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Well-designed Expandable TextBoxes in an Expandable Panel

I have records in my .NET WinForms app that I lay out with enhanced TextBox controls on panels when the records are editable, but I set the TextBoxes to ReadOnly when the records are not editable. Clicking the save button on an editable record saves the text to the database, and then it is displayed as an un-editable record (until the edit button is clicked). Please see the following screen grab:
As you can hopefully see, the first record is not editable, but the second one is. The problem I have is that I would like the TextBox to grow in Height if the text is too much to fit. It seems that the TextBox is doing the WordWrap, but it either only shows one line of the text or only the first two. Something is always cut off at the bottom.
I have looked at several other posts on this site, including, especially, Expandable WinForms TextBox.
Here is some sample code for the panel:
AutoSize = true;
AutoSizeMode = AutoSizeMode.GrowAndShrink;
...
Field1 = new ExpandoField { Multiline = true, WordWrap = true };
Field1.Location = new System.Drawing.Point(42, 3);
if (CanEdit)
{
Field1.BackColor = System.Drawing.Color.White;
Field1.TabIndex = 20;
}
else
{
((ExpandoField) Field1).ReadOnly = true;
Field1.ForeColor = System.Drawing.Color.FromArgb(0, 50, 0);
Field1.BackColor = System.Drawing.Color.Snow;
Field1.TabIndex = 0;
Field1.TabStop = false;
}
Field1.Text = Text1;
Field1.Dock = DockStyle.None;
Field1.Size = new System.Drawing.Size(538 - 25, 34);
Field1.MinimumSize = Field1.Size;
Field1.AutoSize = true;
Controls.Add(Field1);
As you can see, I have AutoSize set to true for the panel. The code for Field2 is similar to Field1.
ExpandoField is based on sample code I saw from a response by dstran in Expandable WinForms TextBox. It seemed to be the most complete implementation of the suggestion marked as the answer to that post. Here's the code:
class ExpandoField : TextBox
{
private double m_growIndex = 0.0;
private Timer m_timer;
public ExpandoField()
{
AutoSize = false;
this.Height = 20;
// Without the timer, I got a lot of AccessViolationException in the System.Windows.Forms.dll.
m_timer = new Timer();
m_timer.Interval = 1;
m_timer.Enabled = false;
m_timer.Tick += new EventHandler(m_timer_Tick);
this.KeyDown += new KeyEventHandler(ExpandoField_KeyDown);
}
void ExpandoField_KeyDown(object sender, KeyEventArgs e)
{
if (e.Modifiers == Keys.Control && e.KeyCode == Keys.A)
this.SelectAll();
}
void m_timer_Tick(object sender, EventArgs e)
{
var sz = new System.Drawing.Size(Width, Int32.MaxValue);
sz = TextRenderer.MeasureText(Text, Font, sz, TextFormatFlags.TextBoxControl);
m_growIndex = (double)(sz.Width / (double)Width);
if (m_growIndex > 0)
Multiline = true;
else
Multiline = false;
int tempHeight = (int) (20 * m_growIndex);
if (tempHeight <= 20)
Height = 20;
else
Height = tempHeight;
m_timer.Enabled = false;
}
public override sealed bool AutoSize
{
get { return base.AutoSize; }
set { base.AutoSize = value; }
}
protected override void OnTextChanged(EventArgs e)
{
base.OnTextChanged(e);
m_timer.Enabled = true;
}
protected override void OnFontChanged(EventArgs e)
{
base.OnFontChanged(e);
m_timer.Enabled = true;
}
protected override void OnSizeChanged(EventArgs e)
{
base.OnSizeChanged(e);
m_timer.Enabled = true;
}
}
This is obviously not quite working. I have the panel set to AutoSize, but it is not growing to accomodate the second TextBox. Also, I need to somehow push the second TextBox down when the first one grows. Is there some good way for the panel to know when ExpandoField gets an OnSizeChanged event? It seems like the growth of that panel would then need to cause the remainder of the list of panels to be redrawn in lower locations. I'm not sure how to get this cascade effect to work right...
I also think the use of the timer seems like an inefficient kluge...
I'm still learning WinForms. Is there some well-designed way I can get the behavior that I want? Is there some event I can catch when the WordWrap takes place (or when the text exceeds the size of the TextBox)? That would allow me to resize the TextBox. And how does the TextBox let the panel know that it has changed? Does it need to call the OnSizeChanged handler for it's parent panel? Does the panel need to call the OnSizeChanged handler for it's parent list?
Any suggestions?

