鼠标悬停折叠/展开字形上的自定义树视图绘制错误

Question

我在绘制所有模式下覆盖树视图的节点绘制事件，如下面的代码。

 Protected Overrides Sub OnDrawNode(ByVal e As System.Windows.Forms.DrawTreeNodeEventArgs)
    Try
        Dim Indent = e.Node.Level * Me.Indent + 32
        Dim font = Me.Font
        'draw selected
        If e.State And TreeNodeStates.Selected Then
            Dim rect As New Rectangle(0, e.Bounds.Location.Y, Me.Width - 1, e.Bounds.Height - 1)
            e.Graphics.FillRectangle(Brushes.AliceBlue, rect)
            e.Graphics.DrawRectangle(Pens.DarkSlateBlue, rect)
        End If


        'draw status icon
        e.Graphics.DrawImage(Me.ImageList.Images(e.Node.ImageIndex), New Point(e.Bounds.X + indent - Me.ImageList.ImageSize.Width + 2, e.Bounds.Y + ((Me.ItemHeight / 2) - (Me.ImageList.ImageSize.Height / 2))))

        'draw collapse glyph
        If e.Node.Nodes.Count > 0 Then
            Dim element As VisualStyleElement
            Dim glyphRect = New Rectangle(e.Bounds.Location.X + 2 + e.Node.Level * Me.Indent, e.Bounds.Location.Y + 8, 16, 16)
            If e.Node.IsExpanded Then
                element = VisualStyleElement.TreeView.Glyph.Opened
            Else
                element = VisualStyleElement.TreeView.Glyph.Closed
            End If

            Dim renderer As New VisualStyleRenderer(element)
            renderer.DrawBackground(e.Graphics, glyphRect)
        End If

        If e.Node.Level.Equals(0) Then
            font = New Font(Me.Font.Name, 12, FontStyle.Regular)
            e.Graphics.DrawString(e.Node.Text, font, Brushes.MidnightBlue, New Point(indent + 5, e.Bounds.Location.Y + 5), New StringFormat())
        ElseIf e.Node.Level.Equals(1) Then
            'action
            Dim params = CType(e.Node, ActionNode).Params

            Dim x = indent + 5
            e.Graphics.DrawString(e.Node.Text, Me.Font, Brushes.Black, New Point(x, e.Bounds.Location.Y + 2), New StringFormat())
            For Each param In params
                e.Graphics.DrawString(param.Key & ":", Me.Font, Brushes.DarkSlateBlue, New Point(x, e.Node.Bounds.Location.Y + 15))
                x += e.Graphics.MeasureString(param.Key & ":", Me.Font).Width - 1
                e.Graphics.DrawString(param.Value, Me.Font, Brushes.SlateGray, New Point(x, e.Node.Bounds.Location.Y + 15))
                x += e.Graphics.MeasureString(param.Value, Me.Font).Width
            Next

        ElseIf e.Node.Level.Equals(2) Then
            'assertion
            Dim params = CType(e.Node, AssertionNode).Params

            Dim x = indent + 5
            e.Graphics.DrawString(e.Node.Text, Me.Font, Brushes.Black, New Point(x, e.Bounds.Location.Y + 2), New StringFormat())
            For Each param In params
                e.Graphics.DrawString(param.Key & ":", Me.Font, Brushes.DarkSlateBlue, New Point(x, e.Node.Bounds.Location.Y + 15))
                x += e.Graphics.MeasureString(param.Key & ":", Me.Font).Width - 1
                e.Graphics.DrawString(param.Value, Me.Font, Brushes.SlateGray, New Point(x, e.Node.Bounds.Location.Y + 15))
                x += e.Graphics.MeasureString(param.Value, Me.Font).Width
            Next
        End If
    Catch ex As Exception

    End Try
End Sub

这完全按照我想要的方式绘制了树视图，但是由于某种原因，当您将鼠标悬停在打开/关闭元素上时，节点似乎被重绘，但在其最后一次重绘的顶部，导致文本看起来粗体，并且任何周围的轮廓图片。但是，这只发生在未选择节点并且如果它被选中则一切都很好的情况下。抱歉，新用户无法发布屏幕转储。

我不确定您是否可以挂钩到鼠标悬停字形事件以使控制无效，甚至检测绘图事件的发送者，但我现在没有想法。

试过了：

• 在绘制节点之前清除绘制时的图形对象
• 设置背景矩形并像选中时一样绘制节点

Answer 1

我只能猜测，因为您无法发布图像，并且您包含的代码不完整（ActioNode？AssertionNode？）。

我知道您提到了清除背景，但您发布的代码并未清除节点区域。试试改成这样，看看能不能用：

Dim rect As New Rectangle(0, e.Bounds.Top, Me.ClientSize.Width - 1, e.Bounds.Height - 1)
If e.State And TreeNodeStates.Selected Then
  e.Graphics.FillRectangle(Brushes.AliceBlue, rect)
  e.Graphics.DrawRectangle(Pens.DarkSlateBlue, rect)
Else
  e.Graphics.FillRectangle(SystemBrushes.Window, rect)
End If

为什么要忽略所有异常？

你还需要处理你的字体。