I have a lot of legacy that was making use of QTextCodec::setCodecForCStrings to handle other languages such as portuguese, swedish and italian. I know of this solution:
QTextCodec::setCodecForCStrings is GONE in Qt5
And have also read that blog
http://www.macieira.org/blog/2012/05/source-code-must-be-utf-8-and-qstring-wants-it/
but it does not help at all. The fact that this function is gone really is a dealbreaker for me.
I have considered writing my own QString class or copying the source code for SetCodecForCStrings and adapting it for Qt5. I will deal with cross-platform issues (it was already dealt with anyway).
Has anyone tried this ? If so what problem did you encounter ? Is there anything already made that could be used instead (library, wrapper, adapter) ? I do not mind paying for it if I need to. Or maybe I just have to stick with qt4 but I really like the new connect syntax...
Edit :
int main(int argv, char** args)
{
// Create test application.
QApplication application(argv, args);
QTextCodec::setCodecForCStrings(QTextCodec::codecForName("GB18030-0"));
//My main form shown here
return application.exec();
}
Related
So I'm trying to have my "button" directly execute a Batch file, important here is that I don't want it to show me a dialogue and make me chose the path, which is the problem I'm having right now with the following code
void MainWindow::on_pushButton_clicked()
{
QString filename=QFileDialog::getOpenFileName(
this,
tr("Open File"),
"C://",
"All files (*.*);;Text File (*.txt);;Music file (*.mp3)");
}
I think this is probably really simple, but i can't get it, I'm not even learning c++ at the moment but my boss asked me to create something out of my scope (wants me to create a GUI for a batch file and have them interact) and I thought of this approach, which is just creating a GUI that executes it.
I've looked at this question: asked to execute an external program with Qt
but they don't talk about how the file path can directly be added into the code, or if I should even be using Qprocess and how, and if I can pass it through "clicked" function.
I'm really inexperienced, all of the code above I got with the help of the internet, but I really don't know how to program using c++
so could someone please be kind enough to show me how a file path can be added to the code, assuming it's in C:\Users\name_goes_here\Downloads
I'd really appreciate it :D
I'd recommend using QProcess for anything "execute external program" with Qt.
You could do it like this:
void MainWindow::on_pushButton_clicked()
{
QProcess process;
process.start("C:/Users/name_goes_here/Downloads/yourfile.bat");
process.waitForFinished(); // Assuming that you do want to wait for it to finish before the code execution resumes
}
Note the "/" in the path. Only Windows uses the messed up "\" for path separation, which would require you to write "C:\\Users\\.." in any string in C++ as "\" needs to be escaped.
Luckily, Qt uses "/" as the universal separator and translates it to whatever the OS needs as required. So you should just use "/" whenever working with Qt.
This is from the Qt documentation:
Qt uses "/" as a universal directory separator in the same way that "/" is used as a path separator in URLs. If you always use "/" as a directory separator, Qt will translate your paths to conform to the underlying operating system.
And finally, if you don't know how to code in C++, shouldn't you be learning that first instead of trying to execute batch files from within a library as complex as Qt? Sounds like you're trying to do too many new things at once.
This is fairly simple merging your source and the one you linked:
void MainWindow::on_pushButton_clicked()
{
QProcess::execute(
QString::fromLatin1(
"cmd.exe /c C:\\Users\\name_goes_here\\Downloads\\file.bat"));
}
Notes:
I used QProcess::execute() instead of QProcess::start() to make things even simpler.
To achieve execution of the batch file, I pass it to cmd32.exe as this is the interpreter which is responsible.
