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INNER {returnImm {Unknow state transition: LINE -> END} {}} CALL {my render_wikit {Tk Sets The Standard by Cameron Laird and Kathryn Soraiz} \ \ \ Title:\ TkSets\ The\ Standard\n\ \ \ Author:\ Cameron\ Laird\n\ \ \ Author:\ Kathryn\ Soraiz\n\ \ \ When:\ 2001-04-13\n\ \ \ At:\ \[http://www.itworld.com/uir000804tk%|%itworld%|%\]\n\n\n**\ Article\ Content\ **\n\nTk\ is\ similar\ to\ Qt\ and\ Motif,\ the\ first\ two\ toolkits\ reviewed\ in\ this\ series,\ in\ that\ it\ is\ a\ library\ coded\ in\ C\ that\ implements\ a\ collection\ of\ widgets.\ However,\ unlike\ Qt\ and\ Motif,\ Tk\ is\ known\ by\ most\ programmers\ through\ its\ binding\ to\ the\ Tcl\ scripting\ language,\ rather\ than\ through\ C\ itself.\n\n\nIt\ is\ widely\ believed\ that\ Tk\ is\ slow\ because\ it\ is\ used\ with\ a\ scripting\ language\ and\ scripting\ languages\ don't\ perform\ like\ C\ or\ assembly.\ This\ is\ simply\ not\ true\ --\ Tk\ is\ comparable\ in\ speed\ to\ other\ leading\ toolkits.\ In\ fact,\ it's\ considerably\ zippier\ than\ Java's\ Abstract\ Windowing\ Toolkit\ (AWT).\ Moreover,\ because\ Tk's\ design\ intentionally\ emphasizes\ easy\ use\ for\ common\ design\ situations,\ Tk\ is\ ripe\ for\ optimization.\ As\ a\ result,\ many\ Tcl/Tk\ applications\ are\ faster\ than\ their\ Motif-based\ counterparts.\n\n\nJohn\ Ousterhout,\ a\ professor\ at\ the\ University\ of\ California\ at\ Berkeley,\ created\ Tcl\ and\ Tk\ in\ the\ late\ 1980s\;\ since\ then,\ users\ and\ developers\ of\ Tcl\ and\ Tk\ have\ generally\ belonged\ to\ the\ same\ demographic.\ The\ toolkits\ are\ not\ identical,\ though.\ Many\ Tk\ programmers\ base\ their\ work\ on\ C,\ Perl,\ Python,\ Ruby,\ Lua,\ or\ Scheme.\ Two\ recent,\ well-received\ books\ on\ Tk\ development\ are\ aimed\ at\ Perl\ and\ Python\ programmers,\ rather\ than\ those\ working\ with\ Tcl.\n\n\nSo\ it\ can\ be\ advantageous\ to\ understand\ the\ roots\ Tk\ shares\ with\ Tcl,\ but\ it's\ not\ necessary\ to\ use\ one\ with\ the\ other.\ Some\ Tk\ characteristics\ are\ bound\ to\ Tcl\;\ some\ are\ more\ generally\ available.\n\n\nPortability\ sets\ Tk\ apart\ from\ other\ toolkits\ --\ it\ is\ more\ portable\ than\ any\ other\ contemporary\ GUI\ toolkit,\ even\ AWT.\ Good\ Tk\ implementations\ are\ available\ for\ all\ Unixes,\ as\ well\ as\ for\ Windows,\ Mac\ OS,\ OpenVMS,\ and\ other\ more\ specialized\ operating\ systems.\n\n\nThat\ dominance\ seems\ likely\ to\ change:\ Java\ Virtual\ Machines\ continue\ to\ improve,\ and\ Qt\ and\ wxWindows\ seem\ to\ be\ on\ course\ to\ release\ Mac\ OS\ versions.\ Tk's\ Mac\ OS\ distribution\ has\ appeared\ to\ weaken\ over\ the\ last\ year.\ Few\ developers\ have\ contributed\ to\ its\ maintenance,\ and\ despite\ frequent\ inquiries\ about\ a\ Tk\ for\ the\ Palm\ OS,\ one\ doesn't\ seem\ likely\ to\ emerge\ soon.