Fix auto-scroll and selection during active output

Sources/SwiftTerm/Apple/AppleTerminalView.swift

@@ -1927,10 +1927,14 @@ extension TerminalView {
         let displayBuffer = terminal.displayBuffer
         if row != displayBuffer.yDisp {
             terminal.setViewYDisp (row)
-
+
+            // Track whether the user has scrolled away from the bottom so that
+            // incoming output does not yank the viewport back down.
+            terminal.userScrolling = displayBuffer.yDisp != displayBuffer.yBase
+
             // tell the terminal we want to refresh all the rows
             terminal.refresh (startRow: 0, endRow: terminal.rows)
-            
+
             // do the display update
             updateDisplay (notifyAccessibility: notifyAccessibility)
             //selectionView.notifyScrolled(source: terminal)
@@ -1978,8 +1982,10 @@ extension TerminalView {
     func feedPrepare()
     {
         search.invalidate()
-        // Preserve manual selection while output is streaming when mouse reporting is disabled.
-        if allowMouseReporting {
+        // Only clear selection when the hosted app has actually requested mouse
+        // reporting — otherwise the user should be able to select text while
+        // output is streaming.
+        if allowMouseReporting && terminal.mouseMode != .off {
             selection.active = false
         }
         startDisplayUpdates()

Sources/SwiftTerm/Mac/MacTerminalView.swift

@@ -762,8 +762,10 @@ open class TerminalView: NSView, NSTextInputClient, NSUserInterfaceValidations,
     }
 
     open func linefeed(source: Terminal) {
-        // Preserve manual selection while output is streaming when mouse reporting is disabled.
-        if allowMouseReporting {
+        // Only clear selection when the hosted app has actually requested mouse
+        // reporting — otherwise the user should be able to select text while
+        // output is streaming.
+        if allowMouseReporting && terminal.mouseMode != .off {
             selection.selectNone()
         }
     }

Sources/SwiftTerm/iOS/iOSTerminalView.swift

@@ -1418,8 +1418,10 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
     }
 
     open func linefeed(source: Terminal) {
-        // Preserve manual selection while output is streaming when mouse reporting is disabled.
-        if allowMouseReporting {
+        // Only clear selection when the hosted app has actually requested mouse
+        // reporting — otherwise the user should be able to select text while
+        // output is streaming.
+        if allowMouseReporting && terminal.mouseMode != .off {
             selection.selectNone()
             disableSelectionPanGesture()
         }
@@ -1430,10 +1432,10 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
         let displayBuffer = terminal.displayBuffer
         contentSize = CGSize (width: CGFloat (displayBuffer.cols) * cellDimension.width,
                               height: CGFloat (displayBuffer.lines.count) * cellDimension.height)
-        //contentOffset = CGPoint (x: 0, y: CGFloat (displayBuffer.lines.count-displayBuffer.rows)*cellDimension.height)
-        contentOffset = CGPoint (x: 0, y: CGFloat (displayBuffer.lines.count-displayBuffer.rows)*cellDimension.height)
-        //Xscroller.doubleValue = scrollPosition
-        //Xscroller.knobProportion = scrollThumbsize
+        // Only scroll to bottom if the user hasn't explicitly scrolled up
+        if !terminal.userScrolling {
+            contentOffset = CGPoint (x: 0, y: CGFloat (displayBuffer.lines.count-displayBuffer.rows)*cellDimension.height)
+        }
     }
 
 #if canImport(MetalKit)
@@ -1541,6 +1543,15 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
                 requestMetalDisplay()
             }
 #endif
+            // When the user is actively scrolling (dragging or decelerating),
+            // track whether they have scrolled away from the bottom so incoming
+            // output does not yank the viewport back down.
+            if isDragging || isDecelerating {
+                let displayBuffer = terminal.displayBuffer
+                let bottomOffset = CGFloat(displayBuffer.lines.count - displayBuffer.rows) * cellDimension.height
+                let atBottom = contentOffset.y >= bottomOffset - 1
+                terminal.userScrolling = !atBottom
+            }
         }
     }
 
@@ -2178,6 +2189,7 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
         guard !terminal.synchronizedOutputActive else { return }
         let displayBuffer = terminal.displayBuffer
         contentOffset = CGPoint (x: 0, y: CGFloat (displayBuffer.lines.count-displayBuffer.rows)*cellDimension.height)
+        terminal.userScrolling = false
     }
 
     public func deleteBackward() {