Is there such a thing as an event listener that can attach itself to a Control (or other) and pickup any events that are fired by Child Controls inside that parent control?
Doubtful, but worth a try asking as I couldnt find anything from google!
I don't think so. Child controls have a reference to their parent, and the parent usually keeps references to the child controls (done automatically by VS's designer), but other than that, they don't touch each other's events.
I'm trying to clear some variable on a panel, for example, if I had a bool which lets me know when I'm click dragging on a panel's surface I set this to false when a MouseUp event occurs (this may or may not be correct way to do this but serves as an example).
If while click dragging I then alt-tab to another application the panel itself doesn't appear to get any notifications, like focus->leave / mouseup for example, is there something I'm missing, an event I've overlooked?
There seems to be a way of doing this by using the forms Deactivate event, which I suppose I could just call a suspend type method on my panel if I create a new Panel class, but I was wondering if something already existed that would propagate all children on a form with some notification that our form is no longer the main focus.
Reliably getting these kind of notifications requires that you use the Capture property. Set it to true on the MouseDown event. It ensures that all mouse messages are directed to your panel, even if the mouse is no longer hovering the panel. That however still doesn't cover rude focus changes, like Alt+Tab or Alt+Esc. You also need to implement the MouseCaptureChanged event to know when the operating system stepped in.
In general, if you are trying to implement Drag + Drop then you ought to use DoDragDrop(). When it returns you can always be sure that the drag operation is completed, for whatever reason. The return value of the method tells you what happened. Note that this also supports switching to another window, albeit that it is not very discoverable, you drag to the task bar button to force a switch.
I've written a custom control (an immediate child of Forms.Control) in C++/CLI that will offload most of its processing and all of its painting to a separate legacy-ish MFC control. I'm wrapping this control in a C# application. I need to be able to drag items onto the C++/CLI control from a UserControl on the same form in the application.
For some reason, my custom control isn't receiving any of the drag/drop events in spite of my setting AllowDrop to true. (I've verified that AllowDrop is true at runtime.) I never get an opportunity to examine/manipulate the DragEventArgs because the callbacks are never called.
I've verified that drag and drop otherwise functions normally. If I replace the custom control with a Panel, for example, I get the dragdrop callbacks just fine.
Is there something additional that must be implemented in a Control to support dragdrop callbacks? Is there something subtle that must be dealt with for the system to recognize that a control is being hovered over and should be the target of a dragdrop operation?
Notes:
The MFC control that will do the painting is not yet available to me, so I'm just painting a simple gradient background (via OnPaintBackground) that I'm trying to paint to. I'm also painting a smaller gradient rectangle in OnPaint.
I have tried setting AllowDrop = true both before the custom control's handle is created (via designer/constructor code) and after the handle is created (via OnHandleCreated override). No difference in behavior.
The drag cursor never changes from the default "no drag available" cursor over the custom control.
I'm calling this.DoDragDrop() from an event handler for a MouseDown event on a subcontrol of the UserControl.
DragDrop seems to work ok with another custom control I created in C# in the same assembly as the user control. It captures the callbacks just fine. Only my C++/CLI control isn't seeing them. The initializecomponent goo is irrelevant. I can comment it all out with no change.
I figured out my mistake, so I'll answer it here in case someone else makes a similar mistake. It looks like I did hint at the answer in my question, though I didn't realize it at the time.
In my question, I stated that
I have tried setting AllowDrop = true
both before the custom control's
handle is created (via
designer/constructor code) and after
the handle is created (via
OnHandleCreated override). No
difference in behavior.
This is actually where the breakdown occurred. I failed to read the OnHandleCreated documentation that specifically states I needed to remember to call the base class' implementation of OnHandleCreated.
Reflector shows that Control::OnHandleCreated is responsible for setting up Control's internal event notification structure. I never called Control::OnHandleCreated, so the internal event notification structure was never getting properly built up. This eventing structure (reflector again shows) is responsible for firing OnDragOver, etc, so the missing eventing structure resulted in my missing events.
Answer:
Be sure that you call the base class implementation of OnHandleCreated when you override it!
