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Skyler Grey 8e246331f6 Add a FunctionBasedURPConnection and a websocket URP connector
- FunctionBasedURPConnection is used to enable a client to open a URP
  connection to a fresh Kit instance in COOL.
- This URP connector can be used with that and
  https://github.com/CollaboraOnline/online/pull/6992 to use a Java Uno
  Remote Protocol client over websockets
- For interoperability with existing Collabora Online websockets a
  prefix (urp ) is added to each message sent and a similar prefix
  (urp: ) is expected on each message recieved. This allows sending over
  the same websocket as other data is being transmitted through. If you
  are writing a bridge to work with this, you will need to add/strip the
  prefixes accordingly
- This commit uses Java WebSocket
  (https://github.com/TooTallNate/Java-WebSocket) to send data over
  websockets.

Change-Id: I2bda3d0b988bef7883f9b6829eeb5b7ae8075f27
Signed-off-by: Skyler Grey <skyler.grey@collabora.com>
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/151171
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>
2023-09-01 16:55:37 +02:00
.git-hooks Fix typo in .git-hooks/pre-commit 2023-06-20 02:10:44 +02:00
.github workflows: Update dessant/repo-lockdown to v3 2023-04-22 03:27:06 +02:00
.vscode vscode: add Cygwin terminal profile and config for VS debugger for Windows 2023-04-18 14:30:11 +02:00
accessibility tdf#104833 a11y Send name changed event for text controls 2023-09-01 16:13:40 +02:00
android android: Update com.google.android.material to 1.9.0 2023-08-07 07:58:45 +02:00
animations loplugin: new global analysis locking2 2023-08-19 17:40:47 +02:00
apple_remote Add support for macOS SDK 12.0 2021-10-27 16:32:04 +02:00
avmedia avmedia : use std::recursive_mutex instead of osl::Mutex. 2023-08-08 14:35:37 +02:00
basctl use concrete type for ChildDescriptor::mxAccessible 2023-08-30 21:36:17 +02:00
basegfx tdf#112687 Simplify polylines from slideshow annotations 2023-08-24 17:54:46 +02:00
basic tdf#130924 replace '*printf' with 'SAL_*' logging macros. 2023-08-31 19:50:23 +02:00
bean Updated README.md files to represent current code / use Markdown format 2021-04-07 17:47:16 +02:00
bin flat-odf-cleanup.py: remove unused table styles and page layouts 2023-08-21 19:40:55 +02:00
binaryurp Use getXWeak in binaryurp 2023-05-28 09:06:11 +02:00
bridges Fix handling of float vs. double values 2023-08-03 14:48:33 +02:00
canvas loplugin: new global analysis locking2 2023-08-19 17:40:47 +02:00
chart2 Drop a leftover 2023-08-21 14:36:10 +02:00
cli_ure Avoid MSVC error C2039 2023-04-17 15:07:57 +02:00
codemaker loplugin:stringadd in c* 2023-03-24 15:29:18 +00:00
comphelper tdf#156967 cal basic, CSV import macro crashes 2023-08-31 15:20:41 +02:00
compilerplugins Fix typo 2023-08-29 14:54:13 +02:00
config_host vcl gtk3: Introduce AT-SPI2 tests for the GTK3 accessibility layer 2023-07-27 20:01:17 +02:00
configmgr SAL_WARN->SAL_INFO in Access::getChild 2023-08-31 21:50:18 +02:00
connectivity tdf#156816 Base handles scale on SQL type TIME as with TIMESTAMP 2023-08-31 20:28:50 +02:00
cppcanvas Fix typo 2023-08-28 14:21:12 +02:00
cppu loplugin:stringadd in c* 2023-03-24 15:29:18 +00:00
cppuhelper tdf#153109 Use any_of instead of loop to check a range 2023-06-12 13:11:07 +02:00
cpputools sp2bv : no need to use fprintf without any formating 2023-08-14 15:01:16 +02:00
