############################################################################
#
#	File:     drag.icn
#
#	Subject:  Procedures for dragging rectangles
#
#	Author:   Gregg M. Townsend
#
#	Date:     August 21, 1998
#
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#
#   This file is in the public domain.
#
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#
#	These procedures drag rectangular objects in a window.
#
#	Drag(x, y, w, h)		provides an opaque move.
#
#	DragOutline(x, y, w, h)		drags only the outline.
#
############################################################################
#
#  Drag(x, y, w, h) lets the user move a rectangular area using the
#  mouse.  Called when a mouse button is pressed, Drag() handles all
#  subsequent events until a mouse button is released.  As the mouse
#  moves, the rectangular area originally at (x,y,w,h) follows it
#  across the screen; vacated pixels at the original location are
#  filled with the background color.  The rectangle cannot be dragged
#  off-screen or outside the clipping region.  When the mouse button
#  is released, Drag() sets &x and &y to the upper-left corner of the
#  new location and returns.
#
#  DragOutline(x, y, w, h) lets the user move a reverse-mode rectangle
#  using the mouse.  Called when a mouse button is pressed, DragOutline
#  draws a reverse-mode rectangle inside the limits of the rectangle
#  (x,y,w,h) and handles all subsequent events until a mouse button is
#  released.  As the mouse moves, the rectangle follows it.  When the
#  mouse button is released, the rectangle disappears, and DragOutline
#  sets &x and &y to the upper-left corner of the new location.  It is
#  up to the calling program to update the display as necessary.
#
############################################################################
#
#  Requires: Version 9 graphics
#
############################################################################

link graphics


#  Drag(x, y, w, h) -- opaque drag

procedure Drag(win, x, y, w, h)			#: opaque rectangle drag
   local dx, dy, x0, y0, x1, y1
   local behind, xoff, yoff, xnew, ynew, xshift, yshift

   if type(win) ~== "window" then
      return Drag((\&window | runerr(140)), win, x, y, w)

   if w < 0 then
      x -:= (w := -w)
   if h < 0 then
      y -:= (h := -h)

   dx := WAttrib(win, "dx")
   dy := WAttrib(win, "dy")

   x0 := -dx				# set limits due to window size
   y0 := -dy
   x1 := WAttrib(win, "width") - dx - w
   y1 := WAttrib(win, "height") - dy - h

   x0 <:= \WAttrib(win, "clipx")	# adjust limits for clipping
   y0 <:= \WAttrib(win, "clipy")
   x1 >:= \WAttrib(win, "clipx") + \WAttrib(win, "clipw") - w
   y1 >:= \WAttrib(win, "clipy") + \WAttrib(win, "cliph") - h

   behind := ScratchCanvas(win, , , "__Drag__") |
      stop("can't get ScratchCanvas in Drag()")
   CopyArea(win, behind, -dx, -dy)
   Bg(behind, Bg(win))
   EraseArea(behind, x + dx, y + dy, w, h)

   xoff := x - &x
   yoff := y - &y

   until Event(win) === (&lrelease | &mrelease | &rrelease) do {

      # move the rectangle
      xnew := &x + xoff
      ynew := &y + yoff
      xnew <:= x0
      ynew <:= y0
      xnew >:= x1
      ynew >:= y1
      CopyArea(win, x, y, w, h, xnew, ynew)

      # repaint the area exposed by its movement
      xshift := xnew - x
      yshift := ynew - y

      if abs(xshift) >= w | abs(yshift) >= h then {

         # completely disjoint from new location
         CopyArea(behind, win, x + dx, y + dy, w, h, x, y)
         }

      else {

         # new area overlaps old
         if xshift > 0 then
            CopyArea(behind, win, x + dx, y + dy, xshift, h, x, y)
         else if xshift < 0 then
            CopyArea(behind, win,
               x + dx + w + xshift, y + dy, -xshift, h, x + w + xshift, y)
         if yshift > 0 then
            CopyArea(behind, win, x + dx, y + dy, w, yshift, x, y)
         else if yshift < 0 then
            CopyArea(behind, win,
               x + dx, y + dy + h + yshift, w, -yshift, x, y + h + yshift)
         }

      x := xnew
      y := ynew
      }

   EraseArea(behind)
   &x := x			
   &y := y
   return win
end


#  DragOutline(x, y, w, h) -- outlined drag

procedure DragOutline(win, x, y, w, h)		#: outlined rectangle drag
   local wrev, xoff, yoff

   if type(win) ~== "window" then
      return DragOutline((\&window | runerr(140)), win, x, y, w)

   if w < 0 then
      x -:= (w := -w)
   if h < 0 then
      y -:= (h := -h)

   wrev := Clone(win, "drawop=reverse")
   xoff := x - &x
   yoff := y - &y

   w -:= 1					# adjust Draw/Fill inconsistency
   h -:= 1

   DrawRectangle(wrev, x, y, w, h)		# draw initial rectangle
   until Event(wrev) === (&lrelease | &mrelease | &rrelease) do {
      DrawRectangle(wrev, x, y, w, h)		# erase old rectangle
      x := &x + xoff
      y := &y + yoff
      DrawRectangle(wrev, x, y, w, h)		# draw new rectangle
      }
   DrawRectangle(wrev, x, y, w, h)		# erase final rectangle
   Uncouple(wrev)

   &x := x			
   &y := y
   return win
end