Document building with qt6 for macos

INSTALL.md

@@ -41,12 +41,14 @@ Building QGIS from source - step by step
          - [4.3.2.1 Build with an SDK](#4321-build-with-an-sdk)
          - [4.3.2.1 Build all the dependencies locally](#4321-build-all-the-dependencies-locally)
 - [5. Building on MacOS X](#5-building-on-macos-x)
-   * [5.1. Install Developer Tools](#51-install-developer-tools)
-   * [5.2. Install CMake and other build tools](#52-install-cmake-and-other-build-tools)
-   * [5.3. Install Qt5 and QGIS-Deps](#53-install-qt5-and-qgis-deps)
-   * [5.4. QGIS source](#54-qgis-source)
-   * [5.5. Configure the build](#55-configure-the-build)
-   * [5.6. Building](#56-building)
+   * [5.1. Building with Mac Packager](#51-building-with-mac-packager)
+     + [5.1.1. Install Developer Tools](#511-install-developer-tools)
+     + [5.1.2. Install CMake and other build tools](#512-install-cmake-and-other-build-tools)
+     + [5.1.3. Install Qt5 and QGIS-Deps](#513-install-qt5-and-qgis-deps)
+     + [5.1.4. QGIS source](#514-qgis-source)
+     + [5.1.5. Configure the build](#515-configure-the-build)
+     + [5.1.6. Building](#516-building)
+   * [5.2. Building with vcpkg](#52-building-with-vcpkg)
 - [6. Setting up the WCS test server on GNU/Linux](#6-setting-up-the-wcs-test-server-on-gnulinux)
    * [6.1. Preparation](#61-preparation)
    * [6.2. Setup mapserver](#62-setup-mapserver)
@@ -832,9 +834,14 @@ If you want to test QGIS, easiest option is to download and install all-in-one s
 
 https://download.qgis.org/downloads/macos/
 
-On the other hand, if you want to build or develop QGIS on your own, you need a set of dependencies and tools.
-These instructions will use the same set of dependencies that are used for all-in-one QGIS bundle,
-but you can build QGIS with Homebrew, MacPorts or Conda dependencies too.
+If you want to build or develop QGIS on your own, you need a set of dependencies and tools.
+You can use
+
+- the same set of dependencies that are used for all-in-one QGIS bundle
+- vcpkg based dependencies for building with Qt6
+- with Homebrew, MacPorts or Conda dependencies (not covered in this guide)
+
+## 5.1. Building with Mac Packager
 
 https://github.com/qgis/QGIS-Mac-Packager
 
@@ -856,7 +863,7 @@ To find out how many CPUs you have available, run the following in Terminal:
 /usr/sbin/sysctl -n hw.ncpu
 ```
 
-## 5.1. Install Developer Tools
+### 5.1.1. Install Developer Tools
 
 Developer tools are not a part of a standard OS X installation.
 As minimum you require command line tools
@@ -867,7 +874,7 @@ sudo xcode-select --install
 
 but installation of Xcode from the App Store is recommended too.
 
-## 5.2. Install CMake and other build tools
+### 5.1.2. Install CMake and other build tools
 
 For example install Homebrew
 
@@ -884,7 +891,7 @@ brew install git cmake ninja pkg-config wget bash-completion curl gnu-sed coreut
 if you have these tools installed from MacPorts or Conda, it is the same, but we will need to be able to
 run `cmake` and others from Terminal in the following steps
 
-## 5.3. Install Qt5 and QGIS-Deps
+### 5.1.3. Install Qt5 and QGIS-Deps
 
 To build QGIS, we need Qt5 and FOSS dependencies on hand. The Qt5 version ideally should match the version that was
 used to build dependency package.
@@ -907,7 +914,7 @@ Note that the QGIS-Deps package is not yet signed, so you may need to add Termin
 to System Preferences -> Security & Privacy -> Privacy -> Developer Tools or manually accept usage
 of the libraries when asked by system.
 
-## 5.4. QGIS source
+### 5.1.4. QGIS source
 
 Unzip the QGIS source to a working folder of your choice.
 If you are reading this from the source, you've already done this.
@@ -925,7 +932,7 @@ select Download .tar.gz. Double-click the tarball to unzip it.
 git clone git://github.com/qgis/QGIS.git
 ```
 
-## 5.5. Configure the build
+### 5.1.5. Configure the build
 
 CMake supports out of source build so we will create a 'build' dir for the
 build process. OS X uses `${HOME}/Applications` as a standard user app folder (it
@@ -964,7 +971,7 @@ cd build
 ccmake ../QGIS
 ```
 
-## 5.6. Building
+### 5.1.6. Building
 
 Now we can start the build process (remember the parallel compilation note at
 the beginning, this is a good place to use it, if you can):
@@ -992,6 +999,67 @@ If you want to create bundle that runs without these dependencies, please read t
 
 https://github.com/qgis/QGIS-Mac-Packager
 
+## 5.2. Building with vcpkg
+
+With [vcpkg](https://github.com/microsoft/vcpkg/) you can develop QGIS using
+Qt6.
+
+Install and initialize vcpkg
+
+```sh
+. <(curl https://aka.ms/vcpkg-init.sh -L)
+```
+
+Install build tools using [homebrew](https://brew.sh/)
+
+```sh
+brew install git cmake flex bison automake autoconf libtool nasm ninja
+```
+
+Get the QGIS source code
+
+```sh
+git clone [email protected]:qgis/QGIS.git
+```
+
+Prepare the env for homebrew tools
+
+```sh
+export PATH=$(brew --prefix bison)/bin:$(brew --prefix flex)/bin:$(brew --prefix libtool)/bin:$PATH
+```
+
+Select the target architecture (arm64 is for M series processors).
+We will assume that you build for the same architecture that you build on.
+If that is not the case (e.g. you build for x64 on a arm64 machine), adjust
+the `HOST_TRIPLET` in the next step.
+
+```sh
+TRIPLET=arm64-osx-dynamic-release
+# TRIPLET=x64-osx-dynamic-release
+```
+
+Configure
+
+```sh
+cmake -S . \
+      -G Ninja \
+      -B build \
+      -D WITH_VCPKG=ON \
+      -D BUILD_WITH_QT6=ON \
+      -D WITH_QTWEBKIT=OFF \
+      -D WITH_BINDINGS=ON \
+      -D QGIS_MACAPP_FRAMEWORK=OFF \
+      -D VCPKG_TARGET_TRIPLET="$TRIPLET" \
+      -D VCPKG_HOST_TRIPLET="$TRIPLET" \
+      -D CREATE_MACOSX_BUNDLE=OFF
+```
+
+Build (switch the target to `Release` if you do not want to debug)
+
+```sh
+cmake --build build --target RelWithDebInfo
+```
+
 # 6. Setting up the WCS test server on GNU/Linux
 
 **Requires:** Ubuntu / Debian derived distro