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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;

}

}

}

}

SplitButton.cs

Comments

  • Anonymous
    February 28, 2006
    David was kind enough to point out some rough spots in the SplitButton sample, so I've gone ahead...
  • Anonymous
    July 04, 2006
    The comment has been removed