为什么在 vb.net 中调整表单顶部或左侧时无边框表单会闪烁？

Question

我看到这段代码可以调整大小和移动我的无边框表单，我将它复制到我的项目中。

这很好我一直在寻找类似的东西，我能看到的都是为 c# 制作的教程。我可以知道使用它是否有缺点吗？还有一件事，当我从顶部或左侧调整它的大小时，表单会闪烁，但如果我从右侧或底部调整它的大小时，它就很好，就像普通表单一样。我不知道可能是什么问题，因为老实说，我不明白下面写的是什么。它似乎使用了一些十六进制值。

我尝试设置表格double buffered = true它不起作用。

Public Class Form2
    Private Const WM_NCHITTEST As Integer = &H84
    Private Const WM_MOUSEMOVE As Integer = &H200
    Private Const WM_LBUTTONDOWN As Integer = &H201
    Private Const WM_LBUTTONUP As Integer = &H202
    Private Const MK_LBUTTON As Integer = &H1
    Private Const HTLEFT As Integer = &HA
    Private Const HTRIGHT As Integer = &HB
    Private Const HTTOP As Integer = &HC
    Private Const HTTOPLEFT As Integer = &HD
    Private Const HTTOPRIGHT As Integer = &HE
    Private Const HTBOTTOM As Integer = &HF
    Private Const HTBOTTOMLEFT As Integer = &H10
    Private Const HTBOTTOMRIGHT As Integer = &H11
    Private OffSet As Point = Point.Empty

    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.FormBorderStyle = FormBorderStyle.None
    End Sub



    Protected Overrides Sub WndProc(ByRef m As Message)
        If m.Msg = WM_NCHITTEST Then
            Dim loc As New Point(m.LParam.ToInt32 And &HFFFF, m.LParam.ToInt32 >> 16)
            loc = PointToClient(loc)
            Dim bTop As Boolean = (loc.Y < ClientRectangle.Y + 4)
            Dim bLeft As Boolean = (loc.X < ClientRectangle.X + 4)
            Dim bRight As Boolean = (loc.X > Width - 4)
            Dim bBottom As Boolean = (loc.Y > Height - 4)
            If bTop And bLeft Then
                m.Result = CType(HTTOPLEFT, IntPtr)
                Return
            ElseIf bTop And bRight Then
                m.Result = CType(HTTOPRIGHT, IntPtr)
                Return
            ElseIf bBottom And bLeft Then
                m.Result = CType(HTBOTTOMLEFT, IntPtr)
                Return
            ElseIf bBottom And bRight Then
                m.Result = CType(HTBOTTOMRIGHT, IntPtr)
                Return
            ElseIf bLeft Then
                m.Result = CType(HTLEFT, IntPtr)
                Return
            ElseIf bTop Then
                m.Result = CType(HTTOP, IntPtr)
                Return
            ElseIf bRight Then
                m.Result = CType(HTRIGHT, IntPtr)
                Return
            ElseIf bBottom Then
                m.Result = CType(HTBOTTOM, IntPtr)
                Return
            End If
        ElseIf m.Msg = WM_LBUTTONDOWN Then
            OffSet = New Point(MousePosition.X - Me.Location.X, MousePosition.Y - Me.Location.Y)
        ElseIf m.Msg = WM_MOUSEMOVE AndAlso m.WParam.ToInt32 = MK_LBUTTON Then
            Me.Location = New Point(MousePosition.X - OffSet.X, MousePosition.Y - OffSet.Y)
        End If
        MyBase.WndProc(m)
    End Sub

End Class

Answer 1

通常，WndProc 是一个应用程序定义的函数，用于处理发送到 window 的消息。在您的示例中，Form2 被认为是无框架 window。在原始无框架 window 中，您不能移动或调整 window 的大小，除非您覆盖其 WndProc 保护函数。在您的示例中，将 m.Msg（指示消息的 ID 号）与不同的操作系统消息（WM_NCHITTEST、WM_LBUTTONDOWN 等）进行比较，以确定应该采取什么操作进行（调整大小，移动，...）。您可以找到系统消息 ID here 的完整列表。关于闪烁问题。老实说，这个问题不会发生在我的系统上。这可能取决于您的操作系统和 windows 版本。

为什么在 vb.net 中调整表单顶部或左侧时无边框表单会闪烁？

why borderless form is flickering when resizing form top or left in vb.net?

.net

vb.net

winforms

visual-studio-2017

borderless