From 590f5dfd9045922a414465e6f6d789c94809ae55 Mon Sep 17 00:00:00 2001
From: Yao Jingxi <23722032@bjtu.edu.cn>
Date: Sun, 15 Nov 2026 01:14:44 +0800
Subject: [PATCH] =?UTF-8?q?fix(ui):=20TextArea=20=E6=8E=A5=E6=94=B6?=
 =?UTF-8?q?=E6=BB=9A=E8=BD=AE=EF=BC=8C=E5=86=85=E5=AE=B9=E8=B6=85=E5=87=BA?=
 =?UTF-8?q?=E6=97=B6=E5=8F=AF=E6=BB=9A=E5=8A=A8?=
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多行输入框此前不处理滚轮，只能随光标滚动，超出高度的内容无法用鼠标浏览。
现在指针位于 TextArea 上时，滚轮先滚动它自己的行；已经到达所需方向的末端时，
事件交还给页面，与浏览器行为一致。

- components: TextareaLayout.Wheel 报告是否真的移动，超出判断只看上次绘制的文本区域。
- ui: Page.Wheel 在下拉框之后、其他滚动路由之前检查 TextArea。
- 测试：components.TestTextareaWheelScrollsUntilItsEnd 覆盖区域外、顶端、末端和正常滚动。

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
---
 components/textarea.go            | 20 ++++++++++++++
 components/textarea_wheel_test.go | 45 +++++++++++++++++++++++++++++++
 ui/page.go                        |  7 +++++
 3 files changed, 72 insertions(+)
 create mode 100644 components/textarea_wheel_test.go

diff --git a/components/textarea.go b/components/textarea.go
index b5363bf4..25f4704d 100644
--- a/components/textarea.go
+++ b/components/textarea.go
@@ -553,6 +553,26 @@ func (layout *TextareaLayout) ScrollBy(dy float32) {
 	layout.scroll = layout.clampScroll(layout.scroll + dy)
 }
 
+// Wheel scrolls the box by a wheel event over the text it last painted, as ScrollBy does, and
+// reports whether the box moved. A wheel the box cannot move with (it is at the end the wheel
+// points to, or it shows all its rows) reports false, so the page scrolls instead.
+func (layout *TextareaLayout) Wheel(event gfx.ScrollEvent) bool {
+	content := layout.content
+	if !layout.painted || event.X < content.X || event.X >= content.X+content.Width ||
+		event.Y < content.Y || event.Y >= content.Y+content.Height {
+		return false
+	}
+	dy := event.DeltaY
+	if !event.Precise && dy > 0 && dy < 24 {
+		dy = 24
+	} else if !event.Precise && dy < 0 && dy > -24 {
+		dy = -24
+	}
+	before := layout.scroll
+	layout.ScrollBy(dy)
+	return layout.scroll != before
+}
+
 // RowCount is how many rows text takes in a box of outer width width: one for
 // each line that fits and as many as a longer one wraps to, and an empty one
 // after a final newline. The rows it wraps are the ones the next paint at that
diff --git a/components/textarea_wheel_test.go b/components/textarea_wheel_test.go
new file mode 100644
index 00000000..c9c2657b
--- /dev/null
+++ b/components/textarea_wheel_test.go
@@ -0,0 +1,45 @@
+package components
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/vivaui/viva/gfx"
+)
+
+// A wheel over a TextareaLayout scrolls it while it can move in that direction, and reports
+// nothing once it is at the end, so the page can scroll instead.
+func TestTextareaWheelScrollsUntilItsEnd(t *testing.T) {
+	var lines []string
+	for index := range 40 {
+		lines = append(lines, "row "+string(rune('a'+index%26)))
+	}
+	text := strings.Join(lines, "\n")
+	box := newWrapBox(t, 100)
+	box.paint(TextareaSnapshot{Value: text, Caret: 0})
+	center := gfx.Point{X: box.layout.content.X + 4, Y: box.layout.content.Y + 4}
+
+	outside := gfx.ScrollEvent{X: box.layout.content.X - 10, Y: center.Y, DeltaY: 30}
+	if box.layout.Wheel(outside) {
+		t.Fatal("a wheel outside the text scrolled the box")
+	}
+	up := gfx.ScrollEvent{X: center.X, Y: center.Y, DeltaY: -30}
+	if box.layout.Wheel(up) {
+		t.Fatal("a wheel up at the top scrolled the box")
+	}
+
+	down := gfx.ScrollEvent{X: center.X, Y: center.Y, DeltaY: 30}
+	if !box.layout.Wheel(down) {
+		t.Fatal("a wheel down over the text did not scroll the box")
+	}
+	for range 200 {
+		box.paint(TextareaSnapshot{Value: text, Caret: 0})
+		if !box.layout.Wheel(down) {
+			break
+		}
+	}
+	box.paint(TextareaSnapshot{Value: text, Caret: 0})
+	if box.layout.Wheel(down) {
+		t.Fatal("a wheel down at the end of the text still scrolled the box")
+	}
+}
diff --git a/ui/page.go b/ui/page.go
index 87de1698..7a252fd4 100644
--- a/ui/page.go
+++ b/ui/page.go
@@ -1127,6 +1127,13 @@ func (p *Page) Wheel(event gfx.ScrollEvent) gfx.EventResult {
 			return state.Wheel(event)
 		}
 	}
+	// A TextArea under the pointer scrolls its own rows first; at its end the wheel goes on
+	// to the page, as in a browser.
+	for _, entry := range p.fields {
+		if entry.field.rows && entry.field.area != nil && entry.field.area.Wheel(event) {
+			return gfx.EventResult{Handled: true, Repaint: true}
+		}
+	}
 	if p.wheelRoute != nil {
 		if result, ok := p.wheelRoute(p, event); ok {
 			return result