Control restoring vertical scroll position for undo with

SC_UNDO_SELECTION_HISTORY_SCROLL flag to SCI_SETUNDOSELECTIONHISTORY.

7 files changed, 21 insertions, 4 deletions

diff --git a/doc/ScintillaDoc.html b/doc/ScintillaDoc.html
index 28010507f..667acb7b3 100644
--- a/doc/ScintillaDoc.html
+++ b/doc/ScintillaDoc.html
@@ -2054,6 +2054,14 @@ struct Sci_TextToFindFull {
           <td>Restore selection for each undo and redo.</td>
         </tr>
 
+        <tr>
+          <th align="left"><code>SC_UNDO_SELECTION_HISTORY_SCROLL</code></th>
+
+          <td>2</td>
+
+          <td>Restore vertical scroll position. Has no effect without <code>SC_UNDO_SELECTION_HISTORY_ENABLED</code>.</td>
+        </tr>
+
       </tbody>
     </table>
 
diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 4d69143ac..4da325dae 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -601,6 +601,10 @@
 	Released 2 April 2025.
 	</li>
 	<li>
+	Add SC_UNDO_SELECTION_HISTORY_SCROLL flag to SCI_SETUNDOSELECTIONHISTORY which controls
+	whether undo and redo restore vertical scroll position.
+	</li>
+	<li>
 	Tweak SC_MARK_BAR to be slightly wider by using next higher whole pixel instead of next lower for margin width / 3.
 	</li>
     </ul>
diff --git a/include/Scintilla.h b/include/Scintilla.h
index 213dde52e..a90dd3571 100644
--- a/include/Scintilla.h
+++ b/include/Scintilla.h
@@ -534,6 +534,7 @@ typedef sptr_t (*SciFnDirectStatus)(sptr_t ptr, unsigned int iMessage, uptr_t wP
 #define SCI_GETCHANGEHISTORY 2781
 #define SC_UNDO_SELECTION_HISTORY_DISABLED 0
 #define SC_UNDO_SELECTION_HISTORY_ENABLED 1
+#define SC_UNDO_SELECTION_HISTORY_SCROLL 2
 #define SCI_SETUNDOSELECTIONHISTORY 2782
 #define SCI_GETUNDOSELECTIONHISTORY 2783
 #define SCI_SETSELECTIONSERIALIZED 2784
diff --git a/include/Scintilla.iface b/include/Scintilla.iface
index e1814eb5a..47896b63f 100644
--- a/include/Scintilla.iface
+++ b/include/Scintilla.iface
@@ -1337,6 +1337,7 @@ get ChangeHistoryOption GetChangeHistory=2781(,)
 enu UndoSelectionHistoryOption=SC_UNDO_SELECTION_HISTORY_
 val SC_UNDO_SELECTION_HISTORY_DISABLED=0
 val SC_UNDO_SELECTION_HISTORY_ENABLED=1
+val SC_UNDO_SELECTION_HISTORY_SCROLL=2
 
 # Enable or disable undo selection history.
 set void SetUndoSelectionHistory=2782(UndoSelectionHistoryOption undoSelectionHistory,)
diff --git a/include/ScintillaTypes.h b/include/ScintillaTypes.h
index 71e2be398..0991a1480 100644
--- a/include/ScintillaTypes.h
+++ b/include/ScintillaTypes.h
@@ -302,6 +302,7 @@ enum class ChangeHistoryOption {
 enum class UndoSelectionHistoryOption {
 	Disabled = 0,
 	Enabled = 1,
+	Scroll = 2,
 };
 
 enum class FoldLevel {
diff --git a/src/EditModel.cxx b/src/EditModel.cxx
index e12aab38e..65d39f9e7 100644
--- a/src/EditModel.cxx
+++ b/src/EditModel.cxx
@@ -172,7 +172,7 @@ int EditModel::GetMark(Sci::Line line) const {
 }
 
 void EditModel::EnsureModelState() {
-	if (!modelState && (undoSelectionHistoryOption == UndoSelectionHistoryOption::Enabled)) {
+	if (!modelState && (undoSelectionHistoryOption != UndoSelectionHistoryOption::Disabled)) {
 		if (ViewStateShared vss = pdoc->GetViewState(this)) {
 			modelState = std::dynamic_pointer_cast<ModelState>(vss);
 		} else {
diff --git a/src/Editor.cxx b/src/Editor.cxx
index ead69617d..334600461 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -2409,12 +2409,14 @@ void Editor::SelectAll() {
 
 void Editor::RestoreSelection(Sci::Position newPos, UndoRedo history) {
 	EnsureModelState();
-	if ((undoSelectionHistoryOption == UndoSelectionHistoryOption::Enabled) && modelState) {
+	if (FlagSet(undoSelectionHistoryOption, UndoSelectionHistoryOption::Enabled) && modelState) {
 		// Undo wants the element after the current as it just undid it
 		const int index = pdoc->UndoCurrent() + (history == UndoRedo::undo ? 1 : 0);
 		const SelectionWithScroll selAndLine = modelState->SelectionFromStack(index, history);
 		if (!selAndLine.selection.empty()) {
-			ScrollTo(selAndLine.topLine);
+			if (FlagSet(undoSelectionHistoryOption, UndoSelectionHistoryOption::Scroll)) {
+				ScrollTo(selAndLine.topLine);
+			}
 			sel = Selection(selAndLine.selection);
 			if (sel.IsRectangular()) {
 				const size_t mainForRectangular = sel.Main();
@@ -2799,7 +2801,7 @@ void Editor::NotifyModified(Document *, DocModification mh, void *) {
 			view.llc.Invalidate(LineLayout::ValidLevel::checkTextAndStyle);
 		}
 	} else {
-		if ((undoSelectionHistoryOption == UndoSelectionHistoryOption::Enabled) &&
+		if (FlagSet(undoSelectionHistoryOption, UndoSelectionHistoryOption::Enabled) &&
 			FlagSet(mh.modificationType, ModificationFlags::User)) {
 			if (FlagSet(mh.modificationType, ModificationFlags::BeforeInsert | ModificationFlags::BeforeDelete)) {
 				RememberSelectionForUndo(pdoc->UndoCurrent());