Building Applications with Oratcl and BLT

As promised, before we leave the world of Tk, we’ll create our own small application for measuring Oracle table space usage. Building this tool, which we’ll call TableSpacer, will extend our use of Tk beyond using downloaded applications as is. This example builds on two excellent Tcl/Tk products: George Howlett’s BLT, described in this section, and Tom Poindexter’s Oratcl, already described in Chapter 3.


BLT is an extension to Tcl/Tk that adds combinations of plotting widgets (graphs, barcharts, etc.) to Tk canvases, saving you hundreds—possibly thousands—of lines of code when creating a typical on-the-fly graph within a Tk canvas object. (Not only is BLT one of the best chart-making packages around, but also the letters BLT can apparently stand for anything you want them to.)

The following are the main web sites for BLT:

General information on the BLT package, upgrades, latest news, and so on.

Central download site for the latest BLT code releases and self-installing pre-compiled Windows executable files.

SourceForge site for all things Tcl/Tk. In this directory you will find two very useful PDF tutorial files (it’s the same tutorial in different layouts), handouts.pdf and slides.pdf.

BLT is also described in Paul Raines and Jeff Tranter’s Tcl/Tk in a Nutshell, referenced in Appendix C.

Installing BLT on Unix

Before you can install BLT, you must have the basic Tcl/Tk environment set up, as we described in Chapter 3. Then follow these steps:

  1. Download BLT from the download site listed earlier in this section.

  2. For the standard installation, issue these commands:

    $ gzip -d bltx.y.tar.gz
    $ tar xvf bltx.y.tar (this will create the bltx.y
    $ cd bltx.y
    $ ./configure --with-tcl=/usr/local/tcl -with-tk=/usr/local/tk

    There are further switches available for the configuration process. The two shown above assume that you have your previous Tcl and Tk installations in their own directories. (For customized installations, check out the README and INSTALL files.)

  3. Carrying on with the basic installation, run make and change directory as follows:

    $ make
    $ cd demos
  4. Before final installation, check that BLT has compiled correctly by running one or two of the example scripts. For example:

    $ ./graph3.tcl
  5. In Figure 4-30, we’ve run this demo graph under Windows. If this works out OK for you too, carry out the final step:

    $ make install

    This final step will install the necessary files in the /usr/local/blt directory (unless directed otherwise with a customized configuration -prefix=my_dir switch).

BLT’s graph3.tcl demo under Win32

Figure 4-30. BLT’s graph3.tcl demo under Win32

Installing BLT on Windows

Windows users can visit the site to find self-installing, precompiled versions of BLT, such as blt2.4u-for-8.3.exe. You can also compile BLT under Windows using various compilers, such as Microsoft VC++ 6.0 (see the INSTALL file again for more details). Before installing BLT on Win32, you must install Tcl/Tk for Win32 first. This is because the key BLT chart-generating program, bltwish, relies upon various Win32 DLL files already supplied by Tcl/Tk. If these DLL files are not present, BLT will simply not work.

In Figure 4-30, we’ve installed BLT under Win32 and then run graph3.tcl from the /demos directory of the standard source code installation tarball, which you may wish to download separately. You can also find these Windows self-installers at:

Using BLT

If you can think of a graph, BLT can probably produce it. BLT’s capabilities range from the most complex NASA Mars mission data charts to the simplest tablespace barcharts. However, BLT isn’t just about graphs. Figure 4-31 demonstrates what typical spline and barchart graphs look like, and Table 4-4 covers the Tcl extension capabilities of BLT. We’re only touching quickly on its capabilities here, though, and we urge you to learn more about this tool.

Examples of spline and barchart BLT graphs

Figure 4-31. Examples of spline and barchart BLT graphs

Table 4-4. BLT Command Summary



graph, barchart, stripchart

Plot various types of highly customizable barcharts that work with BLT vector data objects


Produces on-the-fly hierarchical trees


Generates tearable, notebook-style tabulated widgets in either multitiered or scrollable formats


Provides a geometry manager for widget layout


Creates and manipulates vectors, arrays of changing information for creating dynamic graphs


Enables external programs to be started in the background with monitored output


Locks out windows (preventing user interaction) when required


Provides encapsulated PostScript functionality


Enables dragging and dropping of widgets in Tk


Creates bitmaps for use within Tcl


Provides various types of window operation handling


Provides tracing functionality within Tcl/Tk


Enables logging and monitoring of triggered processes


Computes a spline curve, a graphical functionality for tying images to vectors


Provides a container for another application’s window


Manipulates properties of X Windows cut buffers


Rings bell on keyboard


Manipulates hypertext widgets, particularly for hyper-linking


A variety of tile widget commands corresponding to their Tk counterparts

Coding TableSpacer

In building the TableSpacer code in Example 4-4, we wanted a simple program based on Oratcl that would provide us with important at-a-glance information on tablespace usage within our database. If possible, we also wanted to be able to drill down on this data. To provide this functionality, we coded the program shown here (the corresponding comments should help you navigate your way through the code). The program performs the following steps:

