3 files changed, 49 insertions, 3 deletions

diff --git a/engines/mutationofjb/room.cpp b/engines/mutationofjb/room.cpp
index 1da2730a48..dd9a6dbab5 100644
--- a/engines/mutationofjb/room.cpp
+++ b/engines/mutationofjb/room.cpp
@@ -28,6 +28,7 @@
 #include "mutationofjb/gamedata.h"
 #include "mutationofjb/util.h"
 
+#include "common/rect.h"
 #include "common/str.h"
 #include "common/translation.h"
 
@@ -117,6 +118,13 @@ bool Room::load(uint8 roomNumber, bool roomB) {
 	return decoder.decode(&callback);
 }
 
+// TODO: Take the threshold value from ATN data.
+struct ThresholdBlitOperation {
+	bool operator()(const byte /*srcColor*/, const byte destColor) {
+		return destColor <= 0xBF;
+	}
+};
+
 void Room::drawObjectAnimation(uint8 objectId, int animOffset) {
 	Scene *const scene = _game->getGameData().getCurrentScene();
 	if (!scene) {
@@ -129,8 +137,8 @@ void Room::drawObjectAnimation(uint8 objectId, int animOffset) {
 
 	const int startFrame = _objectsStart[objectId - 1];
 	const int animFrame = startFrame + animOffset;
-	// TODO: Threshold.
-	_screen->blitFrom(_surfaces[animFrame], Common::Point(object->_x, object->_y));
+
+	blit_if(_surfaces[animFrame], *_screen, Common::Point(object->_x, object->_y), ThresholdBlitOperation());
 }
 
 void Room::redraw() {
@@ -140,7 +148,7 @@ void Room::redraw() {
 	}
 
 	Scene *const currentScene = _game->getGameData().getCurrentScene();
-	for (int i = 0; i < currentScene->getNoObjects(); ++i) {
+	for (uint8 i = 0; i < currentScene->getNoObjects(); ++i) {
 		Object *const obj = currentScene->getObject(i + 1);
 		if (obj->_active) {
 			drawObjectAnimation(i + 1, obj->_currentFrame - _objectsStart[i] - 1);
diff --git a/engines/mutationofjb/util.cpp b/engines/mutationofjb/util.cpp
index 6d7c02a293..72d2d0f7e1 100644
--- a/engines/mutationofjb/util.cpp
+++ b/engines/mutationofjb/util.cpp
@@ -21,8 +21,10 @@
  */
 
 #include "mutationofjb/util.h"
+
 #include "common/str.h"
 #include "common/translation.h"
+
 #include "engines/engine.h"
 
 namespace MutationOfJB {
diff --git a/engines/mutationofjb/util.h b/engines/mutationofjb/util.h
index 86ee10f82e..06d1a0b2a1 100644
--- a/engines/mutationofjb/util.h
+++ b/engines/mutationofjb/util.h
@@ -23,15 +23,51 @@
 #ifndef MUTATIONOFJB_UTIL_H
 #define MUTATIONOFJB_UTIL_H
 
+#include "common/rect.h"
+
+#include "graphics/managed_surface.h"
+#include "graphics/surface.h"
+
 namespace Common {
 class String;
 }
 
+
 namespace MutationOfJB {
 
 void reportFileMissingError(const char *fileName);
 Common::String toUpperCP895(const Common::String &str);
 
+template <typename BlitOp>
+void blit_if(const Graphics::Surface &src, const Common::Rect &srcRect, Graphics::ManagedSurface &dest, const Common::Point &destPos, BlitOp blitOp) {
+	const Common::Rect srcBounds = srcRect;
+	const Common::Rect destBounds(destPos.x, destPos.y, destPos.x + srcRect.width(), destPos.y + srcRect.height());
+
+	assert(srcRect.isValidRect());
+	assert(dest.format == src.format);
+
+	for (int y = 0; y < srcBounds.height(); ++y) {
+		const byte *srcP = reinterpret_cast<const byte *>(src.getBasePtr(srcBounds.left, srcBounds.top + y));
+		const byte *srcEndP = srcP + srcBounds.width();
+		byte *destP = reinterpret_cast<byte *>(dest.getBasePtr(destBounds.left, destBounds.top + y));
+
+		while (srcP != srcEndP) {
+			if (blitOp(*srcP, *destP)) {
+				*destP = *srcP;
+			}
+			++srcP;
+			++destP;
+		}
+	}
+
+	dest.getSubArea(destBounds); // This is a hack to invalidate the destination rectangle.
+}
+
+template <typename BlitOp>
+void blit_if(const Graphics::Surface &src, Graphics::ManagedSurface &dest, const Common::Point &destPos, BlitOp blitOp) {
+	blit_if(src, Common::Rect(0, 0, src.w, src.h), dest, destPos, blitOp);
+}
+
 }
 
 #endif