1 files changed, 66 insertions, 1 deletions
diff --git a/engines/xeen/screen.cpp b/engines/xeen/screen.cpp
index d17e01063d..038222bfe2 100644
--- a/engines/xeen/screen.cpp
+++ b/engines/xeen/screen.cpp
@@ -31,8 +31,73 @@ Screen::Screen(XeenEngine *vm) : _vm(vm) {
 }
 
 void Screen::update() {
-	g_system->copyRectToScreen(getPixels(), pitch, 0, 0, w, h);
+	// Merge the dirty rects
+	mergeDirtyRects();
+
+	// Loop through copying dirty areas to the physical screen
+	Common::List<Common::Rect>::iterator i;
+	for (i = _dirtyRects.begin(); i != _dirtyRects.end(); ++i) {
+		const Common::Rect &r = *i;
+		const byte *srcP = (const byte *)getBasePtr(r.left, r.top);
+		g_system->copyRectToScreen(srcP, this->pitch, r.left, r.top,
+			r.width(), r.height());
+	}
+
+	// Signal the physical screen to update
 	g_system->updateScreen();
+	_dirtyRects.clear();
+}
+
+void Screen::addDirtyRect(const Common::Rect &r) {
+	_dirtyRects.push_back(r);
+}
+
+void Screen::transBlitFrom(const XSurface &src, const Common::Point &destPos) {
+	XSurface::transBlitFrom(src, destPos);
+	addDirtyRect(Common::Rect(destPos.x, destPos.y, destPos.x + src.w, destPos.y + src.h));
+}
+
+void Screen::blitFrom(const XSurface &src, const Common::Point &destPos) {
+	XSurface::blitFrom(src, destPos);
+	addDirtyRect(Common::Rect(destPos.x, destPos.y, destPos.x + src.w, destPos.y + src.h));
+}
+
+void Screen::mergeDirtyRects() {
+	Common::List<Common::Rect>::iterator rOuter, rInner;
+
+	// Ensure dirty rect list has at least two entries
+	rOuter = _dirtyRects.begin();
+	for (int i = 0; i < 2; ++i, ++rOuter) {
+		if (rOuter == _dirtyRects.end())
+			return;
+	}
+
+	// Process the dirty rect list to find any rects to merge
+	for (rOuter = _dirtyRects.begin(); rOuter != _dirtyRects.end(); ++rOuter) {
+		rInner = rOuter;
+		while (++rInner != _dirtyRects.end()) {
+
+			if ((*rOuter).intersects(*rInner)) {
+				// these two rectangles overlap or
+				// are next to each other - merge them
+
+				unionRectangle(*rOuter, *rOuter, *rInner);
+
+				// remove the inner rect from the list
+				_dirtyRects.erase(rInner);
+
+				// move back to beginning of list
+				rInner = rOuter;
+			}
+		}
+	}
+}
+
+bool Screen::unionRectangle(Common::Rect &destRect, const Common::Rect &src1, const Common::Rect &src2) {
+	destRect = src1;
+	destRect.extend(src2);
+
+	return !destRect.isEmpty();
 }
 
 } // End of namespace Xeen