\n\n\nOn\ the\ other\ hand,\ Tk\ is\ currently\ undergoing\ its\ most\ significant\ change\ since\ it\ was\ first\ ported\ to\ the\ Mac\ OS\ in\ the\ mid-'90s.\ The\ TkGS\ team,\ led\ by\ Frédéric\ Bonnet,\ is\ reworking\ Tk's\ internal\ design\ to\ improve\ performance\ and\ maintainability.\ It\ is\ widely\ anticipated\ that\ once\ this\ is\ completed,\ Tk\ ports\ to\ Microwindows\ or\ Nanox\ will\ be\ quick\ and\ nimble.\ And\ besides\ the\ complete\ TkGS\ rewrite,\ one\ group\ is\ investigating\ the\ possibility\ of\ a\ rapid\ port\ to\ Microwindows\ or\ Nanox\ from\ the\ current\ code\ base.\n\n\nTk,\ clearly\ in\ the\ lead\ right\ now\ with\ regards\ to\ portability,\ is\ also\ a\ favorite\ among\ developers\ striving\ for\ platform\ neutrality.\n\n***\ Expressiveness\ and\ wise\ defaults\ ***\n\nAnother\ benefit\ of\ Tk\ is\ its\ conciseness.\ The\ classic\ minimal\ Tk\ application\ is\ indeed\ tiny:\n\n======\npack\ \[button\ .mybutton\ -text\ Bye-bye\ -command\ exit\]\n======\n\nThis\ is\ a\ small\ but\ complete\ program\ in\ Tcl/Tk\ that\ puts\ a\ button\ on\ the\ screen\ and\ exits\ when\ the\ button\ is\ pushed,\ with\ proper\ behavior\ for\ iconifying,\ clicking,\ and\ other\ GUI\ conventions.\n\n\nThis\ economy\ of\ expression\ has\ two\ aspects.\ One\ is\ its\ realization\ in\ a\ scripted\ binding.\ All\ GUI\ toolkits\ look\ powerful\ in\ a\ good\ binding\ with\ a\ scripting\ language.\ Typical\ lessons\ in\ Motif\ programming\ require\ explanation\ of\ compilation,\ .h\ headers,\ string\ representations,\ and\ memory\ management\ before\ a\ beginner\ even\ attempts\ to\ create\ a\ working\ application.\ This\ mainly\ reflects\ the\ difference\ between\ C's\ tedium\ and\ other\ scripting\ languages.\n\n\nThe\ second\ aspect\ is\ that\ even\ apart\ from\ its\ usual\ exposure\ through\ a\ scripting\ language,\ Tk\ is\ remarkably\ concise.\ Ousterhout\ deliberately\ defined\ Tk\ to\ behave\ reasonably\ with\ default\ values.\ Tk\ programmers\ often\ write\ skeletal\ implementations\ and\ fill\ in\ details\ as\ requirements\ emerge.\ Tk\ encourages\ this\ style\ more\ than\ any\ other\ toolkit.\ This\ complements\ the\ scripting\ language\ bindings\ nicely,\ because\ these\ languages\ are\ more\ flexible\ than\ C,\ which\ has\ defined\ sequences\ of\ formal\ parameters.\ Scripting\ languages\ are\ comfortable\ with\ variable\ numbers\ of\ arguments,\ default\ arguments,\ and\ arguments\ of\ variable\ type.\ Tk\ uses\ this\ freedom\ wisely.\n\n\nOne\ testimony\ to\ the\ power\ of\ this\ incrementalism\ is\ the\ number\ of\ programmers\ who\ use\ Tk\ by\ accident.\ We\ hear\ many\ anecdotes\ of\ developers\ who\ choose\ Tk\ as\ a\ quick\ prototyping\ tool,\ then\ discover\ they're\ able\ to\ complete\ a\ full-blown\ application\ by\ refinement\ of\ the\ prototype.