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Join us on the #qpm channel

Roadmap

Introduction

qpm is a command line tool for accessing the qpm.io Qt package registry and installing dependencies.

qpm and the corresponding qpm.io service provide a way for Qt developers to search, install and publish source code (QML, JS, C++) components that can be compiled into Qt applications or libraries.

Content

Goals

qpm aims to:

  • Help application and library developers.
  • Provide a central registry of re-usable Qt components.
  • Produce consistent dependencies for applications.

qpm is not:

  • A binary package manager (like apt-get, yum, or brew).
  • A build system (like qmake or qbs).
  • A version control system (like Git or SVN).

How it works

Packages are published to the qpm.io registry by a package author. Only the meta data is stored in the registry, the actual source code resides in a public repository under the author's control (eg: Github).

An application developer installs a package that he or she wishes to use and qpm will fetch the source code for that package and also fetch any nested dependencies that the package has. The application developer can then use those package dependencies in their application.

A package in qpm terms consists of a qpm.json file which contains meta data about the package such as the name, maintainer, version, dependencies, etc. The name of the package must be unique as it is used later to avoid naming collisions.

When an application developer installs a package for use in a Qt app, qpm will automatically create a qpm.json file to track the apps dependencies. Even though apps contain qpm.json files, they should not be published to the registry. The qpm.json file should be checked into your version control system so that the dependencies can be re-created later. Upon installing a package dependency, the qpm tool will create a directory called vendor which contains the source code of the package. This is included in the application (see below) and can used as normal.

Installing

There are currently 4 ways to install the qpm client:

Download a binary

The pre-compiled binaries can be downloaded from http://www.qpm.io.

Install from a package manager

The goal is to make qpm available in the following desktop package managers:

Package Manager Status Command
Homebrew Done brew install qpm
MacPorts Not started
Chocolately Not started
RPM Not started
Debian Not started
Pacman AUR yaourt -S qpm

Use Qt's Maintenance Tool

qpm is a available via a custom repository which can be added to Qt's Maintence Tool which is part of the SDK.

  • Open maintenancetool.
  • Select "Add or remove components" (do not click Continue yet).
  • Click "Settings" in the bottom left.
  • Go to the "Repositories" tab.
  • Scroll to the bottom and select "User defined repositories".
  • Click the "Add" button underneath.
  • Enter the following URL: https://storage.googleapis.com/www.qpm.io/repository.[1]
  • Leave username and password empty.
  • Clicked "Test" to ensure everything is working.
  • Click "Ok" to exit Settings.
  • Click "Continue".
  • Expand the qpm item and choose your platform.

NOTE[1]: You can (and should) use HTTPS for the URL if it works, but at least on Mac OS X Yosemite, there is a problem with Qt's handing of Google's SSL certificate that prevents it from working.

Compile from source

The easiest way to build from source is to use the tools that ship with Go. If you already have Go installed and a workspace setup (GOPATH environment variable), then installing qpm is as simple as:

go get qpm.io/qpm

If you don't want to use go get and would prefer to do it the hard way, then you can do the following:

  • Ensure you have Go installed (tested with 1.4.2 and 1.5)
  • Ensure you have a workspace setup (ie: define GOPATH)
  • Clone this repository into $GOPATH/src/qpm.io

The qpm tool has its dependencies stored in the repo as Git submodules, so to initialize those you need to navigate to the root of the project and run:

git submodule init
git submodule update

Compiling the command line tool is as simple as:

go build qpm.io/qpm

Although you should probably install it as well with (installing runs the build step):

go install qpm.io/qpm

If you are using Go 1.5, then cross compiling is simply a matter of setting ´GOARCH´ and ´GOOS´, for example to generate a 32-bit Windows build:

GOOS=windows GOARCH=386 go install qpm.io/qpm

The compiled binaries are placed in $GOPATH/bin.

