[markdown] IJPL-157064 initial compose-based preview implementation

Now it's hidden under a registry key ("markdown.experimental.use.compose.for.preview") and a checkbox in Markdown settings. It's a very early stage of development, lots of inlines are not unsupported yet, and styling is far from the JCEF-based renderer.


Merge-request: IJ-MR-140719
Merged-by: Alexander Kuznetsov <Aleksander.Kuznetsov@jetbrains.com>

GitOrigin-RevId: b4ad8a44e17aee1cfff32d20a3d2adc52f9fa9c5

.idea/modules.xml

@@ -526,6 +526,7 @@
       <module fileurl="file://$PROJECT_DIR$/plugins/lombok/intellij.lombok.iml" filepath="$PROJECT_DIR$/plugins/lombok/intellij.lombok.iml" />
       <module fileurl="file://$PROJECT_DIR$/plugins/lombok/generated/intellij.lombok.generated.iml" filepath="$PROJECT_DIR$/plugins/lombok/generated/intellij.lombok.generated.iml" />
       <module fileurl="file://$PROJECT_DIR$/plugins/markdown/core/intellij.markdown.iml" filepath="$PROJECT_DIR$/plugins/markdown/core/intellij.markdown.iml" />
+      <module fileurl="file://$PROJECT_DIR$/plugins/markdown/compose/intellij.markdown.compose.preview.iml" filepath="$PROJECT_DIR$/plugins/markdown/compose/intellij.markdown.compose.preview.iml" />
       <module fileurl="file://$PROJECT_DIR$/plugins/markdown/fenceInjection/intellij.markdown.fenceInjection.iml" filepath="$PROJECT_DIR$/plugins/markdown/fenceInjection/intellij.markdown.fenceInjection.iml" />
       <module fileurl="file://$PROJECT_DIR$/plugins/markdown/frontmatter/intellij.markdown.frontmatter.iml" filepath="$PROJECT_DIR$/plugins/markdown/frontmatter/intellij.markdown.frontmatter.iml" />
       <module fileurl="file://$PROJECT_DIR$/plugins/markdown/frontmatter/toml/intellij.markdown.frontmatter.toml.iml" filepath="$PROJECT_DIR$/plugins/markdown/frontmatter/toml/intellij.markdown.frontmatter.toml.iml" />

platform/build-scripts/src/org/jetbrains/intellij/build/CommunityLibraryLicenses.kt

@@ -583,7 +583,7 @@ object CommunityLibraryLicenses {
     )
       .apache("https://github.com/JetBrains/jewel/blob/master/LICENSE")
       .suppliedByOrganizations(Suppliers.JETBRAINS),
-    LibraryLicense(name = "Jetbrains Jewel Markdown LaF Standalone",
+    LibraryLicense(name = "Jetbrains Jewel Markdown IDE LaF Bridge",
                    url = "https://github.com/JetBrains/jewel",
                    libraryName= "jetbrains-jewel-markdown-laf-bridge-styling",
     )

platform/compose/api-dump.txt

@@ -0,0 +1,2 @@
+f:com.intellij.platform.compose.JBComposePanelKt
+- *sf:JBComposePanel(kotlin.jvm.functions.Function2):javax.swing.JComponent

platform/compose/src/com/intellij/platform/compose/JBComposePanel.kt

@@ -22,7 +22,7 @@ import javax.swing.JComponent
 @Suppress("FunctionName")
 @OptIn(ExperimentalComposeUiApi::class, ExperimentalJewelApi::class)
 @Experimental
-internal fun JBComposePanel(
+fun JBComposePanel(
   content: @Composable () -> Unit
 ): JComponent {
   if (ApplicationManager.getApplication().isInternal) {

