Qt 5 Technology Preview

Technology Preview Bindings for the Qt5 Framework.

Please note that this is not production-ready – yet!

Project Goals

• Just Works™ - Drop the dependency into a project, and use it.
• Providing an API that feels native to Crystal
• Focus on the GUI components (That is, QtCore, QtGui, QtWidgets)

Preview Checklist

What works:

• Generation of bindings that feel kinda native
• Sub-classing C++/Qt classes
  • Overriding virtual C++ methods!
• Connecting to Qt signals
• Instantiating pre-specified C++ template containers
  • QList, std::vector, and friends

What's to be done:

• Forwarding qHash() of wrapped types (to Object#hash)
• Integration with LibEvent: Right now, Qt blocks the whole thread.
• The rest of the billion Qt classes of interest

Future

• Everything in the to be done category
• Integration for the Qt Designer UI designer
• Integration for Qt Linguist
  • Localization/Translation for your applications!
• UI test library, with adapter for spec
  • Also, actual tests - Let's catch whacko bugs right in the CI!
• Automated copy (and adaption) of the Qt documentation, for easy Crystal-specific docs
  • Haven't checked the license of the Qt docs yet though, maybe a legal issue?
• Proper bindgen documentation. It being a complex project is no excuse to not having proper docs.

Usage

Add this to your application's shard.yml:

dependencies:
  qt5:
    github: Papierkorb/qt5
    branch: master-ready-to-use

If you want to generate the bindings yourself, use:

dependencies:
  qt5:
    github: Papierkorb/qt5
    branch: master

And then run crystal deps and lib/bindgen/tool.sh qt.yml to generate them.

Sample code

Have a look in samples/!

Though, to make this not look empty, here's the possibly simplest program imaginable:

require "qt5" # Require it!

qApp = Qt::Application.new # Create the application

# Display something on the screen
label = Qt::Label.new "Hello from Crystal/Qt!"
label.show

Qt::Application.exec # And run it!

Name rewriting rules

• Everything resides in the Qt module (As configured)
• Classes get their Q prefix stripped: QWidget -> Qt::Widget
  • This is the only manual rule. All other rules are automatic.
• Method names get underscored: addWidget() -> #add_widget
  • Setter methods are rewritten: setWindowTitle() -> #window_title=
  • Getter methods are rewritten: getWindowTitle() -> #window_title
  • Bool getters are rewritten: getAwesome() -> #awesome?
  • is getters are rewritten: isEmpty() -> #empty?
  • has getters are rewritten: hasSpace() -> #has_space?
• On signal methods:
  • Keep their name for the emit version: pressed() -> #pressed
  • Get an on_ prefix for the connect version: #on_pressed do .. end
• Enum fields get title-cased if not already: color0 -> Color0

Dependencies

Developing with these bindings

• Qt5 of version Qt 5.9.x, development headers and libraries
• A modern C++ compiler

What your user will need

• Only the Qt5 libraries

Contributing

1. Talk to Papierkorb in #crystal-lang about what you're gonna do.
2. You got the go-ahead? The project's in an early state: Things may change without notice under you.
3. Then do the rest, PR and all. You know the drill.

Licenses

The Qt bindings, including the generated and manually-written parts, are subject to the MPL-2 license. You can find a copy attached of the full license text in the LICENSE file.

This project claims no copyright on the Qt framework or of any of its trademarks, source, or any other assets.

Questions? Contact Papierkorb.

Contributors

• Papierkorb Stefan Merettig - creator, maintainer