miqt: android support

.gitignore

@@ -15,4 +15,6 @@ examples/helloworld/helloworld.exe
 examples/mdoutliner/mdoutliner
 examples/mdoutliner/mdoutliner.exe
 examples/windowsmanifest/windowsmanifest
-examples/windowsmanifest/windowsmanifest.exe
+examples/windowsmanifest/windowsmanifest.exe
+
+android-build

README.md

@@ -19,8 +19,9 @@ These bindings were newly started in August 2024. The bindings are functional fo
 
 |Platform|Linkage|Status
 |---|---|---
-|Linux|Static, Dynamic (.so)|✅ Works<br>- Tested with Debian 12 / Qt 5.15 / GCC 12
-|Windows|Static, Dynamic (.dll)|✅ Works<br>- Tested with MXE Qt 5.15 / MXE GCC 5 under cross-compilation<br>- Tested with Fsu0413 Qt 5.15 / Clang 18.1 native compilation
+|Linux x86_64|Static, Dynamic (.so)|✅ Works<br>- Tested with Debian 12 / Qt 5.15 / GCC 12
+|Windows x86_64|Static, Dynamic (.dll)|✅ Works<br>- Tested with MXE Qt 5.15 / MXE GCC 5 under cross-compilation<br>- Tested with Fsu0413 Qt 5.15 / Clang 18.1 native compilation
+|Android ARM64|Dynamic bundled in package|✅ Works<br>- Tested with Raymii Qt 5.15 / Android SDK 31 / Android NDK 22
 |macOS x86_64|Static, Dynamic (.dylib)|Should work, [not tested](https://github.com/mappu/miqt/issues/2)
 |macOS ARM64|Static, Dynamic (.dylib)|[Blocked by #11](https://github.com/mappu/miqt/issues/11)
 
@@ -44,7 +45,11 @@ Yes. You must also meet your Qt license obligations: either use Qt dynamically-l
 
 ### Q3. Why does it take so long to compile?
 
-The first time the Qt bindings are compiled takes a long time. After this, it's fast. In a Dockerfile, you could cache the build step by running `go install github.com/mappu/miqt`.
+The first time the Qt bindings are compiled takes a long time. After this, it's fast.
+
+If you are compiling your app within a Dockerfile, you could cache the build step by running `go install github.com/mappu/miqt`.
+
+If you are compiling your app with a `docker run` command, the compile speed can be improved if you also bind-mount the Docker container's `GOCACHE` directory: `-v $(pwd)/container-build-cache:/root/.cache/go-build`
 
 See also [issue #8](https://github.com/mappu/miqt/issues/8).
 
@@ -91,7 +96,7 @@ For dynamically-linked builds (closed-source or open source application):
 	- `docker run --rm -v $(pwd):/src -w /src miqt/win64-dynamic:latest go build -buildvcs=false -ldflags '-s -w -H windowsgui'`
 3. Copy necessary Qt LGPL libraries and plugin files.
 
-For repeated builds, the compile speed can be improved if you also bind-mount the Docker container's `GOCACHE` directory: `-v $(pwd)/container-build-cache:/root/.cache/go-build`
+See Q3 for advice about docker performance.
 
 To add an icon and other properties to the .exe, you can use [the go-winres tool](https://github.com/tc-hib/go-winres). See the `examples/windowsmanifest` for details.
 