plugins/markdown/compose/intellij.markdown.compose.preview.iml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="FacetManager">
+    <facet type="kotlin-language" name="Kotlin">
+      <configuration version="5" platform="JVM 17" allPlatforms="JVM [17]" useProjectSettings="false">
+        <compilerSettings>
+          <option name="additionalArguments" value="-Xjvm-default=all" />
+        </compilerSettings>
+        <compilerArguments>
+          <stringArguments>
+            <stringArg name="jvmTarget" arg="17" />
+            <stringArg name="apiVersion" arg="1.9" />
+            <stringArg name="languageVersion" arg="1.9" />
+          </stringArguments>
+          <arrayArguments>
+            <arrayArg name="pluginClasspaths">
+              <args>$MAVEN_REPOSITORY$/org/jetbrains/compose/compiler/compiler-hosted/1.5.14/compiler-hosted-1.5.14.jar</args>
+            </arrayArg>
+            <arrayArg name="pluginOptions">
+              <args>plugin:androidx.compose.compiler.plugins.kotlin:suppressKotlinVersionCompatibilityCheck=1.9.25</args>
+            </arrayArg>
+          </arrayArguments>
+        </compilerArguments>
+      </configuration>
+    </facet>
+  </component>
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/main/kotlin" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/main/resources" type="java-resource" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="kotlin-stdlib" level="project" />
+    <orderEntry type="module" module-name="intellij.markdown" />
+    <orderEntry type="module" module-name="intellij.platform.compose" />
+    <orderEntry type="module-library">
+      <library name="jetbrains-jewel-markdown-laf-bridge-styling" type="repository">
+        <properties maven-id="org.jetbrains.jewel:jewel-markdown-ide-laf-bridge-styling-241:0.19.7">
+          <verification>
+            <artifact url="file://$MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-ide-laf-bridge-styling-241/0.19.7/jewel-markdown-ide-laf-bridge-styling-241-0.19.7.jar">
+              <sha256sum>44f90aace7a3f8b9c811294f7705a4591d169f13b5d2299eed9f922be30dafce</sha256sum>
+            </artifact>
+            <artifact url="file://$MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-core-241/0.19.7/jewel-markdown-core-241-0.19.7.jar">
+              <sha256sum>422b42dab33648dcb2b413a06707e100c6e70470918a42a1d760e4b02a1401a3</sha256sum>
+            </artifact>
+            <artifact url="file://$MAVEN_REPOSITORY$/org/commonmark/commonmark/0.22.0/commonmark-0.22.0.jar">
+              <sha256sum>3417909f2997bc8c61d90d64c6af29f4a3f5b6729caceaef97221ceac93df814</sha256sum>
+            </artifact>
+          </verification>
+          <exclude>
+            <dependency maven-id="org.jetbrains.jewel:jewel-ui-241" />
+            <dependency maven-id="org.jetbrains.jewel:jewel-ide-laf-bridge-241" />
+          </exclude>
+        </properties>
+        <CLASSES>
+          <root url="jar://$MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-ide-laf-bridge-styling-241/0.19.7/jewel-markdown-ide-laf-bridge-styling-241-0.19.7.jar!/" />
+          <root url="jar://$MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-core-241/0.19.7/jewel-markdown-core-241-0.19.7.jar!/" />
+          <root url="jar://$MAVEN_REPOSITORY$/org/commonmark/commonmark/0.22.0/commonmark-0.22.0.jar!/" />
+        </CLASSES>
+        <JAVADOC />
+        <SOURCES>
+          <root url="jar://$MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-ide-laf-bridge-styling-241/0.19.7/jewel-markdown-ide-laf-bridge-styling-241-0.19.7-sources.jar!/" />
+          <root url="jar://$MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-core-241/0.19.7/jewel-markdown-core-241-0.19.7-sources.jar!/" />
+          <root url="jar://$MAVEN_REPOSITORY$/org/commonmark/commonmark/0.22.0/commonmark-0.22.0-sources.jar!/" />
+        </SOURCES>
+      </library>
+    </orderEntry>
+  </component>
+</module>

plugins/markdown/compose/src/main/kotlin/com/intellij/markdown/compose/preview/ComposePanelProvider.kt

@@ -0,0 +1,33 @@
+// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.markdown.compose.preview
+
+import com.intellij.idea.AppMode
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.util.registry.Registry
+import com.intellij.openapi.vfs.VirtualFile
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanel
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanelProvider
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanelProvider.AvailabilityInfo
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanelProvider.ProviderInfo
+import org.jetbrains.jewel.foundation.ExperimentalJewelApi
+
+@OptIn(ExperimentalJewelApi::class)
+private class ComposePanelProvider : MarkdownHtmlPanelProvider() {
+
+  override fun createHtmlPanel(): MarkdownHtmlPanel {
+    return MarkdownComposePanel()
+  }
+
+  override fun createHtmlPanel(project: Project, virtualFile: VirtualFile): MarkdownHtmlPanel {
+    return MarkdownComposePanel(project, virtualFile)
+  }
+
+  override fun isAvailable(): AvailabilityInfo {
+    if (Registry.`is`("markdown.experimental.use.compose.for.preview", false) && !AppMode.isRemoteDevHost()) {
+      return AvailabilityInfo.AVAILABLE
+    }
+    return AvailabilityInfo.UNAVAILABLE
+  }
+
+  override fun getProviderInfo() = ProviderInfo("Compose-based", ComposePanelProvider::class.java.name)
+}

plugins/markdown/compose/src/main/kotlin/com/intellij/markdown/compose/preview/MarkdownComposePanel.kt

