如何改善此矩形的选择和绘制? [英] How to improve the selection and drawing of this rectangle?

问题描述

我需要在应用程序上显示一个区域选择器，以便在屏幕上选择一个矩形区域.

I need to show a region selector on my application to select a rectangle region over the screen.

我已采取并尝试修改自己的需求

I've taken and tried to modify to my needs this code example of Hans Passant, the code selects an area with the mouse and draw a rectangle, it works only on a form and not on the screen ...but that is a problem for later 'cause first what I need is improve the functionality of this selector.

目前只能从左上角到右下角进行矩形选择，我需要一个更灵活的选择来一步一步地绘制所有方向(我的意思是一个可以向右选择的矩形，左，下，上等)

At the moment the rectangle selection can be done only starting from top-left to right-bottom, I need a more flexible selection to draw in all directions in one step (I mean a rectangle that can be able to select to right, left, bottom, up, etc)

我需要的选择灵活性的一个真实示例基本上像 Windows资源管理器选择器那样:

A real example of the selection flexibility that I need is basically like the Windows Explorer selector does:

我应该在代码中进行哪些更改?:

What more changes I should do in my code?:

PS:我也接受使用切割刀的方法来模仿Windows选择矩形的灵活性(也许使用WinAPI吗?).

Public Class Form1

Dim SelectionRectangle As Rectangle

Private Shadows Sub Load() Handles MyBase.Load
    Me.DoubleBuffered = True
End Sub

Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    SelectionRectangle = New Rectangle(e.X, e.Y, 0, 0)
    Me.Invalidate()
End Sub

Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)

    If SelectionRectangle.Width > 0 AndAlso SelectionRectangle.Height > 0 Then

        Dim sb As New System.Text.StringBuilder
        sb.AppendFormat("Selection Location: {0}", SelectionRectangle.Location.ToString)
        sb.AppendLine()
        sb.AppendFormat("Selection Size: {0}", SelectionRectangle.Size.ToString)
        MessageBox.Show(sb.ToString)

    End If

End Sub

Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)

    If e.Button = MouseButtons.Left _
    AndAlso (SelectionRectangle.Right >= SelectionRectangle.X) _
    AndAlso (SelectionRectangle.Bottom >= SelectionRectangle.Y) Then

        SelectionRectangle = New Rectangle(SelectionRectangle.Left,
                                           SelectionRectangle.Top,
                                           e.X - SelectionRectangle.Left,
                                           e.Y - SelectionRectangle.Top)
        Me.Invalidate()

    Else
        SelectionRectangle = New Rectangle(SelectionRectangle.X,
                                           SelectionRectangle.Y,
                                           0, 0)
    End If

End Sub

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

    Using pen As New Pen(Color.Red, 1)
        e.Graphics.DrawRectangle(pen, SelectionRectangle)
    End Using

End Sub

End Class

推荐答案

根据 @Digital_Utopia 注释的解决方案:

这种方式与Windows资源管理器选择器具有相同的灵活性，不同之处在于该矩形未填充颜色，并且在鼠标移开"之后未释放"该矩形，原因不是我所需要的.

This way works with the same flexibility as the windows explorer selector, except that the rectangle is not filled with a color and the rectangle is not 'released' after 'mouse up' 'cause that is not what I need.

Dim SelectionRectangle As Rectangle
Dim InitialPosition As Point

Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    ' Store the starting coordinates
    InitialPosition = e.Location
    SelectionRectangle = New Rectangle(InitialPosition.X, InitialPosition.Y, 0, 0)
    Me.Invalidate()
End Sub

Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)

    ' Me.SuspendLayout()

    If e.Button = MouseButtons.Left Then

        If (e.Location.X < InitialPosition.X) _
        AndAlso (e.Location.Y < InitialPosition.Y) Then ' Top-Left

            SelectionRectangle = New Rectangle(e.X,
                                               e.Y,
                                               InitialPosition.X - e.X,
                                               InitialPosition.Y - e.Y)

        ElseIf (e.Location.X > InitialPosition.X) _
        AndAlso (e.Location.Y < InitialPosition.Y) Then ' Top-Right

            SelectionRectangle = New Rectangle(InitialPosition.X,
                                               e.Y,
                                               e.X - InitialPosition.X,
                                               InitialPosition.Y - e.Y)

        ElseIf (e.Location.X < InitialPosition.X) _
        AndAlso (e.Location.Y > InitialPosition.Y) Then ' Bottom-Left

            SelectionRectangle = New Rectangle(e.X,
                                               InitialPosition.Y,
                                               InitialPosition.X - e.X,
                                               e.Y - InitialPosition.Y)

        ElseIf (e.Location.X > InitialPosition.X) _
        AndAlso (e.Location.Y > InitialPosition.Y) Then ' Bottom-Right

            SelectionRectangle = New Rectangle(InitialPosition.X,
                                               InitialPosition.Y,
                                               e.X - InitialPosition.X,
                                               e.Y - InitialPosition.Y)
        End If

        Me.Invalidate()

    End If

    ' Me.ResumeLayout()

End Sub

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

    Using pen As New Pen(Color.Red, 1)
        e.Graphics.DrawRectangle(pen, SelectionRectangle)
    End Using

End Sub

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