cui tdf#157034: FILESAVE loext:theme-type is off by one 2023-09-01 14:24:45 +02:00
dbaccess tdf#156816 Base handles scale on SQL type TIME as with TIMESTAMP 2023-08-31 20:28:50 +02:00
desktop Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
dictionaries@c1ddcf602b Update git submodules 2023-08-30 21:56:28 +02:00
distro-configs Drop --with-system-mariadb from Linux_ubsan_master.conf 2023-08-04 17:09:17 +02:00
docmodel move BGradient to awt::Gradient2 UNO conversion into docmodel 2023-08-21 09:27:12 +02:00
drawinglayer tdf#156808 soft edge effect makes image (except for soft edge) disappear 2023-08-28 18:14:59 +02:00
editeng tdf#103706: tdf#142857: sd: context aware paste for clone format 2023-08-29 11:06:44 +02:00
embeddedobj split Point/Size/Rectangle into AbsoluteScreenPixel* types 2023-08-02 08:13:15 +02:00
embedserv Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
emfio use sal_uInt64 when dealing with stream position 2023-08-09 22:34:16 +02:00
eventattacher Use getXWeak in eventattacher 2023-05-28 10:03:41 +02:00
extensions tdf#146619 Remove unused #includes from C/C++ files 2023-07-28 10:54:18 +02:00
external Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
extras Resolves tdf#155926 - Rename "Line Style 9" 2023-08-25 11:12:02 +02:00
filter show status indicator progress on svg export of slides 2023-09-01 11:25:06 +02:00
forms Convert internal vcl bitmap formats transparency->alpha (II) 2023-07-25 08:38:12 +02:00
formula tdf#104487 - Function wizard: remember last used function category 2023-05-09 17:39:05 +02:00
fpicker tdf#155125 add "Encrypt with GPG key" checkbox in macOS native save dialog 2023-07-13 22:35:30 +02:00
framework tdf#45904: Remove old SwXReferenceMarks Java test 2023-08-27 08:21:26 +02:00
helpcompiler Simplify a bit 2023-08-25 14:30:42 +02:00
helpcontent2@dd8981d39d Update git submodules 2023-09-01 15:08:57 +02:00
hwpfilter ofz#49217 Out-of-memory 2023-07-23 11:52:34 +02:00
i18nlangtag Related: tdf#154832 Official name is Morisyen 2023-04-16 14:11:56 +02:00
i18npool tdf#143148 Use pragma once instead of include guards 2023-08-30 07:11:36 +02:00
i18nutil i18nutil: Make unicode::getUnicodeType() take a UTF-32 code point 2023-07-25 02:14:56 +02:00
icon-themes tdf#156299 Sync Insert Shape & sidebar Shape deck 2023-07-24 15:22:42 +02:00
idl Drop SvStream::WriteCharPtr 2023-04-10 23:13:32 +02:00
idlc/test/parser Use idlc/test/parser/conversion.tests in CustomTarget_unoidl/unoidl-write_test 2022-06-11 09:58:17 +02:00
include Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
instsetoo_native Add configure switch to enable building the installer with WiX. 2023-05-23 11:47:19 +02:00
io Use getXWeak in io 2023-05-27 18:08:00 +02:00
ios merge duplicate CairoTextRender impls 2023-01-12 11:33:24 +00:00
javaunohelper clang-tidy modernize-pass-by-value in io..jvmfwk 2022-06-21 12:59:41 +02:00
jurt Fix Library_jpipe__staticsalhack 2023-02-26 22:07:57 +00:00
jvmaccess
jvmfwk loplugin:stringstatic look for more strings 2023-06-27 13:10:44 +02:00
l10ntools tdf#147021 Use std::size() instead of SAL_N_ELEMENTS() macro 2023-07-28 07:07:11 +02:00
librelogo tdf#147906: Use python's math.hypot() for Pythagorean addition 2023-03-19 18:17:46 +00:00
libreofficekit lok: a11y: when we are inside a table notify table and current cell info 2023-08-14 08:09:53 +02:00
lingucomponent Revert recent LanguageTool commits 2023-07-12 08:57:41 +02:00
