From 2d9bfb81dde9bc1d6a8123009702181e9e9906b9 Mon Sep 17 00:00:00 2001
From: Shai Almog <67850168+shai-almog@users.noreply.github.com>
Date: Tue, 9 Jun 2026 07:24:17 +0300
Subject: [PATCH] TextArea: grow by content reliably while editing (#4854)

A growByContent multi-line TextArea was clipping the previous row while
being edited: text would wrap onto a new visual line but the field would
not grow to follow it until focus moved away.

The during-editing grow gate (#4741) decided whether to revalidate using
estimateLineCount(), a character-column prediction (string length vs
getColumns()). The real renderer wraps using font metrics against
getWidth() - horizontalPadding, so with a proportional font text wraps a
row earlier than the character count predicts. The estimate undercounted,
revalidateLater() did not fire, and the field stayed one row short.
Leaving the field ran a normal layout that used the accurate getLines(),
which is why the size corrected itself.

Fix: drop the wrap prediction entirely. Any growth in text length can push
content onto an extra wrapped row, so textMightGrowByContent() now triggers
on a length increase (or an added hard newline) and lets the layout's
getLines() determine the actual size. revalidateLater() coalesces into a
single layout per paint, so erring toward an extra revalidate is cheap and,
crucially, never under-grows. The gate stays width- and EDT-independent and
does not call getLines() from inside setText(), avoiding any layout
re-entrancy. The bogus estimateLineCount() helper is removed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../src/com/codename1/ui/TextArea.java        | 40 ++++++-------------
 1 file changed, 12 insertions(+), 28 deletions(-)

diff --git a/CodenameOne/src/com/codename1/ui/TextArea.java b/CodenameOne/src/com/codename1/ui/TextArea.java
index 6ff51b351c..b1e3695e99 100644
--- a/CodenameOne/src/com/codename1/ui/TextArea.java
+++ b/CodenameOne/src/com/codename1/ui/TextArea.java
@@ -618,19 +618,21 @@ && textMightGrowByContent(old, text)) {
     }
 
     private boolean textMightGrowByContent(String oldText, String newText) {
-        int oldNewLines = countNewLines(oldText);
-        int newNewLines = countNewLines(newText);
-        if (newNewLines > oldNewLines) {
+        if (newText == null || oldText == null) {
             return true;
         }
-        if (newText == null || oldText == null || newText.length() <= oldText.length()) {
-            return false;
-        }
-        int cols = getColumns();
-        if (cols > 1) {
-            return estimateLineCount(newText, cols) > estimateLineCount(oldText, cols);
+        // An added hard newline always adds a row.
+        if (countNewLines(newText) > countNewLines(oldText)) {
+            return true;
         }
-        return false;
+        // Any growth in length can push the content onto an extra wrapped row.
+        // We deliberately do NOT try to predict the wrap point here: the previous
+        // character-column estimate ignored the font and padding, so proportional
+        // text wrapped a row earlier than predicted and the field clipped the prior
+        // line while editing (#4854). revalidateLater() coalesces and the layout's
+        // getLines() (real font metrics, real width) determines the actual size, so
+        // erring toward an extra revalidate is cheap and never under-grows.
+        return newText.length() > oldText.length();
     }
 
     private int countNewLines(String value) {
@@ -646,24 +648,6 @@ private int countNewLines(String value) {
         return count;
     }
 
-    private int estimateLineCount(String value, int cols) {
-        if (value == null || value.length() == 0) {
-            return 1;
-        }
-        int lines = 0;
-        int segmentLength = 0;
-        for (int i = 0; i < value.length(); i++) {
-            if (value.charAt(i) == '\n') {
-                lines += Math.max(1, (segmentLength + cols - 1) / cols);
-                segmentLength = 0;
-            } else {
-                segmentLength++;
-            }
-        }
-        lines += Math.max(1, (segmentLength + cols - 1) / cols);
-        return lines;
-    }
-
     /// Convenience method for numeric text fields, returns the value as a number or invalid if the value in the
     /// text field isn't a number
     ///