Welcome to LeanQt - the lean, adaptable Qt version

LeanQt is a stripped-down Qt version which includes the essential features and is easy to build from source and to integrate with an application.

My primary motivation for LeanQt was to make my Oberon compiler and IDE easier to compile and deploy on all relevant platforms with as few dependencies as possible. Many of my tools are based on Qt 5, which is an excellent framework that provides all the necessary features in a platform-independent way. Qt 5 has low requirements for the C++ compiler and is available virtually on all platforms where there is a C++98 compiler.

Unfortunately, there has been a certain proliferation over the years where Qt has been bloated with all sorts of features with questionable value. The standard binary installation of Qt is huge and requires a login to a commercial company server, which discourages many people. The official build is rather complicated with a lot of dependencies and sometimes incompatibility issues (depending on the OS and required Qt version). The now initiated development with Qt 6 makes higher demands on compiler and system, and follows a development that I cannot make sense of. For applications using only the non-gui part of Qt, or only basic GUI features, these are significant impediments.

For LeanQt I used the code of Qt 5.6.3 which was the last Qt version available under both LGPL v2.1 and v3. Instead of qmake the BUSY build system (see https://github.com/rochus-keller/BUSY) is used, which was one of the reasons I implemented it. LeanQt has a different source tree structure compared to the original Qt toolkit; a lot of the original subdirectories (e.g. mkspecs, qmake) are no longer required; there are no longer separate subdirectories under corelib or gui since each was depending on every other anyway. I also added additional configuration options so it is possible to use a minimal version even without the file engine and core application (see the BUSY file in the root for more information); many changes were necessary to the original source code for this, but the API is mostly the same and thus the original Qt documentation is still valid.

In contrast to original Qt, where by default everything is included and minimization takes a lot of work, the default configuration of LeanQt is minimal, and features are added on demand using the HAVE_x parameters (where 'x' is e.g. THREADS, FILEIO, SSL, WIDGETS and the like, see below).

It is not necessary to deploy the whole source tree; if an application doesn't e.g. require image or gui support, the corresponding source code directories can be deleted. BUSY has a fallback mechanism for the case when a module is not present; if e.g. the image or net directories are deleted, BUSY loads the "missing.busy" file instead, which acts as a placeholder for the missing modules, and generates a build time error if an application want's to use them anyway; see also the thirdparty/Readme.txt file for potentially removable directories.

State of development

This version is suitable to successfully build and run my Oberon+ compiler and IDE. No modifications to the source code were necessary; I can still either use LeanQt or original Qt to compile my compiler or IDE.

LeanQt and its examples have been successfully tested with different configurations on Windows x86 & x86_64, on macOS x86_64 and M1, and on Linux x86, ARMv7 (Raspi) and x86_64.

The following features are available:

bytearrays, strings, unicode
data compression
localization, mime types
collections, implicit sharing
date/time, time zones
variants/metatypes
codecs: utf, latin
io device abstraction
file engine
text and data streams
regexp
logging
md5 and sha1 hash
geometry, json, url
xml stream, sax and dom
threads, processes
shared memory
application, command line
objects and events
rcc (resource compiler)
moc (meta object compiler)
library and (partially) plugins
async and sync networking
map/reduce, filter/reduce, async computation
image handling, format conversion
window handling, events, 2D bitmap and vector graphics, fonts, rich text
pdf and odf writer
widgets and graphics framework
uic (user interface compiler)

Planned or work-in-progress features

[x] QtCore
[x] QtXml
[x] QtNetwork
[x] QtConcurrent
[x] QImage, QImageReader/Writer (separated from QtGui)
[x] mimetypes
[x] QtGui (see NOTES below)
[x] QtWidgets (see NOTES below)

NOTES:

All widgets (including item and graphics views) work on Linux, Windows and Mac.
The "macintosh" style doesn't fully work yet (some display errors), so LeanQt starts with "fusion" style also on Macintosh. Mac style can be manually enabled e.g. by adding -style macintosh to the application command line.
Also note that on Mac the generated executables must be included in an application bundle using a separate tool if you don't want a terminal window to open to run the app, or the menu has to be explicitly brought to the foreground (e.g. by first clicking on the desktop and then again on the startet application window).
MinGW on Windows works with static builds, but not yet with shared builds; so don't use HAVE_SHARED with MingW on Windows.
Clang on Windows is not compatible with the current LeanQt version; please use MSVC or MinGW instead.

