Stop a render restore saying whether it placed the view

Nothing has read that since the paint started settling the scroll position
before consulting the restore: what the answer was for was deciding whether
the reset the new content was owed still had to happen, and by then it has.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/gui/controllers/helpers/diff_line_restore.go

@@ -376,7 +376,7 @@ func (self *DiffLineHelper) installDiffLineRestore(
 			// revealed with it stranded at the bottom of a half-filled view.
 			return view.OffscreenLineCount() >= foundLine+viewHeight
 		},
-		Apply: func(swapIn func()) bool {
+		Apply: func(swapIn func()) {
 			bufferLine := foundLine
 			if bufferLine == -1 {
 				if line, ok := findComplete(view.OffscreenDiffLineContents()); ok {
@@ -387,14 +387,11 @@ func (self *DiffLineHelper) installDiffLineRestore(
 			swapIn()
 
 			if bufferLine == -1 {
-				return false
+				return
 			}
-			viewLine, ok := view.ViewLineForBufferLine(bufferLine)
-			if !ok {
-				return false
+			if viewLine, ok := view.ViewLineForBufferLine(bufferLine); ok {
+				place(viewLine)
 			}
-			place(viewLine)
-			return true
 		},
 	})
 }

pkg/gui/main_panels.go

@@ -231,10 +231,9 @@ func (gui *Gui) followFocusIntoShownPane(pair types.MainContextPair, panes types
 			// is decided from what is there, and a change line further down would
 			// otherwise be missed.
 			FirstPaintReady: func() bool { return false },
-			Apply: func(swapIn func()) bool {
+			Apply: func(swapIn func()) {
 				swapIn()
 				gui.helpers.DiffLine.EstablishSelection(target, -1)
-				return false
 			},
 		})
 	}

pkg/tasks/tasks.go

@@ -191,10 +191,10 @@ type RenderRestore struct {
 	// while the previous content is still displayed, and the new content is never
 	// drawn at the previous render's scroll position.
 	//
-	// It must call swapIn either way, and reports whether it placed the view: when
-	// it didn't, because what it was looking for is not in the new content, the
-	// task does what it would have done without a restore.
-	Apply func(swapIn func()) bool
+	// It must call swapIn even when it finds nothing to place the view on, in which
+	// case the view keeps the position the paint gave it: the offset it had, or the
+	// top for content the view hasn't seen.
+	Apply func(swapIn func())
 }
 
 // SetRestoreForNextTask arranges for the next command task to put the view back

pkg/tasks/tasks_test.go

@@ -419,14 +419,13 @@ func TestNewCmdTaskRestore(t *testing.T) {
 	manager.SetRestoreForNextTask(&RenderRestore{
 		// Ready once five lines have loaded — well before the view is filled (30).
 		FirstPaintReady: func() bool { return linesWritten() >= 5 },
-		Apply: func(swapIn func()) bool {
+		Apply: func(swapIn func()) {
 			applyCount++
 			applyAtLines = linesWritten()
 			swappedBeforeApply = swappedBeforeApply || swapped
 			resetsBeforeApply = getResetOriginCallCount()
 			swapIn()
 			swappedByApply = swapped
-			return true
 		},
 	})
 
@@ -477,10 +476,9 @@ func TestNewCmdTaskRestoreThatFindsNothing(t *testing.T) {
 
 	manager.SetRestoreForNextTask(&RenderRestore{
 		FirstPaintReady: func() bool { return false },
-		Apply: func(swapIn func()) bool {
+		Apply: func(swapIn func()) {
 			applyCount++
 			swapIn()
-			return false
 		},
 	})
 
@@ -520,10 +518,9 @@ func TestRestoreSurvivesTaskReplacement(t *testing.T) {
 
 	manager.SetRestoreForNextTask(&RenderRestore{
 		FirstPaintReady: func() bool { return false },
-		Apply: func(swapIn func()) bool {
+		Apply: func(swapIn func()) {
 			applyCount.Add(1)
 			swapIn()
-			return true
 		},
 	})