OC-2581: Open .h and .m files side-by-side

platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/EditorWindow.java

@@ -24,6 +24,7 @@ import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.editor.ScrollType;
 import com.intellij.openapi.editor.ScrollingModel;
+import com.intellij.openapi.extensions.Extensions;
 import com.intellij.openapi.fileEditor.FileEditor;
 import com.intellij.openapi.fileEditor.FileEditorManagerListener;
 import com.intellij.openapi.fileEditor.TextEditor;
@@ -665,6 +666,18 @@ public class EditorWindow {
           */
           // open only selected file in the new splitter instead of opening all tabs
           final VirtualFile file = selectedEditor.getFile();
+
+          if (virtualFile == null) {
+            for (FileEditorAssociateFinder finder : Extensions.getExtensions(FileEditorAssociateFinder.EP_NAME)) {
+              VirtualFile associatedFile = finder.getAssociatedFileToOpen(fileEditorManager.getProject(), file);
+
+              if (associatedFile != null) {
+                virtualFile = associatedFile;
+                break;
+              }
+            }
+          }
+
           final VirtualFile nextFile = virtualFile == null ? file : virtualFile;
           final FileEditor[] editors = fileEditorManager.openFileImpl3(res, nextFile, false, null, true).first;
           syncCaretIfPossible(editors);

platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/FileEditorAssociateFinder.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2000-2012 JetBrains s.r.o.
+ *
+ * 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
+ *
+ * http://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.intellij.openapi.fileEditor.impl;
+
+import com.intellij.openapi.extensions.ExtensionPointName;
+import com.intellij.openapi.project.Project;
+import com.intellij.openapi.vfs.VirtualFile;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Created by IntelliJ IDEA.
+ * User: angus
+ * Date: 3/6/12
+ * Time: 1:37 PM
+ */
+public interface FileEditorAssociateFinder {
+  ExtensionPointName<FileEditorAssociateFinder> EP_NAME = ExtensionPointName.create("com.intellij.editorFileAssociateFinder");
+
+  @Nullable
+  VirtualFile getAssociatedFileToOpen(@NotNull Project project, @NotNull VirtualFile original);
+}

platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/FileEditorManagerImpl.java

@@ -122,6 +122,17 @@ public class FileEditorManagerImpl extends FileEditorManagerEx implements Projec
     myDockManager = dockManager;
     myListenerList =
       new MessageListenerList<FileEditorManagerListener>(myProject.getMessageBus(), FileEditorManagerListener.FILE_EDITOR_MANAGER);
+
+    if (Extensions.getExtensions(FileEditorAssociateFinder.EP_NAME).length > 0) {
+      myListenerList.add(new FileEditorManagerAdapter() {
+        @Override
+        public void selectionChanged(FileEditorManagerEvent event) {
+          EditorsSplitters splitters = getSplitters();
+          openAssociatedFile(event.getNewFile(), splitters.getCurrentWindow(), splitters);
+        }
+      });
+    }
+
     myQueue.setTrackUiActivity(true);
   }
 
@@ -597,12 +608,39 @@ public class FileEditorManagerImpl extends FileEditorManagerEx implements Projec
     else {
       wndToOpenIn = getSplitters().getCurrentWindow();
     }
+
+    EditorsSplitters splitters = getSplitters();
+
     if (wndToOpenIn == null) {
-      wndToOpenIn = getSplitters().getOrCreateCurrentWindow(file);
+      wndToOpenIn = splitters.getOrCreateCurrentWindow(file);
     }
+
+    openAssociatedFile(file, wndToOpenIn, splitters);
     return openFileImpl2(wndToOpenIn, file, focusEditor);
   }
 
+  private void openAssociatedFile(VirtualFile file, EditorWindow wndToOpenIn, EditorsSplitters splitters) {
+    EditorWindow[] windows = splitters.getWindows();
+
+    if (file != null && windows.length == 2) {
+      for (FileEditorAssociateFinder finder : Extensions.getExtensions(FileEditorAssociateFinder.EP_NAME)) {
+        VirtualFile associatedFile = finder.getAssociatedFileToOpen(myProject, file);
+
+        if (associatedFile != null) {
+          EditorWindow currentWindow = splitters.getCurrentWindow();
+          int idx = windows[0] == wndToOpenIn ? 1 : 0;
+          openFileImpl2(windows[idx], associatedFile, false);
+
+          if (currentWindow != null) {
+            splitters.setCurrentWindow(currentWindow, false);
+          }
+
+          break;
+        }
+      }
+    }
+  }
+
   @NotNull
   @Override
   public Pair<FileEditor[], FileEditorProvider[]> openFileWithProviders(@NotNull VirtualFile file,
@@ -1309,6 +1347,16 @@ public class FileEditorManagerImpl extends FileEditorManagerEx implements Projec
     final boolean filesEqual = oldData.first == null ? newData.first == null : oldData.first.equals(newData.first);
     final boolean editorsEqual = oldData.second == null ? newData.second == null : oldData.second.equals(newData.second);
     if (!filesEqual || !editorsEqual) {
+      if (oldData.first != null && newData.first != null) {
+        for (FileEditorAssociateFinder finder : Extensions.getExtensions(FileEditorAssociateFinder.EP_NAME)) {
+          VirtualFile associatedFile = finder.getAssociatedFileToOpen(myProject, oldData.first);
+
+          if (associatedFile == newData.first) {
+            return;
+          }
+        }
+      }
+
       final FileEditorManagerEvent event =
         new FileEditorManagerEvent(this, oldData.first, oldData.second, oldData.third, newData.first, newData.second, newData.third);
       final FileEditorManagerListener publisher = getProject().getMessageBus().syncPublisher(FileEditorManagerListener.FILE_EDITOR_MANAGER);

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

@@ -79,6 +79,7 @@
   <extensionPoint name="editorTabTitleProvider" interface="com.intellij.openapi.fileEditor.impl.EditorTabTitleProvider"/>
   <extensionPoint name="editorTabColorProvider" interface="com.intellij.openapi.fileEditor.impl.EditorTabColorProvider"/>
   <extensionPoint name="editorFileSwapper" interface="com.intellij.openapi.fileEditor.impl.EditorFileSwapper"/>
+  <extensionPoint name="editorFileAssociateFinder" interface="com.intellij.openapi.fileEditor.impl.FileEditorAssociateFinder"/>
 
   <extensionPoint name="http.localFileFinder" interface="com.intellij.openapi.fileEditor.impl.http.LocalFileFinder"/>
   <extensionPoint name="http.fileEditorActionProvider" interface="com.intellij.openapi.fileEditor.impl.http.RemoteFileEditorActionProvider"/>