web: add example for dom-based-composables usage in plain JS (#1677)

* web: add example for dom-based-composables usage in plain JS

* web: add example for dom-based-composables usage in plain JS (review improvements)

Co-authored-by: Oleksandr Karpovich <oleksandr.karpovich@jetbrains.com>

examples/web-compose-in-js/.gitignore

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+*.iml
+.gradle
+.idea
+build/
+local.properties

examples/web-compose-in-js/README.MD

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+### How to use HTML based @Composable functions in JS?
+
+Useful links:
+- [Use Kotlin Code from JS](https://kotlinlang.org/docs/js-to-kotlin-interop.html)
+- [JavaScript modules](https://kotlinlang.org/docs/js-modules.html)
+- [webpack bundling](https://kotlinlang.org/docs/js-project-setup.html#webpack-bundling)
+
+1) @Composable functions can't be invoked from JS directly (because every @Composable function has implicit parameters added by compiler plugin)
+2) We can wrap @Composable functions into some usual function (with [@JsExport](https://kotlinlang.org/docs/js-to-kotlin-interop.html#jsexport-annotation)) which can be invoked in JS as is.
+3) Every call to a "wrapping" function will create a composition (part of DOM controlled by Compose runtime)
+4) It's important to `dispose` a composition when it's not needed.
+5) The composition's state can be controlled by creating an arbitrary `Controller` class, which implements and exposes necessary functions for state updates.
+
+
+### Simplified example (see full example in `src/jsMain`):
+
+```kotlin
+// Composables.kt
+
+@JsExport
+abstract class ComposeCounterAppController {
+    abstract fun setCount(newCount: Int)
+    abstract fun dispose()
+}
+
+@JsExport
+fun ComposeCounterApp(rootId: String, onCountChange: (Int) -> Unit = {}): ComposeCounterAppController {
+    var count: Int by mutableStateOf(0)
+
+    val composition = renderComposable(rootElementId = rootId) {
+        // Counter is a @Composable function
+        // see full example in src/jsMain
+        Counter(count) {
+            count = it
+            onCountChange(count)
+        }
+    }
+
+    return object : ComposeCounterAppController() {
+        override fun setCount(newCount: Int) {
+            count = newCount
+        }
+
+        override fun dispose() {
+            composition.dispose()
+        }
+    }
+}
+```
+
+Then in JS we can use `ComposeCounterApp` function:
+
+```javascript
+// see src/jsMain/resources/use_compose.js file for a full example
+
+counterController = MyComposables.ComposeCounterApp('counterByCompose', (newCount) => {
+    console.log(`Counter was updated. New value = ${newCount}`);
+});
+```
+
+The module name was overridden to make it convenient for usage in JS:
+
+```
+// webpack.config.d/configModuleName.js
+
+config.output = config.output || {};
+config.output.library = "MyComposables";
+```
+
+### Building and using the output
+
+```
+./gradlew jsBrowserProductionWebpack
+```
+
+This will produce the output in `build/distributions`.
+Then we can use exported functions from `web-compose-in-js.js` (the filename is defined by the project/module name).
+```html
+<script src="web-compose-in-js.js"></script>
+<script src="use_compose.js"></script>
+```

examples/web-compose-in-js/build.gradle.kts

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+import org.jetbrains.compose.compose
+
+plugins {
+    kotlin("multiplatform") version "1.6.10"
+    id("org.jetbrains.compose") version "1.0.1"
+}
+
+group = "me.user"
+version = "1.0"
+
+repositories {
+    google()
+    mavenCentral()
+    maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
+}
+
+kotlin {
+    js(IR) {
+        browser {
+            testTask {
+                testLogging.showStandardStreams = true
+                useKarma {
+                    useChromeHeadless()
+                    useFirefox()
+                }
+            }
+        }
+        binaries.executable()
+    }
+    sourceSets {
+        val jsMain by getting {
+            dependencies {
+                implementation(compose.web.core)
+                implementation(compose.runtime)
+            }
+        }
+        val jsTest by getting {
+            dependencies {
+                implementation(kotlin("test-js"))
+            }
+        }
+    }
+}

examples/web-compose-in-js/gradle.properties

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+kotlin.code.style=official
+kotlin.mpp.enableGranularSourceSetsMetadata=true
+kotlin.native.enableDependencyPropagation=false
+kotlin.js.webpack.major.version=4

