Don't draw foreground in case it is same as background

investigatin of #26, but still need some amount of work

src/render/mod.rs

@@ -152,12 +152,14 @@ fn draw_cell(
     } else if !line.is_binded_to_item(col) {
         let bg = color_model.cell_bg(cell);
         if let Some(bg) = bg {
+            if bg != &color_model.bg_color {
                 ctx.set_source_rgb(bg.0, bg.1, bg.2);
                 ctx.rectangle(line_x, line_y, char_width, line_height);
                 ctx.fill();
             }
         }
     }
+}
 
 pub fn shape_dirty(
     ctx: &context::Context,