I am trying to make a pdf viewer in Qt5.8 .I know that poppler is a choice for Qt but I want to do this using pdf.js .I dont know how to embed pdf.js with Qt5.8. I have seen the hello world documentation of pdf.js but it didn't helped. Please help me.
Thanks in advance .
The basic idea would be to have some widget to display HTML if you want to make use of pdf.js - it seems that QWebEngineView (makes use of Chromium) could do the job as it takes a minimum of code to get your first implementation done.
Having an installation of pdf.js on your computer and a minimalistic gui application (QT Widgets project) prepared with your QT Creator, you could use the following code to have the basics:
#include "mainwindow.h"
#include <QApplication>
#include <QWebEngineView>
static QString pathToPDFjs = QString("file:///path-to/pdfjs-1.8.170-dist/web/viewer.html");
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MainWindow win;
QWebEngineView *view;
QString pdfFileURL;
//you could parse a widget to get the file name
pdfFileURL = QString("file:///path-to-your/file.pdf");
//init the view and attach it to the ui
view = new QWebEngineView();
win.setCentralWidget(view);
win.show();
//auto-load feature in pdf.js, pass file=filename as parameter
view->load(QUrl::fromUserInput(pathToPDFjs + QString("?file=") + pdfFileURL));
view->show();
return app.exec();
}
From there on you can add extra functionality to your user interface.
You could even add modifications to your installation of pdf.js (if needed).
If you'd need to call JavaScript on your pdf.js, you can make use of the view's page (a QWebEnginePage) which in turn can runJavaScript.
No idea why you want to use pdf.js, but you might want to have a look at QtLabs PDF module. It seems pretty recent and well integrated with current Qt. (and I guess it's more efficient than JavaScript code)
If you want to try it out, here’s how to get started:
git clone git://code.qt.io/qt-labs/qtpdf
cd qtpdf
git submodule update --init --recursive
qmake
make
cd examples/pdf/pdfviewer
qmake
make
./pdfviewer /path/to/my/file.pdf
Related
Having trouble adding background image on the widget, even though I referenced the recent codes online.
This is my current code for main.cpp:
#include <QApplication>
#include <QWidget>
int main (int argc, char **argv){
QApplication app (argc,argv);
QWidget *w=new QWidget();
w->setStyleSheet("background-image: url(:/cover.jpg);");
w->setWindowTitle("Test");
w->show();
return app.exec();
}
After executing the code, how come the widget remains blank? Thanks in advance!
QtCreator is an IDE designed by Qt. It's just an interface.
I checked your implementation and I don't see anything wrong. It also work well on my pc. Can you check your image url or try with another image ?
Btw, if you're on linux, try removing : character after url ;
w->setStyleSheet("background-image: url(/cover.jpg);");
EDİT:
If jpg is in the same directory with your application, it should be ;
w->setStyleSheet("background-image: url(./cover.jpg);");
You can give a full path to avoid this kind of errors.
"Is it possible to add background image on QWidget without using QtCreator?"
Yes, of course it is.
QtCreator is just an IDE. You don't need to use it at all to write code using the Qt library.
Just as you can use it to write code that does not use Qt at all.
We have an application (QCoreApplication) that takes some images as input, does something to them, and exports them again. We now need to add some text to the images, and tried to do this with the QPainter class. It all worked well when using it in one of our other apps (using QApplication), but not in our main QCoreApplication app.
Here is the code:
void drawTextOnImage(QImage* image, const QString& text, const QFont& font)
{
QPainter p;
if (!p.begin(image)) return;
p.setFont(font);
p.drawText(image->rect(), Qt::AlignLeft | Qt::AlignTop | Qt::TextWordWrap, text);
p.end();
}
The application crashes on the drawText line.
Any ideas?
It is a very simple text, so suggestions without using Qt will also be appreaciated.
When using classes from "Qt Gui" like QPainter, you are supposed to use a QGuiApplication, not a QCoreApplication.
You might get lucky and be able to make some GUI stuff works while using only a QCoreApplication. But as you have discovered, it makes your application very brittle. Some classes like QPixmap will print an error message, but others will just crash.
The same is applicable with "Qt Widget": if you use a widget related class, you must use a QApplication.
Note that since QApplication inherits QGuiApplication, if you have a QApplication you can use "Qt Gui".
In case you need to run a non-GUI application on something without a windowing system, you need, aside from creating an instance of QGuiApplication, to also choose an appropriate Qt platform.
For me, offscreen platform worked fine. I was generating images with textual elements and saving them to files on a headless Raspberry Pi. My code then was like the example below. Note that setenv is a POSIX function and may need a replacement on Windows, though I'm not sure whether windowless Windows is a thing at all.
#include <stdlib.h>
#include <QImage>
#include <QPainter>
#include <QGuiApplication>
int main(int argc, char** argv)
{
setenv("QT_QPA_PLATFORM","offscreen",1);
QGuiApplication app(argc,argv);
QImage img(128,128, QImage::Format_RGB888);
img.fill(Qt::white);
QPainter p(&img);
p.drawText(QPoint(0,64), "Works!");
img.save("/tmp/test.png");
}
I have a GUI application written using Qt Widgets. I've added versioning and I'm planning to write an update manager too. In order this to work the update manager must be able to determine the version of my app. I thought of implementing this by running my app with a version switch then parsing it's output. I did a research and I found out that Qt has some kind of built in solution for this.
