From 88663742339816ec2e2d6d8d1a5d6e7254a18f2c Mon Sep 17 00:00:00 2001
From: Aleksey Pivovarov <AMPivovarov@gmail.com>
Date: Mon, 30 Nov 2015 12:22:27 +0300
Subject: [PATCH] diff: calculate diff synchronously in color settings

this should fix blinking DiffColorSettingsTest
---
 .../diff/tools/util/base/DiffViewerBase.java       | 14 +++++++++-----
 .../diff/impl/settings/DiffPreviewPanel.java       |  7 ++++++-
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/platform/diff-impl/src/com/intellij/diff/tools/util/base/DiffViewerBase.java b/platform/diff-impl/src/com/intellij/diff/tools/util/base/DiffViewerBase.java
index d1a6d97ec7a2..96929ad2e752 100644
--- a/platform/diff-impl/src/com/intellij/diff/tools/util/base/DiffViewerBase.java
+++ b/platform/diff-impl/src/com/intellij/diff/tools/util/base/DiffViewerBase.java
@@ -31,8 +31,8 @@ import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Disposer;
 import com.intellij.util.Alarm;
 import com.intellij.util.Function;
-import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.SmartList;
+import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.ui.UIUtil;
 import org.jetbrains.annotations.*;
 
@@ -141,10 +141,7 @@ public abstract class DiffViewerBase implements DiffViewer, DataProvider {
     fireEvent(EventType.BEFORE_REDIFF);
     onBeforeRediff();
 
-    // most of performRediff implementations take ReadLock inside. If EDT is holding write lock - this will never happen,
-    // and diff will not be calculated. This could happen for diff from FileDocumentManager.
-    boolean forceEDT = ApplicationManager.getApplication().isWriteAccessAllowed();
-
+    boolean forceEDT = forceRediffSynchronously();
     int waitMillis = trySync || tryRediffSynchronously() ? ProgressWindow.DEFAULT_PROGRESS_DIALOG_POSTPONE_TIME_MILLIS : 0;
 
     myTaskExecutor.executeAndTryWait(
@@ -204,6 +201,13 @@ public abstract class DiffViewerBase implements DiffViewer, DataProvider {
     return myContext.isWindowFocused();
   }
 
+  @CalledInAwt
+  protected boolean forceRediffSynchronously() {
+    // most of performRediff implementations take ReadLock inside. If EDT is holding write lock - this will never happen,
+    // and diff will not be calculated. This could happen for diff from FileDocumentManager.
+    return ApplicationManager.getApplication().isWriteAccessAllowed();
+  }
+
   protected List<AnAction> createToolbarActions() {
     List<AnAction> group = new ArrayList<AnAction>();
     ContainerUtil.addAll(group, ((ActionGroup)ActionManager.getInstance().getAction(IdeActions.DIFF_VIEWER_TOOLBAR)).getChildren(null));
diff --git a/platform/lang-impl/src/com/intellij/openapi/diff/impl/settings/DiffPreviewPanel.java b/platform/lang-impl/src/com/intellij/openapi/diff/impl/settings/DiffPreviewPanel.java
index e7ee5311220e..9827bbe738bb 100644
--- a/platform/lang-impl/src/com/intellij/openapi/diff/impl/settings/DiffPreviewPanel.java
+++ b/platform/lang-impl/src/com/intellij/openapi/diff/impl/settings/DiffPreviewPanel.java
@@ -59,7 +59,12 @@ public class DiffPreviewPanel implements PreviewPanel {
   private final EventDispatcher<ColorAndFontSettingsListener> myDispatcher = EventDispatcher.create(ColorAndFontSettingsListener.class);
 
   public DiffPreviewPanel(@NotNull Disposable parent) {
-    myViewer = new SimpleThreesideDiffViewer(new SampleContext(), new SampleRequest());
+    myViewer = new SimpleThreesideDiffViewer(new SampleContext(), new SampleRequest()) {
+      @Override
+      protected boolean forceRediffSynchronously() {
+        return true;
+      }
+    };
     myViewer.init();
     Disposer.register(parent, myViewer);