@@ -0,0 +1,115 @@
+// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.markdown.compose.preview
+
+import androidx.compose.foundation.ScrollState
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.rememberScrollbarAdapter
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.intellij.ide.BrowserUtil
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.util.UserDataHolder
+import com.intellij.openapi.util.UserDataHolderBase
+import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.platform.compose.JBComposePanel
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanel
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanelEx
+import org.intellij.plugins.markdown.ui.preview.MarkdownUpdateHandler
+import org.intellij.plugins.markdown.ui.preview.MarkdownUpdateHandler.PreviewRequest
+import org.jetbrains.annotations.ApiStatus
+import org.jetbrains.jewel.foundation.ExperimentalJewelApi
+import org.jetbrains.jewel.intui.markdown.bridge.ProvideMarkdownStyling
+import org.jetbrains.jewel.markdown.Markdown
+import org.jetbrains.jewel.ui.component.VerticalScrollbar
+import javax.swing.JComponent
+
+@ExperimentalJewelApi
+class MarkdownComposePanel(
+  private val project: Project?,
+  private val virtualFile: VirtualFile?,
+  private val updateHandler: MarkdownUpdateHandler = MarkdownUpdateHandler.Debounced()
+) : MarkdownHtmlPanelEx, UserDataHolder by UserDataHolderBase() {
+
+  constructor() : this(null, null)
+
+  private val panelComponent by lazy {
+    JBComposePanel {
+      // TODO temporary styling, we will likely need our own in the future for JCEF-like rendering
+      ProvideMarkdownStyling {
+        MarkdownPanel()
+      }
+    }
+  }
+
+  @Suppress("FunctionName")
+  @Composable
+  private fun MarkdownPanel() {
+    Box {
+      val scrollState = rememberScrollState(0)
+      MarkdownPreviewPanel(scrollState)
+      VerticalScrollbar(
+        modifier = Modifier
+          .align(Alignment.CenterEnd),
+        adapter = rememberScrollbarAdapter(scrollState),
+      )
+    }
+  }
+
+  @Suppress("FunctionName")
+  @Composable
+  private fun MarkdownPreviewPanel(scrollState: ScrollState) {
+    val request by updateHandler.requests.collectAsState(null)
+    (request as? PreviewRequest.Update)?.let {
+      Markdown(
+        it.content,
+        modifier = Modifier
+          .fillMaxWidth()
+          .padding(8.dp)
+          .verticalScroll(scrollState),
+        enabled = true,
+        onUrlClick = { url -> BrowserUtil.open(url) },
+      )
+    }
+  }
+
+  override fun setHtml(html: String, initialScrollOffset: Int, document: VirtualFile?) {
+    updateHandler.setContent(html, initialScrollOffset, document)
+  }
+
+  override fun reloadWithOffset(offset: Int) {
+    updateHandler.reloadWithOffset(offset)
+  }
+
+  override fun getComponent(): JComponent {
+    return panelComponent
+  }
+
+  override fun dispose() {
+  }
+
+  @ApiStatus.Experimental
+  override fun getProject(): Project? = project
+
+  @ApiStatus.Experimental
+  override fun getVirtualFile(): VirtualFile? = virtualFile
+
+  override fun addScrollListener(listener: MarkdownHtmlPanel.ScrollListener) {
+  }
+
+  override fun removeScrollListener(listener: MarkdownHtmlPanel.ScrollListener) {
+  }
+
+  override fun scrollToMarkdownSrcOffset(offset: Int, smooth: Boolean) {
+  }
+
+  override fun scrollBy(horizontalUnits: Int, verticalUnits: Int) {
+  }
+}

plugins/markdown/compose/src/main/resources/intellij.markdown.compose.preview.xml

