Index: src/gfx.cpp
===================================================================
--- src/gfx.cpp	(revision 27323)
+++ src/gfx.cpp	(working copy)
@@ -175,30 +175,24 @@
 
 	assert(width > 0);
 
+	/* Clipping rectangle. Slightly extended so we can ignore the width of the line. */
+	uint extra = CeilDiv(3 * width, 4); // not less then "width * sqrt(2) / 2"
+	Rect clip = { -extra, -extra, screen_width - 1 + extra, screen_height - 1 + extra };
+
 	if (y2 == y) {
 		/* Special case: horizontal line. */
-		blitter->DrawLine(video,
-				Clamp(x, 0, screen_width), y,
-				Clamp(x2, 0, screen_width), y2,
-				screen_width, screen_height, colour, width, dash);
+		if (y >= clip.top && y <= clip.bottom) blitter->DrawLine(video, x, y, x2, y, screen_width, screen_height, colour, width, dash);
 		return;
 	}
 	if (x2 == x) {
 		/* Special case: vertical line. */
-		blitter->DrawLine(video,
-				x, Clamp(y, 0, screen_height),
-				x2, Clamp(y2, 0, screen_height),
-				screen_width, screen_height, colour, width, dash);
+		if (x >= clip.left && x <= clip.right) blitter->DrawLine(video, x, y, x2, y, screen_width, screen_height, colour, width, dash);
 		return;
 	}
 
 	int grade_y = y2 - y;
 	int grade_x = x2 - x;
 
-	/* Clipping rectangle. Slightly extended so we can ignore the width of the line. */
-	uint extra = CeilDiv(3 * width, 4); // not less then "width * sqrt(2) / 2"
-	Rect clip = { -extra, -extra, screen_width - 1 + extra, screen_height - 1 + extra };
-
 	/* prevent integer overflows. */
 	int margin = 1;
 	while (INT_MAX / abs(grade_y) < max(abs(clip.left - x), abs(clip.right - x))) {