I seem to have a problem I am trying to detect when my form loses focus but it has a COM interop based user control on it to display a web cam feed. This is causing the loses and gained focus events to not always fire. Is there a way to detect that the application has lost focus, perhaps through a windows api call.
This SO thread might help you.
Related
I have written an application that currently handles clicks from multiple mouse devices.
I used this project and modified to handle mouse clicks as apposed to keyboards.
This is working fine, however now I need to know if there is a way to suppress a click event if it has been handled by my app. The app is a quiz game so the idea is that the quiz master will have (and still be able to use) 1 mouse, and the other contestants will have their own mouse (as buzzers). So when they buzz in, I don't want the mouse click events to fire in the operating system (or at least this application).
The concept is the familiar override of void WndProc(ref Message message), and so I have tried not calling base.WndProc(ref Message) when I don't want the click events to fire, but this has not worked.
Can anybody point me in the right direction here?
Should I be going down the windows hook route? I have looked at this, but I can't seem to work out how I could hook to each mouse device individually.
Any help would be greatly appreciated.
Edit:
This is a Windows Form UI project, and not WPF. So the MultiPoint SDK from Microsoft won't work.
The solution to this lies within not WndProc, but PreFilterMessage(). By intercepting messages before they even reach the form, you can remove them from the message pump causing them to never reach the control that was clicked. This also works for child controls within the form.
I answered this and posted the full source in the following question:
C# Get Mouse handle (GetRawInputDeviceInfo)
I've a Windows Form Application that does a simple task : the user selects a video in the main form, and the application pops up a new form with a Shockwave Flash Object reproducing it.
What i would like to do now is to move in the Movie timeline when the user scrolls the mouse wheel. The problem is, the Flash object steals the focus from the form as soon as it pops up, and it doesn't support a mousewheel event.
Is there a way to do it, other than hooking the MouseWheel event and redirect it to the application when the popup has the focus?
The window displayed by Flash is owned by a different process. That makes messing with messages difficult, you'll at least need a low-level mouse hook to see the mouse message before it disappears into the other process.
The boilerplate code is available here. Beware that it has a bug that prevents it from working on .NET 4 and up, see this answer for the workaround.
I have a Silverlight control containing an image. I want the user to be able to drag the image out of the Silverlight application and drop it anywhere they would be able to drop an image. For example, to the Desktop or to a PowerPoint slide or Word document. Everything that I have read thus far says it cannot be done but I find that hard to believe. I'm very new to Silverlight and RIA development so any help would be much appreciated.
Below is the code sample in my WinForm Form but the drag never starts.
string[] aString = { imagePath };
DataObject data = new DataObject(DataFormats.FileDrop, aString);
data.SetData(DataFormats.StringFormat, imagePath);
DoDragDrop(data, DragDropEffects.Copy);
Well the trouble is that a drag operation in Silverlight doesn't have simple access to anything outside the browser (by design). Depending on the user's settings you even have to get explicit permission for clipboard operations and sandboxed temporary file storage. This really sounds like a task better suited to a WPF application (perhaps with web deployment?) or some other desktop application technology.
However, that being said here are some things you could try/consider:
Silverlight/Javascript/ActiveX combination hosted in Internet Explorer
Silverlight 5 "Out of Brower" & P/Invoke (I heard P/Invoke will be supported when Silverlight 5 comes out)
Silverlight connecting to a web service running on the same computer (crazy, but you didn't ask for "not crazy", you asked for possible)
I am not very familiar with drag and drop in the Win32 API so it would take a lot of research and experimentation before I could confirm that this was even possible (and I can already tell you it isn't practical).
Edit: Based on the extra information you provided about the question I suspect it is possible to do what you are attempting. First, are you using WPF or WinForms? I assume WPF but one of your comments says WinForms. I wasn't very familiar with WPF drag/drop operations, but having looked into it, I think your code is on the right path. I created a WPF application and initiated a drag during a KeyDown event. This meant that the mouse button was not necessarily pressed. If I initiated the DragDrop while the button was down it worked. If I initiated while the mouse button wasn't down, I had to push the mouse button down and the drag operation would start (this was unexpected since I assumed the mouse would have to already be down). If I pressed the mouse down outside the application, then gave the WPF app focus (ALT+Tab), then initiated the DragDrop while the mouse button was still down, it didn't work. I got a reference to the MouseDevice and checked the LeftButton property, and the state was showing as "Released" even though the button was still being held down. It seems the key here is the way drag/drop interacts with internal mouse state. You might have to find a way to set the mouse state (maybe with the UI Automation API?). At this point it should be painfully obvious that this whole thing is a hack (even though it is probably possible to get it to work somehow).
