Fix input field horizontal scroll offset not clamping after text deletion

When text in an input field overflows the visible width, the viewport
scrolls right to follow the cursor. After deleting characters with
backspace, the scroll origin was not clamped back, leaving empty space
on the right while earlier text remained hidden.

Add GetContentWidth() to TextArea and clamp the horizontal scroll
origin in RenderTextArea and the view resize path so the viewport
never scrolls past the actual content width.

Fixes #5633

Signed-off-by: Gautam Kumar <gautamkumarofficial@users.noreply.github.com>

pkg/gocui/gui.go

@@ -327,6 +327,17 @@ func (g *Gui) SetView(name string, x0, y0, x1, y1 int, overlaps byte) (*View, er
 				newViewCursorX, newOriginX := updatedCursorAndOrigin(0, v.InnerWidth(), cursorX)
 				newViewCursorY, newOriginY := updatedCursorAndOrigin(0, v.InnerHeight(), cursorY)
 
+				contentWidth := v.TextArea.GetContentWidth()
+				usableWidth := v.InnerWidth() - 1
+				maxOriginX := contentWidth - usableWidth
+				if maxOriginX < 0 {
+					maxOriginX = 0
+				}
+				if newOriginX > maxOriginX {
+					newOriginX = maxOriginX
+					newViewCursorX = cursorX - newOriginX
+				}
+
 				v.SetCursor(newViewCursorX, newViewCursorY)
 				v.SetOrigin(newOriginX, newOriginY)
 			}

pkg/gocui/text_area.go

@@ -392,6 +392,14 @@ func (self *TextArea) GetUnwrappedContent() string {
 	return self.content
 }
 
+func (self *TextArea) GetContentWidth() int {
+	if len(self.cells) == 0 {
+		return 0
+	}
+	last := self.cells[len(self.cells)-1]
+	return last.x + last.width
+}
+
 func (self *TextArea) ToggleOverwrite() {
 	self.overwrite = !self.overwrite
 }

pkg/gocui/view.go

@@ -1722,6 +1722,17 @@ func (v *View) RenderTextArea() {
 	newViewCursorX, newOriginX := updatedCursorAndOrigin(prevOriginX, width, cursorX)
 	newViewCursorY, newOriginY := updatedCursorAndOrigin(prevOriginY, height, cursorY)
 
+	contentWidth := v.TextArea.GetContentWidth()
+	usableWidth := width - 1
+	maxOriginX := contentWidth - usableWidth
+	if maxOriginX < 0 {
+		maxOriginX = 0
+	}
+	if newOriginX > maxOriginX {
+		newOriginX = maxOriginX
+		newViewCursorX = cursorX - newOriginX
+	}
+
 	v.SetCursor(newViewCursorX, newViewCursorY)
 	v.SetOrigin(newOriginX, newOriginY)
 }

pkg/gocui/view_test.go

@@ -120,6 +120,40 @@ func TestUpdatedCursorAndOrigin(t *testing.T) {
 	}
 }
 
+func TestRenderTextAreaClampsScrollOffset(t *testing.T) {
+	// View with inner width 10: x0=0, x1=11 → Width=12, InnerWidth=10
+	v := NewView("name", 0, 0, 11, 0, OutputNormal)
+	v.Editable = true
+
+	// Type 15 characters to overflow the viewport
+	for i := 0; i < 15; i++ {
+		v.TextArea.TypeCharacter("a")
+	}
+	// Cursor is at position 15, content width is 15
+	cursorX, _ := v.TextArea.GetCursorXY()
+	assert.Equal(t, 15, cursorX)
+
+	// Simulate scrolling: set origin so viewport shows positions 6-15
+	v.SetOrigin(6, 0)
+	v.RenderTextArea()
+	originX, _ := v.Origin()
+	assert.Equal(t, 6, originX)
+
+	// Now delete 11 characters so content is only 4 chars wide
+	for i := 0; i < 11; i++ {
+		v.TextArea.BackSpaceChar()
+	}
+	// Cursor is at position 4, content width is 4
+	cursorX, _ = v.TextArea.GetCursorXY()
+	assert.Equal(t, 4, cursorX)
+	assert.Equal(t, 4, v.TextArea.GetContentWidth())
+
+	// After rendering, origin should be clamped to 0 since content (4) < viewport (10)
+	v.RenderTextArea()
+	originX, _ = v.Origin()
+	assert.Equal(t, 0, originX, "origin should be clamped to 0 when content is narrower than viewport")
+}
+
 func TestAutoRenderingHyperlinks(t *testing.T) {
 	v := NewView("name", 0, 0, 10, 10, OutputNormal)
 	v.AutoRenderHyperLinks = true