4 files changed, 34 insertions, 15 deletions

diff --git a/engines/zvision/render_manager.cpp b/engines/zvision/render_manager.cpp
index 7f796451f4..bd3e73563f 100644
--- a/engines/zvision/render_manager.cpp
+++ b/engines/zvision/render_manager.cpp
@@ -60,6 +60,10 @@ RenderManager::~RenderManager() {
 }
 
 void RenderManager::update(uint deltaTimeInMillis) {
+	// Clear the dirty rects from last frame
+	_workingWindowDirtyRect = Common::Rect();
+	_backBufferDirtyRect = Common::Rect();
+
 	// An inverse velocity of 0 would be infinitely fast, so we'll let 0 mean no velocity.
 	if (_backgroundInverseVelocity != 0) {
 		_accumulatedVelocityMilliseconds += deltaTimeInMillis;
@@ -78,16 +82,25 @@ void RenderManager::update(uint deltaTimeInMillis) {
 }
 
 void RenderManager::renderBackbufferToScreen() {
-	RenderTable::RenderState state = _renderTable.getRenderState();
-	if (state == RenderTable::PANORAMA || state == RenderTable::TILT) {
-		_renderTable.mutateImage((uint16 *)_workingWindowBuffer.getPixels(), (uint16 *)_backBuffer.getBasePtr(_workingWindow.left, _workingWindow.top), _backBuffer.w);
-	} else {
-		_backBuffer.copyRectToSurface(_workingWindowBuffer.getPixels(), _workingWindowBuffer.pitch, _workingWindow.left, _workingWindow.top, _workingWindowBuffer.w, _workingWindowBuffer.h);
+	if (!_workingWindowDirtyRect.isEmpty()) {
+		RenderTable::RenderState state = _renderTable.getRenderState();
+		if (state == RenderTable::PANORAMA || state == RenderTable::TILT) {
+			_renderTable.mutateImage((uint16 *)_workingWindowBuffer.getPixels(), (uint16 *)_backBuffer.getBasePtr(_workingWindow.left + _workingWindowDirtyRect.left, _workingWindow.top + _workingWindowDirtyRect.top), _backBuffer.w, _workingWindowDirtyRect);
+		} else {
+			_backBuffer.copyRectToSurface(_workingWindowBuffer.getBasePtr(_workingWindowDirtyRect.left, _workingWindowDirtyRect.top), _workingWindowBuffer.pitch, _workingWindow.left + _workingWindowDirtyRect.left, _workingWindow.top + _workingWindowDirtyRect.top, _workingWindowDirtyRect.width(), _workingWindowDirtyRect.height());
+		}
+
+		// Translate the working window dirty rect to screen coords
+		_workingWindowDirtyRect.translate(_workingWindow.left, _workingWindow.top);
+		// Then extend the backbuffer dirty rect to contain it
+		_backBufferDirtyRect.extend(_workingWindowDirtyRect);
 	}
 
 	// TODO: Add menu rendering
 
-	_system->copyRectToScreen(_backBuffer.getPixels(), _backBuffer.pitch, 0, 0, _backBuffer.w, _backBuffer.h);
+	if (!_backBufferDirtyRect.isEmpty()) {
+		_system->copyRectToScreen(_backBuffer.getBasePtr(_backBufferDirtyRect.left, _backBufferDirtyRect.top), _backBuffer.pitch, _backBufferDirtyRect.left, _backBufferDirtyRect.top, _backBufferDirtyRect.width(), _backBufferDirtyRect.height());
+	}
 }
 
 void RenderManager::clearWorkingWindowTo555Color(uint16 color) {
@@ -274,6 +287,8 @@ void RenderManager::renderRectToWorkingWindow(uint16 *buffer, int32 imageWidth,
 		destOffset += _workingWidth;
 		sourceOffset += imageWidth;
 	}
+
+	_workingWindowDirtyRect.extend(Common::Rect(destX, destY, destX + width, destY + height));
 }
 
 const Common::Point RenderManager::screenSpaceToImageSpace(const Common::Point &point) {
diff --git a/engines/zvision/render_manager.h b/engines/zvision/render_manager.h
index 07b2e854ae..fd36ab5730 100644
--- a/engines/zvision/render_manager.h
+++ b/engines/zvision/render_manager.h
@@ -57,6 +57,9 @@ private:
 	Graphics::Surface _workingWindowBuffer;
 	Graphics::Surface _backBuffer;
 
+	Common::Rect _workingWindowDirtyRect;
+	Common::Rect _backBufferDirtyRect;
+
 	/** Width of the working window. Saved to prevent extraneous calls to _workingWindow.width() */
 	const int _workingWidth;
 	/** Height of the working window. Saved to prevent extraneous calls to _workingWindow.height() */
diff --git a/engines/zvision/render_table.cpp b/engines/zvision/render_table.cpp
index 3e7a86e348..5eb208eb8c 100644
--- a/engines/zvision/render_table.cpp
+++ b/engines/zvision/render_table.cpp
@@ -100,14 +100,15 @@ uint16 mixTwoRGB(uint16 colorOne, uint16 colorTwo, float percentColorOne) {
 	return returnColor;
 }
 
-void RenderTable::mutateImage(uint16 *sourceBuffer, uint16* destBuffer, uint32 destWidth) {
-	uint32 destColumnOffset = 0;
+void RenderTable::mutateImage(uint16 *sourceBuffer, uint16* destBuffer, uint32 destWidth, const Common::Rect &subRect) {
+	uint32 destOffset = 0;
 
-	for (uint32 y = 0; y < _numRows; y++) {
-		uint32 sourceColumnOffset = y * _numColumns;
+	for (uint32 y = subRect.top; y < subRect.bottom; y++) {
+		uint32 sourceOffset = y * _numColumns;
 
-		for (uint32 x = 0; x < _numColumns; x++) {
-			uint32 index = sourceColumnOffset + x;
+		for (uint32 x = subRect.left; x < subRect.right; x++) {
+			uint32 normalizedX = x - subRect.left;
+			uint32 index = sourceOffset + x;
 
 			// RenderTable only stores offsets from the original coordinates
 			uint32 sourceYIndex = y + _internalBuffer[index].y;
@@ -119,10 +120,10 @@ void RenderTable::mutateImage(uint16 *sourceBuffer, uint16* destBuffer, uint32 d
 			// Clamp the xIndex to the size of the image
 			sourceXIndex = CLIP<uint32>(sourceXIndex, 0, _numColumns - 1);
 			
-			destBuffer[destColumnOffset + x] = sourceBuffer[sourceYIndex * _numColumns + sourceXIndex];
+			destBuffer[destOffset + normalizedX] = sourceBuffer[sourceYIndex * _numColumns + sourceXIndex];
 		}
 
-		destColumnOffset += destWidth;
+		destOffset += destWidth;
 	}
 }
 
diff --git a/engines/zvision/render_table.h b/engines/zvision/render_table.h
index ba3c7d2f5d..7c8e7d6a2d 100644
--- a/engines/zvision/render_table.h
+++ b/engines/zvision/render_table.h
@@ -66,7 +66,7 @@ public:
 
 	const Common::Point convertWarpedCoordToFlatCoord(const Common::Point &point);
 
-	void mutateImage(uint16 *sourceBuffer, uint16* destBuffer, uint32 destWidth);
+	void mutateImage(uint16 *sourceBuffer, uint16* destBuffer, uint32 destWidth, const Common::Rect &subRect);
 	void generateRenderTable();
 
 	void setPanoramaFoV(float fov);