Option Explicit

Private Sub Command1_Click()

    ' 循环调用 LineDDA 函数, 在其指定的回调中实现简单动画

    Dim i As Long

    Dim point(9) As POINTAPI

    For i = 0 To UBound(point) - 1

        point(i + 1).X = point(i).X + 50

        If point(i).Y = 0 Then point(i + 1).Y = 50 Else point(i + 1).Y = 0

        LineDDA point(i).X, point(i).Y, point(i + 1).X, point(i + 1).Y, AddressOf LineDDAProc, Me.hdc

    Next i

End Sub

Option Explicit

' API 函数声明

Public Declare Function LineDDA Lib "gdi32.dll" (ByVal n1 As Long, ByVal n2 As Long, ByVal n3 As Long, ByVal n4 As Long, ByVal lpLineDDAProc As Long, ByVal lParam As Long) As Long

Public Declare Function DrawText Lib "user32.dll" Alias "DrawTextA" (ByVal hdc As Long, ByVal lpStr As String, ByVal nCount As Long, lpRect As RECT, ByVal wFormat As Long) As Long

Public Declare Sub Sleep Lib "kernel32.dll" (ByVal dwMilliseconds As Long)

' API 类型声明

Public Type RECT

    Left As Long

    Top As Long

    Right As Long

    Bottom As Long

End Type

Public Type POINTAPI

    X As Long

    Y As Long

End Type

' API 常量声明

Private Const DT_CENTER = &H1

Private Const DT_VCENTER = &H4

' LineDDA 函数的回调函数

' 参数: X, Y 为点坐标, lpData 为自定义参数

Public Sub LineDDAProc(ByVal X As Long, ByVal Y As Long, ByVal lpData As Long)

    Dim rct As RECT

    If X Mod 10 = 0 Then

        rct.Left = X

        rct.Right = rct.Left + 18

        rct.Top = Y

        rct.Bottom = rct.Top + 18

        DrawText lpData, "LPP", -1, rct, DT_CENTER Or DT_VCENTER

        Sleep (100)

        DoEvents

    End If

End Sub