\n\n***\ Getting\ the\ most\ from\ Tk\ ***\n\nEffective\ Tk\ programming\ depends\ on\ several\ specific\ technical\ concepts:\n\n\ \ \ *\ The\ power\ of\ the\ text\ and\ canvas\ widgets\n\ \ \ *\ Geometry\ management\n\ \ \ *\ Event\ binding\n\n\nTk\ has\ a\ modest\ complement\ of\ widgets.\ The\ core\ Tk\ distribution\ lacks\ widgets\ for\ tree\ display,\ SpinBox,\ ComboBox,\ graphing,\ and\ several\ others\ that\ are\ now\ commonplace.\ One\ frequent\ complaint\ about\ Tk\ is\ that\ it\ has\ \"become\ rather\ lackluster\ in\ the\ age\ in\ terms\ of\ core\ features,\"\ according\ to\ Jeffrey\ Hobbs\ of\ Ajuba\ Solutions.\ However,\ the\ Tk\ text\ and\ canvas\ are\ so\ powerful,\ and\ Tk\ so\ extensible,\ that\ developers\ have\ lived\ without\ new\ features\ by\ relying\ on\ free\ extensions.\n\n***\ text\ and\ canvas\ powerhouses\ ***\n\n`text's`\ capabilities\ lie\ somewhere\ between\ those\ of\ Java's\ `TextArea`\ and\ `JEditorPane`.\ Text\ embeds\ both\ a\ compact\ visual\ editor\ and\ an\ HTMLv2\ display\ engine,\ and\ defines\ sophisticated\ tag\ programming,\ making\ visual\ effects\ easy.\ text's\ full\ Unicode\ capabilities\ helped\ internationalize\ it\ a\ couple\ of\ years\ ago\ with\ the\ 8.1\ release.\n\n\nIt's\ important\ to\ distinguish\ between\ different\ notions\ of\ \"graphical\"\ when\ discussing\ GUIs.\ One\ usage\ implies\ form-based\ GUI\ programming\ and\ expresses\ the\ difference\ between\ old\ curses\ or\ IBM\ 3270-based\ applications\ and\ typical\ Web\ browsers.\ Browsers\ depend\ on\ cursor\ movement\ and\ selection\ by\ clicking.\ Tk's\ text\ and\ related\ widgets\ such\ as\ button\ and\ label\ suffice\ for\ most\ form-based\ GUI\ programming.\n\n\nApplications\ in\ geographic\ information\ systems,\ electronic\ design\ automation,\ and\ complex\ visualization\ require\ a\ second\ level\ of\ graphics\ to\ display\ and\ manage\ arbitrary\ drawings\ such\ as\ maps,\ engineering\ diagrams,\ and\ images.\ Many\ successful\ programmers\ work\ only\ on\ form-based\ office\ automation\ tasks.\ However,\ Tk's\ canvas\ can\ help\ those\ with\ more\ general\ needs.\n\n\ncanvas\ is\ like\ text\ in\ that\ it\ embeds\ much\ functionality,\ unified\ by\ analogous\ programmability\ in\ terms\ of\ tags\ and\ configuration\ attributes.\ Tk\ is\ the\ established\ basis\ for\ successful\ commercial\ GUI\ applications,\ many\ of\ which\ have\ stringent\ requirements\ for\ scale\ and\ performance.\ One\ is\ Red\ Hat's\ Source-Navigator\ IDE\ (integrated\ development\ environment),\ used\ with\ all\ programming\ languages.\ Red\ Hat\ engineer\ Mo\ DeJong\ recently\ wrote,\ \"We\ are\ really\ pushing\ to\ make\ it\ the\ default\ IDE\ for\ Linux.