@@ -114,3 +119,33 @@ $env:CGO_CXXFLAGS = '-Wno-ignored-attributes -D_Bool=bool' # Clang 18 recommenda
 ```
 
 4. Run `go build -ldflags "-s -w -H windowsgui"`
+
+### Q9. How can I compile for Android?
+
+Miqt supports compiling for Android. Some extra steps are required to bridge the Java, C++, Go worlds.
+
+![](doc/android-architecture.png)
+
+1. Modify your main function to [support `c-shared` build mode](https://pkg.go.dev/cmd/go#hdr-Build_modes).
+	- Package `main` must have an empty `main` function.
+	- Rename your `main` function to `AndroidMain` and add a comment `//export AndroidMain`.
+	- Ensure to `import "C"`.
+	- Check `examples/android` to see how to support both Android and desktop platforms.
+2. Build the necessary docker container for cross-compilation:
+	- `docker build -t miqt/android:latest -f android-armv8a-go1.23-qt5.15-dynamic.Dockerfile .`
+3. Build your application as `.so` format:
+	- `docker run --rm -v $(pwd):/src -w /src miqt/android:latest go build -buildmode c-shared -ldflags "-extldflags -Wl,-soname,my_go_app.so" -o android-build/libs/arm64-v8a/my_go_app.so`
+4. Build the Qt linking stub:
+	- `docker run --rm -v $(pwd):/src -w /src miqt/android:latest android-stub-gen.sh my_go_app.so AndroidMain android-build/libs/arm64-v8a/libRealAppName_arm64-v8a.so`
+	- The linking stub is needed because Qt for Android will itself only call a function named `main`, but `c-shared` can't create one.
+5. Build the [androiddeployqt](https://doc.qt.io/qt-6/android-deploy-qt-tool.html) configuration file:
+	- `docker run --rm -v $(pwd):/src -w /src miqt/android:latest android-mktemplate.sh RealAppName deployment-settings.json`
+6. Build the android package:
+	- `docker run --rm -v $(pwd):/src -w /src miqt/android:latest androiddeployqt --input ./deployment-settings.json --output ./android-build/`
+	- By default, the resulting `.apk` is generated at `android-build/build/outputs/apk/debug/android-build-debug.apk`. 
+	- You can build in release mode by adding `--release`
+
+See Q3 for advice about docker performance.
+
+For repeated builds, if you customize the `AndroidManifest.xml` file or images, they will be used for the next `androiddeployqt` run.
+

cmd/android-mktemplate/android-mktemplate.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+#
+# android-mktemplate generates a template json file suitable for use with the
+# androiddeployqt tool.
+
+set -eu
+
+# QT_PATH is already pre-set in our docker container environment. Includes trailing slash.
+QT_PATH=${QT_PATH:-/usr/local/Qt-5.15.13/}
+
+main() {
+	
+	if [[ $# -ne 2 ]] ; then
+		echo "Usage: android-mktemplate.sh appname output.json" >&2
+		exit 1
+	fi
+	local ARG_APPNAME="$1"
+	local ARG_DESTFILE="$2"
+	
+	# Available fields are documented in the template file at
+	# @ref /usr/local/Qt-5.15.13/mkspecs/features/android/android_deployment_settings.prf
+	cat > "${ARG_DESTFILE}" <<EOF
+{
+	"_description": "Generated by miqt/android-mktemplate",
+	"application-binary": "${ARG_APPNAME}",
+	"architectures": {
+		"arm64-v8a" : "aarch64-linux-android"
+	},
+	
+	"android-extra-libs": "/opt/android_openssl/ssl_1.1/arm64-v8a/libssl_1_1.so,/opt/android_openssl/ssl_1.1/arm64-v8a/libcrypto_1_1.so",
+	
+	"android-min-sdk-version": "23",
+	"android-target-sdk-version": "30",
+	"ndk": "/opt/android-sdk/ndk/22.1.7171670",
+	"ndk-host": "linux-x86_64",
+	"qt": "${QT_PATH}",
+	"sdk": "/opt/android-sdk",
+	"sdkBuildToolsRevision": "30.0.2",
+	"stdcpp-path": "/opt/android-sdk/ndk/22.1.7171670/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/",
+	"tool-prefix": "llvm",
+	"toolchain-prefix": "llvm",
+	"useLLVM": true
+}
+EOF
+}
+
+main "$@"

cmd/android-stub-gen/android-stub-gen.sh

@@ -0,0 +1,84 @@
+#!/bin/bash
+#
+# android-stub-gen generates a .so that runs an exported function from another
+# so file. This is because Qt for Android always tries to run `main`, but Go's
+# c-shared build mode cannot export a function named `main`.
+
+set -eu
+
+# QT_PATH is already pre-set in our docker container environment. Includes trailing slash.
+QT_PATH=${QT_PATH:-/usr/local/Qt-5.15.13/}
+
+main() {
+
+	if [[ $# -ne 3 ]] ; then
+		echo "Usage: android-gen-stub.sh src.so function-name dest.so" >&2
+		exit 1
+	fi
+	local ARG_SOURCE_SOFILE="$1"
+	local ARG_FUNCTIONNAME="$2"
+	local ARG_DEST_SOFILE="$3"
+
+	local tmpdir=$(mktemp -d)
+	trap "rm -r ${tmpdir}" EXIT
+	
+	echo "- Using temporary directory: ${tmpdir}"
