Building a SplitButton
The following sample creates a split button that you can use on your form. It makes use of the ButtonRenderer class to custom draw a button.
Sample code for adding a SplitButton:
SplitButton sb = new SplitButton();
sb.ShowSplit = true;
sb.ContextMenuStrip = new ContextMenuStrip();
sb.ContextMenuStrip.Items.Add("one");
sb.ContextMenuStrip.Items.Add("two");
sb.ContextMenuStrip.Items.Add("three");
this.Controls.Add(sb);
Code for SplitButton:
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;
using System.Drawing;
using System.ComponentModel;
namespace Microsoft.Samples {
public class SplitButton : Button {
private PushButtonState _state;
private const int PushButtonWidth = 14;
private static int BorderSize = SystemInformation.Border3DSize.Width * 2;
private bool skipNextOpen = false;
private Rectangle dropDownRectangle = new Rectangle();
private bool showSplit = true;
public SplitButton() {
this.AutoSize = true;
}
[DefaultValue(true)]
public bool ShowSplit {
set {
if (value != showSplit) {
showSplit = value;
Invalidate();
if (this.Parent != null) {
this.Parent.PerformLayout();
}
}
}
}
private PushButtonState State {
get {
return _state;
}
set {
if (!_state.Equals(value)) {
_state = value;
Invalidate();
}
}
}
public override Size GetPreferredSize(Size proposedSize) {
Size preferredSize = base.GetPreferredSize(proposedSize);
if (showSplit && !string.IsNullOrEmpty(Text) && TextRenderer.MeasureText(Text, Font).Width + PushButtonWidth > preferredSize.Width) {
return preferredSize + new Size(PushButtonWidth + BorderSize * 2, 0);
}
return preferredSize;
}
protected override bool IsInputKey(Keys keyData) {
if (keyData.Equals(Keys.Down) && showSplit) {
return true;
}
else {
return base.IsInputKey(keyData);
}
}
protected override void OnGotFocus(EventArgs e) {
if (!showSplit) {
base.OnGotFocus(e);
return;
}
if (!State.Equals(PushButtonState.Pressed) && !State.Equals(PushButtonState.Disabled)) {
State = PushButtonState.Default;
}
}
protected override void OnKeyDown(KeyEventArgs kevent) {
if (showSplit) {
if (kevent.KeyCode.Equals(Keys.Down)) {
ShowContextMenuStrip();
}
else if (kevent.KeyCode.Equals(Keys.Space) && kevent.Modifiers == Keys.None) {
State = PushButtonState.Pressed;
}
}
base.OnKeyDown(kevent);
}
protected override void OnKeyUp(KeyEventArgs kevent) {
if (kevent.KeyCode.Equals(Keys.Space)) {
if (Control.MouseButtons == MouseButtons.None) {
State = PushButtonState.Normal;
}
}
base.OnKeyUp(kevent);
}
protected override void OnLostFocus(EventArgs e) {
if (!showSplit) {
base.OnLostFocus(e);
return;
}
if (!State.Equals(PushButtonState.Pressed) && !State.Equals(PushButtonState.Disabled)) {
State = PushButtonState.Normal;
}
}
protected override void OnMouseDown(MouseEventArgs e) {
if (!showSplit) {
base.OnMouseDown(e);
return;
}
if (dropDownRectangle.Contains(e.Location)) {
ShowContextMenuStrip();
}
else {
State = PushButtonState.Pressed;
}
}
protected override void OnMouseEnter(EventArgs e) {
if (!showSplit) {
base.OnMouseEnter(e);
return;
}
if (!State.Equals(PushButtonState.Pressed) && !State.Equals(PushButtonState.Disabled)) {
State = PushButtonState.Hot;
}
}
protected override void OnMouseLeave(EventArgs e) {
if (!showSplit) {
base.OnMouseLeave(e);
return;
}
if (!State.Equals(PushButtonState.Pressed) && !State.Equals(PushButtonState.Disabled)) {
if (Focused) {
State = PushButtonState.Default;
}
else {
State = PushButtonState.Normal;
}
}
}
protected override void OnMouseUp(MouseEventArgs mevent) {
if (!showSplit) {
base.OnMouseUp(mevent);
return;
}
if (ContextMenuStrip == null || !ContextMenuStrip.Visible) {
SetButtonDrawState();
if (Bounds.Contains(Parent.PointToClient(Cursor.Position)) && !dropDownRectangle.Contains(mevent.Location)) {
OnClick(new EventArgs());
}
}
}
protected override void OnPaint(PaintEventArgs pevent) {
base.OnPaint(pevent);
if (!showSplit) {
return;
}
Graphics g = pevent.Graphics;
Rectangle bounds = this.ClientRectangle;
// draw the button background as according to the current state.
