomRect As Long, _
	ByVal nXStartArc As Long, _
	ByVal nYStartArc As Long, _
	ByVal nXEndArc As Long, _
	ByVal nYEndArc As Long _
	) As Long
Private Declare Function ReleaseDC Lib "user32" ( _
	ByVal hwnd As Long, _
	ByVal hdc As Long _
	) As Long
Private Declare Function GetDC Lib "user32" ( _
	ByVal hwnd As Long _
	) As Long
 
Dim hdc As Long
 
'取得目前執行視窗的裝置環境代碼(Device Context)
hdc = GetDC(Form1.hwnd)
 
Dim rtvl As Long
 
'在目前執行視窗上的(50, 50)至(200, 200)畫一個弧線
rtvl = Arc(hdc, 50, 50, 200, 200, 100, 75, 180, 180)
 
Dim r As Long
 
'釋放目前執行視窗的裝置環境代碼(Device Context)
r = ReleaseDC(Form1.hwnd, hdc)

RB範例：

檢視原始碼 REALBasic
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'RB的宣告
Declare Function Arc Lib "gdi32" ( _
	hdc As Integer, _
	nLeftRect As Integer, _
	nTopRect As Integer, _
	nRightRect As Integer, _
	nBottomRect As Integer, _
	nXStartArc As Integer, _
	nYStartArc As Integer, _
	nXEndArc As Integer, _
	nYEndArc As Integer _
	) As Boolean
Declare Function ReleaseDC Lib "user32" ( _
	hwnd As Integer, _
	hdc As Integer _
	) As Integer
Declare Function GetDC Lib "user32" ( _
	hwnd As Integer _
	) As Integer
 
Dim hdc As Integer
 
'取得目前執行視窗的裝置環境代碼(Device Context)
hdc = GetDC(Window1.WinHWND)
 
Dim rtvl As Boolean
 
'在目前執行視窗上的(0, 0)畫一個長高為100的矩形
rtvl = Arc(hdc, 50, 50, 200, 200, 100, 75, 180, 180)
 
Dim r As Integer
 
'釋放目前執行視窗的裝置環境代碼(Device Context)
r = ReleaseDC(Window1.WinHWND, hdc)

VB.NET範例：

檢視原始碼 VB.NET
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'VB.NET的宣告
<DllImport("gdi32.dll")> _
Shared Function Arc( _
	ByVal hdc As IntPtr, _
	ByVal nLeftRect As UInteger, _
	ByVal nTopRect As UInteger, _
	ByVal nRightRect As UInteger, _
	ByVal nBottomRect As UInteger, _
	ByVal nXStartArc As UInteger, _
	ByVal nYStartArc As UInteger, _
	ByVal nXEndArc As UInteger, _
	ByVal nYEndArc As UInteger _
	) As Boolean
End Function
<DllImport("user32.dll")> _
Shared Function ReleaseDC( _
	ByVal hwnd As IntPtr, _
	ByVal hdc As IntPtr _
	) As UInteger
End Function
<DllImport("user32.dll")> _
Shared Function GetDC( _
	ByVal hwnd As IntPtr _
	) As IntPtr
End Function
 
Dim hdc As IntPtr
 
'取得目前執行視窗的裝置環境代碼(Device Context)
hdc = GetDC(Me.Handle)
 
Dim rtvl As Boolean
 
'在目前執行視窗上的(50, 50)至(200, 200)畫一個弧線
rtvl = Arc(hdc, 50, 50, 200, 200, 100, 75, 180, 180)
 
Dim r As Integer
 
'釋放目前執行視窗的裝置環境代碼(Device Context)
r = ReleaseDC(Me.Handle, hdc)

C#範例：

檢視原始碼 C#
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//C#的宣告
[DllImport("gdi32")]
public static extern bool Arc(
	IntPtr hdc, 
	uint nLeftRect, 
	uint nTopRect, 
	uint nRightRect, 
	uint nBottomRect, 
	uint nXStartArc, 
	uint nYStartArc, 
	uint nXEndArc, 
	uint nYEndArc
	);
[DllImport("user32")]
public static extern uint ReleaseDC(
	IntPtr hwnd, 
	IntPtr hdc
	);
[DllImport("user32")]
public static extern IntPtr GetDC(
	IntPtr hwnd
	);
 
IntPtr hdc;
 
//取得目前執行視窗的裝置環境代碼(Device Context)
hdc = GetDC(this.Handle);
 
bool rtvl;
 
//在目前執行視窗上的(50, 50)至(200, 200)畫一個弧線
rtvl = Arc(hdc, 50, 50, 200, 200, 100, 75, 180, 180);
 
uint r;
 
//釋放目前執行視窗的裝置環境代碼(Device Context)
r = ReleaseDC(this.Handle, hdc);

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