Question

I am looking for a control that allows users to zoom and scroll at the same time. It basically needs to be something like Sony Sound Forge has, see bottom of this screenshot:

It looks and behaves like a normal scroll bar, with the addition that you can drag the edges to the left and right making the chart zoom in/out. Even if the user would be offered alternative ways to zoom in and scroll (e.g. by dragging an area on the chart itself) I still think such a component is useful because it gives the user a direct visual feedback of the position in the data and the amount of zooming that has been applied.

Does such a component exist or do I need to create it myself? Any help is welcome.

Answer 1

I think that is very specific control and I don’t think that it exists. Also I think it will be faster to create it by yourself, than search for it or even wait when someone answer this question.

To draw custom buttons like in Sound Forge you may use WinAPI function DrawThemeBackground.

I make some short example:

public partial class Form1 : Form
{
    readonly Int32 ScrollBarWidth;
    readonly Int32 ScrollBarHeight;



    public Form1()
    {
        InitializeComponent();

        ScrollBarWidth  = GetSystemMetrics(SM_CYVSCROLL);
        ScrollBarHeight = GetSystemMetrics(SM_CYHSCROLL);
    }



    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        Int32 ZoomMarkerSize = 6;

        Graphics G      = e.Graphics;
        Int32 SBWidth   = ScrollBarWidth;
        Int32 SBHeight  = ScrollBarHeight;

        DrawCustomScrollButton(G, 0, 0, SBWidth, SBHeight, Resources.Plus,
            (int) SCROLLBARSTYLESTATES.SCRBS_NORMAL);
        DrawCustomScrollButton(G, SBWidth, 0, ZoomMarkerSize, SBHeight, null,
            (int) SCROLLBARSTYLESTATES.SCRBS_NORMAL);
        DrawCustomScrollButton(G, SBWidth + ZoomMarkerSize, 0, SBWidth, SBHeight, Resources.Minus,
            (int) SCROLLBARSTYLESTATES.SCRBS_HOT);
    }



    public void DrawCustomScrollButton (Graphics aG, Int32 aX, Int32 aY, Int32 aWidth, Int32 aHeight,
        Image aImage, Int32 aState)
    {
        RECT R = new RECT () { left = aX, top = aY, right = aX + aWidth, bottom = aY + aHeight };
        RECT NotUsed = R;

        IntPtr ThemeHandle  = OpenThemeData(this.Handle, "SCROLLBAR");
        IntPtr HDC          = aG.GetHdc();

        DrawThemeBackground
        (
            ThemeHandle, HDC,
            (int) SCROLLBARPARTS.SBP_THUMBBTNHORZ,
            aState,
            ref R, ref NotUsed
        );

        aG.ReleaseHdc(HDC);
        CloseThemeData(ThemeHandle);

        if (aImage != null)
        {
            aG.DrawImage(aImage,
                aX + ((ScrollBarHeight - aImage.Width   ) / 2),
                aY + ((ScrollBarHeight - aImage.Height  ) / 2));
        }
    }



    public struct RECT
    {
        public Int32 left; 
        public Int32 top; 
        public Int32 right; 
        public Int32 bottom; 
    }

    [DllImport("user32.dll")]
    public static extern int GetSystemMetrics(int smIndex);

    [DllImport("uxtheme.dll", ExactSpelling=true)]
    public extern static Int32 DrawThemeBackground(IntPtr hTheme, IntPtr hdc, int iPartId,
       int iStateId, ref RECT pRect, ref RECT pClipRect);

    [DllImport("uxtheme.dll", ExactSpelling=true, CharSet=CharSet.Unicode)]
    public static extern IntPtr OpenThemeData(IntPtr hWnd, String classList);

    [DllImport("uxtheme.dll", ExactSpelling=true)]
    public extern static Int32 CloseThemeData(IntPtr hTheme);

    public int SM_CYHSCROLL = 3;
    public int SM_CYVSCROLL = 20;

    public int SBP_ARROWBTN = 1;

    public int ABS_UPNORMAL = 1;
    public int ABS_UPHOT = 2;
    public int ABS_UPHOVER = 17;

    public enum ARROWBTNSTATES {
        ABS_UPNORMAL = 1,
        ABS_UPHOT = 2,
        ABS_UPPRESSED = 3,
        ABS_UPDISABLED = 4,
        ABS_DOWNNORMAL = 5,
        ABS_DOWNHOT = 6,
        ABS_DOWNPRESSED = 7,
        ABS_DOWNDISABLED = 8,
        ABS_LEFTNORMAL = 9,
        ABS_LEFTHOT = 10,
        ABS_LEFTPRESSED = 11,
        ABS_LEFTDISABLED = 12,
        ABS_RIGHTNORMAL = 13,
        ABS_RIGHTHOT = 14,
        ABS_RIGHTPRESSED = 15,
        ABS_RIGHTDISABLED = 16,
        ABS_UPHOVER = 17,
        ABS_DOWNHOVER = 18,
        ABS_LEFTHOVER = 19,
        ABS_RIGHTHOVER = 20,
    };

    public enum SCROLLBARSTYLESTATES {
        SCRBS_NORMAL = 1,
        SCRBS_HOT = 2,
        SCRBS_PRESSED = 3,
        SCRBS_DISABLED = 4,
        SCRBS_HOVER = 5,
    };

    public enum SCROLLBARPARTS {
        SBP_ARROWBTN = 1,
        SBP_THUMBBTNHORZ = 2,
        SBP_THUMBBTNVERT = 3,
        SBP_LOWERTRACKHORZ = 4,
        SBP_UPPERTRACKHORZ = 5,
        SBP_LOWERTRACKVERT = 6,
        SBP_UPPERTRACKVERT = 7,
        SBP_GRIPPERHORZ = 8,
        SBP_GRIPPERVERT = 9,
        SBP_SIZEBOX = 10,
    };
}

Here are form source files and two test PNG images for resources:
scrollbar-with-zoom-example.zip

Check MSDN for additional info about this API and PINVOKE.NET site for function signatures.

EDIT

More better solution is to use VisualStyleRenderer class. Sorry for first complicate example. I did not know about that class before. So my DrawCustomScrollButton function should be replaced:

public void DrawCustomScrollButton (Graphics aG, Int32 aX, Int32 aY, Int32 aWidth, Int32 aHeight,
    Image aImage, Int32 aState)
{
    Rectangle R = new Rectangle(aX, aY, aX + aWidth, aY + aHeight);

    VisualStyleRenderer Renderer = new VisualStyleRenderer
    (
        VisualStyleElement.ScrollBar.ThumbButtonHorizontal.Normal
    );

    Renderer.DrawBackground(aG, R);

    if (aImage != null)
    {
        aG.DrawImage(aImage,
            aX + ((ScrollBarHeight - aImage.Width   ) / 2),
            aY + ((ScrollBarHeight - aImage.Height  ) / 2));
    }
}

EDIT 2

Considering your comments, I made new try to recreate this custom control. Main idea was to use standart ScrollBar and put zoom markers above it (two Panel controls). It looks easy at first sight. But to combine these components together was more difficult than I thought.

The main problem is that difficult to alter behavior of system ScrollBar control. I found out that it does not allow to handle some events in windows message queue that I wanted to override. For example MouseUp event and some other.

In the end, I think the only right way is to recreate own copy of ScrollBar control from scratch in which will not have these constraints. Because of that, initially I went the wrong way and unfortunately did not solve your task.

Anyway here my current results (full solution):
scrollbar-with-zoom-3.zip