\"\n\n***\ Geometry\ ***\n\nTk's\ fans\ also\ laud\ the\ toolkit\ for\ its\ geometry\ management.\ Geometry\ is\ the\ positioning\ of\ widgets\ on\ the\ visual\ screen.\ Windows's\ Visual\ Basic\ is\ reputedly\ easy\ for\ beginners\ because\ of\ its\ IDE's\ facility\ for\ dragging\ and\ dropping\ widgets\ into\ a\ form.\ However,\ due\ to\ its\ inflexibility\ in\ managing\ windows\ of\ variable\ sizes,\ this\ approach\ is\ severely\ limited\ in\ building\ professional\ applications.\n\n\nTk,\ by\ contrast,\ offers\ a\ variety\ of\ geometry\ managers,\ most\ of\ which\ can\ intelligently\ handle\ window\ resizing.\ It's\ typical\ in\ Tk\ to\ code\ such\ elements\ as:\n\n======\npack\ \$save_button\ \$cancel_button\ \$help_button\ \\\n\ \ \ \ -side\ left\ -fill\ both\ -expand\ yes\n======\n\nThis\ places\ three\ buttons\ in\ a\ sequence\ from\ left\ to\ right.\ Tk\ makes\ sure\ that\ the\ buttons\ are\ symmetrical\ and\ that\ they\ adjust\ properly\ to\ size\ changes.\n\n\nTk's\ geometry\ management\ is\ so\ widely\ admired,\ one\ common\ complaint\ heard\ about\ Java\ is\ that\ it\ still\ doesn't\ do\ geometry\ well,\ even\ though\ it's\ had\ at\ least\ five\ years\ to\ learn\ from\ Tk.\n\n***\ Events\ ***\n\nEvent\ handling\ distinguishes\ between\ different\ GUI\ toolkits.\ The\ programming\ model\ for\ all\ GUI\ systems\ has\ them\ wait\ for,\ receive,\ and\ communicate\ events\ to\ small\ pieces\ of\ code,\ or\ callbacks.\ Tk's\ event\ handling\ resembles\ its\ other\ programming\ constructs:\ its\ concisely\ expressed\ default\ actions\ are\ adequate\ for\ many\ situations,\ and\ more\ flexibility\ is\ available\ if\ necessary.\ In\ the\ one-line\ program\ near\ the\ top\ of\ this\ article,\ the\ -command\ exit\ phrase\ says,\ \"When\ someone\ pushes\ the\ button,\ perform\ the\ Tcl\ procedure\ named\ 'exit.'\"\ This\ command\ callback\ can\ hold\ arbitrarily\ complex\ instructions.\ A\ PerlTk\ program\ might\ read:\n\n======perl\n\$window->Button(-command\ =>\ sub\ \{\n\ \ \ \ sub1()\;\n\ \ \ \ sub2()\;\n\ \ \ \ #\ Do\ still\ other\ things.\n\ \ \ \ subn()\;\n\})->pack\n======\n\n\nThe\ flexibility\ is\ dual,\ which\ means\ one\ can\ associate\ arbitrary\ callbacks\ to\ standard\ events,\ as\ well\ as\ precisely\ manage\ the\ events\ an\ application\ recognizes.\ Tk's\ bind\ command\ can\ program\ the\ Enter\ key\ to\ duplicate\ an\ on-screen\ button\ click:\n\n======\nbind\ \$my_button\ <Key-Return>\ \"\$my_button\ invoke\"\n======\n\nThis\ precise,\ programmatic\ control\ gives\ Tk\ a\ great\ advantage\ in\ constructing\ highly\ responsive\ GUIs.\ Tk\ makes\ it\ easy\ to\ \"gray\ out\"\ buttons\ for\ actions\ that\ temporarily\ don't\ make\ sense,\ program\ hot\ spots\ on\ a\ screen,\ and\ generally\ implement\ what\ Bell\ Labs\ researcher\ Brian\ Kernighan\ calls\ intelligent\ GUIs,\ which\ are\ sensitive\ to\ context.