[markdown] IJPL-177111 fix IJPL-167949 by adding ProcessImagesExtension

Introduced `ProcessImagesExtension` to handle image resources in the Markdown browser preview. Added a new remote API (`ProjectStructureRemoteApi`) to retrieve project-specific resources.

GitOrigin-RevId: 9a3e8f02e167c23e4954e9ebdaa58a9bfd2330fd

plugins/markdown/core/backend/resources/intellij.markdown.backend.xml

@@ -6,5 +6,7 @@
     <extensions defaultExtensionNs="com.intellij">
       <platform.rpc.backend.remoteApiProvider
         implementation="org.intellij.plugins.markdown.backend.providers.LinkOpenerApiProvider"/>
+      <platform.rpc.backend.remoteApiProvider
+        implementation="org.intellij.plugins.markdown.backend.providers.ProjectStructureProvider"/>
     </extensions>
 </idea-plugin>

plugins/markdown/core/backend/src/org/intellij/plugins/markdown/backend/providers/ProjectStructureProvider.kt

@@ -0,0 +1,14 @@
+package org.intellij.plugins.markdown.backend.providers
+
+import com.intellij.platform.rpc.backend.RemoteApiProvider
+import fleet.rpc.remoteApiDescriptor
+import org.intellij.plugins.markdown.backend.services.ProjectStructureRemoteApiImpl
+import org.intellij.plugins.markdown.service.ProjectStructureRemoteApi
+
+private class ProjectStructureProvider : RemoteApiProvider {
+  override fun RemoteApiProvider.Sink.remoteApis() {
+    remoteApi(remoteApiDescriptor<ProjectStructureRemoteApi>()) {
+      ProjectStructureRemoteApiImpl()
+    }
+  }
+}

plugins/markdown/core/backend/src/org/intellij/plugins/markdown/backend/services/ProjectStructureRemoteApiImpl.kt

@@ -0,0 +1,38 @@
+package org.intellij.plugins.markdown.backend.services
+
+import com.intellij.ide.vfs.VirtualFileId
+import com.intellij.ide.vfs.rpcId
+import com.intellij.ide.vfs.virtualFile
+import com.intellij.openapi.diagnostic.Logger
+import com.intellij.openapi.project.BaseProjectDirectories
+import com.intellij.openapi.vfs.VfsUtil
+import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.platform.project.ProjectId
+import com.intellij.platform.project.findProject
+import org.intellij.plugins.markdown.service.ProjectStructureRemoteApi
+import java.io.File
+import java.net.URL
+
+class ProjectStructureRemoteApiImpl : ProjectStructureRemoteApi {
+  private fun getBaseDirectory(projectId: ProjectId, virtualFileId: VirtualFileId) : VirtualFile?{
+    val project = projectId.findProject()
+    val virtualFile = virtualFileId.virtualFile() ?: return null
+    val baseDirectory = BaseProjectDirectories.getInstance(project).getBaseDirectoryFor(virtualFile)
+    return baseDirectory
+  }
+
+  override suspend fun getFileByResourceName(resourceName: String, virtualFileId: VirtualFileId?, projectId: ProjectId?): VirtualFileId? {
+    if (projectId == null || virtualFileId == null) return null
+    val projectRoot = getBaseDirectory(projectId, virtualFileId)
+    val resource = if (resourceName.startsWith("file:/")) {
+      VfsUtil.findFileByIoFile(File(URL(resourceName).path), true)
+    } else {
+      projectRoot?.findFileByRelativePath(resourceName)
+    } ?: return null
+    return resource.rpcId()
+  }
+
+  companion object {
+    private val logger: Logger = Logger.getInstance(ProjectStructureRemoteApiImpl::class.java)
+  }
+}

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

@@ -398,6 +398,7 @@
     <browserPreviewExtensionProvider implementation="org.intellij.plugins.markdown.extensions.common.InlineStylesExtension$Provider"/>
 