@@ -0,0 +1,14 @@
+<idea-plugin package="com.intellij.markdown.compose.preview">
+  <dependencies>
+    <module name="intellij.platform.compose"/>
+  </dependencies>
+
+  <extensions defaultExtensionNs="org.intellij.markdown">
+    <html.panel.provider implementation="com.intellij.markdown.compose.preview.ComposePanelProvider"/>
+  </extensions>
+  <extensions defaultExtensionNs="com.intellij">
+    <registryKey key="markdown.experimental.use.compose.for.preview"
+                 defaultValue="false"
+                 description="Renders Markdown Preview using Compose instead of JCEF (experimental feature, many inlines are unsupported yet)."/>
+  </extensions>
+</idea-plugin>

plugins/markdown/core/plugin-content.yaml

@@ -9,4 +9,15 @@
   - name: intellij.markdown.images
   - name: intellij.markdown.xml
   - name: intellij.markdown.model
-  - name: intellij.markdown.spellchecker
+  - name: intellij.markdown.spellchecker
+- name: lib/modules/intellij.markdown.compose.preview.jar
+  contentModules:
+  - name: intellij.markdown.compose.preview
+    libraries:
+      jetbrains-jewel-markdown-laf-bridge-styling:
+      - name: $MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-ide-laf-bridge-styling-241/0.19.7/jewel-markdown-ide-laf-bridge-styling-241-0.19.7.jar
+        size: 28320
+      - name: $MAVEN_REPOSITORY$/org/jetbrains/jewel/jewel-markdown-core-241/0.19.7/jewel-markdown-core-241-0.19.7.jar
+        size: 294476
+      - name: $MAVEN_REPOSITORY$/org/commonmark/commonmark/0.22.0/commonmark-0.22.0.jar
+        size: 193845

plugins/markdown/core/resources/META-INF/plugin.xml

@@ -17,6 +17,7 @@
     <module name="intellij.markdown.xml"/>
     <module name="intellij.markdown.model"/>
     <module name="intellij.markdown.spellchecker"/>
+    <module name="intellij.markdown.compose.preview"/>
   </content>
 
   <description><![CDATA[

plugins/markdown/core/src/org/intellij/plugins/markdown/settings/MarkdownPreviewSettings.kt

@@ -9,7 +9,7 @@ import org.jetbrains.annotations.ApiStatus
 @ApiStatus.Experimental
 @Service(Service.Level.APP)
 @State(name = "MarkdownSettings", storages = [(Storage("markdown.xml"))])
-internal class MarkdownPreviewSettings: SimplePersistentStateComponent<MarkdownPreviewSettings.State>(State()) {
+class MarkdownPreviewSettings: SimplePersistentStateComponent<MarkdownPreviewSettings.State>(State()) {
   class State: BaseState() {
     var fontSize by property(defaultFontSize)
   }

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/MarkdownHtmlPanelProvider.java

@@ -40,6 +40,10 @@ public abstract class MarkdownHtmlPanelProvider {
 
   public abstract @NotNull ProviderInfo getProviderInfo();
 
+  public @NotNull SourceTextPreprocessor getSourceTextPreprocessor() {
+    return SourceTextPreprocessor.getDefault();
+  }
+
   public static  @NotNull List<MarkdownHtmlPanelProvider> getProviders() {
     return EP_NAME.getExtensionList();
   }

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/MarkdownPreviewFileEditor.kt

@@ -37,7 +37,6 @@ import kotlinx.coroutines.launch
 import org.intellij.plugins.markdown.MarkdownBundle
 import org.intellij.plugins.markdown.settings.MarkdownExtensionsSettings
 import org.intellij.plugins.markdown.settings.MarkdownSettings
-import org.intellij.plugins.markdown.ui.preview.html.MarkdownUtil.generateMarkdownHtml
 import org.intellij.plugins.markdown.ui.preview.jcef.MarkdownJCEFHtmlPanel
 import org.intellij.plugins.markdown.util.MarkdownPluginScope
 import org.jetbrains.annotations.ApiStatus.Internal
@@ -204,10 +203,12 @@ class MarkdownPreviewFileEditor(
       return
     }
 
-    val html = readAction { generateMarkdownHtml(file, document.text, project) }
+    val settings = MarkdownSettings.getInstance(project)
+    val textPreprocessor = retrievePanelProvider(settings).sourceTextPreprocessor
+    lastRenderedHtml = readAction {
+      textPreprocessor.preprocessText(project, document, file)
+    }
 
