declaration in header file
QColor dialogBoja, dialogBoja1;
.cpp file
dialogBoja = postavke.value("boja", Qt::black).toString();
//postavke means settings
dialogBoja1 = postavke.value("boja1", Qt::white).toString();
As I said on title, when I try to compile this in Qt5 I get error: QVariant::QVariant(Qt::GlobalColor)' is private
How to solve this.
You need to explicitly create a QColor object. This should work:
dialogBoja = postavke.value("boja", QColor(Qt::black)).toString();
The reason for this is explained in the header:
// These constructors don't create QVariants of the type associcated
// with the enum, as expected, but they would create a QVariant of
// type int with the value of the enum value.
// Use QVariant v = QColor(Qt::red) instead of QVariant v = Qt::red for
// example.
Looks like they wanted to divorce QVariant from the QtGui modules, like QColor, and removed that constructor in 5.0. Some syntax is explained here.
Because QVariant is part of the QtCore library, it cannot provide
conversion functions to data types defined in QtGui, such as QColor,
QImage, and QPixmap. In other words, there is no toColor() function.
Instead, you can use the QVariant::value() or the qvariant_cast()
template function.
Related
I have a Qt project, there I have an Object, which is going to be copied a lot of time. Therefor I would like to add move semantics.
#ifndef OBJECTTOCOPY_H
#define OBJECTTOCOPY_H
#include <QColor>
#include <QString>
#include <QDataStream>
namespace level_1 {
namespace level_2 {
class ObjectToCopy {
public:
explicit ObjectToCopy(const QString& _name = "", const QColor& colorBody = QColor() );
// MOVE
ObjectToCopy(ObjectToCopy && other);
static quint32 _valueInt32;
static quint16 _valueInt16;
QString _name;
QColor _colorBody;
private:
};
}
}
#endif // OBJECTTOCOPY_H
How do I steal the pointers of the member variables, since they are no pointers?
ObjectToCopy::ObjectToCopy (ObjectToCopy&& other)
: _valueInt32( other._valueInt32 )
, _valueInt16( other._valueInt16 )
, _name( other._name )
, _colorBody( other._colorBody )
{
other._valueInt32 = 0;
other._valueInt16 = 0;
other.name.clear();
other._colorBody = QColor();
}
Does that make sense for non-pointers?
Is it ok to reset QString 's like string.clear(); to mark that for the garbage collector?
How could I reset a QColor object?
You can add move semantics of course, but in your case there is no need in this at all. quint32, quint16 are moved by copying. QColor is wrapper around union and has no move constructor (and doesn't need one) and will also be moved by copying. QString is reference counted type in QT. It has move constructor in recent versions of library, but the difference in speed will be minimal (difference between swapping pointer and incrementing reference counter).
You are looking for std::move:
ObjectToCopy::ObjectToCopy (ObjectToCopy&& other)
: _valueInt32( other._valueInt32 )
, _valueInt16( other._valueInt16 )
, _name( std::move(other._name) )
, _colorBody( std::move(other._colorBody) )
{
other._valueInt32 = 0; //probably not necessary
other._valueInt16 = 0; //probably not necessary
//other.name.clear(); //not necessary
//other._colorBody = nullptr; //not necessary
}
It makes sense to move non-pointers. You are in the process of making such an object. Moving integers doesn't help, but doesn't hurt either, so you may as well do it for consistancy. Moving things that don't have a move constructor also works: If no move constructor is available the copy constructor is used (moving is not always better, but not worse either).
The implementation above says "move by copying the ints and moving the name and the _colorBody".
Make sure you do not read from variables you moved from.
It is ok, but not necessary. other is supposed to be a temporary that will get destroyed anyways. (C++ does not have a garbage collector in your sense)
Also once an object is moved from it tends to be in the cleared state like for QString, but that is not always the case.
You cannot really. You can assign a default constructed one like other._colorBody = QColor(); but that just means it sets the color to black. A QColor cannot be empty, it always has some color.
