When I run the Qt Creator dbus examples, they couldn't run, is there any settings or stuff for working QtDbus module or any prerequistics?
for example in chat project:
if (!QDBusConnection::sessionBus().isConnected()) {
qWarning("Cannot connect to the D-Bus session bus.\n"
"Please check your system settings and try again.\n");
return 1;
}
returns 1 and program terminated.
Finally I found the solution:
For QtDbus module get working, The 3rd party Dbus module must be installed in Windows:
Dbus Windows Installer Download
After downloading and installing Dbus, it gets working without any configuration. (for working QtDbus, dbus-daemon.exe must be running)
Thankyou, you gave me the clues i needed to get started. However, in order to move with the times and keep this topic up to date...
I am using Qt 5.7.0 and no matter what I tried I could not get dbus v1.4.2 or 1.4.6 from your link to work with Qt.
It seems for Qt 5.7.0 a newer version of DBus is needed (I don't know the technical detail of why this is the case)... luckily I have stumbled across 1.8.10 prebuilt:
http://lists.qt-project.org/pipermail/development/2014-December/019502.html
All credit should go to the original compiler of this package, not to me, but if the link goes down, I will do my best to rehost and update, just drop
me a comment.
All QDBus examples from Qt5.7.0 work out of the box with this version.
For anyone who is inclined to start fiddling with bus addresses, environment variables, config files, etc... try this later build FIRST!
Obviously, this version is just a zip, not an installer - so you need to add the "bin" folder to your $PATH.
Related
I have successfully deployed my Qt application, with all the necessary dll files, and it works fine. However, as soon as I add something which uses Qt5Network, my program crashes with "The application was unable to start correctly (0xc000007b)".
I of course copied the Qt5Network.dll to my deployment dir, and I used a dependency walker, and found out that there was one new dependency compared to what I had before adding the "network" part: libgcc_s_seh-1.dll
I copied that as well, still the same error.
I learned that Qt Network requires OpenSSL, so I found libeay32 and ssleay32, and copied them to my deployment directory as well.
The error is the same. If I remove the requirement for Qt5Network, my program runs fine, and it uses many other modules, like Printsupport, Serialport, etc. without problem.
I tried it on Qt 5.9 and 5.15.
The official Qt binaries (Qt Network in your case) will try to load OpenSLL when first needed, at runtime, not when you first launch your application, see the SSL section here. And I believe that's the reason why dependency walker and windeployt were not able to identify OpenSSL as they can only identify load-time dependendencies.
It seems you were trying to bundle the OpenSSL binaries from an incompatible version. Starting with Qt 5.12.4 the supported OpenSSL version is 1.1.1, see for instance here. If you find the binaries from v1.1.1 and bundle those, your application should work.
I want to use Qt 5.10.1 with Vulkan. I downloaded prebuilt gcc_64 version, opened hellowulkanwindow application, set VULKAN_SDK in build environment. But the compilation gives me a lot of errors, for example 'QVulkanWindow' does not name a type. It looks like the macro QT_CONFIG(vulkan) return false, but I'm pretty sure that prebuilt version should come with Vulkan enabled.
VulkanSDK installed on my system, I can run demos. Also I can run non-qt code which uses Vulkan.
So how to check that feature QT_FEATURE_vulkan is enabled?
Upd: I ran configure -list-features in 5.10.1 sources and it didn't showed me anything related to Vulkan.
You can check the QT_FEATURE_vulkan definition in the qtgui-config.h header file (1 means enabled, -1 means disabled). You can just type QT_FEATURE_vulkan in Qt Creator and press F2 to nagivate to its location in the header file.
Apparently Qt 5.10.0 and 5.10.1 provided by the official installer do not have Vulkan support enabled, at least on Linux.
I have a project which is using Qt 4.7.4 version (also I can't rebuild it using qt4.8 or qt5 – there are a lot of errors appears, project is big and not mine so fixing issues would be even harder than erasing the whole code and write new code). So I need to make this project, well, working on NativeClient.