  1. The necessary Tcl extensions are picked up (e.g., Oratcl and BLT are both available under Unix and Win32).

  2. Oratcl is used to log into the target database.

  3. A SQL cursor supplies the required graphical information.

  4. The cursed output information is plugged into graphical elements via BLT.

  5. Finally, the graph is displayed.

  6. Magical BLT graphical widgets are used to provide zooming capabilities.

Example 4-4. TableSpacer.tcl


package require Tcl
package require Tk

# Step 1 - Pick up the required packages Oratcl and BLT

package require Oratcl
package require BLT

# If we're on Tcl8.x, make use of the namespaces

if { $tcl_version >= 8.0 } {
    namespace import blt::*
    namespace import -force blt::tile::*

# Step 2 - Log on to the database

set userid "system/manager"
set env(ORACLE_SID) "orcl"

set handle [oralogon $userid]
set retcode [catch {set handle [oralogon $userid]}]

# Use BLT to initialize our graph.

set graph .graph

option add *graph.xTitle "Percentage Used"
option add *graph.yTitle "Tablespace"
option add *graph.title \
   "$env(ORACLE_SID) Tablespace Space Usage Percentages"
option add *graph.elemBackground white
option add *graph.elemRelief raised

set visual [winfo screenvisual .]
option add *print.background white

# Now create the barchart, and configure the labels

barchart $graph
$graph xaxis configure -command FormatLabel -descending true
$graph legend configure -hide yes

# Build our Oracle SQL cursor

set query_cursor [oraopen $handle]
orasql $query_cursor {
   select a.tablespace_name,
   from dba_free_space a, dba_data_files b
   where a.tablespace_name = b.tablespace_name and 
   a.file_id = b.file_id
   group by a.tablespace_name, a.file_id
   order by 1

set row [orafetch $query_cursor]

global names(  )
global values(  )

set i 0

# Step 3 - Run through the cursor and fill various arrays

while {$oramsg(rc) == 0} {

   set names($i)  [lindex $row 0]
   set values($i)  [lindex $row 1]

   puts [format "\n%20s %s" $names($i) $values($i)]

   set row [orafetch $query_cursor]
   incr i

global numTabsps
set numTabsps [ array size names ]

# Step 4 - Arrays now filled, build up the graph.

for { set i 0} { $i < $numTabsps } { incr i } {
    $graph element create $i \
        -data { { $numTabsps - $i } $values($i) } \
        -bg black \
        -relief raised \
        -bd 2

# Step 5 - Finish off the graph

table . \
    .graph 1,0 -fill both

table configure . r0 r2 -resize none
wm min . 0 0

# Step 6 - Add several BLT Graphical goodies :-)

Blt_ZoomStack $graph
Blt_Crosshairs $graph
Blt_ActiveLegend $graph
Blt_ClosestPoint $graph

# Format the column labels and stop them being numeric

proc FormatLabel { w value } {
   global names
   global numTabsps
   set i [expr $numTabsps - $value]
   return $names($i)
# That's all there is to it!!! 8-)

Figure 4-32 shows TableSpacer in action.

TableSpacer in action

Figure 4-32. TableSpacer in action

Running on Unix

Before running the program, make sure that the standard wish Tcl/Tk you’re using is able to display the chart, and also be sure that Oratcl can link up to the required Oracle libraries, as described earlier with Oddis:

$ DISPLAY=:0.0
$ export DISPLAY
$ LD_LIBRARY_PATH=/usr/local/lib:$ORACLE_HOME/lib

Under Unix (or Linux), the program should now run properly:

$ ./TableSpacer.tcl

Running on Windows

On Win32 systems, the same code will produce similar results (remember to use the bltwish program installed earlier, because the standard wish program will simply report errors):

C:\Temp>bltwish TableSpacer.tcl

TableSpacer in action

You can see the final TableSpacer program in action in Figure 4-32 for both Linux and Win32. Although the code in Example 4-4 is slightly involved, you may agree with us that this is a lot of bangs per buck. However the real Merlinesque magic of BLT is contained within the following program calls:


In Figure 4-33, we’ve demonstrated how, among many other things, these can give you the possibility of zooming in and out of your on-the-fly graphs ad infinitum via either right-clicks or left-clicks of your mouse.

BLT’s specialized cross-hair zoom option

Figure 4-33. BLT’s specialized cross-hair zoom option

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