Also read What are move semantics?
How should this be done by using the model->setData() method call?
I have derived a class called "MyStandardItemModel" from QStandardItemModel. I have made my third and fourth columns non-editable by overriding the protected virtual flags method. This is how it goes:
#define TX_PACKET_COLUMN (4u)
#define RX_PACKET_COLUMN (5u)
Qt::ItemFlags MyStandardItemModel::flags(const QModelIndex& index) const
{
if (index.column() == TX_PACKET_COLUMN || index.column() == RX_PACKET_COLUMN)
{
return (QStandardItemModel::flags(index) & ~Qt::ItemIsEditable);
}
else
{
return QStandardItemModel::flags(index);
}
}
...
//Set model
ui->testCaseTableView->setModel(model);
Having this done, I am not able to edit the cells in the third and fourth column.
Now, I want that when I double click on these cells, a pop-up dialog comes up. I will modify some data in the editable field of that dialog, and then copy it back to the non editable cells inside the code.
I tried to just write a doubleclick() handler for the QTreeView and just copy some data to the cells just to see if it is possible to copy data to the non-editable cells.
This operation is failing, and the data is not written into the non-editable cells.
Here you can find the double click handler:
void MainWindow::on_testCaseTableView_doubleClicked(const QModelIndex &index)
{
QVariant variant;
variant.toString() = "AA";
if((index.column() == TX_PACKET_COLUMN)||(index.column() == RX_PACKET_COLUMN))
{
model->setData(index, variant); // set new value
}
}
The setData(..) operation is clearing the already written data in the cells, but string "AA" is not getting written. Please suggest how to copy some data to non-editable cells inside the code.
QVariant set is empty. Nothing needs to be wrong in your model. Error is on this line:
variant.toString() = "AA";
change to:
QVariant variant("AA"); // just for testing anyway
As I indicated in my comment, you have to fix this first issue:
instead of:
QVariant variant;
variant.toString() = "AA";
you should write
QVariant variant = QLatin1String("AA");
In general, you would look into the setData(...) implementation for such cases whether you emit the data changed signal properly and so forth, but here you are entering a prior issue which can lead to problems, so let us fix that.
Note, you should use QLatin1String to avoid the unnecessary explicit conversion from raw char* to QString. This is a good practice in general, and this is available with Qt 4 as well as Qt 5.
Although, you could also use the QStringLiteral macro for creating a QString very efficiently with template magic out of your raw literal, but that requires C++11.
I dont know a lot about C++, but I have to make work some C++ code with .NET. I try with DLLImport but I failed. So I try with C++/CLI to make kind of a wrapper.
But I'm not sure to understand everything...
This is the basic C++ H file with the function I want to export (MyFunction)
extern "C"
{
__declspec(dllexport) IplImage* MyFunction(IplImage *src, std::string* name, OneEnumerationType myEnum, bool myBool, float myFloat);
}
This is the Wrapper h code.
#include "MyFunction.h"; // the file containing the h code
#include <string>
namespace MyWrapper{
public ref class MyWrapperClass {
public:
MyWrapper(){};
IplImage^ GetMyFunction(IplImage *src, std::string^ name, OneEnumerationType myEnum, bool myBool, float myFloat);
}
This is the Wrapper cpp code.
#include "MyWrapperCode.h";
namespace MyWrapper{
IplImage^ MyWrapperClass::GetMyFunction(IplImage* src, std:string^ name, OneEnumerationType myEnum, bool myBool, float myFloat){
MyFunction(src, name, myEnum, myBool, myFloat);
}
}
These are my questions :
1) When I'm compiling, the error is "'^ : cannot use this indirection on type IplImage' and same message for type "std::string".
I have followed this logical :
ClasseNative clNat2 = *clNat; --> ClasseManagee clMan2 = *clMan;
ClasseNative &clNat3 = clNat2; --> ClasseManagee %clMan3 = clMan2;
ClasseNative *clNat4 = &clNat2; --> ClasseManagee ^clMan4 = %clMan2;
I have seen, that It was better to use System::String. I try this way but the initial function is using std::string... BTW, why is it better to change ?
