[diff] Enable history navigation through diffs

Currently limited only to those history points that are generated
by the text editors present in (some) diff viewers.

Also limited in the sense that diff previews do not change upon navigation.

GitOrigin-RevId: fffb97e2c12131c686f119af5eb1407956a282ee

platform/diff-impl/resources/META-INF/diff-impl.xml

@@ -0,0 +1,7 @@
+<idea-plugin>
+  <extensions defaultExtensionNs="com.intellij">
+    <registryKey defaultValue="false"
+                 description="Try to include navigation within a diff in the editor's navigation history."
+                 key="include.diffs.in.navigation.history"/>
+  </extensions>
+</idea-plugin>

platform/diff-impl/src/com/intellij/diff/editor/DiffEditorBase.kt

@@ -25,6 +25,7 @@ abstract class DiffEditorBase(
 ) : FileEditorBase() {
   companion object {
     private val LOG = logger<DiffEditorBase>()
+    const val DIFF_IN_NAVIGATION_HISTORY_KEY = "include.diffs.in.navigation.history"
   }
 
   private val panel = MyPanel(component)

platform/diff-impl/src/com/intellij/diff/editor/DiffRequestProcessorEditor.kt

@@ -6,9 +6,13 @@ import com.intellij.diff.impl.DiffRequestProcessorListener
 import com.intellij.diff.tools.combined.editors
 import com.intellij.diff.util.DiffUserDataKeysEx
 import com.intellij.openapi.editor.Editor
+import com.intellij.openapi.fileEditor.FileEditorState
+import com.intellij.openapi.fileEditor.FileEditorStateLevel
 import com.intellij.openapi.fileEditor.FileEditorWithTextEditors
 import com.intellij.openapi.fileEditor.ex.FileEditorManagerEx
+import com.intellij.openapi.fileEditor.impl.text.TextEditorState
 import com.intellij.openapi.util.Disposer
+import com.intellij.openapi.util.registry.Registry
 import com.intellij.openapi.vfs.VirtualFile
 import javax.swing.JComponent
 
@@ -36,6 +40,20 @@ open class DiffRequestProcessorEditor(
     super.dispose()
   }
 
+  override fun getState(level: FileEditorStateLevel): FileEditorState {
+    if (!Registry.`is`(DIFF_IN_NAVIGATION_HISTORY_KEY)) {
+      return FileEditorState.INSTANCE
+    }
+
+    return processor.getState(level)
+  }
+
+  override fun setState(state: FileEditorState) {
+    if (!Registry.`is`(DIFF_IN_NAVIGATION_HISTORY_KEY) || state !is DiffRequestProcessorEditorState) return
+
+    processor.setState(state)
+  }
+
   override fun getPreferredFocusedComponent(): JComponent? = processor.preferredFocusedComponent
 
   override fun selectNotify() {
@@ -55,3 +73,13 @@ open class DiffRequestProcessorEditor(
     return processor.activeViewer?.editors.orEmpty()
   }
 }
+
+data class DiffRequestProcessorEditorState(
+  val embeddedEditorStates: List<TextEditorState>
+) : FileEditorState {
+  override fun canBeMergedWith(otherState: FileEditorState, level: FileEditorStateLevel): Boolean =
+    otherState is DiffRequestProcessorEditorState &&
+    embeddedEditorStates.zip(otherState.embeddedEditorStates).all { (l, r) -> l.canBeMergedWith(r, level) }
+
+  override fun toString(): String = embeddedEditorStates.joinToString()
+}

platform/diff-impl/src/com/intellij/diff/impl/DiffRequestProcessor.java

@@ -7,6 +7,8 @@ import com.intellij.codeInsight.hint.HintUtil;
 import com.intellij.diff.*;
 import com.intellij.diff.FrameDiffTool.DiffViewer;
 import com.intellij.diff.actions.impl.*;
+import com.intellij.diff.editor.DiffRequestProcessorEditor;
+import com.intellij.diff.editor.DiffRequestProcessorEditorState;
 import com.intellij.diff.impl.DiffSettingsHolder.DiffSettings;
 import com.intellij.diff.impl.ui.DiffToolChooser;
 import com.intellij.diff.lang.DiffIgnoredRangeProvider;
@@ -38,6 +40,9 @@ import com.intellij.openapi.diff.DiffBundle;
 import com.intellij.openapi.diff.impl.DiffUsageTriggerCollector;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.editor.LogicalPosition;
+import com.intellij.openapi.fileEditor.FileEditorState;
+import com.intellij.openapi.fileEditor.FileEditorStateLevel;
+import com.intellij.openapi.fileEditor.impl.text.TextEditorProvider;
 import com.intellij.openapi.progress.ProcessCanceledException;
 import com.intellij.openapi.progress.ProgressManager;
 import com.intellij.openapi.project.DumbAware;
@@ -678,6 +683,30 @@ public abstract class DiffRequestProcessor implements CheckedDisposable {
     return myContext;
   }
 
+  public void setState(@NotNull DiffRequestProcessorEditorState state) {
+    DiffViewer viewer = getActiveViewer();
+    if (!(viewer instanceof EditorDiffViewer)) return;
+
+    var editors = ((EditorDiffViewer)viewer).getEditors();
+    var editorStates = state.getEmbeddedEditorStates();
+
+    TextEditorProvider textEditorProvider = TextEditorProvider.getInstance();
+    for (int i = 0; i < Math.min(editorStates.size(), editors.size()); i++) {
+      textEditorProvider.setStateImpl(myProject, editors.get(i), editorStates.get(i), true);
+    }
+  }
+
+  public @NotNull FileEditorState getState(@NotNull FileEditorStateLevel level) {
+    DiffViewer viewer = getActiveViewer();
+    if (!(viewer instanceof EditorDiffViewer)) return FileEditorState.INSTANCE;
+
+    List<? extends Editor> editors = ((EditorDiffViewer)viewer).getEditors();
+
+    TextEditorProvider textEditorProvider = TextEditorProvider.getInstance();
+    return new DiffRequestProcessorEditorState(ContainerUtil.map(editors, (editor) ->
+      textEditorProvider.getStateImpl(null, editor, level)));
+  }
+
   public @Nullable DiffViewer getActiveViewer() {
     if (myState instanceof DefaultState) {
       return ((DefaultState)myState).myViewer;

platform/diff-impl/src/com/intellij/diff/tools/combined/CombinedDiffComponentFactory.kt

