- ScrollMinX = (int)(DisplayMinX - 0.5) * BaseWidth;
- ScrollMinY = (int)(DisplayMinY - 0.5) * BaseWidth;
- ScrollMaxX = (int)(DisplayMaxX + 1.5) * BaseWidth - SXSIZE;
- ScrollMaxY = (int)(DisplayMaxY + 1.5) * BaseWidth - SYSIZE;
+ int border1_offset = (menBorder ? 1 : 2);
+ int border2_offset = (menBorder ? 0 : TILESIZE / 2);
+
+ // scroll correction for border frame (1 tile) or border element (2 tiles)
+ ScrollMinX = 0;
+ ScrollMinY = 0;
+ ScrollMaxX = (DisplayMaxX + border1_offset - SCR_FIELDX) * TILEX;
+ ScrollMaxY = (DisplayMaxY + border1_offset - SCR_FIELDY) * TILEY;
+
+ // scroll correction for border element (half tile on left and right side)
+ ScrollMinX += border2_offset;
+ ScrollMinY += border2_offset;
+ ScrollMaxX -= border2_offset;
+ ScrollMaxY -= border2_offset;
+
+ // scroll correction for even number of visible tiles (half tile shifted)
+ ScrollMinX -= game_sp.scroll_xoffset;
+ ScrollMaxX -= game_sp.scroll_xoffset;
+ ScrollMinY -= game_sp.scroll_yoffset;
+ ScrollMaxY -= game_sp.scroll_yoffset;