linguistic new loplugin:constexprliteral 2023-06-26 13:12:31 +02:00
lotuswordpro ofz#58529 Null-dereference READ 2023-05-02 12:54:04 +02:00
m4 Fix typo 2023-04-06 14:15:12 +02:00
msicreator msicreator: fix hardcoded wix toolset path 2023-04-28 11:22:44 +02:00
nlpsolver Fix title for nlpsolver/README.md 2022-12-19 09:42:02 +00:00
o3tl update loplugin:stringview* for o3tl::iterateCodePoints 2023-05-06 12:09:48 +02:00
odk Point to LO DevGuide instead of OOo 2023-06-29 23:00:22 +02:00
offapi tdf#156816 Base handles scale on SQL type TIME as with TIMESTAMP 2023-08-31 20:28:50 +02:00
officecfg Fix typo 2023-08-24 22:14:34 +02:00
onlineupdate NSS initialization guard 2023-01-25 12:24:34 +00:00
oovbaapi tdf#150281: Fix CentimetersToPoints in Calc 2023-03-13 15:16:24 +00:00
oox tdf#156835 - FILEOPEN XLSX: add SHA-384 encryption support for ooxml import 2023-08-30 14:34:39 +02:00
opencl Drop SvStream::WriteCharPtr 2023-04-10 23:13:32 +02:00
osx Add all source directories as folder references to the Xcode project 2023-07-05 10:30:37 +02:00
package incorrect usage of erase..remove idion 2023-08-28 12:59:32 +02:00
pch merge expwrap into sax library 2023-05-30 08:45:46 +02:00
postprocess Fix postprocess/README packimages.pl has been replaced by pack_images.py 2023-07-16 18:54:15 +02:00
pyuno Categories for link targets in Impress 2023-07-12 07:56:37 +02:00
qadevOOo Fix typo 2023-08-30 07:11:58 +02:00
readlicense_oo Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
registry loplugin:stringadd in registry..sal 2023-03-25 19:03:28 +00:00
remotebridges
reportbuilder Fix some getImplementationName 2023-04-21 08:05:46 +02:00
reportdesign new loplugin:optionalbool 2023-08-28 09:43:40 +02:00
ridljar Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
sal tdf#146619 Remove unused includes from sal/osl/unx 2023-08-30 09:19:55 +02:00
salhelper tdf#146619 Remove unused #includes from C/C++ files 2023-08-01 21:13:47 +02:00
sax tdf#150137 fastparser: don't crash on undeclared namespace 2023-08-07 17:38:30 +02:00
sc sc: filter: rtf: add method "WriteFontTable" 2023-09-01 16:19:48 +02:00
scaddins Drop some defines in scaddins 2023-04-22 14:17:59 +02:00
sccomp Extend loplugin:cppunitassertequals to more argument types 2023-02-23 07:04:09 +00:00
schema tdf#152724 Extend ODF for blank width "_x" 2023-08-25 17:49:17 +02:00
scp2 tdf#71096: xlr filetype not associated with Calc in Windows 2023-06-04 14:31:23 +02:00
scripting Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
sd fix ImpGraphic::operator== 2023-09-01 09:54:21 +02:00
sdext Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
setup_native tdf#144053 Compare version to ProductKey entry in bootstraprc 2023-07-26 14:40:02 +02:00
sfx2 Revert "tdf#100894 lots of Conditional formatting freeze calc Styles sidebar" 2023-09-01 12:33:31 +02:00
shell Use getXWeak in shell 2023-04-30 17:05:28 +02:00
slideshow tdf#112687 Simplify polylines from slideshow annotations 2023-08-24 17:54:46 +02:00
smoketest clang-tidy modernize-pass-by-value in various 2022-08-13 19:11:49 +02:00
solenv update clang asan suppressions 2023-09-01 13:07:45 +02:00
soltools Remove support for AIX 2023-01-27 07:28:16 +00:00
sot Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
starmath Replace a macro with a function 2023-09-01 08:08:32 +02:00
static tdf#151273, tdf#151925: Don’t use QFont text layout by default 2023-07-09 12:02:28 +02:00
