How to integrate Qt into an existing application development workflow? - c++

I have been playing with Qt for a week or so, with the aim of integrating Qt dialogs into an existing application. I've figured out use a basic Qt Message box from my MFC application, eg:
extern "C" __declspec(dllexport) bool showDialog( HWND parent )
{
QWinWidget win( parent );
win.showCentered();
QMessageBox::about( &win, "About QtMfc", "QtMfc Version 1.0\nCopyright (C) 2003" );
return TRUE;
}
I've used Qt Designer to create dialog boxes. What I haven't figured out is how to bring all of these pieces together. Qt Designer leaves me with a .ui file. I've seen that I can use uic to compile that to a .h file, but where are the other parts, like .cpp files? Further, if I want to compile the Qt parts to a dll, which are loaded on demand, what is the process for that? To put it into context, the existing application has 1000's of dialogs that the user may want to use, hence they all live in dll's that are loaded as needed and the dialogs come as additional downloads, kind of a plugin if you will, separately from the main program.
This is probably missing a lot, so please bring on the questions.
thanks,
Daniel

Get the VS plugin, it makes Qt work seamlessly with VS.
It complies ui files into classes which you then call from your code. You can also write dialogs, menus, etc in your C code. Since it uses sizers for layout there isn't a lot of X-Y coords to manage to place every component.
Although if you can I would go for a big-bang approach of replacing the MFC main with a Qt main and moving the functionality over. AFAIK MFC dialogs should work perfectly well in a Qt app.

Related

How to create an Evernote kind of widget for global menu of a MacOS/X desktop using QT?

How to create an application which stays in top of MacOS, something similar to below image. You can see the Evernote elephant icon.
I don't want to use xcode - because my application already built in QT, it has nice GUI, now I wanted to add extended feature something similar to Evernote. If I click on an elephant it will open a dialog box to write notes. In my case- it's a simple event like on/off buttons.
I have tried and created GUI widget apps but how to make one which resides like Evernote app ?
A custom pop up menu like the one pictured can be done several ways in Qt.
QML is the most modern way of making the menu with the customized styling you are looking for.
Apply the appropriate flags to the window/widget so it appears as a popup.
The same effects can also be done in QWidgets, but takes more code and probably will take longer to make. The flags you are looking for will be found under Qt Window Flags and/or under Qt Widget Attributes.
The stock stylings for Qt for different OS's deal mostly with title bars, status bars, buttons, drop downs, etc.
The base styles for Mac can be found here:
http://doc.qt.io/qt-5/gallery-macintosh.html
Once you go to a customized popup, you have to draw all of it yourself... but the native drawing elements in Qt are friendly enough and get you that look you are trying to do.
There are even some tools for exporting from Photoshop or Gimp directly to QML.
http://doc.qt.io/qtcreator/quick-export-to-qml.html
Hope that helps.
You are looking for a tray icon. Qt implements it in QSystemTrayIcon.
Further information
You may take a look at the System Tray Icon Example.
Many StackOverflow posts exist on this topic.
If you already have a program written for Qt, then you can compile and run it under MacOS/X much the same way you could compile it under (whatever OS you're using now). You'll need to install Xcode because Xcode includes the C++ compiler (clang) you'll need in order to compile your Qt program, but you don't have to use the Xcode IDE if you don't want to. Rather, you can either use the QtCreator IDE under MacOS/X, or you can simply open up a Terminal window and do a "qmake ; make" in the directory where your Qt-based program's .pro file is, and build it from the command line that way.
If, on the other hand, your question is actually about how to add an icon to the global menu of a MacOS/X desktop, then I don't think Qt has an API for that, so you'll need to drop down to using one of MacOS/X's native APIs. That will probably involve learning some Objective-C (or Objective-C++, if you prefer), but integrating a bit of Objective-C/C++ into your Qt app is doable with a bit of work.

Compiled Qt for windows is win api at Low Level

Qt is cross platform c++ Gui Library.Code once and compile for different Platform. Let's for instance, I have compiled a Project(decent text editor with few tool bar) or any such program for Windows(x86).
Statement 1: The Program.exe entry point will be WinMain.
Statement 2: The Text editor and tool bar will created using "CreateWindow" win32 api. Qt have its own class to implement but to ask OS(Windows) for creating a tool bar or text editor, Program exe interface with OS(Windows). OS understand what it know it does not know anything about Qt class,so to create tool bar or text editor program have to use win32 api.
Statement 3: All event processing( button click, mouse click) will handles using windows messeging system.
Note: It may seem i am viewing every thing with win32 api glass on my understanding.
Correct. The WinMain implementation is provided by the Qt library.
Half correct. The top-level windows are created using CreateWindow. Child widgets, such as a non-toplevel toolbar are Qt's own widgets and are opaque outside of your application. They are exposed only via the accessibility APIs. This allows you to create more widgets than Windows would be able to deal with. A million child widgets is doable, if not particularly fast.
Correct - there's no other way. Of course Qt immediately translates native messages into QEvent instances and dispatches them internally to various QObject instances. In Qt-land, all events must be received by a QObject instance.
You're incorrect in your assertion that winapi has anything to do with the kernel. Winapi is implemented by a bunch of user-space DLLs. You could implement those DLLs yourself. Those DLLs themselves call into the kernel using the native api. That's the API actually exposed by the kernel to the user space.