As MCVE testQProcessBatch.cc:
// Qt header:
#include <QtWidgets>
void on_pushButton_clicked()
{
#if 0 // WORKS:
QProcess::execute(
QString::fromUtf8("cmd.exe /c C:\\Users\\Scheff\\Downloads\\testBatch.bat"));
#else // WORKS AS WELL:
QProcess::execute(
QString::fromUtf8("C:\\Users\\Scheff\\Downloads\\testBatch.bat"));
#endif // 0
}
int main(int argc, char **argv)
{
qDebug() << "Version:" << QT_VERSION_STR;
// main application
QApplication app(argc, argv);
QMainWindow qWin;
QPushButton qBtn(QString::fromLatin1("Start cmd"));
qWin.setCentralWidget(&qBtn);
qWin.show();
QObject::connect(&qBtn, &QPushButton::clicked,
&on_pushButton_clicked);
// run application
return app.exec();
}
and the test batch file testBatch.bat:
echo "This is testBatch.bat"
pause
Tested with VS2013 on Windows 10:
Thanks for contributing guys!
I tried using the QProcess method but I think I'm too inexperienced when it comes to figuring out problems associated with it (which I did face when using this method). the CMD route is probably good but I also thought it was too difficult and both of these methods didn't work for me.
Here's what I have now (thanks to Detonar and ymoreau) and and it seems to be doing the job, this might not be the most optimal approach, but it worked for me!
I included QDesktopServices and QUrl
void MainWindow::on_pushButton_clicked()
{
QString filename="C:\\Users\\Name_goes_here\\Downloads\\test.bat";(
this);
hide(); //optional
QDesktopServices::openUrl(QUrl("file:///"+filename,QUrl::TolerantMode));
}
Qt recently started crashing without having a reason for it. The most recent one which is currently grinding my nerves down to a pulp is crashing due to starting another form programmatically. The "must construct QApplication before a QWidget" apparently is a common issue with Qt 5.7.* versions and the solutions I have found so far in StackOverflow haven't helped me.
This is a screenshot of the error message I got after the application crashed:
And here is the bit of the code that I remove which allows me to restart the application without any noticeable problems:
#include "operations.h"
Operations o;
void mainWindow::on_thisButton_clicked()
{
o.show();
this->hide();
}
----
The main.cpp as requested :)
#include "mainWindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
mainWindow w;
w.show();
return a.exec();
}
Try this:
#include "operations.h"
void mainWindow::on_thisButton_clicked()
{
Operations *o = new Operations();
o->show();
this->hide();
}
You might want to declare Operations *o as a member of mainWindow and initialize it the the constructor if you don't want to create a new one each time the button is clicked.
"must construct QApplication before a QWidget" is the standard type of error you get with Qt applications, when linking something incompatible ( like mixing debug/release ).
So in most use cases this indicates a build problem and has nothing to with the code itself.
Don't create Operations object as a global variable, as it will be created as a static BEFORE running main(), therefore the error message is simply correct and relevant. This is a C++ issue, not a Qt one.
All other suggestions work because you now create the object at the right time, after the QApplication...
Okay, I have managed to find a solution, however, it is borderline idiotic as it does not make any sense why it does not work in its prior state. Technically, all you need to do in order to have the error not appearing is to stick the declaration of the form class you are referring within the function itself(ie Operations o;).
Here is the code solution itself:
#include "operations.h"
void mainWindow::on_thisButton_clicked()
{
Operations o;
o.show();
this->hide();
}
Bare in mind that this is not the end of all problems as I currently have the problem of the new form closing in the very same 1 second period it opens. If I manage to solve it I will update my solution.
Closed:
Thanks everyone for the ideas, will try to work with your provided suggestions so solve my problem!
Problem:
"C++ main" (which CANNOT #include QObject or any Qt lib) gets data, processes the data and passes it into a separate Qt process (Qt GUI in this case).
Data gets visualized within the Qt GUI and provides feedback, e.g. you can send commands to the "C++ main" (like START/STOP MEASUREMENT).
Visualization of the problem in best paint quality.
Question:
Is there any possible way for the "C++ main" to get feedback from the Qt GUI WITHOUT including Qt in "C++ main" in any way? (The "C++ main" runs on an I/O-card which is not able to process/load the Qt lib.)
Thank you in advance for helpful answers!