-    val currentHtml = "<html><head></head>$html</html>"
-    lastRenderedHtml = currentHtml
     val editor = mainEditor.firstOrNull() ?: return
     writeIntentReadAction {
       val offset = editor.caretModel.offset
@@ -229,7 +230,8 @@ class MarkdownPreviewFileEditor(
   @RequiresEdt
   private suspend fun attachHtmlPanel() {
     val settings = MarkdownSettings.getInstance(project)
-    val panel = retrievePanelProvider(settings).createHtmlPanel(project, file)
+    val panelProvider = retrievePanelProvider(settings)
+    val panel = panelProvider.createHtmlPanel(project, file)
     this.panel = panel
     htmlPanelWrapper.add(panel.component, BorderLayout.CENTER)
     if (htmlPanelWrapper.isShowing) htmlPanelWrapper.validate()

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/MarkdownUpdateHandler.kt

@@ -0,0 +1,50 @@
+// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package org.intellij.plugins.markdown.ui.preview
+
+import com.intellij.openapi.vfs.VirtualFile
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.debounce
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.milliseconds
+
+abstract class MarkdownUpdateHandler {
+
+  abstract val requests: Flow<PreviewRequest>
+  protected abstract fun addRequest(request: PreviewRequest): Boolean
+
+  fun setContent(content: String, initialScrollOffset: Int, document: VirtualFile?) {
+    doRequest(PreviewRequest.Update(content, initialScrollOffset, document))
+  }
+
+  fun reloadWithOffset(offset: Int) {
+    doRequest(PreviewRequest.ReloadWithOffset(offset))
+  }
+
+  private fun doRequest(request: PreviewRequest) {
+    check(addRequest(request))
+  }
+
+  sealed interface PreviewRequest {
+    data class Update(
+      val content: String,
+      val initialScrollOffset: Int,
+      val document: VirtualFile?
+    ) : PreviewRequest
+
+    data class ReloadWithOffset(val offset: Int) : PreviewRequest
+  }
+
+  @OptIn(FlowPreview::class)
+  class Debounced(private val debounceTimeout: Duration = 20.milliseconds) : MarkdownUpdateHandler() {
+
+    private val _updateViewRequests = MutableSharedFlow<PreviewRequest>(replay = 1, onBufferOverflow = BufferOverflow.DROP_OLDEST)
+
+    override val requests: Flow<PreviewRequest>
+      get() = _updateViewRequests.debounce(debounceTimeout)
+
+    override fun addRequest(request: PreviewRequest): Boolean = _updateViewRequests.tryEmit(request)
+  }
+}

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/SourceTextPreprocessor.kt

@@ -0,0 +1,19 @@
+// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package org.intellij.plugins.markdown.ui.preview
+
+import com.intellij.openapi.editor.Document
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.vfs.VirtualFile
+
+interface SourceTextPreprocessor {
+  fun preprocessText(project: Project, document: Document, file: VirtualFile): String
+
+  companion object {
+    @JvmStatic
+    val default: SourceTextPreprocessor = object : SourceTextPreprocessor {
+      override fun preprocessText(project: Project, document: Document, file: VirtualFile): String {
+        return document.text
+      }
+    }
+  }
+}

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/jcef/HtmlSourceTextPreprocessor.kt

@@ -0,0 +1,15 @@
+// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package org.intellij.plugins.markdown.ui.preview.jcef
+
+import com.intellij.openapi.editor.Document
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.vfs.VirtualFile
+import org.intellij.plugins.markdown.ui.preview.SourceTextPreprocessor
+import org.intellij.plugins.markdown.ui.preview.html.MarkdownUtil.generateMarkdownHtml
+
+class HtmlSourceTextPreprocessor : SourceTextPreprocessor {
+  override fun preprocessText(project: Project, document: Document, file: VirtualFile): String {
+    val html = generateMarkdownHtml(file, document.text, project)
+    return "<html><head></head>$html</html>"
+  }
+}

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/jcef/JCEFHtmlPanelProvider.java

@@ -7,10 +7,9 @@ import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.ui.jcef.JBCefApp;
 import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanel;
 import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanelProvider;
+import org.intellij.plugins.markdown.ui.preview.SourceTextPreprocessor;
 import org.jetbrains.annotations.NotNull;
 
-import javax.swing.*;
-
 public final class JCEFHtmlPanelProvider extends MarkdownHtmlPanelProvider {
 
   @NotNull
@@ -39,6 +38,11 @@ public final class JCEFHtmlPanelProvider extends MarkdownHtmlPanelProvider {
     return new ProviderInfo("JCEF Browser", JCEFHtmlPanelProvider.class.getName());
   }
 