examples/web-compose-in-js/gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

examples/web-compose-in-js/gradlew

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+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MSYS* | MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=`expr $i + 1`
+    done
+    case $i in
+        0) set -- ;;
+        1) set -- "$args0" ;;
+        2) set -- "$args0" "$args1" ;;
+        3) set -- "$args0" "$args1" "$args2" ;;
+        4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=`save "$@"`
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+exec "$JAVACMD" "$@"

examples/web-compose-in-js/gradlew.bat

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+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

examples/web-compose-in-js/settings.gradle.kts

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+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+        maven("https://maven.pkg.jetbrains.space/public/p/compose/dev")
+    }
+    
+}
+rootProject.name = "web-compose-in-js"
+

examples/web-compose-in-js/src/jsMain/kotlin/Composables.kt

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+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.setValue
+import org.jetbrains.compose.web.css.*
+import org.jetbrains.compose.web.dom.*
+import org.jetbrains.compose.web.renderComposable
+
+@JsExport
+abstract class ComposeCounterAppController {
+    abstract fun setCount(newCount: Int)
+    abstract fun dispose()
+}
+
+/**
+ * @param rootId - an id of an HTML element which is already added into the DOM.
+ * Compose will manage the content of this element.
+ *
+ * @param onCountChange - a callback to receive state updates in non-compose code.
+ *
+ * @return instance of [ComposeCounterAppController] to control the composition in non-compose code.
+ */
+@JsExport
+fun ComposeCounterApp(rootId: String, onCountChange: (Int) -> Unit = {}): ComposeCounterAppController {
+    var count: Int by mutableStateOf(0)
+
+    val composition = renderComposable(rootElementId = rootId) {
+        Counter(count) {
+            count = it
+            onCountChange(count)
+        }
+    }
+
+    return object : ComposeCounterAppController() {
+        override fun setCount(newCount: Int) {
+            count = newCount
+        }
+
+        override fun dispose() {
+            composition.dispose()
+        }
+    }
+}
+
+@Composable
+private fun Counter(count: Int, onCountChange: (Int) -> Unit) {
+    Div({ style { padding(25.px) } }) {
+        Button(attrs = {
+            onClick {
+                onCountChange(count - 1)
+            }
+        }) {
+            Text("-")
+        }
+
+        Span({ style { padding(15.px) } }) {
+            Text("$count")
+        }
+
+        Button(attrs = {
+            onClick {
+                onCountChange(count + 1)
+            }
+        }) {
+            Text("+")
+        }
+    }
+}

examples/web-compose-in-js/src/jsMain/resources/index.html

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+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>Sample</title>
+</head>
+<body>
+<div id="root">
+    <input type="checkbox" id="showCounter"/>
+    <label for="showCounter">Show counter (managed by Compose)</label>
+    <div id="container" style="padding-top:20px;"></div>
+</div>
+<script src="web-compose-in-js.js"></script>
+<script src="use_compose.js"></script>
+</body>
+</html>

examples/web-compose-in-js/src/jsMain/resources/use_compose.js

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+window.onload = (event) => {
+    // reference for ComposeCounterApp controller
+    let counterController = undefined;
+
+    const showCounterCheckbox = document.getElementById('showCounter');
+    const container = document.getElementById('container');
+
+    showCounterCheckbox.addEventListener('change', (event) => {
+        if (showCounterCheckbox.checked) {
+            // create a div that will serve as a root of Composition
+            const divContainerForCounter = document.createElement('div');
+            container.appendChild(divContainerForCounter);
+            divContainerForCounter.id = 'counterByCompose';
+
+            // create a composition with a root in <div id='counterByCompose'>
+            counterController = MyComposables.ComposeCounterApp('counterByCompose', (newCount) => {
+                console.log(`Counter was updated. New value = ${newCount}`);
+            });
+
+            const randomInitialCount = Math.floor(Math.random() * 1000);
+            // Controller can be used to update the composition's state
+            counterController.setCount(randomInitialCount);
+
+        } else {
+            // the composition is not needed anymore. It's necessary to dispose it:
+            counterController.dispose();
+            counterController = undefined;
+
+            // now we can remove the root of the composition.
+            container.removeChild(document.getElementById('counterByCompose'));
+        }
+    });
+}
+