stoc Small refactor 2023-08-24 08:53:58 +02:00
store Add cstdlib include necessary to build with gcc14 libstdc++ (tdf#155715) 2023-06-08 08:25:47 +02:00
svgio tdf#129356: handle css combinator when the element name is combined... 2023-08-22 20:06:24 +02:00
svl ITEM: preparations for more/easier changes 2023-08-18 10:37:44 +02:00
svtools jsdialog: render font previews with hidpi 2023-08-31 10:15:45 +02:00
svx tdf#157034: FILESAVE loext:theme-type is off by one 2023-09-01 14:24:45 +02:00
sw disable unreliable librelogo uitest 2023-09-01 14:32:02 +02:00
swext Fix typo 2023-06-28 21:44:39 +02:00
sysui Only pass -I... arguments to g-ir-scanner by using pkg-config's --cflags-only-I 2023-07-23 15:10:47 +02:00
test tdf#45904: Move _Footnote Java tests to C++ 2023-08-27 10:51:38 +02:00
testtools Use getXWeak in testtools 2023-05-27 20:14:56 +02:00
toolkit tdf#104833 a11y: Use VCLXAccessibleEdit for VCLXMultiLineEdit 2023-09-01 16:13:31 +02:00
tools Resolves: tdf#127334 Increase tools::Duration accuracy epsilon unsharpness 2023-08-03 21:42:53 +02:00
translations@dc344b7d1c Update git submodules 2023-08-28 21:33:45 +02:00
ucb new loplugin:optionalbool 2023-08-28 09:43:40 +02:00
ucbhelper ucbhelper,ucb,desktop: InternetProxyServer is problematic 2023-08-18 18:33:27 +02:00
udkapi Introduce css.reflection.Dump singleton 2023-03-22 08:46:35 +00:00
uitest tdf#154131 Add Detect scientific number option 2023-05-26 23:57:16 +02:00
UnoControls Use getXWeak in UnoControls 2023-05-27 15:20:51 +02:00
unodevtools new loplugin:constexprliteral 2023-06-26 13:12:31 +02:00
unoidl tdf#147021 Use std::size() instead of SAL_N_ELEMENTS() macro 2022-11-06 01:22:27 +01:00
unoil allow native compile for windows aarch64 2023-04-11 12:06:25 +02:00
unotest loplugin:unnecessarygetstr 2023-05-05 10:11:54 +02:00
unotools Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
unoxml Use getXWeak in unoxml 2023-05-27 12:46:01 +02:00
ure Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
uui ignore exception in UUIInteractionHelper::handlerequest 2023-08-18 18:34:13 +02:00
vbahelper Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
vcl adjust VclTextTest::testSimpleText 2023-09-01 12:59:43 +02:00
winaccessibility wina11y: Drop CAccActionBase::GetXInterface 2023-08-22 22:27:22 +02:00
wizards Fix typo 2023-08-22 14:16:41 +02:00
writerfilter Revert "use more Reference::query instead of UNO_QUERY_THROW" 2023-08-25 14:15:56 +02:00
writerperfect cid#1541185 Operands don't affect result 2023-08-24 10:03:53 +02:00
xmerge cid#1509209 DCN: Don't Catch NullPointer Exception 2022-09-15 15:29:57 +02:00
xmlhelp Use getXWeak in xmlhelp 2023-05-06 12:27:42 +02:00
xmloff sc: add ODF import/export of the Theme + tests 2023-09-01 10:12:11 +02:00
xmlreader clang-tidy modernize-pass-by-value in xmlreader 2022-07-29 13:10:15 +02:00
xmlscript Use getXWeak in xmlscript 2023-05-06 12:28:01 +02:00
xmlsecurity Fix typo 2023-08-27 18:46:24 +02:00
.buckconfig Add build toolchain to upload LibreOffice API to Maven Central 2015-12-03 23:32:11 +00:00
.buckversion Add build toolchain to upload LibreOffice API to Maven Central 2015-12-03 23:32:11 +00:00
.clang-format Document that .clang-format would benefit from StatementMacros 2022-11-06 15:38:07 +01:00
.editorconfig We have some Objective-C source files, too 2017-12-01 12:59:43 +02:00
.git-blame-ignore-revs tdf#123936 Add formatting commit to .git-blame-ignore-revs 2022-07-04 09:09:50 +02:00