I believe I have the answer, after 3 or 4 failed attempts...
class ExpandoField : TextBox
{
private bool UpdateInProgress = false;
private static System.Text.RegularExpressions.Regex rgx = new System.Text.RegularExpressions.Regex(#"\r\n");
public delegate void CallbackFn();
CallbackFn VSizeChangedCallback;
public ExpandoField(CallbackFn VSizeChanged)
{
AutoSize = false;
VSizeChangedCallback = VSizeChanged;
this.KeyDown += new KeyEventHandler(ExpandoField_KeyDown);
}
public void ExpandoField_KeyDown(object sender, KeyEventArgs e)
{
if (e.Modifiers == Keys.Control && e.KeyCode == Keys.A)
this.SelectAll();
}
public void UpdateSize()
{
if (UpdateInProgress == false && Text.Length > 0)
{
UpdateInProgress = true;
int numLines = 0;
System.Drawing.Size baseSize = new System.Drawing.Size(Width, Int32.MaxValue);
System.Drawing.Size lineSize = baseSize; // compiler thinks we need something here...
// replace CR/LF with single character (paragraph mark '¶')
string tmpText = rgx.Replace(Text, "\u00B6");
// split text at paragraph marks
string[] parts = tmpText.Split(new char[1] { '\u00B6' });
numLines = parts.Count();
foreach (string part in parts)
{
// if the width of this line is greater than the width of the text box, add needed lines
lineSize = TextRenderer.MeasureText(part, Font, baseSize, TextFormatFlags.TextBoxControl);
numLines += (int) Math.Floor(((double) lineSize.Width / (double) Width));
}
if (numLines > 1)
Multiline = true;
else
Multiline = false;
int tempHeight = Margin.Top + (lineSize.Height * numLines) + Margin.Bottom;
if (tempHeight > Height || // need to grow...
Height - tempHeight > lineSize.Height) // need to shrink...
{
Height = tempHeight;
VSizeChangedCallback();
}
UpdateInProgress = false;
}
}
public override sealed bool AutoSize
{
get { return base.AutoSize; }
set { base.AutoSize = value; }
}
protected override void OnTextChanged(EventArgs e)
{
base.OnTextChanged(e);
UpdateSize();
}
protected override void OnFontChanged(EventArgs e)
{
base.OnFontChanged(e);
UpdateSize();
}
protected override void OnSizeChanged(EventArgs e)
{
base.OnSizeChanged(e);
UpdateSize();
}
}
Note that on the constructor this subclass of TextBox now accepts a delegate callback to let the parent class know that the TextBox has changed its size. (I suppose I should have handled the possibility of a null value here...)
Thankfully, this solution no longer required a timer.
I have tested this code pretty well, and I have watched it both grow & shrink. It respects MaximumSize, and it even handles the presence of carriage-return/line-feed pairs. (This code assumes Windows; it should be trivial to modify it for Linux, etc.) Feel free to suggest improvements.