The solution we came up with was as follows. The RIA i.e. Silverlight sends a message to our Desktop application WinForms with the path of the image to drag along with the bounding rectangle in screen coordinates that we want to start the drag from. The Desktop code creates and places a Panel over the area that we want to drag from. This panel is where we use DoDragDrop to initiate the native drag when the user left clicks. Since this panel is placed outside and above the silverlight control, everything works perfect. Sandbox defeated.
I have been working on some Silverlight apps for the past few months and fully investigated your exact requirements only to find it was not possible. I believe you can drag from the file system, from Silverlight control to control, but not to the file system.
Does Silverlight 4 support drag and drop from app to desktop?
http://msdn.microsoft.com/en-us/library/dd772166%28v=vs.95%29.aspx
I've written a c# application which automates an instance of IE. I'd like to know when internet explorer gains focus and when it looses focus.
From the SHDocVw.InternetExplorer object I can get it's HWND. From there how can I create a message hook to receive WM_KILLFOCUS and WM_FOCUS events (assuming those are the correct events to be listening for :))?
Thanks everyone!!
UPDATE: I found a way I could use to accomplish the above goal without using hooks (which I haven't quite figured out how to do in c# yet), using the .NET framework in this question.
The problem with this code
AutomationFocusChangedEventHandler focusHandler
= new AutomationFocusChangedEventHandler(OnFocusChanged);
Automation.AddAutomationFocusChangedEventHandler(focusHandler);
is that it is easy for a window to be the foreground window and that event won't fire when that window is switched to because it's waiting for a specific UI Element to be in focus. (To test this you can use a function that uses that code and prints a message everytime a new window is in focus, such as the MSDN sample TrackFocus, and then click on a webbrowser. When most webpages or a blank page is being displayed in the browser the event wont fire until the address bar or some other element is selected.) It could probably work if there was a way to modify so that it could throw the event if either no UI Element is in focus or every time an element lost focus (instead being thrown when it gains focused). Anyone have any ideas on how I could fix the above code to solve my problem?
Update 2: I just came across this (article claims you can only hook to mouse and keyboard from c#) as well which may mean I can't use hooks at all for what I'd like to do.
Detailed instructions on setting up a hook from C# are here: http://support.microsoft.com/kb/318804/en-us?fr=1
I have a WinForms app that is retrieving data from a web service on a worker thread and I need to disable all input to my app until the data is loaded.
Currently, I create a semi-transparent form and place it over my application. When the data call completes I close this overlay form. This works fine accept that it causes considerable performance problems for users running the application over terminal services. I tried making the overlay entirely transparent but that still triggers two redraws of the entire window so this did not help at all.
I know that a common recommendation for handling this is to disable all the controls, but that would also redraw much of the screen so I'm looking for another way to block all user input. Any assistance would be greatly appreciated!
UPDATE: I should have mentioned that we have considered the modal dialog. Currently we show the overlay, start the data access thread then construct the form. If there is no better way to block input (App.BlockInput() might be nice) then we could use the modal dialog idea, but we would need to wait until the form construction had completed and there isn't currently a nice, central location to do this.
You could display a small modal (modalForm.ShowDialog(yourForm)) form with progress bar rolling on top of your app. This won't cause big areas to be redrawed.
If your app really is blocked while the operation is running, I'd do what Microsoft frequently does: open a modal dialog box with some kind of throbber animation or ProgressBar, and a Cancel button. Redraw is limited because you're only drawing the size of the new dialog, and input to the rest of your application is blocked because the dialog is modal. Also, users are much more willing to wait when you have some kind of status updates and or animation, because it looks like the computer is "working".
However, if there are operations your user can do while your web service request is running, it's better to leave the controls accessible. At very least, there should always be a way to interrupt/abort the process.
Update: Since you now changed the question: How long is it taking to construct the modal dialog? Why not simply construct the dialog empty, and then populate its controls? If all you have is a small dialog box with a single button and a single ProgressBar, then calling dialog.ShowDialog() should happen faster than your user can interact with your UI. Is that not the case?
One thing you could try for keyboard input is setting the KeyPreview property of the form to True. This will pass all keyboard events to the Form object first instead of to the individual controls. Create an event handler for the KeyPress event of the form and in there you can set the Handled property of the KeyPressEventArgs to True to prevent the key stroke from being passed to any of the controls. If you're currently retrieving data from the web service, set the Handled property True otherwise set it to False and the key stroke will be passed to the controls.
If someone has a good idea on how to handle the mouse input yet you're set.
I'd typically create a LockUI() and UnlockUI() functions in my form that toggle controls and flip a local form field that acts a flag to indicate a long running process. This approach works really well if you use a command pattern.
As previously mentioned, you could toggle keyboard input by using the KeyPreview property of the form (as suggested by TLiebe).
As far as mouse input is concerned, you could disable mouse activity by hooking the WinProc messages and intercepting mouse input messages. This is basically what KeyPreview does.