ACCESS: Implement dirty rect merging

engines/access/screen.cpp

@@ -89,13 +89,19 @@ void Screen::setPanel(int num) {
 }
 
 void Screen::updateScreen() {
-	for (uint i = 0; i < _dirtyRects.size(); ++i) {
-		const Common::Rect &r = _dirtyRects[i];
+	// 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();
 }
@@ -321,4 +327,43 @@ void Screen::addDirtyRect(const Common::Rect &r) {
 	assert(r.isValidRect() && r.width() > 0 && r.height() > 0);
 }
 
+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 Access

engines/access/screen.h

@@ -63,9 +63,13 @@ class Screen: public ASurface {
 	int _startCycle;
 	int _cycleStart;
 	int _endCycle;
-	Common::Array<Common::Rect> _dirtyRects;
+	Common::List<Common::Rect> _dirtyRects;
 
 	void updatePalette();
+
+	void mergeDirtyRects();
+
+	bool unionRectangle(Common::Rect &destRect, const Common::Rect &src1, const Common::Rect &src2);
 public:
 	int _vesaMode;
 	int _startColor, _numColors;