C# WPF Pop is being drawn multiple times

All I have created a custom hex viewer tool for viewing a particular file type.
As part of the requirements I need to highlight certain bit values once I hover over a hex range (which is implemented via C# Run class).
The problem is about 50% of the time I get multiple popups drawn on top of each other rather than one.
See below:
Here my relevant code snippet in C#:
private Popup popup = new Popup();
void ToolTip_MouseEnter(object sender, EventArgs e)
{
//TODO: base popup action on data value
if (popup.IsOpen!=true)
{
if (sender is Run && HexDocumentUIHelperUtility.zftSequenceBitsMouseUp)
{
Run runControl = sender as Run;
if (runControl != null)
{
//popup.HorizontalAlignment = HorizontalAlignment.Center;
//popup.VerticalAlignment = VerticalAlignment.Center;
TextBox textBox = new TextBox();
textBox.Text = this.getZftBitsVisualization().getBinaryString();
int startHighlight = this.getZftBitsVisualization().getHighlightIndex();
int length = this.getZftBitsVisualization().getHighlightLength();
//textBox.SelectionStart = startHighlight;
//textBox.SelectionLength = length;
textBox.SelectionBrush = Brushes.Gold;
textBox.Select(startHighlight, length);
textBox.FontSize = 15;
popup.Child = textBox;
//get the current mouse position
//I adjusted the mouse Y coordinate by minus 20 pixels in order to avoid the popup vbeing displayed on top of the hex range
int mouseYCoordinate = System.Windows.Forms.Control.MousePosition.Y + 20;
popup.HorizontalOffset = System.Windows.Forms.Control.MousePosition.X;
popup.VerticalOffset = mouseYCoordinate;
popup.IsOpen = true;
textBox.Focus();
}
}
}//if the pop is not already opened
}
void ToolTip_MouseLeave(object sender, EventArgs e)
{
if (sender is Run)
{
Run runControl = sender as Run;
if (runControl != null)
{
if (popup != null)
{
popup.IsOpen = false;
popup.Child = null;
}
if (highlightedRunList != null)
{
highlightedRunList.Clear();
}
}
}
}

You are testing if the popup is already open at the top of the method but not actually setting that it is until much further down.
This gives the mouse enter event chance to fire several times before finally setting IsOpen to true preventing further popups opening.
Move the setting of IsOpen to immediately after the test for the popup not being open. You can always set it back to false if the popup fails.

TabPage title alignment being wrong after drag'n'dropping

I have the class that extends System.Windows.Forms.TabControl and had implemented drag'n'drop mechanism for its TabPages as following:
#region Overriden base methods
protected override void OnDragOver(DragEventArgs e)
{
if (PointedTabPage == null) return;
e.Effect = DragDropEffects.Move;
var dragTab = e.Data.GetData(typeof (ManagedTabPage)) as ManagedTabPage;
if (dragTab == null) return;
int dropIndex = TabPages.IndexOf(PointedTabPage);
int dragIndex = TabPages.IndexOf(dragTab);
if (dragIndex == dropIndex) return;
var modifiedTabPages = new List<ManagedTabPage>(from ManagedTabPage tabPage in TabPages
where TabPages.IndexOf(tabPage) != dragIndex
select TabPages[TabPages.IndexOf(tabPage)] as ManagedTabPage);
modifiedTabPages.Insert(dropIndex, dragTab);
for (byte i = 0; i < TabPages.Count; ++i)
{
var managedTabPage = TabPages[i] as ManagedTabPage;
if (managedTabPage != null && managedTabPage.Uid == modifiedTabPages[i].Uid)
continue;
TabPages[i] = modifiedTabPages[i];
}
SelectedTab = dragTab;
}
protected override void OnMouseDown(MouseEventArgs e)
{
try
{
switch (e.Button)
{
case MouseButtons.Left:
DoDragDrop(PointedTabPage, DragDropEffects.Move);
break;
case MouseButtons.Middle:
CloseTab(PointedTabPage);
break;
}
}
catch (InvalidOperationException)
{
}
finally
{
TabPages.Insert(0, String.Empty);
TabPages.RemoveAt(0);
}
}
#endregion
Nota bene that in the finally clause of OnMouseDown method there are 2 lines for workarounding the
problem: for some reason w/o these lines after drag'n'dropping any of TabPages alignment of their titles is being wrong:
What should I do to correct this behavior without this smelly workaround? Maybe sending some Windows messages could do the trick?
Thanks a lot for any suggestions.
Edit 1. Code of ManagedTabPage is 100% unimportant (it's just extends TabPage with some specific properties).
PointedTabPage is unimportant too, but this is it:
return (from ManagedTabPage tabPage in TabPages
let tabPageIndex = TabPages.IndexOf(tabPage)
where GetTabRect(tabPageIndex).Contains(PointToClient(Cursor.Position))
select TabPages[tabPageIndex]).Single() as ManagedTabPage;
I'm trying to achieve fully-centered alignment of labels. You see, labels on the screenshot didn't centered horizontally?