Is it even possible? I use Windows and Visual Studio, I was trying to google instructions about qt+nacl on Windows but just can’t find nothing.
Also which pepper version should I use if it depends on it?
Is your qt build supporting native client?
Please check out this
Windows
The Qt-Nacl is not support, for now, in Windows.
By the way, here is the github repository dedicated for it -> https://github.com/msorvig/qt5-qtbase-nacl
In the file nacl-readme it is written :
[...] Windows is not supported as a host platform.
Linux
If you want to compile in Linux, I have made a script that will compile Qt5.4 with NaCl with all the dependencies needed.
https://gist.github.com/theshadowx/438297ac465874a5e226
I also made a video that will show the different steps and a showCase at the end :
https://www.youtube.com/watch?v=q2pMv1Svtqw
I'm trying to access a MySql database from a Qt application but I get the following error:
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QSQLITE2
I find this very strange cause I have libqsqlmysql.so on my Qt folder. I have even tried to compile the MySql driver as a static plugin and add it to my .pro file as:
QTPLUGIN += qsqlmysql
But this also generates the same runtime error (it must've found the plugin cause there's no error compiling the application)
What am I missing? I would like to avoid having to compile Qt from source cause this will have to work seamlessly on the deploy machines as well.
BTW: Even though I'm developing and testing on Linux I will need to support Windows. Will I experience this same issue on Windows? How can I compile and link the MySql driver in both Linux and Windows?
The solution:
After following #Sergey's recommendations I did an strace of the application redirecting the output to grep so I could search for 'mysql' and for my surprise the application wasn't looking for the plugin at QTDIR/plugins/sqldrivers where I had libqsqlmysql.so, it was looking at QTDIR/lib. After copying the plugin to the lib folder the MySql connection worked.
Try opening the shared library with dlopen() and see if it loads and if not, what dlerror() tells you. I always run into similar problems on Windows. LoadLibrary()/GetLastError() saved me numerous times (last time it was because of a wrong version of some libiconv/libintl DLL). Running ldd on the plugin may also help.
If dlopen() works fine, try to load the plugin with QPluginLoader. If it doesn't load, then check the buildkey of the plugin. I usually do it the dirty way by running strings on the plugin and then looking for strings like "buildkey" or "QT_PLUGIN_VERIFICATION_DATA". Just looking at the build key and around it may give you an idea. For example, you may realize that you have compiled your plugin in the release mode while your application is compiled in the debug mode. In such case the build key won't match and the plugin won't load. Everything in the build key must match your configuration. Note that the version and the build key are checked differently: the build key must match exactly (or match some black magic called QT_BUILD_KEY_COMPAT), but in the version only the major version must match exactly, the minor version must be the version of Qt the plugin was compiled with or later and the patch level is ignored. So if your plugin was compiled with Qt 4.x.y then it will work with Qt versions 4.z.* where z>=x. This actually makes sense.
If the build key looks okay (which is unlikely if you got to this point), you may wish to look at QLibraryPrivate::isPlugin() source code to figure out what's wrong, but that doesn't look like an easy task to me (although running this in a debugger may help).
If QPluginLoader does load the plugin, check if it is in the right directory and has correct permissions. If you still didn't solve the problem by this point, it's time to look at the SQL module source code that actually loads these plugins. But it is extremely unlikely. I ran into this problem many, many times and it was always either the library not loading or the build key not matching.
Another way to go after QPluginLoader loads the plugin successfully is to use strace to figure out whether the program at least tries to open the plugin file. Searching for something like "sqldrivers" or "plugins" in the strace output should also give away the directory where Qt is searching for its plugins and specifically SQL drivers.
