From d810bb7451ba5335a3f3ff7cb4b7b8ebd529b446 Mon Sep 17 00:00:00 2001
From: Bastien Bouclet
Date: Sun, 27 Oct 2019 20:18:49 +0100
Subject: MOHAWK: MYST: Fix misuse of OSystem::fillScreen

OSystem::fillScreen is documented to only accept values between 0 and
255, and thus cannot be sanely used for hi-color graphics. This is
probably an unfortunate leftover of when hi-color support was added.

Fixes videos playing on a white background on the 3DS.
---
 engines/mohawk/myst_graphics.cpp | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/engines/mohawk/myst_graphics.cpp b/engines/mohawk/myst_graphics.cpp
index 55a92b2b08..b5222c6d91 100644
--- a/engines/mohawk/myst_graphics.cpp
+++ b/engines/mohawk/myst_graphics.cpp
@@ -892,10 +892,15 @@ void MystGraphics::replaceImageWithRect(uint16 destImage, uint16 sourceImage, co
 }
 
 void MystGraphics::clearScreen() {
-	if (_vm->getFeatures() & GF_ME)
-		_vm->_system->fillScreen(_pixelFormat.RGBToColor(0, 0, 0));
-	else
-		_vm->_system->fillScreen(0);
+	Graphics::Surface *screen = _vm->_system->lockScreen();
+	if (screen) {
+		if (_vm->getFeatures() & GF_ME)
+			screen->fillRect(_viewport, _pixelFormat.RGBToColor(0, 0, 0));
+		else
+			screen->fillRect(_viewport, 0);
+
+		_vm->_system->unlockScreen();
+	}
 }
 
 } // End of namespace Mohawk
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