\n\nState\ of\ the\ toolkit\ 2000\n\nHobbs's\ own\ history\ with\ Tk\ is\ typical.\ \"I\ was\ originally\ a\ C/Motif\ programmer.\ Once\ I\ learned\ Tk,\ I\ never\ did\ another\ project\ in\ Motif,\"\ he\ said.\ In\ fact,\ one\ Tcl\ insider\ claims\ to\ have\ once\ overheard\ Tim\ O'Reilly\ of\ O'Reilly\ &\ Associates\ (ORA)\ saying\ that\ Tk's\ introduction\ cut\ the\ sales\ of\ ORA\ Motif\ manuals.\n\n\nThe\ future\ of\ Tk\ is\ uncertain,\ though.\ Recent\ generations\ of\ programmers,\ based\ in\ Windows\ and\ Linux,\ tend\ to\ regard\ Tk\ applications\ as\ old-fashioned\ in\ appearance.\ The\ absence\ of\ an\ officially\ supported\ drag-and-drop\ visual\ builder\ for\ Tk\ is\ a\ barrier\ for\ many.\ Tk's\ commitment\ to\ Mac\ OS\ support\ seems\ tentative,\ and\ other\ toolkits\ are\ improving\ their\ portability.\ Where\ does\ this\ leave\ Tk\ in\ the\ year\ 2000?\n\n\nHobbs\ said:\n===\n\ \ \ \ Tk\ has\ a\ rich\ set\ of\ extensions\ that\ expand\ the\ widget\ set\ considerably\ ...\ Many\ of\ the\ complaints\ that\ Tk\ hasn't\ aged\ well\ are\ fairly\ near-sighted,\ because\ they\ never\ take\ account\ of\ the\ wealth\ of\ widget\ extensions\ available.\ Hopefully\ the\ new\ sumo\ Tcl\ distribution\ will\ finally\ address\ those\ concerns,\ along\ with\ fostering\ a\ more\ open\ development\ community\ that\ is\ interested\ in\ working\ with\ a\ larger\ Tcl\ distribution.\ \n===\n\nSo\ the\ Tcl\ development\ community\ is\ reorganizing\ itself\ to\ accelerate\ release\ cycles.\ Moreover,\ Hobbs\ and\ his\ colleagues\ are\ repackaging\ Tcl\ distributions\ to\ make\ popular\ extensions\ more\ accessible\ to\ nonexperts.\ \"8.4\ should\ be\ the\ first\ distribution\ that\ has\ a\ coexisting\ 'batteries\ included'\ release,\"\ said\ Hobbs.\ \"Major\ extensions\ that\ work\ with\ TEA\ (Tcl\ Extension\ Architecture)\ would\ be\ gathered\ together\ and\ all\ released.\"\n\n\nThose\ aren't\ the\ only\ structural\ changes.\ Tk's\ stewards\ are\ working\ to\ capture\ more\ of\ the\ open\ source\ buzz\ competing\ toolkits\ now\ receive.\ Consolidation\ of\ the\ internationalization\ and\ performance\ benefits\ of\ versions\ 8.0\ to\ 8.2\ has\ already\ led\ to\ opportunities\ for\ specific\ new\ features.\ Hobbs\ reported,\ \"More\ recently,\ the\ core\ of\ Tk\ incorporated\ popular\ paths\ that\ enhanced\ the\ existing\ widget\ set.\ The\ entry\ widget\ can\ validate\ input\ easier\ than\ before,\ the\ already\ feature-rich\ canvas\ receives\ even\ more\ features,\ the\ list\ box\ gets\ individualized\ color,\ and\ the\ text\ widget\ can\ now\ have\ hidden\ text\ fields.\"\ The\ official\ 8.4\ release\ is\ scheduled\ to\ include\ a\ new\ megawidget\ system\ \"to\ make\ Tcl-level\ \[graphical\ extensions\]\ easier\ to\ create\ than\ ever\ before.