Markdown Rendering in the What's New Panel (#432)

This is a PR for markdown file (.md) rendering and formatting for the
"What's New at Slack!" side panel in the Skate plugin. This change went
through a few iterations because I was having trouble using intelliJ's
markdown plugin in Skate, so I had done custom CSS formatting before.
However, now I was able to use MarkdownJCEFHtmlPanel to properly format
the md files. Here is what it looks like as it depends on the formatting
for the markdown plugin with intelliJ:

<img width="665" alt="Screenshot 2023-07-06 at 5 31 07 PM"
src="https://github.com/slackhq/slack-gradle-plugin/assets/67719108/d8198ce1-224d-4e31-8f47-f6c4df60776d">


<img width="466" alt="Screenshot 2023-07-06 at 6 02 59 PM"
src="https://github.com/slackhq/slack-gradle-plugin/assets/67719108/1d74e9dc-0985-4277-ac34-e158353abb4c">

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---------

Co-authored-by: Zac Sweers <[email protected]>

skate-plugin/build.gradle.kts

@@ -16,7 +16,7 @@ intellij {
   version.set("2022.2.5")
   type.set("IC") // Target IDE Platform
 
-  plugins.set(listOf(/* Plugin Dependencies */ ))
+  plugins.add("org.intellij.plugins.markdown")
 }
 
 tasks {

skate-plugin/src/main/kotlin/com/slack/sgp/intellij/ChangelogParser.kt

@@ -101,7 +101,6 @@ object ChangelogParser {
           }
         }
         .trimEnd()
-
     // If the changelog substring is blank, set it as null
     // If the previous entry equals to the latest entry, or if no date is found,
     // use the previous entry date as the latest date instead of the current date.

skate-plugin/src/main/kotlin/com/slack/sgp/intellij/SkateService.kt

@@ -18,20 +18,25 @@ package com.slack.sgp.intellij
 import com.intellij.openapi.components.service
 import com.intellij.openapi.project.Project
 import com.intellij.openapi.project.guessProjectDir
+import com.intellij.openapi.util.Disposer
 import com.intellij.openapi.vfs.VfsUtil
 import com.intellij.openapi.wm.ToolWindowAnchor
 import com.intellij.openapi.wm.ToolWindowManager
+import com.slack.sgp.intellij.ui.WhatsNewPanelFactory
 import java.util.function.Supplier
 
 interface SkateProjectService {
   fun showWhatsNewWindow()
 }
 
+/**
+ * This file's intended purpose is to pass in the changelog file from the file path into the What's
+ * New UI of the Skate Plugin
+ */
 class SkateProjectServiceImpl(private val project: Project) : SkateProjectService {
 
   override fun showWhatsNewWindow() {
     // TODO
-    //  Make the file configurable?
     //  Only show when changed
     //  Only show latest changes
     val settings = project.service<SkatePluginSettings>()
@@ -40,13 +45,21 @@ class SkateProjectServiceImpl(private val project: Project) : SkateProjectServic
     val changeLogFile = VfsUtil.findRelativeFile(projectDir, settings.whatsNewFilePath) ?: return
     val changeLogString = VfsUtil.loadText(changeLogFile)
     val toolWindowManager = ToolWindowManager.getInstance(project)
+
     toolWindowManager.invokeLater {
       val toolWindow =
         toolWindowManager.registerToolWindow("skate-whats-new") {
           stripeTitle = Supplier { "What's New in Slack!" }
           anchor = ToolWindowAnchor.RIGHT
         }
-      WhatsNewPanelFactory().createToolWindowContent(toolWindow, changeLogString)
+
+      // The Disposable is necessary to prevent a substantial memory leak while working with
+      // MarkdownJCEFHtmlPanel
+      val parentDisposable = Disposer.newDisposable()
+
+      WhatsNewPanelFactory()
+        .createToolWindowContent(toolWindow, project, changeLogString, parentDisposable)
+
       toolWindow.show()
     }
   }

