Develop Reference

C# Winforms How to override scroll events?

I have a TableLayoutPanel with autoscroll set to false, anchor to topleft. It's parent is a Panel with autoscroll set to true.
The TableLayoutPanel is being populated all the time with dynamic controls.
The scrolling itself works very good when there are few controls, just hundreds. However, when I get more and more controls the performance of scrolling downgrades and sometimes it freezes my PC.
Basically when I click on the vertical Scrollbar it fires an unlimited amount of ThumbPosition messages.
Part of my program
Using the Scroll event on the panel, not the tablelayoutpanel, I can catch some user events like LargeDecrement, ThumbTrack, ThumbPosition, etc but I can't see EndScroll being triggered which is the one I want. Or atleast I want to cancel scrolling on ThumbPosition.
private void FormaDinámicaGrisG_Scroll(object sender, ScrollEventArgs e)
{
MessageBox.Show(e.Type + "");
if (e.Type == ScrollEventType.ThumbPosition)
{
//I want to prevent scrolling here
}
else
{
// Here I want to let it scroll.
}
}
I try using the following code to catch messages when user is scrolling but nothing happens.
private const int WM_VSCROLL = 0x0115;
private const int WM_HSCROLL = 0x0114;
protected override void WndProc(ref Message m)
{
if (m.Msg == WM_VSCROLL)
{
MessageBox.Show("Vertical Scroll");
}
if (m.Msg == WM_HSCROLL)
{
MessageBox.Show("HorzScroll");
}
base.WndProc(ref m);
}
I believe the problem is that since it has so many dynamic controls, and the events triggers so rapidly in succession it hangs on drawing it.
So any idea to stop scrolling on certain events and let other events scroll?

Transparent panel can't receive WM_NCHITTEST

In my c# winform project, I put a panel in a form. The panel's BackColor is the same as the form's TransparencyKey, so it looks 'transparent'.
I want the form to be moved when clicking/dragging inside the 'transparent' panel. So I override the panel's WndProc as below:
public class UnclickablePanel : Panel {
protected override void WndProc(ref Message m) {
if (m.Msg == 0x84) { // WM_NCHITTEST
m.Result = new IntPtr(-1);
return;
}
base.WndProc(ref m);
}
}
In my opinion, the panel returns "-1"(transparent) and then the form can handle the mouse down/up/move events.
It works fine in Win7 with Aero theme. But if win xp or win7 + basic theme, the panel can't receive WM_NCHITTEST at all. It just click through the form.
Any solution or workaround?

WM_MOUSEWHEEL message does not propagate to parent

I have a RichTextBox with ScrollBars set to None. According to MSDN
The DefWindowProc function propagates the message to the window's
parent. There should be no internal forwarding of the message, since
DefWindowProc propagates it up the parent chain until it finds a
window that processes it.
I interpret this as, I should not need to hook into the message pump (IMessageFilter) and manually forward WM_MOUSEWHEEL events to the parent Form containing the richtextbox. When I am inside of RichTextBox and perform a mouse scroll, the Form does not scroll. Why not? How can I get the Form to scroll?
Keep in mind that scrollbars are set to none for RichTextBox and enabled for the Form. So why isn't the form getting the scroll event?
public partial class Form4 : Form
{
public Form4()
{
InitializeComponent();
this.AutoScroll = true;
richTextBox1.ScrollBars = RichTextBoxScrollBars.None;
}
}

For my derived TextBox, rather than ignore the mouse wheel as the above does, I instead wanted to pass it on up to my Parent control... which is what the TextBox SHOULD do in any case, in my opinion. Here's what I put in my derived TextBox's WndProc:
switch (m.Msg)
{
case 0x020A: // WM_MOUSEWHEEL
case 0x020E: // WM_MOUSEHWHEEL
if (this.ScrollBars == ScrollBars.None && this.Parent != null)
m.HWnd = this.Parent.Handle; // forward this to your parent
base.WndProc(ref m);
break;
default:
base.WndProc(ref m);
break;
}