Update
Is it possible to compile the driver as a static plugin and don't worry about anything? Let's try:
d:\Qt4\src\plugins\sqldrivers\psql>qmake CONFIG+=static LIBS+=-Ld:/programs/Post
greSQL/lib INCLUDEPATH+=d:/programs/PostgreSQL/include
d:\Qt4\src\plugins\sqldrivers\psql>make
It compiles fine and now I got libqsqlpsql.a (release) and libqsqlpsqld.a (debug) in QTDIR/plugins/sqldrivers (it is the right place on Windows). I am using PostgreSQL driver here, but I don't think it will be any different for MySQL which I just don't have installed. Ok, let's compile some real program with it:
d:\alqualos\pr\archserv>qmake QTPLUGIN+=qsqlpsql PREFIX=d:/alqualos LIBS+=-Ld:/g
nu/lib INCLUDEPATH+=d:/gnu/include LIBS+=-Ld:/programs/PostgreSQL/lib LIBS+=-lpq
Note that I had to manually link to libpq, otherwise the linker would complain about undefined references. The funny thing is, qmake knows that qsqlpsql is located in QTDIR/plugins/sqldrivers and sets compiler and linker options accordingly. So it still needs to be in the right place to work, only you don't have to worry about your users running into the same problem as it is only used during compilation. An alternative would be to just use LIBS+=-Lpath/to/plugin LIBS+=-lqsqlpsql instead of QTPLUGIN+=qsqlpsql, at least the docs say that it should work, but I haven't tested it.
In order for the application to actually use the plugin I had to put the following in my main unit (CPP file):
#include <QtPlugin>
Q_IMPORT_PLUGIN(qsqlpsql)
It works! Also, from what I've been able to figure out from the sources, the build key and the version are checked only when a plugin is dynamically loaded (all the relevant stuff is in the QLibrary's private class, not even QPluginLoader's). So the resulting executable may (or may not, depending on the binary compatibility) work even with different versions and builds of Qt, although using it with older versions may trigger some bugs that were fixed later.
It is also worth noting that the order for loading SQL drivers is this: use the driver statically linked into Qt if available, then look for a driver registered manually with QSqlDatabase::registerSqlDriver(), then look for a driver statically imported into the application (the way described above), and finally try to load a shared plugin. So when you link statically, your users won't be able to use dynamically linked drivers they may already have, but will be able to use drivers linked statically into Qt (like in Ubuntu).
I compiled QT first and then realised that I need mysql as well. So I compiled mysql plugin by
executing following command in QT-DIR\src\plugins\sqldrivers\mysql folder.
Mysql plugin compile command
qmake "INCLUDEPATH+=$$quote(C:\Program Files\MySQL\MySQL Server 5.5\include)" "LIBS+=$$quote(C:\Program Files\MySQL\MySQL Server 5.5\lib\libmysql.lib)" mysql.pro
Plugings are then created in created in folder QT-DIR\plugins\sqldrivers.
However, when I tried to use it in my code. It failed with following error.
Error msg
QSqlDatabase: QMYSQLDriver driver not loaded
Solution
After some googling and checking Path variable I realised that the Mysql server lib
( C:\Program Files\MySQL\MySQL Server 5.5\lib) directory was not in my Path variable. I expect that the dll in this folder are used by the plugin at runtime. After including Mysql server lib in Path variable everything worked smoothly. Hope this information saves some hair on other programmers scalp, as I uprooted quite a few. :D
Last time I looked at this you needed to rebuild Qt from source and include the appropriate MySQL source.
Building Qt from the sources is not hard, it just takes a while. You are likely to have the required tools already.
A possible workaround may be to access the back-end over ODBC instead.
In order for your app to pick up the plugin at runtime, the shared library implementing the MySQL plugin needs to be placed in the correct directory. The best way of determining that directory is to check the output of QCoreApplication::libraryPaths. You can also force specific paths by using a qt.conf file.
Please note that plugins must be placed in subdirectories within the plugin path, and the final part of the path name (i.e., the parent directory of the shared libraries) cannot be changed. SQL drivers need to go in a directory named sqldrivers, i.e. <pluginpath>/sqldrivers. For more details on plugin directories, see How to Create Qt Plugins.