Here is an example:
#include "mainwindow.h"
#include <QApplication>
#include <QCommandLineParser>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QApplication::setApplicationVersion("1.0.0");
QCommandLineParser parser;
auto versionOption = parser.addVersionOption();
parser.process(app);
if (parser.isSet(versionOption))
{
MainWindow w;
w.show();
return app.exec();
}
return 0;
}
If I launch this app with a -v or --version command line switch, I get a message box containing the version information.
I need to achieve the same, only the information should be printed to standard output. If the app is launched with the version switch it should only display the version in the console then close.
How could I print the version information to the standard console output with a GUI app?
As we cleared some points in comments let's move on. ;)
Take a look at the documentation (http://doc.qt.io/qt-5/qapplication.html#details). In the detail section you see a sane way how to properly parse and handle command line options.
And here (https://stackoverflow.com/a/3886128/6385043) you can see a possibility for writing to standard output. Notice the QDebug caveat.
In my opinion, stick to the text file. You may generate it during build with qmake using the variable VERSION, which you can also use with QApplication::setApplicationVersion(QString).
There is a simple code for translating. It runs in Ubuntu 14.04.
#include <QtGui>
#include <QApplication>
#include <QLabel>
#include <QTextCodec>
int main (int argc,char *argv[])
{
QApplication app(argc,argv);
QTranslator qtr;
qtr.load("hello.qm");
app.installTranslator(&qtr);
//QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
QLabel *label=new QLabel(QObject::tr("hello"));
label->show();
retrun app.exec();
}
I had followed the below steps to translate hello to the chinese 你好 by Qt linguist:
add TRANSLATIONS +=hell0.ts to hello.pro and lupdate.
open the Qt linguist and find that the interface is
It is not like the normal Qt linguist interface. This is my first problem. How can i fix it?
Then i print 你好 to translate 'hello', but nothing is displayed in the blank.
I still push the 'done' button.
I use gedit to open the hello.ts and see that it has been tranlated to 你好.
The picture is
(3) I use 'lrelease' command and get the hello.qm
Last, i run the code as aboved. But the result is just to print 'hello' out.
It doesn't translate 'hello' to 你好. This is my second problem.
I also had used other methods like QtTextCodec::setCodecForTr instead of Qt linguist,but it still doesn't work.
Try to call retranslateUI(this) so the Translation will be updated
I am going to write program using Qt for some image processing and I want it to be able to run in non-gui mode (daemon mode?). I'm inspired by VLC player, which is "typically" GUI program, where you can configure it using GUI, but you can also run it in non-gui option when it runs without GUI. Then it uses some configuration file created in GUI mode.
Question is how should be such a program design? Should be some program core, which is GUI independent and depending on options it is being connected with GUI interface?
Yes, you could use a "headless" or "gui" option for the binary using QCommandLineParser. Note that it is only available from 5.3, but the migration path is pretty smooth within the major series if you still do not use that.
main.cpp
#include <QApplication>
#include <QLabel>
#include <QDebug>
#include <QCommandLineParser>
#include <QCommandLineOption>
int main(int argc, char **argv)
{
QApplication application(argc, argv);
QCommandLineParser parser;
parser.setApplicationDescription("My program");
parser.addHelpOption();
parser.addVersionOption();
// A boolean option for running it via GUI (--gui)
QCommandLineOption guiOption(QStringList() << "gui", "Running it via GUI.");
parser.addOption(guiOption);
// Process the actual command line arguments given by the user
parser.process(application);
QLabel label("Runninig in GUI mode");
if (parser.isSet(guiOption))
label.show();
else
qDebug() << "Running in headless mode";
return application.exec();
}
main.pro
TEMPLATE = app
TARGET = main
QT += widgets
SOURCES += main.cpp
Build and Run
qmake && make && ./main
qmake && make && ./main --gui
Usage
Usage: ./main [options]
My program
Options:
-h, --help Displays this help.
-v, --version Displays version information.
--gui Running it via GUI.
You can pass an argument to your application when starting to show in gui or non-gui modes. For example if you pass -non-gui parameter when running in command line then the application should not show the main window and it should do some other stuff :
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
bool GUIMode=true;
int num = qApp->argc() ;
for ( int i = 0; i < num; i++ )
{
QString s = qApp->argv()[i] ;
if ( s.startsWith( "-non-gui" ) )
GUIMode = false;
}
if(GUIMode)
{
w.show();
}
else
{
//start some non gui functions
}
return a.exec();
}
The example by lpapp above didn't work for me, as I got
qt.qpa.screen: QXcbConnection: Could not connect to display localhost:10.0
Could not connect to any X display.
when running without an X display (any value for DISPLAY, not just localhost:10.0).
There was a workaround - export QT_QPA_PLATFORM='offscreen' - but that's not a command line option, your user is expected to do it, which isn't nice.
So, following posting a question here, further research lead me to the following QT5 document that explains the "approved" way to start up with or without a GUI depending on command line options:
https://doc.qt.io/qt-5/qapplication.html#details
However, your mileage may vary. The example there didn't "just work" for me, either!
I had to use the command line arg to then choose one of two methods to run. Each method created its own app object (QCoreApplication for headless, QApplication for GUI, as the docs show) and then running the app.
It may be because I'm working with "mostly Qt 4" code and compiling on Qt 5 that things are being a bit odd but this method now works, so I've not investigated further.
With Qt5, running a Qt application with the command line argument -platform offscreen does draw offscreen.
See the documentation https://doc.qt.io/qt-5/qguiapplication.html#QGuiApplication
The options currently supported are the following:
-platform platformName[:options], specifies the Qt Platform Abstraction (QPA) plugin.
Overrides the QT_QPA_PLATFORM environment variable.
The supported platform names are listed in the platformName docs.
Tested with Qt 5.15.1