I can't do much with the posted code. Let's take a completely different tack and create a tabcontrol that supports dragging a tabpage with the mouse. Add a new class to your project and paste this code:
using System;
using System.Drawing;
using System.Windows.Forms;
class TabControlEx : TabControl {
private Point downPos;
private Form draggingHost;
private Rectangle draggingBounds;
private Point draggingPos;
public TabControlEx() {
this.SetStyle(ControlStyles.UserMouse, true);
}
}
The usage of the variable becomes clear later. First thing we need is to get mouse events from the TabControl so we can see the user trying to drag a tab. That requires turning on the UserMouse control style, it is off by default for controls (like TabControl) that are built-in Windows controls and use their own mouse handling.
Use Build > Build and drag the new control from the top of the toolbox onto a form. Everything still looks and acts like a regular TabControl, but do note that clicking tabs no longer changes the active tab. A side-effect of turning the UserMouse style on. Let's fix that first, paste:
protected override void OnMouseDown(MouseEventArgs e) {
for (int ix = 0; ix < this.TabCount; ++ix) {
if (this.GetTabRect(ix).Contains(e.Location)) {
this.SelectedIndex = ix;
break;
}
}
downPos = e.Location;
base.OnMouseDown(e);
}
We are storing the click location, that's needed later to detect the user dragging the tab. That requires the MouseMove event, we need to start dragging when the user moved the mouse far enough away from the original click position:
protected override void OnMouseMove(MouseEventArgs e) {
if (e.Button == MouseButtons.Left && this.TabCount > 1) {
var delta = SystemInformation.DoubleClickSize;
if (Math.Abs(e.X - downPos.X) >= delta.Width ||
Math.Abs(e.Y - downPos.Y) >= delta.Height) {
startDragging();
}
}
base.OnMouseMove(e);
}
The startDragging method needs to create a toplevel window that can be moved around with the mouse, containing a facsimile of the tab we're dragging around. We'll display it as an owned window, so it is always on top, that has the exact same size as the tab control:
private void startDragging() {
draggingBounds = this.RectangleToScreen(new Rectangle(Point.Empty, this.Size));
draggingHost = createDraggingHost(draggingBounds);
draggingPos = Cursor.Position;
draggingHost.Show(this.FindForm());
}
The createDraggingHost needs to do the heavy lifting and create a window that looks just like the tab. A borderless form we'll move around with the mouse. We'll use the TransparencyKey property to make it look similar to the dragged TabPage with a tab sticking out at the top. And make it look the same by simply letting it display a screenshot of the tabpage:
private Form createDraggingHost(Rectangle bounds) {
var host = new Form() { FormBorderStyle = FormBorderStyle.None, ControlBox = false, AutoScaleMode = AutoScaleMode.None, Bounds = this.draggingBounds, StartPosition = FormStartPosition.Manual };
host.BackColor = host.TransparencyKey = Color.Fuchsia;
var tabRect = this.GetTabRect(this.SelectedIndex);
var tabImage = new Bitmap(bounds.Width, bounds.Height);
using (var gr = Graphics.FromImage(tabImage)) {
gr.CopyFromScreen(bounds.Location, Point.Empty, bounds.Size);
gr.FillRectangle(Brushes.Fuchsia, new Rectangle(0, 0, tabRect.Left, tabRect.Height));
gr.FillRectangle(Brushes.Fuchsia, new Rectangle(tabRect.Right, 0, bounds.Width - tabRect.Right, tabRect.Height));
}
host.Capture = true;
host.MouseCaptureChanged += host_MouseCaptureChanged;
host.MouseUp += host_MouseCaptureChanged;
host.MouseMove += host_MouseMove;
host.Paint += (s, pe) => pe.Graphics.DrawImage(tabImage, 0, 0);
host.Disposed += delegate { tabImage.Dispose(); };
return host;
}
Note the use of the Capture property, that's how we detect that the user released the mouse button or interrupted the operation by any other means. We'll use the MouseMove event to move the window around:
private void host_MouseMove(object sender, MouseEventArgs e) {
draggingHost.Location = new Point(draggingBounds.Left + Cursor.Position.X - draggingPos.X,
draggingBounds.Top + Cursor.Position.Y - draggingPos.Y);
}
And finally we need to handle the completion of the drag. We'll swap tabs, inserting the dragged tab at the mouse position and destroy the window:
private void host_MouseCaptureChanged(object sender, EventArgs e) {
if (draggingHost.Capture) return;
var pos = this.PointToClient(Cursor.Position);
for (int ix = 0; ix < this.TabCount; ++ix) {
if (this.GetTabRect(ix).Contains(pos)) {
if (ix != this.SelectedIndex) {
var page = this.SelectedTab;
this.TabPages.RemoveAt(this.SelectedIndex);
this.TabPages.Insert(ix, page);
this.SelectedIndex = ix;
}
break;
}
}
draggingHost.Dispose();
draggingHost = null;
}
Looks pretty good.