The form doesn't scroll because the RichTextBox handles the WM_MOUSEWHEEL itself and doesn't call DefWindowProc to forward it to its parent. Apparently that doesn't change when disabling the scroll bars.
So you either need to implement an IMessageFilter or create a subclass of RichTextEdit that will forward the WM_MOUSEWHEEL as shown here:
public class NoScrollRichTextBox : RichTextBox
{
const int WM_MOUSEWHEEL = 0x020A;
protected override void WndProc(ref Message m)
{
// This will completely ignore the mouse wheel, which will disable zooming as well
if (m.Msg != WM_MOUSEWHEEL)
base.WndProc(ref m);
}
}

Activate a form and process button click at the same time?

I'm using Windows Forms in C#.
I have a main form with a couple of toolbars that contain toolStripButtons. After working with another form that contains data, the main form loses focus and clicking on a toolStripButton does not trigger OnClick event: the first click activates the main form, and only the second click actually pushes the button. I need the user to click a button only once to trigger a Click event, any ideas on how to do that? Thanks.
Notes:
I was using MDI and there were no problems clicking on the parent's form buttons. But now the paramount is to have forms freely floating across multiple displays.
The worker forms have the main form as the Owner property, this way they stay on top of the main form.
When I click on the button of an inactive form, none of MouseHover, MouseEnter, MouseDown nor MouseUp fires. It's just main form's Activate event that fires.
There is a treeView (inside a tabControl, inside a splitContainer, inside a panel), on the main form. Its items are selected upon a first mouse click, even if the main form is inactive. I guess not all controls are equal!

What you need to do is create a class that inherits ToolStrip and handles the WndProc. This is one way to do it. There are others.
private class MyToolStrip : ToolStrip
{
private const uint WM_LBUTTONDOWN = 0x201;
private const uint WM_LBUTTONUP = 0x202;
private static bool down = false;
protected override void WndProc(ref Message m)
{
if (m.Msg == WM_LBUTTONUP && !down)
{
m.Msg = (int)WM_LBUTTONDOWN;
base.WndProc(ref m);
m.Msg = (int)WM_LBUTTONUP;
}
if (m.Msg == WM_LBUTTONDOWN) down = true;
if (m.Msg == WM_LBUTTONUP) down = false;
base.WndProc(ref m);
}
}
I've also seen this solution:
protected override void WndProc(ref Message m)
{
// WM_MOUSEACTIVATE = 0x21
if (m.Msg == WM_MOUSEACTIVATE && this.CanFocus && !this.Focused)
this.Focus();
base.WndProc(ref m);
}
I ran into this at the last place I worked, I think the solution I came up with worked more like the latter, but I don't have access to the exact code I used.

if u have Form without borders, so this logic was working for you built in :)
form.FormBorderStyle = FormBorderStyle.None

How can I trap all mouse events on a control?

I need to capture all mouse events on a .NET's WebBrowser, process them and prevent the WebBrowser from getting them. Is there any way to achieve this? I wonder if there is any way I can handle mouse events if the control is disabled.

You'll have to override WndProc() to intercept the mouse messages. Like this:
using System;
using System.Windows.Forms;
class MyBrowser : WebBrowser {
protected override void WndProc(ref Message m) {
if (m.Msg >= 0x200 && m.Msg <= 0x20a) {
// Handle mouse messages
//...
}
else base.WndProc(ref m);
}
}

There IS a solution to this. You need to capture the mouse events that are associated with the Document object that is associated with the webBrowser control.
After the DocumentCompleted event occurs, and inside you DocumentCompleted event handler, do the following:
myWebBrowser.Document.MouseDown += new HtmlElementEventHandler(myMouseDown);
and have the related handler:
void myMouseDown(object sender, HtmlElementEventArgs e)
{
your code to handle the mouse event... such as ...
if (e.MouseButtonsPressed == MouseButtons.Right)
{
}
}