Without much code on what goes on in your "C++ main" it is difficult to answer. But if you have class with a proper interface that is created in main and then used for the IO you could do something like the following:
class MyIoHandler {
public:
enum Command {START, STOP};
MyIoHandler() {}
void command(Command command) { d_command = command; } // Set the command
void getData(MyData& data) { data = d_data; } // Do a deep copy
private:
void run()
{
while(d_command == START) {
readDataFromIO();
d_data = data;
}
}
Command d_command;
MyData d_data;
};
Then the GUI just need to call the correct functions on the class to interface with the IO handler. There is no need for the main class to know how the GUI looks, but the GUI must know how the class looks.
This is also working on the assumption that they are in the same executable (from the comments) and
You just need to take care about threading etc.
But as mentioned, without some structure or code examples it is very difficult to give a useful answer.
I normally use QUdpSocket (in the Qt world) to talk to my other apps (effectively for IPC). Then your c++ world you can use normal sockets sys/socket.h for the same job. Since your comms is simplistic - i.e. message passing this is quite easy to do. There is some effort creating your c++ / Qt class to handle your UDP, but from then on its really easy.
The main drawback for me is that the two programs have to agree on a port to use (The IP address would be loop back address 127.0.0.1). So you may have a configuration file, or a command line parameter to set this...
I'm having a bit of trouble in my attempts to learn WXWidgets. I'm currently trying to work with file Dialogs, and I've got one opening just fine. But I run into trouble whenever I try to apply styles to the window. I get an undeclared identifier for whatever style I use.
My code is as follows (yes, I know, hello world app. I'm experimenting with all the things I need to learn to do before actually making a fully fledged app)
#include "wx/wx.h"
#include "wx/filedlg.h"
#include "HelloWorldApp.h"
IMPLEMENT_APP(HelloWorldApp)
bool HelloWorldApp::OnInit()
{
wxFrame *frame = new wxFrame((wxFrame*) NULL, -1, _T("Hello wxWidgets World"));
wxFileDialog* OpenDialog = new wxFileDialog(frame, _("Choose a file to open"), wxEmptyString, wxEmptyString,
_("Image Files (*.jpg, *.png, *.gif, *.bmp)|*.jpg;*.png;*.gif;*.bmp|Sound Files (*.wav, *.mp3)|*.wav;*.mp3"),
wxFD_MULTIPLE);
frame->CenterOnScreen();
frame->Show(true);
OpenDialog->ShowModal();
SetTopWindow(frame);
return true;
}
It runs just fine without the "wxFD_MULTIPLE" argument. I'm using version 2.8.12 of wxWidgets.
Thanks for reading. I really appreciate any help or guidance anyone can give. Sorry if it's something really obvious I'm missing.
In very old wxWidgets versions (2.6), this style was known as wxMULTIPLE but wxFD_MULTIPLE is definitely available in any 2.8.x version. You should give the (beginning of) the errors you get to allow us to understand what is really going on.
Completely independently, your code is wrong because it contains a memory leak: the dialog must be destroyed as modal dialogs are exceptions to the usual rule that all windows should be allocated on the heap and can be allocated on the stack, i.e. used as simple local variables, see the example in the documentation. Looking at the "dialogs" sample code is also strongly recommended.
I am brand new to c++ so I apologize if this is a stupid question but I can't seem to find the answer to it.
I have been using Processing for a while now and would like to start using c++ because I heard it is faster and a program I made is too long/dense for Processing to run at a reasonable speed.
In Processing there is a setup void which runs once and then the draw void which runs continuously after that. This is what I am used to and I need it to make remake a program in c++ (a chess AI).
Is there a way to get int main to run continuously? If not can I have it call a function that will run continuously?
Also is there a way to make a window pop up when you run the program which you can draw geometry to? (I will need to make pieces that can be manipulated by a mouse ideally)
I'm using Xcode by the way
main() should typically do your setup and then start the main message-processing loop provided by your toolkit. The message processing loop will run continuously until the user requests your application to quit (or you ask the toolkit to shut down your app).
