ContextMenuStrip scroll up or down button

Question

I am currently working on a windows touch application. Some winForm code remains. As you can see the height of the scroll/arrow buttons height is really too small for a touch button. Is there a way to increase the height to 35/40pixels?

The following link is a VS2012 c# example project download page. download example here

Thank you.

Answer 1

This solution enumerates the child windows of the ContextMenuStrip. It might happen that there are two child windows (scroll buttons) or zero child windows.

The control used for the scroll buttons is a label, and the default uses a small 9x5 image. The image is updated to a larger image (using the Marlett font), and then AutoSize is set to true which causes the label to resize itself.

Edit: changed implementation to an extension method for better flexibility

using System;
using System.Collections;
using System.Collections.Generic;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Opulos.Core.UI {

///<summary>Extension class to increase the size of the scroll up-down arrows on a drop down context menu or tool strip menu. The default up-down arrows are only 5 pixels high.</summary>
public static class ToolStripEx {

    private static Hashtable htData = new Hashtable();

    private class Data {
        public bool needsUpdate = true;
        public bool disposeLastImage = false;
        public ToolStrip toolStrip = null;
        public List<Image> currentImages = new List<Image>();
    }

    public static void BigButtons(this ToolStrip toolStrip) {
        htData[toolStrip] = new Data() { toolStrip = toolStrip };
        toolStrip.VisibleChanged += toolStrip_VisibleChanged;
        toolStrip.ForeColorChanged += toolStrip_ForeColorChanged;
        toolStrip.Disposed += toolStrip_Disposed;
    }

    static void toolStrip_Disposed(object sender, EventArgs e) {
        Data d = (Data) htData[sender];
        if (d != null && d.currentImages != null) {
            foreach (var img in d.currentImages)
                img.Dispose();
            d.currentImages = null;
            htData.Remove(sender);
        }
    }

    static void toolStrip_ForeColorChanged(object sender, EventArgs e) {
        Data d = (Data) htData[sender];
        d.needsUpdate = true;
        UpdateImages(d);
    }

    static void toolStrip_VisibleChanged(object sender, EventArgs e) {
        Data d = (Data) htData[sender];
        UpdateImages(d);
    }

    private static void UpdateImages(Data d) {
        if (!d.needsUpdate)
            return;

        d.toolStrip.BeginInvoke((Action) delegate {
            try {
                var list = GetChildWindows(d.toolStrip.Handle);
                if (list.Count == 0)
                    return;

                List<Image> newImages = new List<Image>();
                int k = 0;

                foreach (var i in list) {
                    var c = Control.FromHandle(i) as Label;
                    if (c != null && d.needsUpdate) {
                        String glyph = (k == 0 ? "t" : "u");
                        using (Font f = new System.Drawing.Font("Marlett", 20f)) {
                            Size s = TextRenderer.MeasureText("t", f);
                            var oldImage = c.Image;
                            c.Image = new Bitmap(s.Width, s.Height);
                            newImages.Add(c.Image);
                            // avoid disposing the default image
                            // might cause problems, not sure
                            if (d.disposeLastImage)
                                oldImage.Dispose();
                            using (Graphics g = Graphics.FromImage(c.Image)) {
                                using (Brush b = new SolidBrush(d.toolStrip.ForeColor))
                                    g.DrawString(glyph, f, b, 0, 0);
                            }
                            c.AutoSize = true;
                        }
                        k++;
                    }
                }
                if (newImages.Count > 0) {
                    d.needsUpdate = false;
                    d.disposeLastImage = true;
                    d.currentImages = newImages;
                }
            } catch {} // protect against crash (just in case)
        });
    }

    private static List<IntPtr> GetChildWindows(IntPtr parent) {
        List<IntPtr> result = new List<IntPtr>();
        GCHandle listHandle = GCHandle.Alloc(result);
        try {
            EnumChildWindows(parent, enumProc, GCHandle.ToIntPtr(listHandle));
        } finally {
            if (listHandle.IsAllocated)
                listHandle.Free();
        }
        return result;
    }

    private delegate bool EnumChildProc(IntPtr hWnd, IntPtr lParam);
    private static EnumChildProc enumProc = new EnumChildProc(CallChildEnumProc);
    private static bool CallChildEnumProc(IntPtr hWnd, IntPtr lParam) {
        GCHandle gch = GCHandle.FromIntPtr(lParam);
        List<IntPtr> list = gch.Target as List<IntPtr>;
        if (list == null)
            throw new InvalidCastException("GCHandle Target could not be cast as List<IntPtr>");

        list.Add(hWnd);
        return true;
    }

    [DllImport("user32.dll")]
    private static extern bool EnumChildWindows(IntPtr hWndParent, EnumChildProc lpEnumFunc, IntPtr lParam);
}
}

        [STAThread]
        static void Main() {
            Application.EnableVisualStyles();
            var cms = new ContextMenuStrip();
            cms.BigButtons();
            for (int i = 0; i < 20; i++)
                cms.Items.Add(new ToolStripMenuItem("Item " + i));
            cms.MaximumSize = new Size(200, 400);
            Form f = new Form();
            f.ContextMenuStrip = cms;
            Application.Run(f);
        }