From ffdcc16af513555773b19020f7bef3c1a7cf1c46 Mon Sep 17 00:00:00 2001
From: Peter Veenstra <qbix79@users.sourceforge.net>
Date: Sun, 2 Jun 2019 19:40:59 +0000
Subject: [PATCH] Always clear drawing area. Should fix certain linux
 instalations that use triple buffering

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@4229
---
 src/gui/sdlmain.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/gui/sdlmain.cpp b/src/gui/sdlmain.cpp
index 24807125..b0635487 100644
--- a/src/gui/sdlmain.cpp
+++ b/src/gui/sdlmain.cpp
@@ -1004,6 +1004,10 @@ void GFX_EndUpdate( const Bit16u *changedLines ) {
 		break;
 #if C_OPENGL
 	case SCREEN_OPENGL:
+		// Clear drawing area. Some drivers (on Linux) have more than 2 buffers and the screen might
+		// be dirty because of other programs.
+		glClearColor (0.0, 0.0, 0.0, 1.0);
+		glClear(GL_COLOR_BUFFER_BIT);
 		if (sdl.opengl.pixel_buffer_object) {
 			glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_EXT);
 			glBindTexture(GL_TEXTURE_2D, sdl.opengl.texture);