canvas_sqmap man page on MacOSX

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canvas::sqmap(n)	    Variations on a canvas	      canvas::sqmap(n)

______________________________________________________________________________

NAME
       canvas::sqmap - Canvas with map background based on square tiles

SYNOPSIS
       package require Tcl  8.4

       package require Tk  8.4

       package require snit

       package require uevent::onidle

       package require cache::async

       package require canvas::sqmap  ?0.3.1?

       ::canvas::sqmap pathName ?options?

       canvasName image set cell image

       canvasName image unset cell

       canvasName flush

_________________________________________________________________

DESCRIPTION
       This package provides an extended canvas widget for the display of maps
       based on a set of square image tiles. The tiles are the	background  of
       the  canvas, with all other canvas items added always shown in front of
       them. The number of tiles shown, tile size, and where to get the images
       to show are all configurable.

API
       ::canvas::sqmap pathName ?options?
	      Creates  the  canvas  pathName and configures it. The new widget
	      supports all of the options and methods  of  a  regular  canvas,
	      plus the options and methods described below.

	      The result of the command is pathName.

   OPTIONS
       -grid-cell-width
	      The  value  for this option is a non-negative integer. It speci‐
	      fies the width of the cells the background is made up of.

       -grid-cell-height
	      The value for this option is a non-negative integer.  It	speci‐
	      fies the height of the cells the background is made up of.

       -grid-cell-command
	      The  value  for  this  option is a command prefix. It is invoked
	      whenever the canvas needs the image for a specific cell  of  the
	      background,  with	 two additional arguments, the id of the cell,
	      and a command prefix to invoke when the image is ready, or known
	      to not exist.

	      The  id  of  the cell is a 2-element list containing the row and
	      column number of the cell, in this  order.  The  result  command
	      prefix  (named "$result" in the example below) has to be invoked
	      with either two or three arguments, i.e.

		  $result set	$cellid $image ; # image is known and ready
		  $result unset $cellid	       ; # image does not exist

	      This option may be left undefined, i.e. the canvas  can  operate
	      without it. In that case the only images shown in grid cells are
	      those explicitly set with the method image  set,	see  the  next
	      section. All other grid cells will simply be empty.

       -viewport-command
	      This  option specifies a command prefix to invoke when the view‐
	      port of the canvas is changed, to	 allow	users  keep  track  of
	      where  in	 the  scroll-region  we	 are at all times. This can be
	      used, for example, to drive derivate displays, or to keep	 items
	      in view by moving them as the viewport moves.

       -image-on-load
	      The value for this option is an image. If specified the image is
	      shown in a cell while the actual image for that cell is  getting
	      loaded through the callback specified by the -grid-cell-command.

       -image-on-unset
	      The value for this option is an image. If specified the image is
	      shown in a cell for which the callback specified by  the	-grid-
	      cell-command reported that there is no actual image to be shown.

   METHODS
       canvasName image set cell image
	      Invoking this method places the image into the specified cell of
	      the background. The cell is given as a 2-element list containing
	      row and column number, in this order.

	      Note  that  an  image  is allowed to be associated with and dis‐
	      played in multiple cells of the canvas.

       canvasName image unset cell
	      Invoking this method declares the specified cell	of  the	 back‐
	      ground  as  empty,  an existing image shown by this cell will be
	      forgotten.  The cell is given as a 2-element list containing row
	      and column number, in this order.

       canvasName flush
	      Invoking	this method forces the canvas to completely reload the
	      images for all cells. Do not use this method if  the  canvas  is
	      operated	without a -grid-cell-command, as in that case the can‐
	      vas will simply forget all images without being able  to	reload
	      them.

IMAGE OWNERSHIP
       Note  that the canvas does not take ownership of the images it shows in
       the background. In other words, when we say that the canvas forgets  an
       image  this  means  only	 that  the association between a grid cell and
       shown image is broken. The image is not deleted. Managing the lifecycle
       of  the images shown by the canvas is responsibility of the user of the
       canvas.

KEYWORDS
       canvas, cell, grid, image, map, square map, tile

canvas				     0.3.1		      canvas::sqmap(n)
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