Usage for App Developers

Installing package dependencies with qpm requires no login or registration. You can search for packages using the following command:

qpm search <package name>

This will list a package and version number as well as the author. To get more information about the package, you can run:

qpm info <package name>

If the package sounds useful, you can install it:

qpm install <package name>

By default qpm will install the latest version of the component, however you can request a specific version using the following syntax:

qpm install package@1.0.1

Installing a package for the first time will create a new file called qpm.json. Subsequent installs will update this file with the new package. If you want to install all of the packages listed in your qpm.json file, then you use:

qpm install

With no arguments, this will install your dependent packages. Upon installing a new package, there will be a directory called vendor which contains the code for each package in its own subdirectory. The vendor directory will also contain a file called vendor.pri which should be included in your applications .pro file like so:

include(vendor/vendor.pri)

The vendor.pri takes care of including each package's .pri file which will expose the contents of the package to your project's build. Package .pri typically add files to SOURCES, HEADERS and RESOURCES so that they can be accessible to your app.

If the package contains QML or Javascript code, then you need to register it with the QML engine, like so in your main.cpp (or wherever):

    QQmlApplicationEngine engine;
	QPM_INIT(engine)
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

It is important that you call QPM_INIT before calling engine.load() because otherwise you will errors about missing components.

For packages that contain C++ code, these need to be manually exposed to QML for the time being, but perhaps we can find something clever here in the future.

Uninstalling package can be done with:

qpm uninstall <package name>

Usage for Package Authors

If you have an idea for a Qt component that you would like to share, you can publish it on qpm.io. qpm can help you get started by running the following interactive command:

qpm init

This asks some basic questions to get you going and to generate a qpm.json file containing your package's meta data. If you are starting from scratch, you can let the init command generate some boilerplate code for you. This generates some basic files that you can extend as you create your module. The boilerplate currently generated is:

  • qmldir: QML module definition file
  • package.pri: Pri file for inclusion (indirectly) by apps
  • package.qrc: A Qt resource file for listing embedded source such as QML, JS, etc.

To simplify deployment of applications that use your package, we recommend package authors to add as much as possible (QML, JS, PNG, etc.) to the resource file so everything gets compiled into the application binary.

If you don't use the init command to generate the boilerplate, then you should use the following command to ensure that everything is in the right place with the right format:

qpm check

This command checks for common mistakes that will likely result in yor package not working correctly.

Finally, when your package is ready to go, you can run the following command:

qpm publish

This command will prompt you to login or register and is required every time you publish a package. This is to prevent other people from publishing your package. In the future, it will be possible to have several contributors that can publish the same package.

Example Package

There is as example package which can be used as a template here:

https://github.com/Cutehacks/qpm-example

Package Naming

Due to the nature of qpm and the way it compiles everything into the same compilation unit, we strongly recommend (enforce in fact) that packages be namespaced at several levels. The package name itself should use the same reverse DNS naming scheme that is used by Java (io.qpm.example). This is done to avoid popular package names (eg: components) being used exclusively by a single person or company.

Package names should not include superfluous information such as "qt" or "qml". In the context of qpm, it is understood that a package is specific to Qt or QML so there is no need to state this explicitly. Note that the repository name can be completely independent of the package name. In that context, it most certainly can make sense to use "qt" or "qml" to differentiate the repository.

A note on versioning

qpm is somewhat strict on versioning. This is because one of the goals of qpm is to have consistent dependencies. If two applications use the same version of a package, they will contain the same code.

A version consists of a label (eg: 0.0.1) and a revision (eg: Git SHA1 or tag). For package authors, this means that once a version has been published, it cannot be republished with a different revision. Publishing a new revision entails publishing a new version. Multiple labels can point to the same revision though. This is to handle the case where, for example, a release candidate (1.0.0-rc1) is identical to the final release (1.0.0).

Publishing a new version of a package, is simply a matter of modifying the respective fields in the qpm.json file and running qpm publish. The meta data for a package is not versioned, so changing the description or author will affect all versions of a package. Nested dependencies for a package are versioned so publishing a new version with new dependencies will not affect previous versions.