Your toolkit will call your draw function whenever your window needs to be painted. It will call other functions when user input such as keypresses or mouse clicks happen.
For example, if you were using the GLUT toolkit (for OpenGL, a very popular drawing API supported on Mac, Windows, Linux, and many mobile devices), your main function might look like this (complete tutorial here):
void main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DEPTH | GLUT_SINGLE | GLUT_RGBA);
glutInitWindowPosition(100,100);
glutInitWindowSize(500,500);
glutCreateWindow("My First openGL Program");
glutDisplayFunc(render);
glutMainLoop();
}
For Cocoa, the OSX native API, it might look like this (more information and links here):
#import <Cocoa/Cocoa.h>
int main(int argc, const char** argv)
{
return NSApplicationMain(argc, argv);
}
May I suggest that instead of asking very rudimentary questions like this on StackOverflow, you go and invest your time reading one of the thousands of introductory C++ tutorials that are scattered all over the web.
After a couple of hours of reading you'll find that questions like this are answered faster via a Google search.
Good luck with your learning.
You should not try to get main() to run continuously.
You may instead do something like this:
int main() {
while (true) {
//call functions here
}
return 1;
}
In C++, each function is defined by it's call and it's return. For example:
void foo()
{
cout << "hello world!";
return;
}
int main()
{
foo();
return 0;
}
When foo() is called, it runs until the return statement. If we want foo to run for some indeterminate amount of time, we could, for example:
void foo()
{
bool isExiting = false;
char input;
while( isExiting != true )
{
cout << "Exit? ";
cin >> input;
if ( input == 'y' )
{
isExiting = true;
}
return;
}
}
int main()
{
foo();
return 0;
}
This is a kind of ugly example - using cin to a char and whatnot - but it gets the idea across. The while loop will run forever and the innards of it (well, it's logic, anyway) could be replaced with whatever your program needed to do.
Make sense?
There are plenty of options as far as graphics libraries go; you can use SDL, GLUT/OpenGL, DirectX, even good ol' Win32. However, for someone who is relatively new to things as rudimentary as while loops, I suggest that you stay off the C++ for a while, as there are many peculiarities that might prove to be enormous roadblocks. If you really need every ounce of speed, I recommend that you make a DLL with your time-critical algorithms and use it in conjunction with a simpler language that supports DLL's, and provides a relatively developer-friendly interface. Game Maker comes immediately to mind, although I'm sure there are many options out there.
Best of luck.
I'd recommend having a look at Cinder or OpenFrameworks as a neat transition from Processing.org - especially if you're planning on doing multimedia applications (which, if you were using Processing, is likely)
They both provide a very similar layer to that of Processing, and will ease your journey somewhat.
You could also implement your own basic framework on top of SDL if you feel up to it.
As a more general answer to your question, the main() function is basically the same as the setup() function in Processing.org - with the main distinction being that it has to call a (user-provided) draw() function or equivalent.
So a rudimentary equivalent would be:
bool quit = FALSE;
void setup() {
// initialise the screen and so forth
}
void draw() {
// perform some drawing and update tasks
}
int main(int argc, char *argv[]) {
setup();
while (!quit) {
draw();
}
shutdown();
return 0;
}
NB: the above will probably compile, but it would do nothing except loop and potentially bog up your machine since it's not connected to any graphics library and is getting no user input to modify the quit boolean.
finally, I'll quote a section from the Cinder faq:
I’m experienced with Processing, but I
think I’m ready to try something new.
Is Cinder right for me?
Very possibly.
First though, be sure you really need
to move on to Cinder. Have you already
experimented with using an external
IDE like Eclipse? Are you using native
OpenGL calls instead of PGraphics?
What about experimenting with Toxi’s
excellent libraries? You’ll learn some
things that will make an eventual
transition to Cinder much easier, and
as much as we’re into C++, it’s easy
to underestimate how far Processing
can take you. All that said, don’t let
us talk you out of this either — if
you’re excited about learning Cinder,
we’re excited to have you, and we bet
you’ll find it’s easier to get started
than you might imagine.