Qt build improvements and documentation (#277)

* Qt build improvements and documentation

* Update include/mbgl/actor/actor_ref.hpp

Co-authored-by: Oliver Wipfli <oliver.wipfli@leichteralsluft.ch>

.github/workflows/qt-ci.yml

@@ -70,6 +70,11 @@ jobs:
     strategy:
       matrix:
         include:
+          - name: Linux
+            os: ubuntu-latest
+            static: OFF
+            qt: 5.15.2
+            qt_target: desktop
           - name: macOS
             os: macos-latest
             static: OFF
@@ -80,11 +85,11 @@ jobs:
             static: ON
             qt: 5.15.2
             qt_target: desktop
-#          - name: iOS_static
-#            os: macos-latest
-#            static: ON
-#            qt: 5.15.2
-#            qt_target: ios
+          - name: iOS_static
+            os: macos-latest
+            static: ON
+            qt: 5.15.2
+            qt_target: ios
           - name: macOS
             os: macos-latest
             static: ON
@@ -97,7 +102,7 @@ jobs:
             qt_target: desktop
     runs-on: ${{ matrix.os }}
     env:
-      BUILD_TYPE: Debug
+      BUILD_TYPE: RelWithDebInfo
       BUILD_MODE: ${{ matrix.static }}
       QT_VERSION: ${{ matrix.qt }}
 
@@ -109,7 +114,7 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
-      - name: Install dependencies
+      - name: Install macOS dependencies
         if: runner.os == 'macOS'
         env:
           HOMEBREW_NO_AUTO_UPDATE: 1
@@ -120,6 +125,7 @@ jobs:
           brew list ninja || brew install ninja
 
       - name: Setup Xcode
+        if: runner.os == 'macOS'
         uses: maxim-lobanov/setup-xcode@v1
         with:
           xcode-version: latest-stable
@@ -128,9 +134,11 @@ jobs:
         uses: jurplel/install-qt-action@v2
         with:
           version: ${{ env.QT_VERSION }}
+          dir: ${{ github.workspace }}
           target: ${{ matrix.qt_target }}
 
       - name: Prepare ccache
+        if: runner.os == 'macOS'
         run: |
           ccache --clear
           ccache --set-config cache_dir=~/.ccache
@@ -148,6 +156,7 @@ jobs:
             ${{ env.cache-name }}-${{ runner.os }}-${{ matrix.name }}-${{ matrix.qt }}-${{ github.job }}
 
       - name: Clear ccache statistics
+        if: runner.os == 'macOS'
         run: |
           ccache --zero-stats
           ccache --max-size=2G
@@ -161,7 +170,6 @@ jobs:
             -G Ninja \
             -DMBGL_WITH_QT=ON \
             -DMBGL_QT_STATIC=${BUILD_MODE} \
-            -DMBGL_QT_WITH_INTERNAL_SQLITE=OFF \
             -DCMAKE_BUILD_TYPE=${BUILD_TYPE} \
             -DCMAKE_INSTALL_PREFIX=../install \
             -DCMAKE_C_COMPILER_LAUNCHER=ccache \
@@ -174,22 +182,25 @@ jobs:
         run: |
           mkdir build && cd build
           cmake ../source/ \
-            -DCMAKE_TOOLCHAIN_FILE=../source/platform/ios/platform/ios/toolchain.cmake \
-            -G XCode \
-            -DPLATFORM=OS64COMBINED \
-            -DDEPLOYMENT_TARGET=12.0 \
-            -DENABLE_BITCODE=ON \
+            -G"Ninja Multi-Config" \
+            -DCMAKE_SYSTEM_NAME=iOS \
+            -DCMAKE_CONFIGURATION_TYPES="Release;Debug" \
+            -DCMAKE_OSX_ARCHITECTURES="arm64;x86_64" \
+            -DCMAKE_OSX_DEPLOYMENT_TARGET=12.0 \
             -DMBGL_WITH_QT=ON \
-            -DMBGL_WITH_WERROR=OFF \
-            -DMBGL_QT_LIBRARY_ONLY=ON \
             -DMBGL_QT_STATIC=${BUILD_MODE} \
-            -DMBGL_QT_WITH_INTERNAL_SQLITE=OFF \
+            -DMBGL_QT_LIBRARY_ONLY=ON \
             -DMBGL_QT_WITH_IOS_CCACHE=ON \
-            -DCMAKE_BUILD_TYPE=${BUILD_TYPE} \
-            -DCMAKE_INSTALL_PREFIX=../install
+            -DCMAKE_INSTALL_PREFIX=../install \
+            -DCMAKE_FIND_ROOT_PATH="$Qt5_Dir" \
+            -DCMAKE_PREFIX_PATH="$Qt5_Dir"
           cmake --build . --config Release
           cmake --install . --config Release
 
+      - name: Build maplibre-gl-native (Linux)
+        if: runner.os == 'Linux'
+        uses: ./source/.github/actions/qt5-build
+
       - name: Upload artifacts
         uses: actions/upload-artifact@v2
         with:
@@ -197,5 +208,6 @@ jobs:
           path: install
 
       - name: Show ccache statistics
+        if: runner.os == 'macOS'
         run: |
           ccache --show-stats -v