From c91bda4acb074751e1a48c73e9b243313dc795c8 Mon Sep 17 00:00:00 2001
From: kasemir <ky9@ornl.gov>
Date: Tue, 21 May 2024 15:09:24 -0400
Subject: [PATCH] Text fields: Keep scroll position when vertically "middle"
 aligned

---
 .../widgets/TextEntryRepresentation.java       | 18 +++++++++++++++++-
 .../widgets/TextUpdateRepresentation.java      | 14 ++++++++++++--
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextEntryRepresentation.java b/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextEntryRepresentation.java
index 9829da1c64..c3f8934c3a 100644
--- a/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextEntryRepresentation.java
+++ b/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextEntryRepresentation.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2015-2018 Oak Ridge National Laboratory.
+ * Copyright (c) 2015-2024 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -20,6 +20,7 @@
 import org.csstudio.display.builder.model.WidgetPropertyListener;
 import org.csstudio.display.builder.model.persist.NamedWidgetColors;
 import org.csstudio.display.builder.model.persist.WidgetColorService;
+import org.csstudio.display.builder.model.properties.VerticalAlignment;
 import org.csstudio.display.builder.model.properties.WidgetColor;
 import org.csstudio.display.builder.model.widgets.PVWidget;
 import org.csstudio.display.builder.model.widgets.TextEntryWidget;
@@ -423,7 +424,22 @@ else if(jfx_node instanceof TextArea){
         if (! active)
         {
             if (dirty_content.checkAndClear())
+            {
+                // For middle-aligned multi-line text, keep the scroll position
+                TextArea area = null;
+                double pos = 0;
+                if (jfx_node instanceof TextArea  &&  
+                    model_widget.propVerticalAlignment().getValue() == VerticalAlignment.MIDDLE)
+                {
+                    area = (TextArea) jfx_node;
+                    pos = area.getScrollTop();
+                }
+
                 jfx_node.setText(value_text);
+
+                if (area != null)
+                    area.setScrollTop(pos);
+            }
         }
         // When not managed, trigger layout
         if (!jfx_node.isManaged())
diff --git a/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextUpdateRepresentation.java b/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextUpdateRepresentation.java
index b6b010e24c..4287458de9 100644
--- a/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextUpdateRepresentation.java
+++ b/app/display/representation-javafx/src/main/java/org/csstudio/display/builder/representation/javafx/widgets/TextUpdateRepresentation.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2015-2020 Oak Ridge National Laboratory.
+ * Copyright (c) 2015-2024 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -281,8 +281,18 @@ public void updateChanges()
             else
             {   // Implies 'interactive' mode
                 final TextArea area = (TextArea)jfx_node;
+
+                // Before updating the text, get scroll position just in case we need it later
+                final double top = area.getScrollTop();
+
                 area.setText(value_text);
-                if (model_widget.propVerticalAlignment().getValue() == VerticalAlignment.BOTTOM)
+
+                final VerticalAlignment alignment = model_widget.propVerticalAlignment().getValue();
+                if (alignment == VerticalAlignment.MIDDLE)
+                {   // In 'middle' alignment mode, keep the scroll position.
+                    area.setScrollTop(top);
+                }
+                else if (alignment == VerticalAlignment.BOTTOM)
                 {
                     // For bottom-aligned widget, scroll to bottom,
                     // but area.setScrollTop(Double.MAX_VALUE) has no effect.