+  @Override
+  public @NotNull SourceTextPreprocessor getSourceTextPreprocessor() {
+    return new HtmlSourceTextPreprocessor();
+  }
+
   public static boolean canBeUsed() {
     return !AppMode.isRemoteDevHost() && JBCefApp.isSupported();
   }

plugins/markdown/core/src/org/intellij/plugins/markdown/ui/preview/jcef/MarkdownJCEFHtmlPanel.kt

@@ -24,10 +24,7 @@ import com.intellij.ui.jcef.JCEFHtmlPanel
 import com.intellij.util.application
 import com.intellij.util.net.NetUtils
 import kotlinx.coroutines.*
-import kotlinx.coroutines.channels.BufferOverflow
-import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.collectLatest
-import kotlinx.coroutines.flow.debounce
 import org.cef.browser.CefBrowser
 import org.cef.browser.CefFrame
 import org.cef.handler.CefRequestHandlerAdapter
@@ -41,6 +38,7 @@ import org.intellij.plugins.markdown.extensions.MarkdownConfigurableExtension
 import org.intellij.plugins.markdown.settings.MarkdownPreviewSettings
 import org.intellij.plugins.markdown.settings.MarkdownSettingsConfigurable.Companion.fontSizeOptions
 import org.intellij.plugins.markdown.ui.preview.*
+import org.intellij.plugins.markdown.ui.preview.MarkdownUpdateHandler.PreviewRequest
 import org.intellij.plugins.markdown.ui.preview.jcef.impl.*
 import org.intellij.plugins.markdown.ui.preview.jcef.zoomIndicator.PreviewZoomIndicatorManager
 import org.intellij.plugins.markdown.util.MarkdownApplicationScope
@@ -101,6 +99,8 @@ class MarkdownJCEFHtmlPanel(
     styles.map { PreviewStaticServer.getStaticUrl(resourceProvider, it) }
   )
 
+  private val updateHandler = MarkdownUpdateHandler.Debounced()
+
   private fun buildIndexContent(): String {
     // language=HTML
     return """
@@ -126,18 +126,6 @@ class MarkdownJCEFHtmlPanel(
 
   private val coroutineScope = project?.let(MarkdownPluginScope::createChildScope) ?: MarkdownApplicationScope.createChildScope()
 
-  private sealed interface PreviewRequest {
-    data class Update(
-      val content: String,
-      val initialScrollOffset: Int,
-      val document: VirtualFile?,
-    ) : PreviewRequest
-
-    data class ReloadWithOffset(val offset: Int) : PreviewRequest
-  }
-
-  private val updateViewRequests = MutableSharedFlow<PreviewRequest>(replay = 1, onBufferOverflow = BufferOverflow.DROP_OLDEST)
-
   private val projectRoot = coroutineScope.async(context = Dispatchers.Default) {
     if (virtualFile != null && project != null) {
       BaseProjectDirectories.getInstance(project).getBaseDirectoryFor(virtualFile)
@@ -186,7 +174,7 @@ class MarkdownJCEFHtmlPanel(
       val fileSchemeResourcesProcessor = createFileSchemeResourcesProcessor(projectRoot)
 
       loadIndexContent()
-      updateViewRequests.debounce(20.milliseconds).collectLatest { request ->
+      updateHandler.requests.collectLatest { request ->
         when (request) {
           is PreviewRequest.Update -> {
             val (html, initialScrollOffset, document) = request
@@ -239,7 +227,7 @@ class MarkdownJCEFHtmlPanel(
   }
 
   override fun setHtml(html: String, initialScrollOffset: Int, document: VirtualFile?) {
-    check(updateViewRequests.tryEmit(PreviewRequest.Update(content = html, initialScrollOffset, document)))
+    updateHandler.setContent(html, initialScrollOffset, document)
   }
 
   @ApiStatus.Internal
@@ -253,7 +241,7 @@ class MarkdownJCEFHtmlPanel(
   }
 
   override fun reloadWithOffset(offset: Int) {
-    check(updateViewRequests.tryEmit(PreviewRequest.ReloadWithOffset(offset)))
+    updateHandler.reloadWithOffset(offset)
   }
 
   override fun dispose() {

plugins/markdown/plugin/intellij.markdown.plugin.iml

@@ -12,5 +12,6 @@
     <orderEntry type="module" module-name="intellij.markdown.model" />
     <orderEntry type="module" module-name="intellij.markdown.spellchecker" />
     <orderEntry type="module" module-name="intellij.markdown.xml" />
+    <orderEntry type="module" module-name="intellij.markdown.compose.preview" />
   </component>
 </module>