canvas::zoom(3tk) Variations on a canvas canvas::zoom(3tk)__________________________________________________________________________________________________________________________________________________NAME
canvas::zoom - Zoom control for canvas::sqmap
SYNOPSIS
package require Tcl 8.4
package require Tk 8.4
package require canvas::zoom ?0.1?
::canvas::zoom pathName ?options?
_________________________________________________________________DESCRIPTION
This package provides a widget to enable the user of a map display to control the zoom level.
API
::canvas::zoom pathName ?options?
Creates the zoom control widget pathName and configures it. The methods and options supported by the new widget are described in the
following sections.
The result of the command is pathName.
OPTIONS
-orient
The value for this option is either vertical, or horizontal, specifying the orientation of the major axis of the widget. The default
is vertical.
-levels
The value for this option is a non-negative integer. It specifies the number of zoom levels to support.
-variable
The value for this option is the name of a global or namespaced variable which is connected with the widget. changes to the zoom
level made the widget are propagated to this variable, and in turn changes to the variable are imported into the widget.
-command
This option specifies a command prefix. This callback will be invoked whenever the zoom level is changed. It is called with two
additional arguments, the zoom control widget, and the new zoom level, in this order.
METHODS
The widget supports no methods beyond the standard (configure, cget, etc.).
KEYWORDS
zoom
canvas 0.1 canvas::zoom(3tk)
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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 specifies 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 specifies 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 back-
ground, 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 viewport 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 displayed in multiple cells of the canvas.
canvasName image unset cell
Invoking this method declares the specified cell of the background 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 oper-
ated without a -grid-cell-command, as in that case the canvas 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 lifecy-
cle 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)