Filling text in qwidget using win32 api

I have a problem. I am using C++ to develop an application in Win32 that among other scopes automatize some user input process in an external app in order for the user to be ready to operate.
Particularly I would like to use Win32 API to fill some text in a Qt QWidget control. I wrote a DLL in pure C to get this task done. I tested it on a MFC application and it works very well.
Anyway I could not get it to work for Qt QWidget controls.
I was able to get the right handle via the EnumChildWindows function (stored in the struct Field).
SendMessage(Field.hFound,WM_SETTEXT,(WPARAM)NULL,(LPARAM)_T("bla bla bla"));
But the SendMessage doesn't seem to work because maybe the control (most probably a QLineedit) supports other messages to get this job done.
Is there any specification for these events, I googled a lot but I could not find anything suitable.
What is the most straightforward way to get this code working? Is there an Event table mapping for Qt I could use? Do I have to use some Qt headers and link it against a DLL (this could be a problem because of licensing)?
Thanks in advance.
Qt, at least 4.8 and 5.x, uses foreign controls. None of the widgets, beyond the window, have native handles. Your EnumChildWindows is most likely not finding what you think it's finding.
If you don't have access to the Qt application's source code, there's nothing else you can do, short of injecting your own code into the running application. If the application is dynamically linked, you can figure out what version of Qt it's using, and what compiler it was compiled with, and the likely set of Qt configuration options. You can then compile your own code with the same compiler and using same Qt version, and inject it into the running application. You can then enumerate visible windows, and their children, and find the control you're after.

How can I create an MDI application from a DLL (c++/mfc)

I hope this isn't too confusing but I have the following situation:
SDI Application that dynamically loads DLLs.
These DLLs perform various tasks, spawn dialogs, etc.
Normally these dialogs that the DLLs create are fairly simple. However I have many controls and need the features of an MDI application. I can't separate this window into a new project, so I'm looking for a way to create it within the DLL and then initialize it as if it were a simple dialog. I'm not particularly sure if this is possible but if so can someone point me in the correct direction.
Thanks!

QT How to embed an application into QT widget

In our project we have three independent applications, and we have to develop a QT control application that controls these three applications. The main window will be seperated to three sub windows - each one display another one application.
I thought to use QX11EmbedWidget and QX11EmbedContainer widgets, but two problems with that:
The QX11Embed* is based on X11 protocol and I dont know if it's supported on non-x11 systems like Windows OS.
Since QT 5 these classes are not existing, and the QT documentation doesn't mention why.
So that I dont know whether to use it or not - I'll be happy to get an answers.
In addition, I see that the QT 5.1 contains QWidget::createWindowContainer(); function that in some posts it looks like this should be the replacement to the X11Embed. Can anyone please explian me more how can I use this function to create a QT widget that will run another application (a Calculator for example) inside its?
I have searched a lot in Google, and didn't find answers to my Qs.
Can anyone please help me? Am I on the right way?
Thanks!
If all three independent applications are written with Qt, and you have their source, you should be able to unify them just through the parenting of GUI objects in Qt.
http://qt-project.org/doc/qt-4.8/objecttrees.html
http://qt-project.org/doc/qt-4.8/widgets-and-layouts.html
http://qt-project.org/doc/qt-4.8/mainwindows-mdi.html
If you don't have access to them in that way, what you are talking about is like 3rd party window management. It is kind of like writing a shell, like Windows Explorer, that manipulates the state and the size of other window applications.
Use a program like Spy++ or AutoIt Spy for Windows and the similar ones for other OS's, and learn the identifying markings of your windows you want to control, like the class, the window title, etc. Or you can launch the exe yourself in a QProcess::startDetached() sort of thing.
http://qt-project.org/doc/qt-5.1/qtcore/qprocess.html#startDetached
Then using the OS dependent calls control the windows. The Qt library doesn't have this stuff built in for third party windows, only for ones under the QApplication that you launched. There are a lot of examples of doing things like this by AutoHotKey, or AHK. It is a scripting language that is made for automating a lot of things in the windows environment, and there is port for Mac as well (though I haven't tried the mac port myself).
So in the end you are looking at finding your window probably with a call like this:
#include <windows.h>
HWND hwnd_1 = ::FindWindow("Window_Class", "Window Name");
LONG retVal = GetWindowLongA(hwnd_1, GWL_STYLE); // to query the state of the window
Then manipulate the position and state of the window like so:
::MoveWindow(hwnd_1, x, y, width, height, TRUE);
::ShowWindow(hwnd_1, SW_SHOWMAXIMIZED);
You can even draw widgets on top of the windows you are controlling if you set your window flags correctly for the windows you are manipulating.
transparent QLabel with a pixmap
Cannot get QSystemTrayIcon to work correctly with activation reason
Some gotchas that come up in Windows when doing all of this, is finding out the quirks of the Windows UI when they set the Display scaling different from what you expect, and if you want to play nice with the Task bar, and handling all the modal windows of your programs you are manipulating.
So overall, it is do-able. Qt will make a nice interface for performing these commands, but in the end you are looking at a lot of work and debugging to get it in a beautiful, reliable, window manager.
Hope that helps.
I never tried it myself, but from the docs in Qt 5.1 I would try QWindow::fromId(WId id), which gives you a QWindow, which should be embeddable with createWindowContainer:
QWindow * QWindow::fromWinId(WId id) [static] Creates a local
representation of a window created by another process or by using
native libraries below Qt.
Given the handle id to a native window, this method creates a QWindow
object which can be used to represent the window when invoking methods
like setParent() and setTransientParent(). This can be used, on
platforms which support it, to embed a window inside a container or to
make a window stick on top of a window created by another process.
But no guarantee. :-)