This is a follow up to an outstanding question, the solution to which appears to be that I have to make my Qt application the child of another application, specifically the active window that has input focus. I need to do this so that my Qt application automatically has input focus, without the user having to first click on it. (This is necessary because the Qt application is launched by a background process.)
I am aware of QWinWidget -- "a Qt widget that can be child of a native Win32 widget". Unfortunately, my application is based on QMainWindow and there is no obvious way to make it derive from QWinWidget.
The solution to which appears to be that I have to make my Qt application the child of another application, specifically the active window that has input focus...
Similar Win32 solutions where the other process app captures some window inside own canvas are usually driven by SetParent API call. Here is one. It works for me with the other process rendering within Qt widget but you need to make it the other way around. How do you get that Qt window handle? Well, for me QWidget::winId() is working even in Qt 5.3 but I lately stumbled upon discussion and a bit confused whether it always works or not. Anyway, you need to get an active window in your Qt app as well before you get its winId() which supposed to be window handle.
P.S. Olumide, please dismiss my initial comment. I thought, the other way around, what app parents what window and it turns out non-Qt takes Qt.
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I'm working on a cross-platform command-line application (in C++ on
Win/Linux and ObjC++ on OSX) which sometimes creates an OpenGL
context. The OpenGL context and window creation code is obviously
different for the different platforms, but on OSX it's done through
NSOpenGLView and NSWindow. There's no nib, and it's not built with
Xcode (it uses a cross-platform build script).
On OSX, the window is created and works fine, but the OpenGL window
doesn't show up in the Application Switcher (Cmd-Tab). This means
that it's tricky to find the window if you 'lose it' behind other
windows, and can often only be found by going to Mission
Control/Expose.
My question is: is there a programmatic way (i.e. a message to send to
the NSWindow object or NSApplication) to ensure that a (unix-style)
command line application will show up in the Cmd-Tab list once the
window is created?
You need to transform the process from an accessory to a regular app. Call [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular].
Once you do that, though, the app will also have a menu bar when it's active. This is good because it's what users expect. However, you probably need to add appropriate items to the menus in that menu bar to get a decent user experience.
Your app will appear in the Dock as well as the Command-Tab application switcher. By default, an unbundled executable will get an icon that looks like a CRT display showing the word "exec". You can use [NSApp setApplicationIconImage:someImage] to set a better icon, although the Dock will revert to showing the generic executable icon briefly as the process exits.
I have a VB6 executable we use as a Starter executable for our real program.
The problem is that windows 7 shows a new icon in the taskbar for the new process, instead of the one i clicked on to start my program (of course, because the starter exe has already ended, and the new exe seems to be a new program).
Currently I use the Shell object to start the other exe. Is there a better way to do it from vb6, maybe by using a native C function with declare that does start an exe in the current process, without spawning a new process?
EDIT:
Thanks to atzz for the great information about Application Model IDs. I now have a shortcut to my app starter with a well defined id, and my app also sets the ID when started, and is now accesssible beautifully from the right icon in the toolbar. However, two problems persist:
The app is a Java App started with Exe4J, and I don't have any chance to set the AppID before Exe4J shows the splash screen, so while showing the splash screen there is a second icon in the taskbar.
If I don't manually drag my starter app icon from the Desktop to the toolbar, but instead use my apps icon and set it to be "sticky", the real app is sticked, and not the launcher.
Both problems would be beautifully solved if my launcher would start the app from within its own process. I heard something of using exec() instead of fork() for linux programs to achive this... is there something similar for windows?
I believe there is a way to accomplish what you need via Windows 7 taskbar API, though I never did it myself and thus don't remember clearly enough what I've read on the subject. Look around the Application ID concept.
Some links:
Developing for the Windows 7 Taskbar – Application ID
Inside Windows 7 - Introducing The Taskbar APIs
If the problem is the icon, why not give both programs the same icon (and the same App.Title). Then the user won't be able to tell the difference between the two taskbar entries. Presumably they aren't both visible at the same time.
Alternatively set your starter app not to appear in the taskbar (Form property ShowInTaskbar = False in the design view)
I'm writing a Win32 plug-in DLL for a third-party MFC app. The DLL needs to display a modal dialog. When I do this using DialogBox() or other plain Win32 API (e.g. I tried to write my own modal loop), the main application's window doesn't redraw all elements: it redraws standard elements, but not the client area. Modeless dialogs display just fine.
I suspect this happens because MFC doesn't really have modal dialogs in Win32 sense. It can only have one message loop and a separate loop in DialogBox() disrupts its delicate machinery. Here's a CodeProject article that explains this. But this CodeProject article is 9 years old, so maybe things have changed since then. Could somebody shed some light on this? The app uses MFC 8 (i.e. mfc80.dll).
