Add API to change the history size

Author: migueldeicaza

Sources/SwiftTerm/Buffer.swift

@@ -470,6 +470,32 @@ public final class Buffer {
         cols = newCols
     }
 
+    public func changeHistorySize (_ newScrollback: Int?)
+    {
+        self.scrollback = newScrollback
+        self.hasScrollback = newScrollback != nil
+        
+        let newMaxLength = getCorrectBufferLength(rows)
+        let oldMaxLength = lines.maxLength
+        
+        if newMaxLength != oldMaxLength {
+            if newMaxLength > oldMaxLength {
+                // Increase buffer size - just update maxLength
+                lines.maxLength = newMaxLength
+            } else {
+                // Decrease buffer size - need to trim and adjust
+                let amountToTrim = lines.count - newMaxLength
+                if amountToTrim > 0 {
+                    lines.trimStart(count: amountToTrim)
+                    yBase = max(yBase - amountToTrim, 0)
+                    yDisp = max(yDisp - amountToTrim, 0)
+                    savedY = max(savedY - amountToTrim, 0)
+                }
+                lines.maxLength = newMaxLength
+            }
+        }
+    }
+    
     func translateBufferLineToString (lineIndex: Int, trimRight: Bool, startCol: Int = 0, endCol: Int = -1) -> String
     {
         let line = _lines [lineIndex]

Sources/SwiftTerm/Terminal.swift

@@ -4902,6 +4902,24 @@ open class Terminal {
         refresh (startRow: 0, endRow: self.rows - 1)
     }
 
+    /**
+     * Changes the scrollback (history) size of the terminal after it has been instantiated.
+     * The new scrollback size only affects the normal buffer, not the alternate buffer.
+     *
+     * - Parameter newScrollback: The new scrollback size in lines. Pass `nil` to disable scrollback.
+     */
+    public func changeHistorySize (_ newScrollback: Int?)
+    {
+        // Only the normal buffer has scrollback, the alt buffer should never have scrollback
+        normalBuffer.changeHistorySize(newScrollback)
+        
+        // Update the options to reflect the new scrollback size
+        options.scrollback = newScrollback ?? 0
+        
+        // Refresh the display to ensure proper rendering after history size change
+        refresh (startRow: 0, endRow: self.rows - 1)
+    }
+    
     func syncScrollArea ()
     {
         // This should call the viewport sync-scroll-area