since you hasn't shared ManagedTabPage code, i used default TabPage control
changes are made in method OnDragOver
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Windows.Forms;
namespace Demo
{
public class MyTabControl : TabControl
{
public MyTabControl()
{
SizeMode = TabSizeMode.Fixed;
ItemSize = new Size(224, 20);
}
#region Overriden base methods
protected override void OnDragOver(DragEventArgs e)
{
if (DesignMode)
return;
if (PointedTabPage == null) return;
e.Effect = DragDropEffects.Move;
var dragTab = e.Data.GetData(typeof(TabPage)) as TabPage;
if (dragTab == null) return;
int dropIndex = TabPages.IndexOf(PointedTabPage);
int dragIndex = TabPages.IndexOf(dragTab);
if (dragIndex == dropIndex) return;
// change position of tab
TabPages.Remove(dragTab);
TabPages.Insert(dropIndex, dragTab);
SelectedTab = dragTab;
base.OnDragOver(e);
}
protected override void OnMouseDown(MouseEventArgs e)
{
if (DesignMode)
return;
switch (e.Button)
{
case MouseButtons.Left:
DoDragDrop(PointedTabPage, DragDropEffects.Move);
break;
case MouseButtons.Middle:
TabPages.Remove(PointedTabPage);
break;
}
}
#endregion
TabPage PointedTabPage
{
get
{
return TabPages.OfType<TabPage>()
.Where((p, tabPageIndex) => GetTabRect(tabPageIndex).Contains(PointToClient(Cursor.Position)))
.FirstOrDefault();
}
}
}
}

Prevent ToolStripMenuItems from jumping to second screen

I have an application that is mostly operated through NotifyIcon's ContextMenuStrip
There are multiple levels of ToolStripMenuItems and the user can go through them.
The problem is, that when the user has two screen, the MenuItems jump to second screen when no space is available. like so:
How can I force them to stay on the same screen? I've tried to search through the web but couldn't find an appropriate answer.
Here is a sample piece of code i'm using to test this senario:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
var resources = new ComponentResourceManager(typeof(Form1));
var notifyIcon1 = new NotifyIcon(components);
var contextMenuStrip1 = new ContextMenuStrip(components);
var level1ToolStripMenuItem = new ToolStripMenuItem("level 1 drop down");
var level2ToolStripMenuItem = new ToolStripMenuItem("level 2 drop down");
var level3ToolStripMenuItem = new ToolStripMenuItem("level 3 drop down");
notifyIcon1.ContextMenuStrip = contextMenuStrip1;
notifyIcon1.Icon = ((Icon)(resources.GetObject("notifyIcon1.Icon")));
notifyIcon1.Visible = true;
level2ToolStripMenuItem.DropDownItems.Add(level3ToolStripMenuItem);
level1ToolStripMenuItem.DropDownItems.Add(level2ToolStripMenuItem);
contextMenuStrip1.Items.Add(level1ToolStripMenuItem);
}
}

