GRAPHICS: Fix discrepancy in the thick line drawing function

The shortcuts for horizontal and vertical lines should draw the extra
thickness pixels around the line, not below it or to the right

1 files changed, 2 insertions, 6 deletions

diff --git a/graphics/primitives.cpp b/graphics/primitives.cpp
index ac1c58b1d8..a879fc9e45 100644
--- a/graphics/primitives.cpp
+++ b/graphics/primitives.cpp
@@ -108,15 +108,11 @@ void drawThickLine2(int x1, int y1, int x2, int y2, int thick, int color, void (
 	int dy = abs(y2 - y1);
 
 	if (dx == 0) {
-		if (y1 > y2)
-			SWAP(y1, y2);
-		Common::Rect r(x1, y1, x1 + thick - 1, y2);
+		Common::Rect r(x1 - thick / 2, MIN(y1, y2), x1 + thick / 2, MAX(y1, y2));
 		drawFilledRect(r, color, plotProc, data);
 		return;
 	} else if (dy == 0) {
-		if (x1 > x2)
-			SWAP(x1, x2);
-		Common::Rect r(x1, y1, x2, y1 + thick - 1);
+		Common::Rect r(MIN(x1, x2), y1 - thick / 2, MAX(x1, x2), y1 + thick / 2);
 		drawFilledRect(r, color, plotProc, data);
 		return;
 	}