Fixed scrollEffect() regression introduced when move_screen() was removed.

I have tested this on all the cases I know of where scrollEffect() is used:

* The diving scene in Monkey Island 2
* The camel and balloon rides in Fate of Atlantis
* The arrival of the thunder storm in Day of the Tentacle
* Seeing the loose end in Sam & Max

So far it seems to work fine. Knock on wood.

svn-id: r14908

3 files changed, 52 insertions, 0 deletions

diff --git a/scumm/gfx.cpp b/scumm/gfx.cpp
index 369f4b236b..e25151f7cc 100644
--- a/scumm/gfx.cpp
+++ b/scumm/gfx.cpp
@@ -2768,6 +2768,12 @@ void ScummEngine::dissolveEffect(int width, int height) {
 }
 
 void ScummEngine::scrollEffect(int dir) {
+	// It is at least technically possible that this function will be
+	// called without _scrollBuffer having been set up, but will it ever
+	// happen? I don't know.
+	if (!_scrollBuffer)
+		warning("scrollEffect: No scroll buffer. This may look bad");
+
 	VirtScreen *vs = &virtscr[0];
 
 	int x, y;
@@ -2789,6 +2795,11 @@ void ScummEngine::scrollEffect(int dir) {
 				vs->pitch,
 				0, vs->h - y,
 				vs->w, y);
+			if (_scrollBuffer)
+				_system->copyRectToScreen(_scrollBuffer + y * vs->w,
+					vs->w,
+					0, 0,
+					vs->w, vs->h - y);
 			_system->updateScreen();
 			waitForTimer(kPictureDelay);
 
@@ -2803,6 +2814,11 @@ void ScummEngine::scrollEffect(int dir) {
 				vs->pitch,
 				0, 0,
 				vs->w, y);
+			if (_scrollBuffer)
+				_system->copyRectToScreen(_scrollBuffer,
+					vs->w,
+					0, y,
+					vs->w, vs->h - y);
 			_system->updateScreen();
 			waitForTimer(kPictureDelay);
 
@@ -2817,6 +2833,11 @@ void ScummEngine::scrollEffect(int dir) {
 				vs->pitch,
 				vs->w - x, 0,
 				x, vs->h);
+			if (_scrollBuffer)
+				_system->copyRectToScreen(_scrollBuffer + x,
+					vs->w,
+					0, 0,
+					vs->w - x, vs->h);
 			_system->updateScreen();
 			waitForTimer(kPictureDelay);
 
@@ -2831,6 +2852,11 @@ void ScummEngine::scrollEffect(int dir) {
 				vs->pitch,
 				0, 0,
 				x, vs->h);
+			if (_scrollBuffer)
+				_system->copyRectToScreen(_scrollBuffer,
+					vs->w,
+					x, 0,
+					vs->w - x, vs->h);
 			_system->updateScreen();
 			waitForTimer(kPictureDelay);
 
@@ -2838,6 +2864,9 @@ void ScummEngine::scrollEffect(int dir) {
 		}
 		break;
 	}
+
+	free(_scrollBuffer);
+	_scrollBuffer = NULL;
 }
 
 void ScummEngine::unkScreenEffect6() {
diff --git a/scumm/scumm.cpp b/scumm/scumm.cpp
index 1fb63414a9..d8c50f348b 100644
--- a/scumm/scumm.cpp
+++ b/scumm/scumm.cpp
@@ -598,6 +598,7 @@ ScummEngine::ScummEngine(GameDetector *detector, OSystem *syst, const ScummGameS
 	_newEffect = 0;
 	_switchRoomEffect2 = 0;
 	_switchRoomEffect = 0;
+	_scrollBuffer = NULL;
 	_doEffect = false;
 	memset(&_flashlight, 0, sizeof(_flashlight));
 	_roomStrips = 0;
@@ -2260,6 +2261,26 @@ void ScummEngine::startScene(int room, Actor *a, int objectNr) {
 		VAR(VAR_NEW_ROOM) = room; // gamevars, eg Zak cashcards
 
 	runExitScript();
+
+	if (_switchRoomEffect >= 130 && _switchRoomEffect <= 133) {
+		// We're going to use scrollEffect(), so we'll need a copy of
+		// the current VirtScreen zero.
+
+		VirtScreen *vs = &virtscr[0];
+
+		free(_scrollBuffer);
+		_scrollBuffer = (byte *) malloc(vs->h * vs->w);
+
+		byte *src = vs->getPixels(0, 0);
+		byte *dst = _scrollBuffer;
+
+		for (int y = 0; y < vs->h; y++) {
+			memcpy(dst, src, vs->w);
+			src += vs->w;
+			dst += vs->pitch;
+		}
+	}
+
 	killScriptsAndResources();
 	clearEnqueue();
 	if (_version >= 4 && _heversion <= 60)
diff --git a/scumm/scumm.h b/scumm/scumm.h
index 6b54b1387c..51ef188288 100644
--- a/scumm/scumm.h
+++ b/scumm/scumm.h
@@ -890,6 +890,8 @@ protected:
 
 	byte _newEffect, _switchRoomEffect2, _switchRoomEffect;
 	bool _doEffect;
+
+	byte *_scrollBuffer;
 	
 	struct {
 		int x, y, w, h;