Tips

Self-registering packages

Package authors should aim to make their packages self-registering. This means that application developers should require very little boilerplate code to start using your package. Typical boilerplate code is registering various types with Qt's various classes.

If you have QML items that are written in C++, your package can automatically register these types by using the Q_COREAPP_STARTUP_FUNCTION macro. For example, in one of your cpp files, you can do the following:

static void registerTypes() {
    qmlRegisterType<MyType>("io.qpm.MyPackage", 1, 0, "MyItem");
}

Q_COREAPP_STARTUP_FUNCTION(registerTypes)

The above function will automatically be called after Q[Core|Gui]Application is constructed so the application developer needs to do nothing else in order to start using your item 👌.

If you have items or types that are written in QML or Javascript, they get registered with the QML type system through a qmldir file. The pattern promoted by qpm involves putting your qmldir file inside a resource file to make it more self-contained, but this then creates the problem of how does the QML import engine find it? This is the reason that we added the QML_INIT macro which basically expands to this:

engine.addImportPath(QStringLiteral("qrc:/"));

This is somewhat suboptimal though and is the kind of boilerplate we would like to avoid when using qpm. In Qt 5.7 there was a change that updated the default import path with a path in the resource system. The path used was qrc:/qt-project.org/imports. This implies that it should now be possible for packages to write self-registering QML as well by adding the additional prefix to their qrc file. For example:

<RCC>
    <qresource prefix="/qt-project.org/imports/io/qpm/mypackage">
        <file>qmldir</file>
        <file>MyItem.qml</file>
        <file>...</file>
    </qresource>
</RCC>

Contributing

qpm is open source and we encourage other developers to contribute if they see an opportunity. The tool is written in Go so following the steps above to compile from source is a good place to start.

qpm uses Google's Protocol Buffers to communicate between the command line tool and the server. More specifically, it uses the new "proto3" version which has support for Go and also gRPC which is also used.

If you make change to the .proto files you need to follow the steps below.

Code Style

Since the app is written in Go, we request that all contributions be formatted with the go fmt tool. More info on this tool can be found here.

Additionally, if you edit the .proto file, you should follow the Protocol Buffers Style Guide.

Prerequisites

Ensure the following component is installed and the protoc command is in your path somewhere. Note that repository is independent of Go so it should be cloned and installed globally.

Generating Protocol Buffers

The generated code for the protocol buffers is checked in to the repo so the following steps are only needed if you modify the .proto file(s).

In order to use the source generator you need to first build the protoc-gen-go tool:

cd src/github.com/golang/protobuf/protoc-gen-go
go build
go install

You can verify that the binary was built correctly in $GOPATH/bin. The above is only done once.

Every time you make a modification to a .proto file, you need to regenerate some code by doing the following:

cd src/qpm.io/common/messages
protoc --go_out=plugins=grpc:. *.proto

This will generate files of the format *.pb.go in the same directory. You should check in the generated files for now.

FAQ

How stable is it?

This project is very young so your mileage may vary. At this point we are at the "Developer Preview" stage where feedback is the most important thing. We took a few shortcuts to get this out quickly, but we hope it scratches an itch for a few people at least.

Why did you make qpm?

Having now worked on frameworks outside of Qt, we saw that there was a big hole in Qt's developer offering. iOS has CocoaPods, Android has Maven/Gradle, Node has npm, Ruby has gem, Python has pip, Go has.. well Go. We wanted something that integrated well with Qt so we made something. We took inspiration from all of the above tools in some way or another.

Why Go?

The decision came down to Node.js, Go and Qt. Ideally we wanted to use a language that allowed us to share code between the client and server. Node and Go have stronger server side support than Qt/C++ so that eliminated Qt. There are plenty of cloud providers that support Go and Node but very few (any?) that support C++.

The beautiful thing about Go is that it compiles to a single static binary which is exactly what we wanted for a command line tool. It also makes server deploys easy :)

Why is the binary so big?

This seems to be a result of using Go which presumably has a rather large runtime associated with it.

How do I add a new FAQ?

Submit a pull request to this file with your question and create an issue for us to answer it!