On my main form, there is another (floatable) window. This floatable window works sort of like a popupwindow in that it will close when the user clicks somewhere else outside of this window. This is handled by the Deactivate event. But what I want to do is, if the user clicks on a different control (say a button), I want to both close this float window and then activate that button with just one click. Currently, the user has to click twice (one to deactivate the window and once more to activate the desired button). Is there a way to do this with just one click?
foreach(Control c in parentForm.Controls)
{
c.Click += delegate(object sender, EventArgs e)
{
if(floatyWindow != null && floatyWindow.IsFloating)
{
floatyWindow.Close();
}
};
}
And then add your handlers as normal. This additional handler can close the floaty window.
Make sure you floaty window isn't a dialog too as this will not allow your parent form's controls to be clicked.
I had a slightly hacky solution. In your Deactivate event, fire another custom event to your main form. Then when you main form is handling the custom event, enumerate through your control(this.Controls) and locate the control under the mouse by checking all their bound then call Focus(). You might need to sort by the one with the smallest surface area, or you can have a separate list of "focus-able" control like button just for this purpose.
Another way might be to switch focus to your main form immediately after OnMouseLeave of the floatable window, or OnMouseHover of your main window, but keep the floatable windows on top, just no focus. Handle the global mouse down of your main form, and close the floatable window by then.
These are just theories, not tested.
I had an issue like this once too, when a customer wanted "floaty" windows all over there application. I used used an approach similar to the one described in this article:
http://www.vbaccelerator.com/home/NET/Code/Controls/Popup_Windows/Popup_Windows/article.asp
Code sample available here:
http://www.vbaccelerator.com/home/NET/Code/Controls/Popup_Windows/Popup_Windows/Popup_Form_Demonstration.asp
By extending this a bit we created "floaty" windows similar to the ones VS uses when you get a runtime error while debugging code.
At the very least reading the code may give you some insight, however, quarrelsome's response may be the more simple solution.
Rep steps:
create example .NET form application
put a TextBox on the form
wire a function up to the TextBox's Enter event
When you run this application, the Control.Enter event fires when focus first goes to the TextBox. However, if you click away into another application and then click back into the test application, the event will not fire again.
So moving between applications does not trigger Enter/Leave.
Is there another alternative Control-level event that I can use, which will fire in this scenario?
Ordinarily, I would use Form.Activated. Unfortunately, that is troublesome here because my component is hosted by a docking system that can undock my component into a new Form without notifying me.
What are you trying to do in the Enter event?
I can't find another control-level event that fires in your example program but when my test app does regain focus, the control that last had focus still has it.
Interesting question but it needs a little more context.
If I try your example and click outside the control on another window, desktop, etc, I can get the Got and Lost Focus events to fire, but if you're only trying to click within a form or a control with only 1 control, these event will never be fired because it is the only thing to focus on. Neither will Entered or left, unless you change the dynamics or overload the controls, you cannot get this to happen
In your example, I think you need another control. The reason being is that the first control (tabIndex 0) is the one with focus. With no other control to switch focus to, this control will always be focused, and therefore can never be entered. Switching to another application or form will not change the focus or active control in this form so when you return you will still not get the event fired.
With added controls control.entered should work fine. If this is your only control, why not call the event on formLoad, or TextChanged, when the form gets focus?
Thanks, I'll give some background.
My control is a UserControl that contains a grid and a toolbar. A user will typically launch several of these controls to view different slices of the system's data.
There are several keyboards shortcuts that can launch actions from the selected row in the current grid. However, it is a requirement that these keyboard shortcuts should apply not only to the currently focused grid. If the user is currently focused on one of the many other areas of the application, then this keyboard shortcut should still work, and it should be routed to the last focused grid.
So I wired a function to the Control.Enter event of my UserControl to basically say LastFocusedGrid = this.
And it would work, except for the docking and undocking...
See, these controls are hosted inside an application with docking features, somewhat similar to visual studio.
By default, the control launches as a tab within the main working area of the application, similar to the way a source file opens in visual studio.
However, the user can "rip out" a tab by grabbing the tab header and dragging it out of the main application. At this point, the application creates a new "float form" to host the control. Switching between the main application and this float form is the same as switching between apps, for the purposes of the Control.Enter and Form.Activated events.