     <browserPreviewExtensionProvider implementation="org.intellij.plugins.markdown.extensions.jcef.ProcessLinksExtension$Provider"/>
+    <browserPreviewExtensionProvider implementation="org.intellij.plugins.markdown.extensions.jcef.ProcessImagesExtension$Provider"/>
     <browserPreviewExtensionProvider implementation="org.intellij.plugins.markdown.extensions.jcef.commandRunner.CommandRunnerExtension$Provider"/>
 
     <fenceLanguageProvider id="DefaultMermaidCodeFenceLanguageProvider"

plugins/markdown/core/src/org/intellij/plugins/markdown/extensions/jcef/ProcessImagesExtension.kt

@@ -0,0 +1,56 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package org.intellij.plugins.markdown.extensions.jcef
+
+import com.intellij.ide.vfs.rpcId
+import com.intellij.ide.vfs.virtualFile
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.platform.project.projectId
+import kotlinx.coroutines.runBlocking
+import org.intellij.plugins.markdown.extensions.MarkdownBrowserPreviewExtension
+import org.intellij.plugins.markdown.service.ProjectStructureRemoteApi
+import org.intellij.plugins.markdown.ui.preview.MarkdownHtmlPanel
+import org.intellij.plugins.markdown.ui.preview.ResourceProvider
+
+internal class ProcessImagesExtension(
+  private val baseFile: VirtualFile?,
+  private val project: Project?
+): ResourceProvider, MarkdownBrowserPreviewExtension {
+  override val resourceProvider: ResourceProvider = this
+
+  override fun canProvide(resourceName: String): Boolean {
+    return hasImageExtension(resourceName)
+  }
+
+  override fun loadResource(resourceName: String): ResourceProvider.Resource? {
+    val baseFileId = baseFile?.rpcId()
+    val projectId = project?.projectId()
+    val resource = runBlocking {
+      ProjectStructureRemoteApi.getInstance().getFileByResourceName(resourceName, baseFileId, projectId)?.virtualFile()
+    } ?: return null
+    return ResourceProvider.loadExternalResource(resource)
+  }
+
+  override fun dispose() = Unit
+
+  companion object{
+    fun hasImageExtension(name: String): Boolean {
+      val lowerName = name.lowercase()
+      return lowerName.endsWith(".jpeg") ||
+             lowerName.endsWith(".jpg")  ||
+             lowerName.endsWith(".png")  ||
+             lowerName.endsWith(".gif")  ||
+             lowerName.endsWith(".bmp")  ||
+             lowerName.endsWith(".svg")  ||
+             lowerName.endsWith(".webp") ||
+             lowerName.endsWith(".tiff") ||
+             lowerName.endsWith(".tif")
+    }
+  }
+
+  class Provider: MarkdownBrowserPreviewExtension.Provider {
+    override fun createBrowserExtension(panel: MarkdownHtmlPanel): MarkdownBrowserPreviewExtension {
+      return ProcessImagesExtension(panel.virtualFile, panel.project)
+    }
+  }
+}

plugins/markdown/core/src/org/intellij/plugins/markdown/service/ProjectStructureRemoteApi.kt

@@ -0,0 +1,23 @@
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package org.intellij.plugins.markdown.service
+
+import com.intellij.ide.vfs.VirtualFileId
+import com.intellij.platform.project.ProjectId
+import com.intellij.platform.rpc.RemoteApiProviderService
+import fleet.rpc.RemoteApi
+import fleet.rpc.Rpc
+import fleet.rpc.remoteApiDescriptor
+import org.jetbrains.annotations.ApiStatus
+
+@ApiStatus.Internal
+@Rpc
+interface ProjectStructureRemoteApi : RemoteApi<Unit> {
+  suspend fun getFileByResourceName(resourceName: String, virtualFileId: VirtualFileId?, projectId: ProjectId?): VirtualFileId?
+
+  companion object {
+    @JvmStatic
+    suspend fun getInstance(): ProjectStructureRemoteApi {
+      return RemoteApiProviderService.resolve(remoteApiDescriptor<ProjectStructureRemoteApi>())
+    }
+  }
+}