if (State != PushButtonState.Pressed && IsDefault && !Application.RenderWithVisualStyles) {
Rectangle backgroundBounds = bounds;
backgroundBounds.Inflate(-1, -1);
ButtonRenderer.DrawButton(g, backgroundBounds, State);
// button renderer doesnt draw the black frame when themes are off =(
g.DrawRectangle(SystemPens.WindowFrame, 0, 0, bounds.Width - 1, bounds.Height - 1);
}
else {
ButtonRenderer.DrawButton(g, bounds, State);
}
// calculate the current dropdown rectangle.
dropDownRectangle = new Rectangle(bounds.Right - PushButtonWidth - 1, BorderSize, PushButtonWidth, bounds.Height - BorderSize * 2);
int internalBorder = BorderSize;
Rectangle focusRect =
new Rectangle(internalBorder,
internalBorder,
bounds.Width - dropDownRectangle.Width - internalBorder,
bounds.Height - (internalBorder * 2));
bool drawSplitLine = (State == PushButtonState.Hot || State == PushButtonState.Pressed || !Application.RenderWithVisualStyles);
if (RightToLeft == RightToLeft.Yes) {
dropDownRectangle.X = bounds.Left + 1;
focusRect.X = dropDownRectangle.Right;
if (drawSplitLine) {
// draw two lines at the edge of the dropdown button
g.DrawLine(SystemPens.ButtonShadow, bounds.Left + PushButtonWidth, BorderSize, bounds.Left + PushButtonWidth, bounds.Bottom - BorderSize);
g.DrawLine(SystemPens.ButtonFace, bounds.Left + PushButtonWidth + 1, BorderSize, bounds.Left + PushButtonWidth + 1, bounds.Bottom - BorderSize);
}
}
else {
if (drawSplitLine) {
// draw two lines at the edge of the dropdown button
g.DrawLine(SystemPens.ButtonShadow, bounds.Right - PushButtonWidth, BorderSize, bounds.Right - PushButtonWidth, bounds.Bottom - BorderSize);
g.DrawLine(SystemPens.ButtonFace, bounds.Right - PushButtonWidth - 1, BorderSize, bounds.Right - PushButtonWidth - 1, bounds.Bottom - BorderSize);
}
}
// Draw an arrow in the correct location
PaintArrow(g, dropDownRectangle);
// Figure out how to draw the text
TextFormatFlags formatFlags = TextFormatFlags.HorizontalCenter | TextFormatFlags.VerticalCenter;
// If we dont' use mnemonic, set formatFlag to NoPrefix as this will show ampersand.
if (!UseMnemonic) {
formatFlags = formatFlags | TextFormatFlags.NoPrefix;
}
else if (!ShowKeyboardCues) {
formatFlags = formatFlags | TextFormatFlags.HidePrefix;
}
if (!string.IsNullOrEmpty(this.Text)) {
TextRenderer.DrawText(g, Text, Font, focusRect, SystemColors.ControlText, formatFlags);
}
// draw the focus rectangle.
if (State != PushButtonState.Pressed && Focused) {
ControlPaint.DrawFocusRectangle(g, focusRect);
}
}
private void PaintArrow(Graphics g, Rectangle dropDownRect) {
Point middle = new Point(Convert.ToInt32(dropDownRect.Left + dropDownRect.Width / 2), Convert.ToInt32(dropDownRect.Top + dropDownRect.Height / 2));
//if the width is odd - favor pushing it over one pixel right.
middle.X += (dropDownRect.Width % 2);
Point[] arrow = new Point[] { new Point(middle.X - 2, middle.Y - 1), new Point(middle.X + 3, middle.Y - 1), new Point(middle.X, middle.Y + 2) };
g.FillPolygon(SystemBrushes.ControlText, arrow);
}
private void ShowContextMenuStrip() {
if (skipNextOpen) {
// we were called because we're closing the context menu strip
// when clicking the dropdown button.
skipNextOpen = false;
return;
}
State = PushButtonState.Pressed;
if (ContextMenuStrip != null) {
ContextMenuStrip.Closing += new ToolStripDropDownClosingEventHandler(ContextMenuStrip_Closing);
ContextMenuStrip.Show(this, new Point(0, Height), ToolStripDropDownDirection.BelowRight);
}
}
void ContextMenuStrip_Closing(object sender, ToolStripDropDownClosingEventArgs e) {
ContextMenuStrip cms = sender as ContextMenuStrip;
if (cms != null) {
cms.Closing -= new ToolStripDropDownClosingEventHandler(ContextMenuStrip_Closing);
}
SetButtonDrawState();
if (e.CloseReason == ToolStripDropDownCloseReason.AppClicked) {
skipNextOpen = (dropDownRectangle.Contains(this.PointToClient(Cursor.Position)));
}
}
private void SetButtonDrawState() {
if (Bounds.Contains(Parent.PointToClient(Cursor.Position))) {
State = PushButtonState.Hot;
}
else if (Focused) {
State = PushButtonState.Default;
}
else {
State = PushButtonState.Normal;
}
}
}
}