From 59c124aa609bc872ac00175729728bdd825e6f1d Mon Sep 17 00:00:00 2001
From: Paul Gilbert
Date: Tue, 17 Mar 2015 00:01:12 -0400
Subject: SHERLOCK: Add dirty rect handling

---
 engines/sherlock/screen.cpp | 68 ++++++++++++++++++++++++++++++++++++++++++++-
 engines/sherlock/screen.h   |  8 ++++++
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/engines/sherlock/screen.cpp b/engines/sherlock/screen.cpp
index d3fe68e367..6dcb37c448 100644
--- a/engines/sherlock/screen.cpp
+++ b/engines/sherlock/screen.cpp
@@ -44,8 +44,21 @@ void Screen::setFont(int fontNumber) {
 }
 
 void Screen::update() {
-	g_system->copyRectToScreen(getPixels(), this->w, 0, 0, this->w, this->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::getPalette(byte palette[PALETTE_SIZE]) {
@@ -104,4 +117,57 @@ void Screen::fadeToBlack() {
 	} while (repeatFlag && !_vm->shouldQuit());
 }
 
+/**
+ * Adds a rectangle to the list of modified areas of the screen during the
+ * current frame
+ */
+void Screen::addDirtyRect(const Common::Rect &r) {
+	_dirtyRects.push_back(r);
+	assert(r.isValidRect() && r.width() > 0 && r.height() > 0);
+}
+
+/**
+ * Merges together overlapping dirty areas of the screen
+ */
+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;
+			}
+		}
+	}
+}
+
+/**
+ * Returns the union of two dirty area rectangles
+ */
+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 Sherlock
diff --git a/engines/sherlock/screen.h b/engines/sherlock/screen.h
index 3d1ad785e6..62d3944d04 100644
--- a/engines/sherlock/screen.h
+++ b/engines/sherlock/screen.h
@@ -23,6 +23,7 @@
 #ifndef SHERLOCK_SCREEN_H
 #define SHERLOCK_SCREEN_H
 
+#include "common/list.h"
 #include "common/rect.h"
 #include "graphics/surface.h"
 
@@ -40,6 +41,13 @@ private:
 	SherlockEngine *_vm;
 	int _fontNumber;
 	Surface _backBuffer1, _backBuffer2;
+	Common::List<Common::Rect> _dirtyRects;
+
+	void mergeDirtyRects();
+
+	bool unionRectangle(Common::Rect &destRect, const Common::Rect &src1, const Common::Rect &src2);
+protected:
+	virtual void addDirtyRect(const Common::Rect &r);
 public:
 	Screen(SherlockEngine *vm);
 
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