From dd12857ba8d9fc2d46be1fe66d79f3e11f821b02 Mon Sep 17 00:00:00 2001
From: Gary Talent <gary@drinkingtea.net>
Date: Thu, 31 Mar 2022 01:38:59 -0500
Subject: [PATCH] [nostalgia/studio] Add UndoCommand::mergeWith

---
 src/nostalgia/studio/lib/undostack.cpp | 12 ++++++++++--
 src/nostalgia/studio/lib/undostack.hpp |  1 +
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/nostalgia/studio/lib/undostack.cpp b/src/nostalgia/studio/lib/undostack.cpp
index b15f7a4fd..dd736ae72 100644
--- a/src/nostalgia/studio/lib/undostack.cpp
+++ b/src/nostalgia/studio/lib/undostack.cpp
@@ -6,16 +6,24 @@
 
 namespace nostalgia::studio {
 
+bool UndoCommand::mergeWith(const UndoCommand*) noexcept {
+	return false;
+}
+
 void UndoStack::push(UndoCommand *cmd) noexcept {
 	for (const auto i = m_stackIdx; i < m_stack.size();) {
 		oxIgnoreError(m_stack.erase(i));
 	}
-	m_stack.emplace_back(cmd);
-	++m_stackIdx;
 	auto cmdId = cmd->commandId();
 	cmd->redo();
 	redoTriggered.emit(cmdId);
 	changeTriggered.emit(cmdId);
+	if (!m_stack.size() || !m_stack.back().value->mergeWith(cmd)) {
+		m_stack.emplace_back(cmd);
+		++m_stackIdx;
+	} else {
+		delete cmd;
+	}
 }
 
 void UndoStack::redo() noexcept {
diff --git a/src/nostalgia/studio/lib/undostack.hpp b/src/nostalgia/studio/lib/undostack.hpp
index 0e52035a2..b46f0e249 100644
--- a/src/nostalgia/studio/lib/undostack.hpp
+++ b/src/nostalgia/studio/lib/undostack.hpp
@@ -18,6 +18,7 @@ class UndoCommand {
 		virtual void undo() noexcept = 0;
 		[[nodiscard]]
 		virtual int commandId() const noexcept = 0;
+		virtual bool mergeWith(const UndoCommand *cmd) noexcept;
 };
 
 class UndoStack {