I am a little rusty with QT but I've had to use it for projects before.
I was wondering if I could make a pop-up window, a small window with it's height/width disabled so the user can't expand it. It should also lock the screen until they press a button on this window.
I could do all of this in a separate class, but I was wondering. Are there any built-in QT classes that have a little popup like this that I could just modify? I mean making a class just for an error message seems to me a little wasteful. I'm trying to keep the project small.
But if a class is required to be made in order to accomplish this, that is fine. The only problem is I have no clue how to lock the application windows so that you have to do something one window before you can go back to the main application.
I'm not asking for someone to type out all this code for me, just give me a link or something. I've looked for it but I couldn't find it. Cheers.
QMessageBox messageBox;
messageBox.critical(0,"Error","An error has occured !");
messageBox.setFixedSize(500,200);
The above code snippet will provide the required message box.
For a simple error message, I would suggest you look into the QMessageBox (the documentation contains little example that should show you how to easily achieve what you need), which is modal too. Using a QDialog for displaying a simple error message is possible too, but maybe too much for such a simple task.
I believe what you are looking for is something along the lines of QDialog. Dialogs can be modal or nonmodal. Modal dialogue "block" interaction with the calling window until the Dialog window has been handled.
You can either subclass QDialog or check to see if one of the default dialog classes will be enough for what you need.
Related
I am new to qt and I have an issue I cannot understand.
I have created my own QDialog and now I want to add it to an existing application.
In QT creator, everything works fine but when I add either my custom dialogue or even a
message box to the existing code, something odd happens.
The dialogue works just fine but when I hover over the main area of the dialogue
the icon changes to a Qt::BusyCursor the busy wait icon.
At first I assumed this must be a threading issue but then isn't .exec() suppose to block?
Also when I hover over the title bar or the message box / dialogue, it seems fine i.e it shows a Qt::ArrowCursor, in both cases the dialogue functionally works fine also.
I have tried to set the .setCursor() on both and it did not work still a busy icon.
can anyone give me some hints as to what I might look at to investigate this more.
Thanks a lot!!!
I can suggest you to use
QApplication::setOverrideCursor(QCursor(Qt::ArrowCursor));
and reset it with
QApplication::restoreOverrideCursor();.
I'm turning mad with a little problem with Visual Studio 2008 and MFC. I'm working on a project actually and I'm trying to create an SDI Application. Right, now I want to add a dockable DialogBar. Well, the first time I added it with the resource view, I could create the bar without problems.
But... I want to add some controls like a couple of ListBox, buttons and so on. The program doesn't allows me to create member variables for these controls. The option appears in grey.
Searching a little, I found that it's mandatory to create a new class derived from CDialogBar and "enhance" it with the Message handler and so on. I've been reading some tutorials and it didn't work for me.
Can you please help me? I'm starting to get nervous, the use of dialogbars is mandatory in my design and I've never implemented them before.
Thank you very much, and sorry for my poor english.
You can add a control member variable by hand instead of using the wizard. All it takes is a call to DDX_Control in the dialog bar's DoDataExchange function.
But CDialogBar-derived classes do not handle control clicks. The CDialogBar class forwards all of those messages to the dialog bar's parent window. So be prepared to add the message handlers to the parent (usually CMainFrame).
For learning purposes you might try creating your dialog bar as a CDialog first, to see the proper code lines and message map entries supplied by the wizard. Then you can copy/move these details as appropriate into your actual code project.
I always been interested on how we can accomplish this (hide/show the main menu using the alt key), and now some applications do this very often. One that really please me is the visual studio 2010 with this plugin:
http://visualstudiogallery.msdn.microsoft.com/bdbcffca-32a6-4034-8e89-c31b86ad4813?SRC=VSIDE
(firefox also do this, but i think that is in a different way)
Can anyone explain me how this can be achieved or if you known of any sample project that demonstrate this please tell me.
(what i can see in some replies here in stack is that we have to destroy the menu when is to hide and create it when is to show?! but this seems a bit bad solution...)
Thanks
The SetMenu function lets you add/remove the menu from the window. It does not destroy the menu.
Note that most applications which have the dynamic menu hide/show behavior are not really showing a menu. They're showing a custom control that looks like a menu.