\"\n\n\nHobbs\ concluded,\ \"Tk\ is\ a\ simple\ and\ elegant\ UI\ toolkit\ that\ works\ across\ platforms\ without\ any\ code\ changes.\ Development\ time\ for\ a\ Tk\ app\ is\ significantly\ less\ than\ for\ the\ equivalent\ Java\ or\ C++\ UI\ toolkit\ app.\"\n\n***\ Broader\ context\ ***\n\nTk\ can\ certainly\ hold\ its\ own\ with\ other\ GUI\ toolkits.\ Its\ variety\ of\ available\ language\ bindings\ means\ almost\ anyone\ curious\ about\ Tk\ can\ quickly\ find\ a\ version\ in\ a\ familiar\ language.\ It\ only\ takes\ a\ few\ minutes\ to\ begin\ producing\ meaningful\ applications,\ and\ there\ are\ plenty\ of\ books\ and\ tutorials\ to\ help.\n\n\nHowever,\ there's\ a\ broader\ context\ that,\ at\ least\ temporarily,\ falsifies\ some\ of\ what\ we've\ already\ written\ --\ for\ the\ last\ couple\ of\ years,\ our\ true\ toolkit\ of\ choice\ was\ not\ Tk,\ but\ HTML.\ As\ Tim\ O'Reilly\ told\ us\ about\ the\ aforementioned\ incident\ regarding\ Motif\ book\ sales,\ \"I\ don't\ remember\ saying\ anything\ of\ the\ sort\ ...\ What\ eventually\ wounded\ both\ Tk\ and\ Motif,\ perhaps\ fatally,\ was\ the\ rise\ of\ the\ Web,\ which\ took\ the\ frontier\ of\ application\ development\ away\ from\ the\ desktop\ and\ put\ it\ instead\ in\ the\ browser-server\ interaction.\"\n\n\nThe\ current\ Silicon\ Valley\ rush\ to\ Webification\ is\ as\ silly\ as\ the\ aversion\ to\ the\ same\ architecture\ displayed\ by\ large\ corporations\ just\ a\ few\ years\ ago.\ Plenty\ of\ applications\ require\ the\ rich\ feature\ set\ of\ a\ toolkit\ such\ as\ Tk.\n\n\nThere's\ no\ doubt,\ though,\ that\ fashion\ can\ dominate\ computing\ for\ long\ stretches.\ One\ can\ easily\ conceive\ of\ a\ world\ that\ turns\ its\ back\ on\ Tk.\ The\ toolkit's\ usage\ might\ become\ limited\ to\ a\ core\ of\ developers\ and\ administrators\ who\ realize\ its\ indispensability\ for\ extremely\ rapid\ production\ of\ portable,\ intelligent,\ fully\ internationalized,\ visually\ well-behaved\ GUI\ applications.\n\n\nThere\ are\ at\ least\ a\ couple\ more\ wrinkles\ in\ this\ speculation.\ O'Reilly\ is\ one\ of\ many\ commentators\ to\ foresee\ open\ source\ Mozilla\ as\ the\ basis\ for\ the\ standardized\ toolkit\ of\ the\ future.\ This\ might\ make\ Tk\ more\ popular\ than\ ever,\ because\ Steve\ Ball\ of\ Zveno\ is\ working\ with\ TkGecko\ to\ create\ a\ Tk\ extension\ that\ allows\ the\ NewLayout\ rendering\ engine\ to\ be\ embedded\ in\ a\ Tk\ application\ as\ a\ Tk\ widget.\ Ball\ hopes\ this\ new\ widget\ will\ be\ as\ configurable\ as\ other\ Tk\ widgets,\ with\ all\ configuration\ options\ able\ to\ be\ queried\ and\ changed\ at\ runtime.\n\n\nThere\ are\ several\ interesting\ client-side\ Tk\ Web\ stories.