@@ -11,6 +11,9 @@ import com.intellij.diff.util.DiffUserDataKeysEx
 import com.intellij.diff.util.DiffUtil
 import com.intellij.openapi.actionSystem.AnAction
 import com.intellij.openapi.diagnostic.logger
+import com.intellij.openapi.fileEditor.FileEditorState
+import com.intellij.openapi.fileEditor.FileEditorStateLevel
+import com.intellij.openapi.fileEditor.impl.text.TextEditorProvider
 import com.intellij.openapi.util.Disposer
 import com.intellij.util.concurrency.annotations.RequiresEdt
 import java.awt.Dimension
@@ -48,6 +51,31 @@ open class CombinedDiffComponentFactory(val model: CombinedDiffModel) {
 
   internal fun getMainComponent() = mainUi.getComponent()
 
+  internal fun getState(level: FileEditorStateLevel): FileEditorState {
+    val viewer = combinedViewer
+    if (viewer == null) return FileEditorState.INSTANCE
+
+    val textEditorProvider = TextEditorProvider.getInstance()
+    return CombinedDiffEditorState(
+      model.requests.map { it.id }.toSet(),
+      viewer.getCurrentBlockId(),
+      viewer.getCurrentDiffViewer()?.editors?.map { textEditorProvider.getStateImpl(null, it, level) } ?: listOf()
+    )
+  }
+
+  internal fun setState(state: CombinedDiffEditorState) {
+    val viewer = combinedViewer ?: return
+    if (model.requests.map { it.id }.toSet() != state.currentBlockIds) return
+
+    val textEditorProvider = TextEditorProvider.getInstance()
+    state.activeEditorStates.zip(viewer.getDiffViewerForId(state.activeBlockId)?.editors ?: listOf()) { st, editor ->
+      textEditorProvider.setStateImpl(null, editor, st, true)
+    }
+
+    viewer.selectDiffBlock(state.activeBlockId, true)
+    viewer.scrollToCaret()
+  }
+
   private fun createMainUI(): CombinedDiffMainUI {
     return CombinedDiffMainUI(model, createGoToChangeAction()).also { ui ->
       Disposer.register(ourDisposable, ui)

platform/diff-impl/src/com/intellij/diff/tools/combined/CombinedDiffEditor.kt

@@ -3,8 +3,12 @@ package com.intellij.diff.tools.combined
 
 import com.intellij.diff.editor.DiffEditorBase
 import com.intellij.openapi.editor.Editor
+import com.intellij.openapi.fileEditor.FileEditorState
+import com.intellij.openapi.fileEditor.FileEditorStateLevel
 import com.intellij.openapi.fileEditor.FileEditorWithTextEditors
+import com.intellij.openapi.fileEditor.impl.text.TextEditorState
 import com.intellij.openapi.util.Disposer
+import com.intellij.openapi.util.registry.Registry
 import javax.swing.JComponent
 
 class CombinedDiffEditor(file: CombinedDiffVirtualFile, val factory: CombinedDiffComponentFactory) :
@@ -15,9 +19,34 @@ class CombinedDiffEditor(file: CombinedDiffVirtualFile, val factory: CombinedDif
     super.dispose()
   }
 
+  override fun getState(level: FileEditorStateLevel): FileEditorState {
+    if (!Registry.`is`(DIFF_IN_NAVIGATION_HISTORY_KEY)) return FileEditorState.INSTANCE
+
+    return factory.getState(level)
+  }
+
+  override fun setState(state: FileEditorState) {
+    if (state !is CombinedDiffEditorState) return
+
+    factory.setState(state)
+  }
+
   override fun getPreferredFocusedComponent(): JComponent? = factory.getPreferredFocusedComponent()
 
   override fun getEmbeddedEditors(): List<Editor> {
     return factory.model.context.getUserData(COMBINED_DIFF_VIEWER_KEY)?.editors.orEmpty()
   }
 }
+
+data class CombinedDiffEditorState(
+  val currentBlockIds: Set<CombinedBlockId>,
+  val activeBlockId: CombinedBlockId,
+  val activeEditorStates: List<TextEditorState>
+) : FileEditorState {
+  override fun canBeMergedWith(otherState: FileEditorState, level: FileEditorStateLevel): Boolean {
+    return otherState is CombinedDiffEditorState &&
+           (currentBlockIds != otherState.currentBlockIds ||
+            (activeBlockId == otherState.activeBlockId &&
+             activeEditorStates.zip(otherState.activeEditorStates).all { (l, r) -> l.canBeMergedWith(r, level) } ))
+  }
+}

platform/platform-resources/src/META-INF/PlatformLangPlugin.xml

@@ -148,6 +148,9 @@
     <applicationInitializedListener implementation="com.intellij.openapi.fileTypes.impl.associate.OSFileAssociationStartupConfigurator"/>
   </extensions>
 
+  <xi:include href="/META-INF/diff-impl.xml">
+    <xi:fallback/>
+  </xi:include>
   <xi:include href="/META-INF/VCS.xml">
     <xi:fallback/>
   </xi:include>