Custom ComboBox with editable text possible?

[Wardo]

Hello, i've been trying to customize the .Net combox and have a good result for DropDownList style of combobox, but i want to be able to write the input of the combobox as in DropDown style. As soon as i change the style, the textbox area stops responding to my OnPaint event.
Is it an impediment from Windows or is there a workaround to have a customized and editable combobox?

This would be my constructor

Public Sub New()

        InitializeComponent()

        Me.SetStyle(ControlStyles.UserPaint _
                Or ControlStyles.AllPaintingInWmPaint _
                Or ControlStyles.Opaque _
                Or ControlStyles.ResizeRedraw, True)
        Me.DrawMode = DrawMode.OwnerDrawFixed

        Me.m_ControlBuffer = New Bitmap(Me.Width, Me.Height)
        Me.m_ControlGraphics = Graphics.FromImage(m_ControlBuffer)
        Me.m_BackBuffer = New Bitmap(Me.Width, Me.Height)
        Me.m_BackGraphics = Graphics.FromImage(m_BackBuffer)

        Dim backcolor As Color = If(Enabled, m_UITheme.TextBoxColor, Color.White)
        BackgroundBrush = New SolidBrush(backcolor)
    End Sub

and this the function i call on my paint method

Public Sub CustomPaint(screenGraphics As Graphics)
        ' If there is body to be drawn.
        If Me.Width > 0 AndAlso Me.Height > 0 Then
            ' Clear the background image graphics 
            If Me.m_backImage Is Nothing Then
                '	Cached Background Image
                Me.m_backImage = New Bitmap(Me.Width, Me.Height)
                Dim backGraphics As Graphics = Graphics.FromImage(Me.m_backImage)
                backGraphics.Clear(Color.Transparent)
                Me.PaintTransparentBackground(backGraphics, Me.ClientRectangle)
            End If

            m_BackGraphics.Clear(Color.Transparent)
            m_BackGraphics.DrawImageUnscaled(Me.m_backImage, 0, 0)

            m_ControlGraphics.Clear(Color.Transparent)
            m_ControlGraphics.SmoothingMode = SmoothingMode.HighQuality

            ' Begin drawing
            Dim path As GraphicsPath = GetBoxBorder()
            m_ControlGraphics.FillPath(BackgroundBrush, path)

            PaintArrowAndLine(m_ControlGraphics)

            ' Draw text
            DrawText(m_ControlGraphics)

            m_ControlGraphics.Flush()

            m_BackGraphics.DrawImage(m_ControlBuffer,
                                         New Rectangle(0, 0,
                                                       m_ControlBuffer.Width,
                                                       m_ControlBuffer.Height),
                                         0, 0,
                                         m_ControlBuffer.Width,
                                         m_ControlBuffer.Height,
                                         GraphicsUnit.Pixel)
            m_BackGraphics.Flush()

            '	Now paint this to the screen
            screenGraphics.DrawImageUnscaled(m_BackBuffer, 0, 0)
        End If
    End Sub

Thanks in advance

[jmcilhinney]

When the DropDowenStyle is set to DropDown, there is actually a Win32 edit control embedded in the .NET control. You'd have to access that to be able to custom draw on that part of the control.

[Wardo]

Can you guide me on how to do that? Is it through the DRAWITEMSTRUCT? https://docs.microsoft.com/en-us/win...drawitemstruct

[jmcilhinney]

I have no idea how it would be done.

[Wardo]

I found that WM_CTLCOLOREDIT could help me, from the docs:

An edit control that is not read-only or disabled sends the WM_CTLCOLOREDIT message to its parent window when the control is about to be drawn. By responding to this message, the parent window can use the specified device context handle to set the text and background colors of the edit control.

How can i accomplish this? I'm searching to do it from the WndProc of my ComboBox, but don't know how to:

If an application processes this message, it must return the handle of a brush. The system uses the brush to paint the background of the edit control.

Just for the sake of of showing code, this is what i've tried in the last couple of minutes since i asked.

<DllImport("gdi32.dll")>
    Public Shared Function CreateSolidBrush(ByVal color As Integer) As IntPtr
    End Function
    Protected Overrides Sub WndProc(ByRef m As Message)
        If (m.Msg = &H133) Then
            Dim brush As IntPtr = CreateSolidBrush(RGB(255, 0, 0))
            m.Result = brush
        End If
        MyBase.WndProc(m)

    End Sub

Any advice?

[.paul.]

I found that WM_CTLCOLOREDIT could help me, from the docs:


How can i accomplish this? I'm searching to do it from the WndProc of my ComboBox, but don't know how to:


Just for the sake of of showing code, this is what i've tried in the last couple of minutes since i asked.

<DllImport("gdi32.dll")>
    Public Shared Function CreateSolidBrush(ByVal color As Integer) As IntPtr
    End Function
    Protected Overrides Sub WndProc(ByRef m As Message)
        If (m.Msg = &H133) Then
            Dim brush As IntPtr = CreateSolidBrush(RGB(255, 0, 0))
            m.Result = brush
        End If
        MyBase.WndProc(m)

    End Sub

Any advice?

Looking at what you've posted, you're calling CreateSolidBrush and returning a pointer to a brush. The docs text you quoted says it can be used to change the edit control (part of the Combo) colors and text. I think it wouldn't be possible to achieve what you're hoping for in that way. You're looking for a usable edit control, and what you've posted isn't that.