\ The\ Tk\ plug-in\ is\ a\ module\ compatible\ with\ Microsoft's\ Internet\ Explorer\ and\ Netscape\ Navigator,\ which\ allows\ Web\ presentations\ to\ be\ scripted\ in\ Tcl,\ as\ they\ are\ currently\ done\ in\ JavaScript.\ The\ plug-in,\ a\ remarkably\ capable\ extension,\ has\ proved\ itself\ in\ several\ production\ systems.\ Although\ its\ maintenance\ was\ largely\ dormant\ for\ a\ couple\ of\ years,\ Ajuba\ is\ now\ making\ it\ compatible\ with\ the\ latest\ browser\ and\ Tk\ versions.\n\n***\ Summary\ ***\n\nTk's\ prospects\ involve\ so\ many\ free\ variables\ that\ the\ toolkit's\ future\ defies\ predictions.\ What's\ certain\ is\ that\ Tk's\ fans\ find\ the\ toolkit\ exceptionally\ useful\ right\ now,\ and\ that\ new\ widgets,\ books,\ and\ language\ bindings\ are\ making\ it\ easier\ for\ a\ newcomer\ to\ learn\ and\ for\ a\ mature\ programmer\ to\ use\ expertly.\n\n***\ Resources\ ***\n\n\ \ \ *\ Cameron\ Laird's\ personal\ notes\ on\ Tk:\ http://starbase.neosoft.com/~claird/comp.lang.tcl/tk.html\n\ \ \ *\ Cameron\ Laird's\ personal\ notes\ on\ Motif:\ http://starbase.neosoft.com/~claird/comp.windows.x.motif/motif.html\n\ \ \ *\ \"Qt\ 2.x\ and\ Python\ 1.6\ bind\ together\ well,\"\ Boudewijn\ Rempt\ and\ Cameron\ Laird:\ http://www.itworld.com/AppDev/4073/UIR000530qt/\n\ \ \ *\ John\ K.\ Ousterhout:\ http://www.scriptics.com/people/john.ousterhout\n\ \ \ *\ wxWindows\ Home:\ http://www.wxwindows.org\n\ \ \ *\ TkGS\ Specification:\ the\ Tk\ Graphics\ System:\ http://www.multimania.com/fbonnet/Tcl/TkGS/specs.htm\n\ \ \ *\ Cameron\ Laird's\ personal\ notes\ on\ Scriptics\ Corporation\ (or\ Ajuba\ Solutions):\ http://starbase.neosoft.com/~claird/comp.lang.tcl/scriptics.html\n\ \ \ *\ Red\ Hat's\ and\ Cygnus\ Solutions'\ Source-Navigator:\ http://www.cygnus.com/sn\n\ \ \ *\ Zveno\ XML\ tools\ and\ training:\ http://www.zveno.com\n\ \ \ *\ TkGecko:\ http://www.usenix.org/publications/library/proceedings/tcl2k/ball.html regexp2} CALL {my render {Tk Sets The Standard by Cameron Laird and Kathryn Soraiz} \ \ \ Title:\ TkSets\ The\ Standard\n\ \ \ Author:\ Cameron\ Laird\n\ \ \ Author:\ Kathryn\ Soraiz\n\ \ \ When:\ 2001-04-13\n\ \ \ At:\ \[http://www.itworld.com/uir000804tk%|%itworld%|%\]\n\n\n**\ Article\ Content\ **\n\nTk\ is\ similar\ to\ Qt\ and\ Motif,\ the\ first\ two\ toolkits\ reviewed\ in\ this\ series,\ in\ that\ it\ is\ a\ library\ coded\ in\ C\ that\ implements\ a\ collection\ of\ widgets.\ However,\ unlike\ Qt\ and\ Motif,\ Tk\ is\ known\ by\ most\ programmers\ through\ its\ binding\ to\ the\ Tcl\ scripting\ language,\ rather\ than\ through\ C\ itself.\n\n\nIt\ is\ widely\ believed\ that\ Tk\ is\ slow\ because\ it\ is\ used\ with\ a\ scripting\ language\ and\ scripting\ languages\ don't\ perform\ like\ C\ or\ assembly.\ This\ is\ simply\ not\ true\ --\ Tk\ is\ comparable\ in\ speed\ to\ other\ leading\ toolkits.