2) How do I get the MyFunction IplImage result ? Thru a private member and a get I suppose but I dont know how to initialize it...
3) Tricky question. Is it possible for me to put the CLI obtains IplImage structure (from the OpenCV library) (the result of my function) inside a IplImage .NET structure, when I ll called my wrapper ? Dont know if the question is understandable...
Thanks a lot for your help.
Turning around for 3 days on this problem...
Your wrapper class needs to create a new std::string based on the content of a System::String^ parameter then pass to your native function. Otherwise you need to rewrite the function to take something else as the string input, for example a LPWSTR or LPCSTR.
You can write a ref class to have properties for all data that an IplImage would have, then pass that to your wrapper class. Your wrapper class then create an IplImage object based on the data of the ref class and pass to the native function. Reverse the data copying direction for the return value.
1) just by adding ^ you cannot change a native object to become managed, you have to create wrappers or transfer the data for example:
std::string nativeString = "my string";
String^ managedString = gcnew String(nativeString.c_str());
//now you can return it as
2) create a managed wrapper or use primitive datatype to transfer the data
3) note sure if this will help but look at Emgu.CV
try reading abit more about C++\CLI here are a few nice tutorials:
Quick C++/CLI - Learn C++/CLI in less than 10 minutes
C++/CLI for the C# programmer
QDir *temp = new QDir("%USERPROFILE%");
bool ok = temp->mkdir("abc");
and it does not work.
For portable Qt code, use static method QProcessEnvironment::systemEnvironment():
QProcessEnvironment env(QProcessEnvironment::systemEnvironment());
QDir *temp = new QDir(env.value("USERPROFILE")); // returns empty string for unset variable
bool ok = temp->mkdir("abc");
Alternative, as suggested in a comment of the actual question, you can also use
#include <cstdio>
QString envValue(QString::fromLocal8bit(::getenv("USERPROFILE"))); // standard, yet deprecated in Windows...
I'd prefer using the first alternative, letting Qt take care of character encoding stuff. If you want to use non-Qt functions, I think in Windows you should use getenv_s or _wgetenv_s to do this "properly".
I am trying to compile a library written in Qt 4.6. On my current Linux machine I have only Qt 4.7 installed. The following code part:
/*file try.h*/
void fileOpen(QString s = NULL) ;
/*file try.cpp*/
void MainWindow::fileOpen(QString s) {
QString filename ;
if(s.isNull()) filename = QFileDialog::getOpenFileName(
this,
"Choose a file",
".",
"Source file (*.)");
else filename = s ;
}
compiles with the following error (I used cmake but the corresponding line code is the one listed above):
In member function ‘virtual int MainWindow::qt_metacall(QMetaObject::Call, int,
void**)’:
/homes/combi/hodorog/Developments/axelOld/build/axel/src/QGui/moc_MainWindow.cxx:141:26:
error: conversion from ‘long int’ to ‘QString’ is ambiguous
/homes/combi/hodorog/Developments/axelOld/build/axel/src/QGui/moc_MainWindow.cxx:141:26:
note: candidates are:
/usr/include/QtCore/qstring.h:426:43: note: QString::QString(const char*)
/usr/include/QtCore/qstring.h:105:14: note: QString::QString(const QChar*)
So I am guessing the problem is that in qt. 4.7. there are two QString constructors that can take a pointer as an argument (as listed in the compilation error), whereas in qt 4.6. there is only one QString constructor that can take a pointer as an argument. How can I force QString to call the constructor with const char * as an argument?
Thank a lot for your help in advance,
madalina
void fileOpen(QString s = NULL);
You are trying to construct a QString object with 0. It seems you are confusing the null of pointers with a null QString. A null QString is one which is created with the constructor QString(). Given how your function is implemented (referring to s.isNull()), you should change the function declaration to
void fileOpen(QString s = QString());