I was experiencing this same issue as well. I've been installing and experimenting with a lot of different Python tools and UIs. I then uninstalled everything python related. I did a fresh install of Python 3.2, PyQT 3.2, and Eric5. No more errors with the QMySQL driver.
well i have had this issue, and after a lot of time, and different tools, i found that QT ( on windows, have not been able to test on Linux.) loads the "QSQLMYSQL.." when requested, but before runtime the lib ("QSQLMYSQL..") file must reside on one of the searched paths (QApp.libraryPaths()) inside a folder called "sqldrivers".. otherwise QT will just ignore the file, even if it is at some other point inside the searched path.
what i did was to monitor the dependency of a sample app, and when i removed the "QSQLMYSQL.." dll from "plugins\sqldrivers\" it failed, but when i maded a folder inside the app folder, called "sqldrivers" and placed the "QSQLMYSQL..." inside there, it loaded.
what i have is mysql 5.5, qt 4.7.4.
hope anyone can use this, and if anyone knows more about it, i would like to know where to find it(http://doc.qt.nokia.com/stable/sql-driver.html, is the closest you can get to the information about the folder structur). :P
This may also happen if your QMYSQL plugin is linked against the "wrong" mysql_client.a or it isn't in the LD_LIBRARY_PATH. I had this problem on OSX because mysql was installed via ports, and I fixed it with:
install_name_tool -change libmysqlclient.18.dylib /usr/local/mysql/lib/libmysqlclient_r.18.dylib libqsqlmysql.dylib
I have downloaded QT SDK LGLP (Creator + libraries) 4.6 and I am having problems compiling projects. After install I have added C:\Qt\2010.02\qt;C:\Qt\2010.02\qt\bin to PATH and added QTDIR env varaible containing C:\Qt\2010.02\qt, the I run "configure -platform win32-g++" to compile it. Everything went good.
I the tried to use QT Creator to create and compile a project.
The problem is everytime I try to compile I get the following error message:
No valid Qt version set. Set one in Tools/Options
Error while building project GUITest
When executing build step 'QMake'
Canceled build.
When I go to Tools/Options the manual version is set to v4.6.2, Location c:\qt\2010.02\qt\bin\qmake.exe. The auto detected version is set to even though I have added the dirs in Path. Is there something I am doing wrong here? Has anyone encountered this problem in Vista.
I have been working on this for 2 days, change configurations, reinstalled etc...
The QtDir value is compiled into the
qmake-binary. You can only change this
by recompiling qmake and passing on a
different value to qt-configure (I'm
not sure which setting or variable is
passed on to qmake) When using
precompiled, downloaded binaries,
you'll have to keep the QtDir at
c:\Qt\4.6.2
EDIT:
What I said was incorrect. The locations of qmake, moc,... are located in the file:
<Qt>/4.x.x/.qmake.cache
Try uninstalling/reinstalling qt creator
But i highly suspect you didnt compile qt properly as this problem seems really odd. I had alot of problems compiling so i know myself from the past mistakes.
Make sure you carefully reread install instructions for your environment, also if you have visual studio you need to follow procedure to install it in compliance with it. Same if you use another c compiler
If nothing goes right, the easiest way to install qt imo is directy from their git hub, chec installin qt from git, on their git site there is wiki that explains how to do it
its really easy and after that all you need to do is add the qt to creator
Hey, it QT emulators have lot of problems in vista, i have tried several times,it didnt work for me.. it works well with windows XP. though ill tell you in brief what you need to do
1)install latest perl
2)install carbide c++ editor
3)install Qt SDK
4)install s60 or N97 emulators
make sure that except perl all the items which are mentioned above will be in same drive,and also
make sure that folder names which you give while installation should not have spaces at all..
i.e suppose if you are going to place any of the above items in a folder whose name is having spaces it will not work.
if you have any doubts feel free to ask.