Merge pull request #622 from OwnDing/fix-reset-scroll-area

Notify the view when a full reset replaces the buffer (blank terminal after RIS)

Author: migueldeicaza

Sources/SwiftTerm/Terminal.swift

@@ -5578,6 +5578,14 @@ open class Terminal {
         cursorHidden = savedCursorHidden
         refresh (startRow: 0, endRow: rows-1)
         syncScrollArea ()
+        // A full reset replaces the buffer, so the view's scroll geometry — which
+        // is derived from `lines.count` and `yDisp` — is stale. `syncScrollArea()`
+        // is a no-op stub, and none of the other paths that recompute it fire
+        // here (no buffer switch, no scrolled line, no keystroke, no resize), so
+        // notify explicitly. Without this the view keeps the contentSize and
+        // contentOffset of a buffer that no longer exists and renders blank until
+        // some unrelated layout pass happens to correct it.
+        tdel?.bufferActivated (source: self)
     }
 
     // Support for:

Tests/SwiftTermTests/ResetScrollAreaTests.swift

@@ -0,0 +1,48 @@
+import Testing
+@testable import SwiftTerm
+
+/// A full reset (RIS, `ESC c`) replaces the buffer, so any view that derives its
+/// scroll geometry from `lines.count` / `yDisp` has to be told about it.
+/// `syncScrollArea()` is a no-op stub, and none of the other paths that make a
+/// view recompute that geometry run here — there is no buffer switch, no scrolled
+/// line, no keystroke and no resize — so `resetToInitialState()` notifies
+/// explicitly. Without that, a view keeps the contentSize/contentOffset of the
+/// buffer that was just discarded and renders blank.
+@Suite("Full reset scroll area")
+struct ResetScrollAreaTests {
+    @Test("RIS notifies the delegate that the buffer changed")
+    func fullResetNotifiesDelegate() {
+        let (terminal, delegate) = TerminalTestHarness.makeTerminal(cols: 80, rows: 24, scrollback: 500)
+
+        // Build up scrollback so the reset is a real change in buffer size.
+        for i in 0..<200 {
+            terminal.feed(text: "line \(i)\r\n")
+        }
+        #expect(terminal.buffer.lines.count > terminal.rows)
+
+        let before = delegate.bufferActivatedCount
+        terminal.feed(text: "\u{1b}c")
+
+        // The buffer really did shrink back to a single screen...
+        #expect(terminal.buffer.lines.count == terminal.rows)
+        #expect(terminal.buffer.yBase == 0)
+        #expect(terminal.buffer.yDisp == 0)
+        // ...and the delegate heard about it exactly once.
+        #expect(delegate.bufferActivatedCount == before + 1)
+    }
+
+    @Test("Keypad mode changes do not claim the buffer changed")
+    func keypadModeDoesNotNotify() {
+        let (terminal, delegate) = TerminalTestHarness.makeTerminal(cols: 80, rows: 24, scrollback: 500)
+
+        let before = delegate.bufferActivatedCount
+        terminal.feed(text: "\u{1b}=")   // application keypad
+        terminal.feed(text: "\u{1b}>")   // numeric keypad
+
+        // These also call syncScrollArea(), but they do not touch the buffer, so
+        // they must not be reported as a buffer activation: on iOS that resets
+        // the scroll-follow state and would yank a user who has scrolled back
+        // down to the bottom.
+        #expect(delegate.bufferActivatedCount == before)
+    }
+}

Tests/SwiftTermTests/TerminalTestHarness.swift

@@ -3,6 +3,7 @@ import Testing
 
 final class TerminalTestDelegate: TerminalDelegate {
     private(set) var sentData: [[UInt8]] = []
+    private(set) var bufferActivatedCount = 0
     var cellSizeInPixelsValue: (width: Int, height: Int)? = nil
 
     func showCursor(source: Terminal) {}
@@ -13,7 +14,7 @@ final class TerminalTestDelegate: TerminalDelegate {
     func sizeChanged(source: Terminal) {}
     func scrolled(source: Terminal, yDisp: Int) {}
     func linefeed(source: Terminal) {}
-    func bufferActivated(source: Terminal) {}
+    func bufferActivated(source: Terminal) { bufferActivatedCount += 1 }
     func bell(source: Terminal) {}
 
     func send(source: Terminal, data: ArraySlice<UInt8>) {