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发信人: bloom (├┝┞┟┠┢┣�), 信区: VB
标  题: API函数使用手册之 ArcTo(转载)
发信站: 哈工大紫丁香 (2000年09月07日18:35:03 星期四), 转信

【以下文字转载自 cnTemp 讨论区】
【原文由 catchy 所发表】
发信人: espn (小楼一夜听春雨), 信区: VisualBasic
发信站: BBS 水木清华站 (Wed Mar 29 20:35:07 2000)

Declare Function ArcTo Lib "gdi32.dll" (ByVal hdc As Long, ByVal X1 As
Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long, ByVal X3
As Long, ByVal Y3 As Long, ByVal X4 As Long, ByVal Y4 As Long) As Long

Platforms: Win NT

Arc draws an elliptical arc on a graphics-capable device and sets the
current point to the endpoint of the arc. The arc constitutes all or
part of an ellipse. The ellipse is determined by the first set of
(x,y) pairs. The ellipse is the largest possible ellipse which can fit
inside the bounding rectangle determined by those two points. The
third (x,y) pair determines the starting point of the arc. The arc
will start at the point determined by the intersection of the ellipse
and a ray starting at the ellipse's center and passing through (x,y).
The end point of the arc is determined in a similar fashion. The arc
is drawn using the device's currently selected drawing color. The
direction the arc is drawn in is determined by SetArcDirection. The
function returns 1 if successful, or 0 if an error occured.

hdc
The device context of the device to draw the arc on.

X1
The x coordinate of the upper-left point of the ellipse's bounding
rectangle.
Y1
The y coordinate of the upper-left point of the ellipse's bounding
rectangle.
X2
The x coordinate of the lower-right point of the ellipse's bounding
rectangle.
Y2
The y coordinate of the lower-right point of the ellipse's bounding
rectangle.
X3
The x coordinate of the point that determines the arc's starting
point.
Y3
The y coordinate of the point that determines the arc's starting
point.
X4
The x coordinate of the point that determines the arc's ending point.
Y4
The y coordinate of the point that determines the arc's ending point.
Example:

' Draw the arc that forms the top half of an ellipse.  The ellipse
' is centered at (100, 100), has a width of 200, and has a height of
100.  The arc is drawn
' in red on the window Form1.
Dim retval As Long  ' return value

Form1.ForeColor = RGB(255, 0, 0)  ' set the drawing color to red
' Make sure the arc is drawn counterclockwise.
retval = SetArcDirection(Form1.hDC, AD_COUNTERCLOCKWISE)
' The ellipse is determined by the bounding rectangle
(0,50)-(200,150).
' The ray to (200, 100) is due right; the ray to (0, 100) is due left.
retval = ArcTo(Form1.hDC, 0, 50, 200, 150, 200, 100, 0, 100)

--
Standing on the bridge that crosses
The river that goes out to the sea,
The wind is full of a thousand voices
They pass by the bridge and me...

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