You might also take a look at MFC support for auto hiding menus. I used this technique and it worked really well.
in CMainFrame::OnCreate I did
m_wndMenuBar.ShowWindow(SW_HIDE);
which actually works fine in our project
I stumbled across a related pit fall that will show a hidden main frame without your consent:
Whenever the focus for a child window in an MDI application changes (e.g. due to right clicking in it), the function CMDIChildWnd::OnMDIActivate will be called, which in turn shows the main menu (even if it was removed or destroyed previously) of the MDI application.
This works basically by adding the saved main manu from the underlying's CMDIChildWnd m_hMenuShared variable.
A quick&dirty hack to prevent this, is setting m_hMenuShared to NULL (it's protected in CMDIChildWnd so this needs a custom derived child class of CMDIChildWnd) for all child frames.
I have tried to make the fullscreen feature of a SDI application with splitter windows by following the forum link. However, my status bar, system menu as well as the title bar of the application have disappeared. Do you have any suggestions on any easy ways of getting these back (or if I have to use different method of making the application maximized during startup instead of fullscreen)? Thanks in advance.
I got rid of any manipulations on the cs structure in the PreCreateWindow handler and used a ShowWindow(SW_MAXIMIZE) function call in the OnCreate function implementation of my MainFrame function, and it works quite well.
It sounds like you just want the window to be maximized. Take a look at the SetWindowPlacement function or ShowWindow.
I want to make a C++ button on Start>Run i.e but when I do it will not do signalled event?
Im sorry I have seen that you do not get the question.
Ok basically when you create a button with CreateWindowEx(); I want to do that but put on a different window with SetPArent which I have already done now the button does not work so I need my program to someone get when it is clicked from the Run window as example!
And yes you have it, but it's not making the button is the problem it's getting when it's clicked with my program since it does not belong to it anymore!
You need to apply the ancient but still-supported technique known in Windows as subclassing; it is well explained here (15-years-old article, but still quite valid;-). As this article puts it,
Subclassing is a technique that allows
an application to intercept messages
destined for another window. An
application can augment, monitor, or
modify the default behavior of a
window by intercepting messages meant
for another window.
You'll want "instance subclassing", since you're interested only in a single window (either your new button, or, the one you've SetParented your new button to); if you decide to subclass a window belonging to another process, you'll also need to use the injection techniques explained in the article, such as, injecting your DLL into system processes and watching over events with a WH_CBT hook, and the like. But I think you could keep the button in your own process even though you're SetParenting it to a window belonging to a different process, in which case you can do your instance subclassing entirely within your own process, which is much simpler if feasible.
"Superclassing" is an alternative to "subclassing", also explained in the article, but doesn't seem to offer that many advantages when compared to instance subclassing (though it may compared with global subclassing... but, that's not what you need here anyway).
You'll find other interesting articles on such topics here, here, and here (developing a big, rich C++ library for subclassing -- but, also showing a simpler approach based on hooks which you might prefer). Each article has a pretty difference stance and code examples, so I think that having many to look at may help you find the right mindset and code for your specific needs!
OK, I'll do my very best - as I understand you, you're trying to inject a button into some existing window. That meaning: Your tool creates a button in some window that does not belong to your application. Now, you want to be notified when that button is pressed. Am I correct so far?
To be notified about the button being pressed, you need to get the respective window message, which will only work if you also "inject" a different WndProc into the window. Actually I have no idea how that should work, but I faintly remember functions like GetWindowLong and SetWindowLong. Maybe they will help?
EDIT
I've searched MSDN a little: While you can get the address of a window's WndProc using GetWindowLong, you can not set the WndProc using SetWindowLong on Windows NT/2000/XP (and up I suppose). See here (MSDN).
So what you could do is install a global message hook that intercepts all window messages, filter those for the window you've injected the button into and then find your message. If you have trouble with this, however, I'm the wrong person to ask, because it's been years ago since I've done anything like that, but it would be stuff for a new question.
EDIT 2
Please see Alex Martinellis answer for how to define the hook. I think he's describing the technique I was referring to when I talked about defining global message hooks to intercept the window messages for the window you injected your button into.