It is not easy, but you can write code in the DropDownOpening event to look at where the menu is at (its bounds), the current screen, and then set the DropDownDirection of the ToolStripMenuItem:
private void submenu_DropDownOpening(object sender, EventArgs e)
{
ToolStripMenuItem menuItem = sender as ToolStripMenuItem;
if (menuItem.HasDropDownItems == false)
{
return; // not a drop down item
}
// Current bounds of the current monitor
Rectangle Bounds = menuItem.GetCurrentParent().Bounds;
Screen CurrentScreen = Screen.FromPoint(Bounds.Location);
// Look how big our children are:
int MaxWidth = 0;
foreach (ToolStripMenuItem subitem in menuItem.DropDownItems)
{
MaxWidth = Math.Max(subitem.Width, MaxWidth);
}
MaxWidth += 10; // Add a little wiggle room
int FarRight = Bounds.Right + MaxWidth;
int CurrentMonitorRight = CurrentScreen.Bounds.Right;
if (FarRight > CurrentMonitorRight)
{
menuItem.DropDownDirection = ToolStripDropDownDirection.Left;
}
else
{
menuItem.DropDownDirection = ToolStripDropDownDirection.Right;
}
}
Also, make sure you have the DropDownOpening event hooked up (you would really need to add this to every menu item):
level1ToolStripMenuItem += submenu_DropDownOpening;

I have solved it this way:
For the ContextMenuStrip itself to open on a desired screen, I created a ContextMenuStripEx with the following methods:
protected override void SetBoundsCore(int x, int y, int width, int height, BoundsSpecified specified)
{
Rectangle dropDownBounds = new Rectangle(x, y, width, height);
dropDownBounds = ConstrainToBounds(Screen.FromPoint(dropDownBounds.Location).Bounds, dropDownBounds);
base.SetBoundsCore(dropDownBounds.X, dropDownBounds.Y, dropDownBounds.Width, dropDownBounds.Height, specified);
}
internal static Rectangle ConstrainToBounds(Rectangle constrainingBounds, Rectangle bounds)
{
if (!constrainingBounds.Contains(bounds))
{
bounds.Size = new Size(Math.Min(constrainingBounds.Width - 2, bounds.Width), Math.Min(constrainingBounds.Height - 2, bounds.Height));
if (bounds.Right > constrainingBounds.Right)
{
bounds.X = constrainingBounds.Right - bounds.Width;
}
else if (bounds.Left < constrainingBounds.Left)
{
bounds.X = constrainingBounds.Left;
}
if (bounds.Bottom > constrainingBounds.Bottom)
{
bounds.Y = constrainingBounds.Bottom - 1 - bounds.Height;
}
else if (bounds.Top < constrainingBounds.Top)
{
bounds.Y = constrainingBounds.Top;
}
}
return bounds;
}
(ConstrainToBounds method is taken from the base class ToolStripDropDown via Reflector)
for the nested MenuItems to open on the same screen as ContextMenuStrip, I created a ToolStripMenuItemEx (which derives from ToolStripMenuItem). In my case it looks like this:
private ToolStripDropDownDirection? originalToolStripDropDownDirection;
protected override void OnDropDownShow(EventArgs e)
{
base.OnDropDownShow(e);
if (!Screen.FromControl(this.Owner).Equals(Screen.FromPoint(this.DropDownLocation)))
{
if (!originalToolStripDropDownDirection.HasValue)
originalToolStripDropDownDirection = this.DropDownDirection;
this.DropDownDirection = originalToolStripDropDownDirection.Value == ToolStripDropDownDirection.Left ? ToolStripDropDownDirection.Right : ToolStripDropDownDirection.Left;
}
}

The code of #David does not fix if the menu is opened in the left side of second screen. I have improved that code to work on all screen corner.
private void subMenu_DropDownOpening(object sender, EventArgs e)
{
ToolStripMenuItem mnuItem = sender as ToolStripMenuItem;
if (mnuItem.HasDropDownItems == false)
{
return; // not a drop down item
}
//get position of current menu item
var pos = new Point(mnuItem.GetCurrentParent().Left, mnuItem.GetCurrentParent().Top);
// Current bounds of the current monitor
Rectangle bounds = Screen.GetWorkingArea(pos);
Screen currentScreen = Screen.FromPoint(pos);
// Find the width of sub-menu
int maxWidth = 0;
foreach (var subItem in mnuItem.DropDownItems)
{
if (subItem.GetType() == typeof(ToolStripMenuItem))
{
var mnu = (ToolStripMenuItem) subItem;
maxWidth = Math.Max(mnu.Width, maxWidth);
}
}
maxWidth += 10; // Add a little wiggle room
int farRight = pos.X + mnuMain.Width + maxWidth;
int farLeft = pos.X - maxWidth;
//get left and right distance to compare
int leftGap = farLeft - currentScreen.Bounds.Left;
int rightGap = currentScreen.Bounds.Right - farRight;
if (leftGap >= rightGap)
{
mnuItem.DropDownDirection = ToolStripDropDownDirection.Left;
}
else
{
mnuItem.DropDownDirection = ToolStripDropDownDirection.Right;
}
}