At that point we have the "one control within a form" scenario simulated with the example application described in the original post.
Now, there are some ways around this. I could leverage the Form.Activated event, which DOES fire when switching between forms. If you add an event in the test application to the Form's Activated event, you will see that it works great.
The problem is that my UserControl's relationship with its parent Form is fluid, making the solution somewhat complicated. I tried wiring up to "this.ParentForm.Activated" which worked okay. The problem is when do you call this? What happens when you are undocked/redocked? I ended up with a nasty bunch of code with things like "previousParentForm" so that I could unhook from the old form, and then I was still facing the problem that the docking system doesn't notify me when my parent Form is being changed, so I was going to have to make a bunch of changes there, too.
These problems are not unsolvable, but if there is a simpler control-level "parent form was activated" event, then that would be a lot more elegant.
That's rather long, but I hope it clarifies the situation.
So when creating your grid, can you not set the KeyPressed, or KeyUp, etc. event? If so, all the grids can make use of the same event handler. Just make sure that when you get into the event handler to do something like:
Grid currentGrid = (Grid)sender;
Then you should be able to apply that block of code to any grid that gets sent in without having to worry about keeping track.
Since all the event handler really is, it's location is a mute point really as long as everything you need to execute it is accessible.
Frye, the problem is that the keyboard shortcuts should work no matter where the user is in the application. They are gloabl commands, handled at the top level, and then routed to the "last focused grid."
So handling the keystrokes at the grid level will not help.
To be more specific, assume user launches grids A, B, and C. But he also launches other controls X, Y, and Z that have nothing to do with my code.
User clicks on A, then on C. Then he clicks on Y, then on Z. With focus on Z, he hits my keyboard shortcut. In this case, grid C should respond since it was the last grid the user was focused in.
It sounds like the issue that you're having is not directly related to the Enter event and more to the point, if you have controls "that have nothing to do with your code" then you really aren't looking at a control level event.
Guess I wasn't clear.
My control lives in a container application. So do other unrelated controls by other teams. Think of it like visual studio -- my control is the code editing tab, but there is also the pending changes list and the properties window, which cohabitate with the source files but aren't directly related.
The keyboard shortcut is handled by the container application. Then it should be routed to the last one of my controls that the user was focused on.
Maintaing this "LastFocusedGrid" reference is what I do in the Enter event.
If you want to see similar functionality at work in visual studio, try this:
open a few source files
navigate to the "Start Page" tab.
Hit Ctrl-F and search "current document" for some string
Notice that the serach feature auto-navigates to the LAST FOCUSED source file to perform the search.
So even though you weren't focused in the source file, the ctrl-F command was processed by visual studio and routed to the last focused source file tab.
Now try the same thing with Ctrl-G. It doesn't work unless you are focused directly in the source file.
My keyboard commands need to work like Ctrl-F here, not like Ctrl-G. That is why I don't just capture the keyboard events directly in my control.
Does that clarify or make things worse?
Have you tried just a simple Control.GotFocus?
in this example if you toggle between clicking the textboxes neither the enter or got focus will do as expected, however if you click the child forms instead both will behave as expected.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
namespace EnterBrokenExample
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Form Form1 = new Form();
Form c1 = new Form();
Form c2 = new Form();
Form1.IsMdiContainer = true;
c1.MdiParent = Form1;
c2.MdiParent = Form1;
c1.Show();
c2.Show();
TextBox tb1 = new TextBox();
c1.Controls.Add(tb1);
tb1.Enter += ontbenter;
tb1.Text = "Some Text";
tb1.GotFocus += ongotfocus;
TextBox tb2 = new TextBox();
c2.Controls.Add(tb2);
tb2.Enter += ontbenter;
tb2.Text = "some other text";
tb2.GotFocus += ongotfocus;
Application.Run(Form1);
}
static void ontbenter(object sender, EventArgs args)
{
if (!(sender is TextBox))
return;
TextBox s = (TextBox)sender;
s.SelectAll();
}
static void ongotfocus(object sender, EventArgs args)
{
if (!(sender is TextBox))
return;
TextBox s = (TextBox)sender;
s.SelectAll();
}
}
}