تعلم الأوراكل بالعربى: SCROLL

الـ SCROLL_VIEW Built-in تقوم بتحريك الـ View فى الـ Canvas التى بها على حسب الاتجاه المحدد فى معامل الـ X و الـ Y ، و يؤدى ذلك بدوره الى أظهار بعض المناطق من الـ Canvas التى كانت مخفية الى الـ End User ، و لكنه فى نفس الوقت لا يغير من وضع - Position - الـ View بالنسبة للـ Window.

هذا الأجراء يظهر كيفية أستخدام الـ SCROLL_VIEW Built-in



/* 
** Built-in: SCROLL_VIEW 
** Example: Scroll the view whose name is passed in 10% to 
** the right or left depending on the 'direction' 
** parameter. 
*/ 
PROCEDURE Scroll_ten_percent 
     (viewname   VARCHAR2, 
      direction  VARCHAR2) 
IS 
  vw_id        VIEWPORT; 
  vw_wid       NUMBER; 
  vw_x         NUMBER; 
  cn_id        CANVAS; 
  cn_wid       NUMBER; 
  ten_percent  NUMBER; 
  new_x        NUMBER; 
  old_y        NUMBER; 
BEGIN 
  /* 
** Get the id's for the View and its corresponding canvas 
*/ 
  vw_id := Find_view(viewname); 
   
  cn_id := Find_canvas(viewname); 
   
  /* 
** Determine the view width and corresponding canvas 
** width. 
*/ 
  vw_wid := Get_view_property(vw_id,width); 
   
  cn_wid := Get_canvas_property(cn_id,width); 
   
  /* 
** Calculate how many units of canvas width are outside of 
** view, and determine 10% of that. 
*/ 
  ten_percent := 0.10 * (cn_wid - vw_wid); 
   
  /* 
** Determine at what horizontal position the view 
** currently is on the corresponding canvas 
*/ 
  vw_x := Get_view_property(vw_id,viewport_x_pos_on_canvas); 
   
  /* 
** Calculate the new x position of the view on its canvas 
** to effect the 10% scroll in the proper direction. 
** Closer than ten percent of the distance to the edge 
** towards which we are moving, then position the view 
** against that edge. 
*/ 
  IF direction = 'LEFT' THEN 
    IF vw_x > ten_percent THEN 
      new_x := vw_x - ten_percent; 
    ELSE 
      new_x := 0; 
    END IF; 
  ELSIF direction = 'RIGHT' THEN 
    IF vw_x < cn_wid - vw_wid - ten_percent THEN 
      new_x := vw_x + ten_percent; 
    ELSE 
      new_x := cn_wid - vw_wid; 
    END IF; 
  END IF; 
   
  /* 
** Scroll the view that much horizontally 
*/ 
  old_y := Get_view_property(vw_id,viewport_y_pos_on_canvas); 
   
  Scroll_view(vw_id,new_x,old_y); 
END;