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
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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)
Mac OS X 10.8 - Generated Wed Sep 5 15:51:04 CDT 2012