Update. Here's a link to the original question; it may contain some additional information.
Update 2. Thanks everyone; I really appreciate all the advice, it certainly helps me to get the big picture of how things fit together. The first path I'm going to explore is to use native MFC 'modal' dialogs. (Since I do all this from Python, I'll use Python bindings for MFC, pywin32). This will take some time; when it's ready, I'll update the post with results.
Every thread can have a message loop. Put your modal dialog into a separate thread and emulate the standard behavior of Windows by disabling the parent window.
Edit: after some discussion (see below) it appears that the parent code behaves incorrectly.
Still, I think there are possible workarounds. One could be a parent window (to the modal dialog, but child to the one that currently behaves incorrectly) that overlays the erroneous window content, but redraws it from a DC in memory to mimic correct behavior. Of course the parent window still would have to be disabled. Another solution may be to subclass the parent window, to correct the behavior. Since the plugin would run within the same process, the implementation should be straightforward.
I am debugging an application which, in its message loop, calls IsDialogMessage(). Occasionally, IsDialogMessage() never returns (where never is an interval greater than 1 hour). Based on the symbols for user32.dll available from Microsoft's symbol server, it appears to be stuck in GetNextDlgGroupItem() (or an internal variant of the same), iterating over some set of windows.
The application is multithreaded and frequently receives notification of external events, which arrive as DCOM calls. I suspect that such a call is handled incorrectly in a way that corrupts some window state. If I can learn what sort of state corruption might cause an infinite loop in IsDialogMessage(), I think I will be more easily able to identify the source of the corruption.
I know this is old, but answering for posterity since no one here mentioned it.
More than likely what is going on is trouble with the windows manager determining where to forward a message. If you have a hierarchy of windows, as you probably do, then you need to ensure that non-top-level windows that contain controls themselves must have the WS_EX_CONTROLPARENT style set. If it is a dialog, you use the DS_CONTROL style. The presence of these flags modify the behavior of IsDialogMessage; they identify a window as having its own controls which can receive focus and handle tab order, etc, rather than just being a control itself.
For example, if you have a main frame window, which has a child window with WS_EX_CONTROLPARENT, which has a child window without WS_EX_CONTROLPARENT, which has a child window that has focus, and you hit TAB, you will likely encounter an infinite loop at the same place you mention.
Setting the second child's extended style to include WS_EX_CONTROLPARENT will resolve the issue.
Are you maybe disabling controls (using ::EnableWindow()) without checking first whether that control has the focus? If yes, then the focus gets lost and GetNextDlgGroupItem() gets confused.
Another reason this can happen is if you reparent a modeless dialog. At least this can happen with wxWidgets...
I've made some investigation, trying to answer this question. But only in situation, when parent window is in native MFC project and child is a managed C# Windows Forms. If you have such situation, then you may try 3 resolutions:
Run MFC dialog message loop on Windows Forms side. Here is more info: Integrate Windows Forms Into Your MFC Applications Through C++ Interop
Create 2 threads: one for Windows Forms dialog and one for native dialog. Here you can create dialog in Windows Forms, then with SetParent() set it's parent to native dialog. But be ware: if you add TabControl to Windows Forms, than hang with "IsDialogMessage() never return" will occur.
Make a wrapper for Windows Forms dialog to use in native project. For ex., wrapper may be WPF, see here: Windows Form as child window of an unmanaged app
I've taken information mostly from: http://msdn.microsoft.com/en-us/library/ms229600.aspx
And the temporary cure can be to change focus behavior. For example, disable them, or SetFocus() to parent or child windows only. But I strongly recommend to investigate the real reason, why IsDialogMessage() never return in your case.
Is it possible to start a new process and set it's main window as a child window of my MDI application?
The scenario is: I have a MDI application and I want to start Adobe Acrobat as a child window of my MDI application.
In theory, I believe it's possible using SetParent.
However, in practice, this may be a bit more difficult than you'd expect. Also, you'll need to do work to syncronize the styles, etc.
Just a thought, though - If you are trying to embed Acrobat Reader (not full Acrobat), you may be able to do this easier by embedding a webcontrol and having the acrobat reader plugin used in that...
Here are some samples of people making this work (at least partially):
Related SO question with workarounds for specific issues.
CodeProject article using SetParent
Experts-exchange question about embedding a java app in a win32 app.
I don't believe this is possible, at least not using SetParent. To quote from the SetParent documentation:
An application can use the SetParent
function to set the parent window of a
pop-up, overlapped, or child window.
The new parent window and the child
window must belong to the same
application.
I don't think what you want is easily done, but it could be an option to try to integrate one of the open-source PDF-viewers (if you're prepared to go GPL as that is probably the license on most of them). Some links:
epdfview
xpdf
evince
okular