skate-plugin/src/main/kotlin/com/slack/sgp/intellij/ui/WhatsNewPanelFactory.kt

@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2023 Slack Technologies, LLC
+ *
+ * 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.
+ */
+package com.slack.sgp.intellij.ui
+
+import com.intellij.openapi.Disposable
+import com.intellij.openapi.application.runReadAction
+import com.intellij.openapi.project.DumbAware
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.util.Disposer
+import com.intellij.openapi.wm.ToolWindow
+import com.intellij.testFramework.LightVirtualFile
+import com.intellij.ui.content.ContentFactory
+import com.intellij.ui.content.ContentManagerEvent
+import com.intellij.ui.content.ContentManagerListener
+import java.awt.BorderLayout
+import javax.swing.JComponent
+import javax.swing.JPanel
+import org.intellij.lang.annotations.Language
+import org.intellij.plugins.markdown.ui.preview.html.MarkdownUtil
+import org.intellij.plugins.markdown.ui.preview.jcef.MarkdownJCEFHtmlPanel
+
+/**
+ * The WhatsNewPanelFactory class takes the markdown file string from SkateService and displays it
+ * in a tool window. It uses MarkdownJCEFHtmlPanel and has dependency on intellij markdown plugin to
+ * properly format the markdown file and its contents
+ */
+class WhatsNewPanelFactory : DumbAware {
+
+  // Function that creates the tool window
+  fun createToolWindowContent(
+    toolWindow: ToolWindow,
+    project: Project,
+    markdownFileString: String,
+    parentDisposable: Disposable
+  ) {
+
+    val toolWindowContent = WhatsNewPanelContent(project, markdownFileString, parentDisposable)
+    val content =
+      ContentFactory.getInstance().createContent(toolWindowContent.contentPanel, "", false)
+    toolWindow.contentManager.addContent(content)
+    toolWindow.contentManager.addContentManagerListener(
+      object : ContentManagerListener {
+        override fun contentRemoved(event: ContentManagerEvent) {
+          if (event.content.component == toolWindowContent.contentPanel) {
+            Disposer.dispose(parentDisposable)
+            toolWindow.contentManager.removeContentManagerListener(this)
+          }
+        }
+      }
+    )
+  }
+
+  private class WhatsNewPanelContent(
+    project: Project,
+    @Language("Markdown") markdownFileString: String,
+    parentDisposable: Disposable
+  ) {
+
+    // Actual panel box for What's New at Slack
+    val contentPanel: JPanel =
+      JPanel().apply {
+        layout = BorderLayout(0, 20)
+        add(createWhatsNewPanel(project, markdownFileString, parentDisposable), BorderLayout.CENTER)
+      }
+
+    // Control Panel that takes in the current project, markdown string, and a Disposable.
+    private fun createWhatsNewPanel(
+      project: Project,
+      @Language("Markdown") markdownFileString: String,
+      parentDisposable: Disposable
+    ): JComponent {
+      // to take in the parsed Changelog:
+      // val parsedChangelog = ChangelogParser.readFile(markdownFileString)
+      // then, pass in parsedChangelog instead of markdownFileString
+
+      val file = LightVirtualFile("changelog.md", markdownFileString)
+
+      val panel = MarkdownJCEFHtmlPanel(project, file)
+      Disposer.register(parentDisposable, panel)
+      val html = runReadAction {
+        MarkdownUtil.generateMarkdownHtml(file, markdownFileString, project)
+      }
+
+      panel.setHtml(html, 0)
+      return panel.component
+    }
+  }
+}

skate-plugin/src/main/resources/META-INF/plugin.xml

@@ -20,6 +20,7 @@
     <!-- Product and plugin compatibility requirements.
          Read more: https://plugins.jetbrains.com/docs/intellij/plugin-compatibility.html -->
     <depends>com.intellij.modules.platform</depends>
+    <depends>org.intellij.plugins.markdown</depends>
 
     <!-- Extension points defined by the plugin.
          Read more: https://plugins.jetbrains.com/docs/intellij/plugin-extension-points.html -->