From 6eb62971f881736882877024b99a7c8b40ba39be Mon Sep 17 00:00:00 2001
From: myst6re <myst6re@gmail.com>
Date: Tue, 16 Jan 2024 22:53:15 +0100
Subject: [PATCH] Trying to display correctly shifted backgrounds

---
 src/core/field/BackgroundTiles.cpp | 10 ++++++++--
 src/widgets/BackgroundEditor.cpp   | 12 +++++++-----
 src/widgets/BackgroundEditor.h     |  2 +-
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/core/field/BackgroundTiles.cpp b/src/core/field/BackgroundTiles.cpp
index c9f93d2e..42496992 100644
--- a/src/core/field/BackgroundTiles.cpp
+++ b/src/core/field/BackgroundTiles.cpp
@@ -453,12 +453,18 @@ QPoint BackgroundTiles::dstShift(quint8 tileSize) const
 		}
 
 		if (!shiftXComputed && tile.dstX != 0) {
-			shiftX = std::abs(tile.dstX) % tile.size;
+			shiftX = tile.dstX < 0 ? tile.size - (-tile.dstX % tile.size) : tile.dstX % tile.size;
+			if (shiftX == tile.size) {
+				shiftX = 0;
+			}
 			shiftXComputed = true;
 		}
 
 		if (!shiftYComputed && tile.dstY != 0) {
-			shiftY = std::abs(tile.dstY) % tile.size;
+			shiftY = tile.dstY < 0 ? tile.size - (-tile.dstY % tile.size) : tile.dstY % tile.size;
+			if (shiftY == tile.size) {
+				shiftY = 0;
+			}
 			shiftYComputed = true;
 		}
 
diff --git a/src/widgets/BackgroundEditor.cpp b/src/widgets/BackgroundEditor.cpp
index 8410ca8b..0ded4e82 100644
--- a/src/widgets/BackgroundEditor.cpp
+++ b/src/widgets/BackgroundEditor.cpp
@@ -389,14 +389,14 @@ void BackgroundEditor::updateImageLabel(int layer, int section, ParamState param
 	updateSelectedTiles(_backgroundLayerWidget->selectedCells());
 }
 
-QPoint BackgroundEditor::backgroundPositionFromTile(const QPoint &tile, quint8 cellSize)
+QPoint BackgroundEditor::backgroundPositionFromTile(const QPoint &tile, const QPoint &shift)
 {
-	return tile + QPoint(MAX_TILE_DST, MAX_TILE_DST) - QPoint(tile.x() % cellSize, tile.y() % cellSize);
+	return tile + QPoint(MAX_TILE_DST, MAX_TILE_DST) - shift;
 }
 
 QPoint BackgroundEditor::tilePositionFromCell(const QPoint &cell, quint8 cellSize, const QPoint &shift)
 {
-	return cell * cellSize - QPoint(MAX_TILE_DST, MAX_TILE_DST) - shift;
+	return cell * cellSize - QPoint(MAX_TILE_DST, MAX_TILE_DST) + shift;
 }
 
 void BackgroundEditor::refreshImage(int layer, int section, ParamState paramState, const QList<quint16> &effectTileIds)
@@ -432,7 +432,7 @@ void BackgroundEditor::refreshImage(int layer, int section, ParamState paramStat
 	QPoint shift = layerTiles.dstShift(tileSize);
 	
 	qDebug() << "BackgroundEditor::refreshImage" << "area" << area << shift;
-
+	
 	_shiftX->setMaximum(tileSize - 1);
 	_shiftY->setMaximum(tileSize - 1);
 	_shiftX->setValue(shift.x());
@@ -484,7 +484,9 @@ void BackgroundEditor::refreshImage(int layer, int section, ParamState paramStat
 	QSize gridSize((MAX_TILE_DST - shift.x()) * 2, (MAX_TILE_DST - shift.y()) * 2);
 	_backgroundLayerWidget->setGridSize(gridSize / tileSize);
 
-	_backgroundLayerWidget->setPixmap(backgroundPositionFromTile(layerTiles.minTopLeft(), tileSize), pix);
+	_backgroundLayerWidget->setPixmap(backgroundPositionFromTile(layerTiles.minTopLeft(), shift), pix);
+	
+	qDebug() << "gridSize" << gridSize;
 
 	QList<QLine> axis;
 	axis.append(QLine(0, gridSize.height() / 2, gridSize.width(), gridSize.height() / 2)); // x
diff --git a/src/widgets/BackgroundEditor.h b/src/widgets/BackgroundEditor.h
index c095a43d..a5761c2f 100644
--- a/src/widgets/BackgroundEditor.h
+++ b/src/widgets/BackgroundEditor.h
@@ -57,7 +57,7 @@ private slots:
 	void refreshList(int layer);
 	void refreshImage(int layer, int section, ParamState paramState, const QList<quint16> &effectTileIds);
 	void refreshTexture();
-	static QPoint backgroundPositionFromTile(const QPoint &cell, quint8 cellSize);
+	static QPoint backgroundPositionFromTile(const QPoint &tile, const QPoint &shift);
 	static QPoint tilePositionFromCell(const QPoint &cell, quint8 cellSize, const QPoint &shift);
 
 	QSplitter *_topBottomSplitter;