Long term plan

[ ] printing
[ ] SIMD support
[ ] Linux framebuffer platform
[ ] Make "macintosh" style work (use "fusion" style for the time being)

No support planned

qmake
statemachine
other than minimal codecs
animation (except in the graphics module)
dbus
sql
svg
nfc
bluetooth
multimedia
web and browser stuff
testlib
scripting, quick stuff
opengl, direct2d, directfb
qml
graphics effects
accessibility (requires dbus)
wacom tablets
gestures
all not mentioned add-ons
ios, winrt, wince, android, blackberry, nacl, vxworks, haiku

Other differences to original Qt

QMimeData and QTextBoundaryFinder belong to the gui module, not the core module
QEasingCurve belong to the widgets module, not the core module
QModelIndex, QPersistentModelIndex, QAbstractItemModel, QAbstractListModel, QAbstractProxyModel, QIdentityProxyModel, QItemSelectionRange, QItemSelectionModel, QItemSelection, QSortFilterProxyModel, and QStringListModel belong to the itemviews module, not the core module
QModelIndex, QPersistentModelIndex and QEasingCurve are no longer well-known types to QVariant and QMetaType
QStandardItemModel belong to the itemviews module, not the gui module
QTimeLine belongs to the widgets module, not the core module
All moved classes still have include file redirects in their original module for backward compatibility

How to build the Oberon+ command line compiler version with LeanQt

Note that compiling LeanQt on Linux requires the build essentials, xcb, libxcb1-dev and libx11-dev packages. On Mac and Windows there are no additional requirements than a toolchain.

Create a new directory; we call it the root directory here
Download https://github.com/rochus-keller/Oberon/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "Oberon".
Download https://github.com/rochus-keller/PeLib/archive/refs/heads/OBX.zip and unpack it to the root directory; rename the resulting directory to "PeLib".
Download https://github.com/rochus-keller/MonoTools/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "MonoTools".
Download https://github.com/rochus-keller/LeanQt/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "LeanQt".
Download https://github.com/rochus-keller/BUSY/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "build".
Open a command line in the build directory and type cc *.c -O2 -lm -O2 -o lua or cl /O2 /MD /Fe:lua.exe *.c depending on whether you are on a Unix or Windows machine; wait a few seconds until the Lua executable is built.
Now type ./lua build.lua ../Oberon (or lua build.lua ../Oberon on Windows); wait a few minutes until the OBXMC executable is built; you find it in the output subdirectory.

How to build the Oberon+ IDE with LeanQt

Create a new directory; we call it the root directory here
Download https://github.com/rochus-keller/Oberon/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "Oberon".
Download https://github.com/rochus-keller/PeLib/archive/refs/heads/OBX.zip and unpack it to the root directory; rename the resulting directory to "PeLib".
Download https://github.com/rochus-keller/MonoTools/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "MonoTools".
Download https://github.com/rochus-keller/GuiTools/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "GuiTools".
Download https://github.com/rochus-keller/LeanQt/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "LeanQt".
Download https://github.com/rochus-keller/BUSY/archive/refs/heads/master.zip and unpack it to the root directory; rename the resulting directory to "build".
Open a command line in the build directory and type cc *.c -O2 -lm -O2 -o lua or cl /O2 /MD /Fe:lua.exe *.c depending on whether you are on a Unix or Windows machine; wait a few seconds until the Lua executable is built.
Now type ./lua build.lua ../Oberon -T ide (or lua build.lua ../Oberon -T ide on Windows); wait until the ObxIDE executable is built; you find

LeanQt

Install / Use

README