STARTREK: Fix .BAN file rendering behind textboxes

engines/startrek/graphics.cpp

@@ -304,14 +304,14 @@ void Graphics::drawSprite(const Sprite &sprite, ::Graphics::Surface *surface) {
 
 // rect is the portion of the sprite to update. It must be entirely contained within the
 // sprite's actual, full rectangle.
-void Graphics::drawSprite(const Sprite &sprite, ::Graphics::Surface *surface, const Common::Rect &rect) {
+void Graphics::drawSprite(const Sprite &sprite, ::Graphics::Surface *surface, const Common::Rect &rect, int rectLeft, int rectTop) {
 	Common::Rect spriteRect = Common::Rect(sprite.drawX, sprite.drawY,
 	        sprite.drawX + sprite.bitmap->width, sprite.drawY + sprite.bitmap->height);
 
 	assert(_screenRect.contains(rect));
 	assert(spriteRect.contains(rect));
 
-	byte *dest = (byte *)surface->getPixels() + rect.top * SCREEN_WIDTH + rect.left;
+	byte *dest = (byte *)surface->getPixels() + (rect.top - rectTop) * SCREEN_WIDTH + (rect.left - rectLeft);
 
 	switch (sprite.drawMode) {
 	case 0: { // Normal sprite
@@ -583,8 +583,9 @@ void Graphics::drawAllSprites(bool updateScreen) {
 		this->updateScreen();
 }
 
-void Graphics::drawAllSpritesInRect(const Common::Rect &rect) {
-	::Graphics::Surface *surface = _vm->_system->lockScreen();
+void Graphics::drawAllSpritesInRectToSurface(const Common::Rect &rect, ::Graphics::Surface *surface) {
+	surface->copyFrom(*_vm->_system->lockScreen());
+	_vm->_system->unlockScreen();
 
 	for (int i = 0; i < _numSprites; i++) {
 		Sprite *sprite = _sprites[i];
@@ -595,8 +596,6 @@ void Graphics::drawAllSpritesInRect(const Common::Rect &rect) {
 		if (!intersect.isEmpty())
 			drawSprite(*sprite, surface, intersect);
 	}
-
-	_vm->_system->unlockScreen();
 }
 
 void Graphics::forceDrawAllSprites(bool updateScreen) {

engines/startrek/graphics.h

@@ -105,13 +105,21 @@ class Graphics {
 
 	void drawTextChar(::Graphics::Surface *surface, const Sprite &sprite, int x, int y, const Common::Rect &rect);
 	void drawSprite(const Sprite &sprite, ::Graphics::Surface *surface);
-	void drawSprite(const Sprite &sprite, ::Graphics::Surface *surface, const Common::Rect &rect);
+	/**
+	 * @param sprite The sprite to draw
+	 * @param surface The surface to draw to
+	 * @param rect The part of the sprite to draw (only draw the part of the sprite that
+	 *             intersects with it)
+	 @ @param rectLeft X-offset to subtract before drawing to surface.
+	 @ @param rectTop  Y-offset to subtract before drawing to surface.
+	 */
+	void drawSprite(const Sprite &sprite, ::Graphics::Surface *surface, const Common::Rect &rect, int rectLeft = 0, int rectTop = 0);
 	void drawAllSprites(bool updateScreen = true);
 	/**
 	 * This function should only be called after "drawAllSprites" (so that sprite rects
 	 * are updated).
 	 */
-	void drawAllSpritesInRect(const Common::Rect &rect);
+	void drawAllSpritesInRectToSurface(const Common::Rect &rect, ::Graphics::Surface *surface);
 	/**
 	 * Sets "bitmapChanged" to true on all sprites before calling drawAllSprites.
 	 */

engines/startrek/startrek.cpp

@@ -884,23 +884,63 @@ void StarTrekEngine::renderBanAboveSprites() {
 			rect.top    = _banFiles[i]->readSint16();
 			rect.right  = _banFiles[i]->readSint16() + 1;
 			rect.bottom = _banFiles[i]->readSint16() + 1;
-			_gfx->drawAllSpritesInRect(rect);
 
-			// Just read through the BAN data to get the end address, not doing anything
-			// with it.
+			// Draw all sprites in this rectangle to a custom surface, and only update the
+			// specific pixels that were updated by the BAN file this frame.
+			// Rationale behind this is that, since the background may not have been
+			// redrawn, the transparent sprites (ie. textboxes) would further darken any
+			// pixels behind them that haven't been updated this frame. So, we can't just
+			// update everything in this rectangle.
+			// FIXME: This copies the entire screen surface for temporary drawing, which
+			// is somewhat wasteful. Original game had one more graphics layer it drew to
+			// before the screen was updated...
+			::Graphics::Surface surface;
+			_gfx->drawAllSpritesInRectToSurface(rect, &surface);
+
+			byte *destPixels = _gfx->lockScreenPixels();
+			byte *src = (byte *)surface.getPixels() + offset;
+			byte *dest = destPixels + offset;
+
+			/*
+			_banFiles[i]->seek(_banFileOffsets[i], SEEK_SET);
+			renderBan(destPixels, _banFiles[i]);
+			*/
+			// This is similar to renderBan(), except it copies pixels from the surface
+			// above instead of drawing directly to it. (Important since sprites may be
+			// drawn on top.)
 			while (--size >= 0) {
+				assert(dest >= destPixels && dest < destPixels + SCREEN_WIDTH * SCREEN_HEIGHT);
 				int8 b = _banFiles[i]->readByte();
-				if (b == -128)
-					_banFiles[i]->readUint16();
-				else if (b < 0) {
-					_banFiles[i]->readByte();
+				if (b == -128) {
+					uint16 skip = _banFiles[i]->readUint16();
+					dest += skip;
+					src  += skip;
+				} else if (b < 0) {
+					byte c = _banFiles[i]->readByte();
+					if (c == 0) {
+						dest += (-b) + 1;
+						src  += (-b) + 1;
+					}
+					else {
+						for (int j = 0; j < (-b) + 1; j++)
+							*(dest++) = *(src++);
+					}
 				} else {
 					b++;
-					while (b-- != 0)
-						_banFiles[i]->readByte();
+					while (b-- != 0) {
+						byte c = _banFiles[i]->readByte();
+						if (c == 0) {
+							dest++;
+							src++;
+						} else
+							*(dest++) = *(src++);
+					}
 				}
 			}
 
+			_gfx->unlockScreenPixels();
+			surface.free();
+
 			_banFileOffsets[i] = _banFiles[i]->pos();
 		}
 	}