for (i=-40;  i<280;i++) GrayDrawClipLine(120,64,i,-40,used_color);
        for (i=-40;  i<168;i++) {if (i >= 13) GrayDrawClipLine(120,64,280,i,used_color);}
        for (i=280;i>=-40; i--) GrayDrawClipLine(120,64,i,168,used_color);
        for (i=168;i>=-40; i--) GrayDrawClipLine(120,64,-40,i,used_color);

and

        for (i=-40;  i<280;i++) {rect.x1 = i; DrawClipLine(&rect,&(SCR_RECT){{0, 0, 239, 127}},A_XOR); }
        for (i=-40;  i<168;i++) if (i >= 13) {rect.y1 = i; DrawClipLine(&rect,&(SCR_RECT){{0, 0, 239, 127}},A_XOR); }
        for (i=280;i>=-40; i--) {rect.x1 = i; DrawClipLine(&rect,&(SCR_RECT){{0, 0, 239, 127}},A_XOR); }
        for (i=168;i>=-40; i--) {rect.y1 = i; DrawClipLine(&rect,&(SCR_RECT){{0, 0, 239, 127}},A_XOR); }

fix the crashes, but some lines from the top-right and bottom-left corners (drawn by the first and third lines) are missing, and a bit of garbage is drawn at the top-left border of the screen. That shouldn't happen