synchronous toolwindows initializing to prevent re-layout during startup:

return async api

platform/platform-impl/src/com/intellij/openapi/wm/impl/CommandProcessor.java

@@ -15,9 +15,13 @@
  */
 package com.intellij.openapi.wm.impl;
 
+import com.intellij.openapi.application.Application;
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.application.ModalityState;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.util.Condition;
 import com.intellij.openapi.util.Conditions;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.openapi.wm.impl.commands.FinalizableCommand;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -43,7 +47,7 @@ public final class CommandProcessor implements Runnable {
    * commands with BlockFocusEventsCmd - UnblockFocusEventsCmd. It's required to
    * prevent focus handling of events which is caused by the commands to be executed.
    */
-  public final void execute(@NotNull List<FinalizableCommand> commandList, @NotNull Condition expired) {
+  void execute(@NotNull List<FinalizableCommand> commandList, @NotNull Condition expired, boolean synchronously) {
     synchronized (myLock) {
       final boolean isBusy = myCommandCount > 0;
 
@@ -52,16 +56,44 @@ public final class CommandProcessor implements Runnable {
       myCommandCount += commandList.size();
 
       if (!isBusy) {
-        run();
+        if (synchronously) {
+          //noinspection StatementWithEmptyBody
+          while (runNext()) {
+          }
+        }
+        else {
+          run();
+        }
       }
     }
   }
 
   public final void run() {
     synchronized (myLock) {
-      //noinspection StatementWithEmptyBody
-      while (runNext()) {
+
+      final CommandGroup commandGroup = getNextCommandGroup();
+      if (commandGroup == null || commandGroup.isEmpty()) return;
+
+      final Condition conditionForGroup = commandGroup.getExpireCondition();
+
+      final FinalizableCommand command = commandGroup.takeNextCommand();
+      myCommandCount--;
+
+      final Condition expire = command.getExpireCondition() != null ? command.getExpireCondition() : conditionForGroup;
+
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("CommandProcessor.run " + command);
       }
+      // max. I'm not actually quite sure this should have NON_MODAL modality but it should
+      // definitely have some since runnables in command list may (and do) request some PSI activity
+      final boolean queueNext = myCommandCount > 0;
+      Application application = ApplicationManager.getApplication();
+      ModalityState modalityState = Registry.is("ide.perProjectModality") ? ModalityState.current() : ModalityState.NON_MODAL;
+      application.getInvokator().invokeLater(command, modalityState, expire == null ? application.getDisposed() : expire).doWhenDone(() -> {
+        if (queueNext) {
+          this.run();
+        }
+      });
     }
   }
 

platform/platform-impl/src/com/intellij/openapi/wm/impl/ToolWindowManagerImpl.java

@@ -522,7 +522,11 @@ public final class ToolWindowManagerImpl extends ToolWindowManagerEx implements
    * This is helper method. It delegated its functionality to the WindowManager.
    * Before delegating it fires state changed.
    */
-  public void execute(@NotNull List<FinalizableCommand> commandList) {
+  void execute(@NotNull List<FinalizableCommand> commandList) {
+    execute(commandList, false);
+  }
+
+  private void execute(@NotNull List<FinalizableCommand> commandList, boolean synchronously) {
     for (FinalizableCommand each : commandList) {
       if (each.willChangeState()) {
         fireStateChanged();
@@ -533,7 +537,7 @@ public final class ToolWindowManagerImpl extends ToolWindowManagerEx implements
     for (FinalizableCommand each : commandList) {
       each.beforeExecute(this);
     }
-    myWindowManager.getCommandProcessor().execute(commandList, myProject.getDisposed());
+    myWindowManager.getCommandProcessor().execute(commandList, myProject.getDisposed(), synchronously);
   }
 
   @Override
@@ -2442,7 +2446,7 @@ public final class ToolWindowManagerImpl extends ToolWindowManagerEx implements
         myManager.registerToolWindowsFromBeans(list);
         myManager.initAll(list);
         EdtInvocationManager.getInstance().invokeLater(() -> {
-          myManager.execute(list);
+          myManager.execute(list, true);
         });
       }
     }