I did not try the solution by tombam. But since the others didn't seem to work, I came up with this simple solution:
private void MenuDropDownOpening(object sender, EventArgs e)
{
var menuItem = sender as ToolStripDropDownButton;
if (menuItem == null || menuItem.HasDropDownItems == false)
return; // not a drop down item
// Current bounds of the current monitor
var upperRightCornerOfMenuInScreenCoordinates = menuItem.GetCurrentParent().PointToScreen(new Point(menuItem.Bounds.Right, menuItem.Bounds.Top));
var currentScreen = Screen.FromPoint(upperRightCornerOfMenuInScreenCoordinates);
// Get width of widest child item (skip separators!)
var maxWidth = menuItem.DropDownItems.OfType<ToolStripMenuItem>().Select(m => m.Width).Max();
var farRight = upperRightCornerOfMenuInScreenCoordinates.X + maxWidth;
var currentMonitorRight = currentScreen.Bounds.Right;
menuItem.DropDownDirection = farRight > currentMonitorRight ? ToolStripDropDownDirection.Left :
ToolStripDropDownDirection.Right;
}
Note that in my world, I was not concerned about multiple levels of cascading menus (as in the OP), so I did not test my solution in that scenario. But this works correctly for a single ToolStripDropDownButton on a ToolStrip.

Button Overlay on ListView Hides on MouseMove

In the details view of ListView control, I need additional functionality of editing the entry pointed to by the cursor so I simply added a button overlay onto the ListView control.
The following code was intended to show the button on the rightmost part of each cell of the details view of ListView control when the cursor is on the ListView control.
To determine which cell was hovered, HitTest method was used.
The problem is, the button show correctly only when the cursor is on the rectangle area the button is supposed to show up. In other words, when the cursor is on non-rightmost area of any field, redraw occurs in ListView control and erases the button (and the content of the cell). Also, BringToFront method doesn't work.
How to correct this behavior?
class DocumentView {
Button btn = new Button();
ListView lv; // designer-generated
public DocumentView(Document doc)
{
btn.AutoSize = true;
btn.AutoSizeMode = AutoSizeMode.GrowAndShrink;
btn.AutoEllipsis = false;
btn.Hide();
this.Controls.Add(btn);
InitializeComponent();
}
ListViewItem mouseMoveHitTestItem = null;
ListViewItem.ListViewSubItem mouseMoveHitTestSubItem = null;
int iCol_MouseMove = -1;
int iRow_MouseMove = -1;
private void lv_MouseMove(object sender, MouseEventArgs e)
{
var mousePos = lv.PointToClient(Control.MousePosition);
var hitTest = lv.HitTest(mousePos);
mouseMoveHitTestItem = hitTest.Item;
mouseMoveHitTestSubItem = hitTest.SubItem;
if (mouseMoveHitTestItem != null)
{
var iCol = hitTest.Item.SubItems.IndexOf(hitTest.SubItem);
var iRow = hitTest.Item.Index;
if (iCol != iCol_MouseMove || iRow != iRow_MouseMove)
{ //Reposition button if the cursor moved to a different cell
var bounds = hitTest.SubItem.Bounds;
btn.SetBounds(
bounds.Right - btn.Width + lv.Left,
bounds.Top + lv.Top,
bounds.Width, bounds.Height);
if (!btn.Visible)
{
btn.Show();
btn.BringToFront();
}
btn.Text = "" + iRow + ", " + iCol; //test hittest row, col calc.
}
}
btn.BringToFront(); //takes no effect
}
}

Missed status update so invalidatation occurred on every MouseMove:
btnAddName.SetBounds(
bounds.Right - btnAddName.Width + lvVertices.Left,
bounds.Top + lvVertices.Top,
bounds.Width, bounds.Height);
//-->
iColBtnAdd = iCol;
iRowBtnAdd = iRow;
//<--
if (!btnAddName.Visible)
{
Warnings help. (CS0169)