From 9ff614095f907d92ad8f11cb79653fc7c4399788 Mon Sep 17 00:00:00 2001
From: Gary Talent <gary@drinkingtea.net>
Date: Thu, 8 May 2025 01:57:59 -0500
Subject: [PATCH] [nostalgia/gfx/studio/tilesheet] Fix Delete Tile
 functionality

---
 .../commands/deletetilescommand.cpp           | 29 ++++++++++++-------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/src/nostalgia/modules/gfx/src/studio/tilesheeteditor/commands/deletetilescommand.cpp b/src/nostalgia/modules/gfx/src/studio/tilesheeteditor/commands/deletetilescommand.cpp
index e7cf50ae..f985e156 100644
--- a/src/nostalgia/modules/gfx/src/studio/tilesheeteditor/commands/deletetilescommand.cpp
+++ b/src/nostalgia/modules/gfx/src/studio/tilesheeteditor/commands/deletetilescommand.cpp
@@ -8,14 +8,14 @@
 
 namespace nostalgia::gfx {
 
-gfx::DeleteTilesCommand::DeleteTilesCommand(
+DeleteTilesCommand::DeleteTilesCommand(
 		TileSheet &img,
 		TileSheet::SubSheetIdx idx,
-		std::size_t tileIdx,
-		std::size_t tileCnt) noexcept:
+		std::size_t const tileIdx,
+		std::size_t const tileCnt) noexcept:
 		m_img(img),
 		m_idx(std::move(idx)) {
-	const unsigned bytesPerTile = m_img.bpp == 4 ? PixelsPerTile / 2 : PixelsPerTile;
+	constexpr unsigned bytesPerTile = PixelsPerTile;
 	m_deletePos = tileIdx * bytesPerTile;
 	m_deleteSz = tileCnt * bytesPerTile;
 	m_deletedPixels.resize(m_deleteSz);
@@ -31,13 +31,17 @@ gfx::DeleteTilesCommand::DeleteTilesCommand(
 ox::Error gfx::DeleteTilesCommand::redo() noexcept {
 	auto &s = getSubSheet(m_img, m_idx);
 	auto &p = s.pixels;
-	auto srcPos = m_deletePos + m_deleteSz;
-	auto const src = &p[srcPos];
+	auto const srcPos = m_deletePos + m_deleteSz;
 	auto const dst1 = &p[m_deletePos];
 	auto const dst2 = &p[(p.size() - m_deleteSz)];
 	OX_ALLOW_UNSAFE_BUFFERS_BEGIN
-	ox::memmove(dst1, src, p.size() - srcPos);
-	ox::memset(dst2, 0, m_deleteSz * sizeof(decltype(p[0])));
+	if (srcPos < p.size()) {
+		auto const src = &p[srcPos];
+		ox::memmove(dst1, src, p.size() - srcPos);
+		ox::memset(dst2, 0, m_deleteSz * sizeof(decltype(p[0])));
+	} else {
+		ox::memset(dst1, 0, p.size() - m_deletePos);
+	}
 	OX_ALLOW_UNSAFE_BUFFERS_END
 	return {};
 }
@@ -46,11 +50,14 @@ ox::Error DeleteTilesCommand::undo() noexcept {
 	auto &s = getSubSheet(m_img, m_idx);
 	auto &p = s.pixels;
 	auto const src = &p[m_deletePos];
-	auto const dst1 = &p[m_deletePos + m_deleteSz];
-	auto const dst2 = src;
 	auto const sz = p.size() - m_deletePos - m_deleteSz;
+	auto const srcPos = m_deletePos + m_deleteSz;
 	OX_ALLOW_UNSAFE_BUFFERS_BEGIN
-	ox::memmove(dst1, src, sz);
+	if (srcPos < p.size()) {
+		auto const dst1 = &p[m_deletePos + m_deleteSz];
+		ox::memmove(dst1, src, sz);
+	}
+	auto const dst2 = src;
 	ox::memcpy(dst2, m_deletedPixels.data(), m_deletedPixels.size());
 	OX_ALLOW_UNSAFE_BUFFERS_END
 	return {};