+	echo "- Found Qt path: ${QT_PATH}"
+
+	echo "Generating stub..."
+	
+	cat > $tmpdir/miqtstub.cpp <<EOF
+#include <android/log.h>
+#include <dlfcn.h>
+#include <stdlib.h>
+
+typedef void goMainFunc_t();  
+
+int main(int argc, char** argv) {
+    __android_log_print(ANDROID_LOG_VERBOSE, "miqt_stub", "Starting up");
+        
+    void* handle = dlopen("$(basename "$ARG_SOURCE_SOFILE")", RTLD_LAZY);
+    if (handle == NULL) {
+        __android_log_print(ANDROID_LOG_VERBOSE, "miqt_stub", "miqt_stub: null handle opening so: %s", dlerror());
+        exit(1);
+    }
+    
+    void* goMain = dlsym(handle, "${ARG_FUNCTIONNAME}");
+    if (goMain == NULL) {
+        __android_log_print(ANDROID_LOG_VERBOSE, "miqt_stub", "miqt_stub: null handle looking for function: %s", dlerror());
+        exit(1);        
+    }
+    
+    __android_log_print(ANDROID_LOG_VERBOSE, "miqt_stub", "miqt_stub: Found target, calling");
+    
+    // Cast to function pointer and call
+    goMainFunc_t* f = (goMainFunc_t*)goMain;
+    f();
+    
+    __android_log_print(ANDROID_LOG_VERBOSE, "miqt_stub", "miqt_stub: Target function returned");
+    return 0;
+}
+	
+EOF
+	
+	# Compile
+	# Link with Qt libraries so that androiddeployqt detects us as being the
+	# main shared library
+	$CXX -shared \
+        -ldl \
+        -llog \
+        ${QT_PATH}plugins/platforms/libplugins_platforms_qtforandroid_arm64-v8a.so \
+        ${QT_PATH}lib/libQt5Widgets_arm64-v8a.so /usr/local/Qt-5.15.13/lib/libQt5Gui_arm64-v8a.so \
+        ${QT_PATH}lib/libQt5Core_arm64-v8a.so \
+        ${QT_PATH}lib/libQt5Svg_arm64-v8a.so \
+        ${QT_PATH}lib/libQt5AndroidExtras_arm64-v8a.so \
+        -fPIC -DQT_WIDGETS_LIB -I${QT_PATH}include/QtWidgets -I${QT_PATH}include/ -I${QT_PATH}include/QtCore -DQT_GUI_LIB -I${QT_PATH}include/QtGui -DQT_CORE_LIB \
+        $tmpdir/miqtstub.cpp \
+        "-Wl,-soname,$(basename "$ARG_DEST_SOFILE")" \
+        -o "$ARG_DEST_SOFILE"
+
+	
+	echo "Done."
+}
+
+main "$@"

docker/android-armv8a-go1.23-qt5.15-dynamic.Dockerfile

@@ -0,0 +1,17 @@
+FROM raymii/qt:5.15-android-source
+
+RUN wget 'https://go.dev/dl/go1.23.1.linux-amd64.tar.gz' && \
+	tar x -C /usr/local/ -f go1.23.1.linux-amd64.tar.gz && \
+	rm go1.23.1.linux-amd64.tar.gz
+
+COPY ../cmd/android-stub-gen/android-stub-gen.sh /usr/local/bin/android-stub-gen.sh
+COPY ../cmd/android-stub-gen/android-mktemplate.sh /usr/local/bin/android-mktemplate.sh
+
+ENV PATH=/usr/local/go/bin:/opt/cmake/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/Qt-5.15.13/bin:/opt/android-sdk/cmdline-tools/tools/bin:/opt/android-sdk/tools:/opt/android-sdk/tools/bin:/opt/android-sdk/platform-tools
+
+ENV CC=/opt/android-sdk/ndk/22.1.7171670/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android30-clang
+ENV CXX=/opt/android-sdk/ndk/22.1.7171670/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android30-clang++
+ENV CGO_ENABLED=1
+ENV GOOS=android
+ENV GOARCH=arm64
+ENV GOFLAGS=-buildvcs=false

examples/android/main.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/mappu/miqt/qt"
+)
+
+func myRealMainFunc() {
+
+	qt.NewQApplication(os.Args)
+
+	btn := qt.NewQPushButton2("Hello world!")
+	btn.SetFixedWidth(320)
+
+	var counter int = 0
+
+	btn.OnPressed(func() {
+		counter++
+		btn.SetText(fmt.Sprintf("You have clicked the button %d time(s)", counter))
+	})
+
+	btn.Show()
+
+	qt.QApplication_Exec()
+
+	fmt.Println("OK!")
+}

examples/android/startup_android.go

@@ -0,0 +1,14 @@
+// +build android
+
+package main
+
+import "C" // Required for export support
+
+//export AndroidMain
+func AndroidMain() {
+	myRealMainFunc()
+}
+
+func main() {
+	// Must be empty
+}

examples/android/startup_other.go

@@ -0,0 +1,7 @@
+// +build !android
+
+package main
+
+func main() {
+	myRealMainFunc()
+}

qt/cflags_android.go

@@ -0,0 +1,9 @@
+package qt
+
+/*
+
+#cgo CXXFLAGS: -fPIC -DQT_WIDGETS_LIB -I/usr/local/Qt-5.15.13/include/QtWidgets -I/usr/local/Qt-5.15.13/include/ -I/usr/local/Qt-5.15.13/include/QtCore -DQT_GUI_LIB -I/usr/local/Qt-5.15.13/include/QtGui -DQT_CORE_LIB
+#cgo LDFLAGS: /usr/local/Qt-5.15.13/lib/libQt5Widgets_arm64-v8a.so /usr/local/Qt-5.15.13/lib/libQt5Gui_arm64-v8a.so /usr/local/Qt-5.15.13/lib/libQt5Core_arm64-v8a.so /usr/local/Qt-5.15.13/lib/libQt5Svg_arm64-v8a.so /usr/local/Qt-5.15.13/lib/libQt5AndroidExtras_arm64-v8a.so
+
+*/
+import "C"

qt/cflags_linux.go

@@ -1,3 +1,5 @@
+// +build linux,!android
+
 package qt
 
 /*