.gitattributes SVG is a textual XML format after all 2022-06-24 16:36:36 +02:00
.gitignore Add .cache (Qt Creator) and gdbtrace.log (gdb) 2023-04-28 21:54:20 +02:00
.gitmodules gitmodules: use relative paths 2020-10-21 21:51:54 +02:00
.gitpod.dockerfile Upgrade .gitpod.dockerfile to Ubuntu focal 2021-05-22 19:35:47 +02:00
.gitpod.yml Install C++ VSCode extension for Gitpod 2020-03-09 15:54:14 +01:00
.gitreview git-review: Use the hostname instead of alias. 2019-05-15 15:13:47 +02:00
antivirusDetection.vbs tdf#84553 Correctly handle failures while getting a WMI Object. 2020-02-12 09:14:03 +01:00
autogen.sh Remove support for AIX 2023-01-27 07:28:16 +00:00
BUCK Adapt buck build to jars merged into libreoffice.jar 2020-11-30 11:27:47 +01:00
config.guess Update config.guess & .sub to latest 2022-12-12 15:46:46 +00:00
config.sub Update config.guess & .sub to latest 2022-12-12 15:46:46 +00:00
config_host.mk.in Drop JAVA_CLASSPATH_NOT_SET which is always TRUE 2023-08-18 20:14:30 +02:00
config_host_lang.mk.in don't export the various language lists and consolidate them 2022-12-15 21:07:37 +00:00
configure.ac Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
COPYING Licencing files 2011-01-11 21:49:39 +00:00
COPYING.LGPL Licencing files 2011-01-11 21:49:39 +00:00
COPYING.MPL Targetted text updates, with seasonable changes before l10n freeze. 2013-12-13 17:00:07 +00:00
cpp.hint Add a VisualStudio cpp.hint file 2022-08-22 16:01:16 +02:00
download.lst Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
g git-hooks: remove hint in './g -z' 2023-04-01 13:28:14 +02:00
hardened_runtime.xcent.in Fix typos 2021-08-16 23:34:24 +02:00
install-sh Fix typos 2019-08-12 22:12:57 +02:00
install_deps.sh Make some scripts more portable 2021-08-20 12:32:22 +02:00
leak-suppress.txt
Library_merged.mk gbuild: Remove MSVC 2013 legacy code 2017-04-21 18:18:44 +02:00
lo.xcent.in Set entitlements in non-release in $(INSTROOTBASE) and .dmg package 2023-06-07 22:08:50 +02:00
logerrit Use ed25519 as default for ssh key pair generation 2021-09-29 09:34:21 +02:00
Makefile.fetch Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
Makefile.gbuild create pocheck convenience target 2022-12-15 22:10:23 +00:00
Makefile.in add fetch to dependencies of gbuildtojson / Rdb target 2023-04-11 12:39:46 +02:00
README.cross Add missing autogen.input entries to README.cross 2020-03-25 16:25:14 +01:00
README.help.md Fix typo 2022-07-30 23:26:39 +02:00
README.md Update Android baseline in README.md 2023-02-16 20:33:15 +00:00
README.Solaris remove use of Archive::Zip 2016-06-04 08:09:56 +02:00
Repository.mk kf6: Add a kf6 VCL plugin 2023-06-22 22:16:11 +02:00
RepositoryExternal.mk Add a FunctionBasedURPConnection and a websocket URP connector 2023-09-01 16:55:37 +02:00
RepositoryFixes.mk WASM more initial bits and pieces 2022-01-19 10:49:40 +01:00
RepositoryModule_build.mk introduce docmodel comp., model::ThemeColor, use it in SvxColorItem 2023-01-12 23:15:58 +00:00
RepositoryModule_host.mk introduce docmodel comp., model::ThemeColor, use it in SvxColorItem 2023-01-12 23:15:58 +00:00
sanitize-ubsan-excludelist replace usage of blacklist with denylist 2020-07-10 01:34:54 +02:00
setup.cfg
TEMPLATE.SOURCECODE.HEADER Make it clear that the text is in addition to the previous 2021-01-27 08:02:35 +01:00
tsan-suppress.txt fix duplicate I introduced to tsan-suppress 2023-08-28 14:33:10 +02:00

LibreOffice

Coverity Scan Build Status CII Best Practices Translation status

LibreOffice is an integrated office suite based on copyleft licenses and compatible with most document formats and standards. Libreoffice is backed by The Document Foundation, which represents a large independent community of enterprises, developers and other volunteers moved by the common goal of bringing to the market the best software for personal productivity. LibreOffice is open source, and free to download, use and distribute.

A quick overview of the LibreOffice code structure.

Overview

You can develop for LibreOffice in one of two ways, one recommended and one much less so. First the somewhat less recommended way: it is possible to use the SDK to develop an extension, for which you can read the API docs and Developers Guide. This re-uses the (extremely generic) UNO APIs that are also used by macro scripting in StarBasic.

The best way to add a generally useful feature to LibreOffice is to work on the code base however. Overall this way makes it easier to compile and build your code, it avoids any arbitrary limitations of our scripting APIs, and in general is far more simple and intuitive - if you are a reasonably able C++ programmer.

The Build Chain and Runtime Baselines

These are the current minimal operating system and compiler versions to run and compile LibreOffice, also used by the TDF builds:

  • Windows:
    • Runtime: Windows 7
    • Build: Cygwin + Visual Studio 2019 version 16.10
  • macOS:
    • Runtime: 10.15
    • Build: 12 (13 for aarch64) + Xcode 14
  • Linux:
    • Runtime: RHEL 7 or CentOS 7
    • Build: either GCC 7.0.0; or Clang 8.0.1 with libstdc++ 7.3.0
  • iOS (only for LibreOfficeKit):
    • Runtime: 11.4 (only support for newer i devices == 64 bit)
    • Build: Xcode 9.3 and iPhone SDK 11.4
  • Android:
    • Build: NDK r23 and SDK 30.0.3
  • Emscripten / WASM:
    • Runtime: a browser with SharedMemory support (threads + atomics)
    • Build: Qt 5.15 with Qt supported Emscripten 1.39.8
    • See README.wasm

Java is required for building many parts of LibreOffice. In TDF Wiki article Development/Java, the exact modules that depend on Java are listed.

The baseline for Java is Java Development Kit (JDK) Version 11 or later. It is possible to build LibreOffice with JDK version 9, but it is no longer supported by the JDK vendors, thus it should be avoided.

If you want to use Clang with the LibreOffice compiler plugins, the minimal version of Clang is 12.0.1. Since Xcode doesn't provide the compiler plugin headers, you have to compile your own Clang to use them on macOS.

You can find the TDF configure switches in the distro-configs/ directory.

To setup your initial build environment on Windows and macOS, we provide the LibreOffice Development Environment (LODE) scripts.

For more information see the build instructions for your platform in the TDF wiki.

The Important Bits of Code

Each module should have a README.md file inside it which has some degree of documentation for that module; patches are most welcome to improve those. We have those turned into a web page here:

https://docs.libreoffice.org/

However, there are two hundred modules, many of them of only peripheral interest for a specialist audience. So - where is the good stuff, the code that is most useful. Here is a quick overview of the most important ones:

Module Description
sal/ this provides a simple System Abstraction Layer
tools/ this provides basic internal types: Rectangle, Color etc.
vcl/ this is the widget toolkit library and one rendering abstraction
framework/ UNO framework, responsible for building toolbars, menus, status bars, and the chrome around the document using widgets from VCL, and XML descriptions from /uiconfig/ files
sfx2/ legacy core framework used by Writer/Calc/Draw: document model / load/save / signals for actions etc.
svx/ drawing model related helper code, including much of Draw/Impress

Then applications

Module Description
desktop/ this is where the main() for the application lives, init / bootstrap. the name dates back to an ancient StarOffice that also drew a desktop
sw/ Writer
sc/ Calc
sd/ Draw / Impress

There are several other libraries that are helpful from a graphical perspective:

Module Description
basegfx/ algorithms and data-types for graphics as used in the canvas
canvas/ new (UNO) canvas rendering model with various backends
cppcanvas/ C++ helper classes for using the UNO canvas
drawinglayer/ View code to render drawable objects and break them down into primitives we can render more easily.

Rules for #include Directives (C/C++)

Use the "..." form if and only if the included file is found next to the including file. Otherwise, use the <...> form. (For further details, see the mail Re: C[++]: Normalizing include syntax ("" vs <>).)

The UNO API include files should consistently use double quotes, for the benefit of external users of this API.

loplugin:includeform (compilerplugins/clang/includeform.cxx) enforces these rules.

Finding Out More

Beyond this, you can read the README.md files, send us patches, ask on the mailing list libreoffice@lists.freedesktop.org (no subscription required) or poke people on IRC #libreoffice-dev on irc.libera.chat - we're a friendly and generally helpful mob. We know the code can be hard to get into at first, and so there are no silly questions.