\ In\ fact,\ it's\ considerably\ zippier\ than\ Java's\ Abstract\ Windowing\ Toolkit\ (AWT).\ Moreover,\ because\ Tk's\ design\ intentionally\ emphasizes\ easy\ use\ for\ common\ design\ situations,\ Tk\ is\ ripe\ for\ optimization.\ As\ a\ result,\ many\ Tcl/Tk\ applications\ are\ faster\ than\ their\ Motif-based\ counterparts.\n\n\nJohn\ Ousterhout,\ a\ professor\ at\ the\ University\ of\ California\ at\ Berkeley,\ created\ Tcl\ and\ Tk\ in\ the\ late\ 1980s\;\ since\ then,\ users\ and\ developers\ of\ Tcl\ and\ Tk\ have\ generally\ belonged\ to\ the\ same\ demographic.\ The\ toolkits\ are\ not\ identical,\ though.\ Many\ Tk\ programmers\ base\ their\ work\ on\ C,\ Perl,\ Python,\ Ruby,\ Lua,\ or\ Scheme.\ Two\ recent,\ well-received\ books\ on\ Tk\ development\ are\ aimed\ at\ Perl\ and\ Python\ programmers,\ rather\ than\ those\ working\ with\ Tcl.\n\n\nSo\ it\ can\ be\ advantageous\ to\ understand\ the\ roots\ Tk\ shares\ with\ Tcl,\ but\ it's\ not\ necessary\ to\ use\ one\ with\ the\ other.\ Some\ Tk\ characteristics\ are\ bound\ to\ Tcl\;\ some\ are\ more\ generally\ available.\n\n\nPortability\ sets\ Tk\ apart\ from\ other\ toolkits\ --\ it\ is\ more\ portable\ than\ any\ other\ contemporary\ GUI\ toolkit,\ even\ AWT.\ Good\ Tk\ implementations\ are\ available\ for\ all\ Unixes,\ as\ well\ as\ for\ Windows,\ Mac\ OS,\ OpenVMS,\ and\ other\ more\ specialized\ operating\ systems.\n\n\nThat\ dominance\ seems\ likely\ to\ change:\ Java\ Virtual\ Machines\ continue\ to\ improve,\ and\ Qt\ and\ wxWindows\ seem\ to\ be\ on\ course\ to\ release\ Mac\ OS\ versions.\ Tk's\ Mac\ OS\ distribution\ has\ appeared\ to\ weaken\ over\ the\ last\ year.\ Few\ developers\ have\ contributed\ to\ its\ maintenance,\ and\ despite\ frequent\ inquiries\ about\ a\ Tk\ for\ the\ Palm\ OS,\ one\ doesn't\ seem\ likely\ to\ emerge\ soon.\n\n\nOn\ the\ other\ hand,\ Tk\ is\ currently\ undergoing\ its\ most\ significant\ change\ since\ it\ was\ first\ ported\ to\ the\ Mac\ OS\ in\ the\ mid-'90s.\ The\ TkGS\ team,\ led\ by\ Frédéric\ Bonnet,\ is\ reworking\ Tk's\ internal\ design\ to\ improve\ performance\ and\ maintainability.\ It\ is\ widely\ anticipated\ that\ once\ this\ is\ completed,\ Tk\ ports\ to\ Microwindows\ or\ Nanox\ will\ be\ quick\ and\ nimble.\ And\ besides\ the\ complete\ TkGS\ rewrite,\ one\ group\ is\ investigating\ the\ possibility\ of\ a\ rapid\ port\ to\ Microwindows\ or\ Nanox\ from\ the\ current\ code\ base.\n\n\nTk,\ clearly\ in\ the\ lead\ right\ now\ with\ regards\ to\ portability,\ is\ also\ a\ favorite\ among\ developers\ striving\ for\ platform\ neutrality.\n\n***\ Expressiveness\ and\ wise\ defaults\ ***\n\nAnother\ benefit\ of\ Tk\ is\ its\ conciseness.\ The\ classic\ minimal\ Tk\ application\ is\ indeed\ tiny:\n\n======\npack\ \[button\ .mybutton\ -text\ Bye-bye\ -command\ exit\]\n======\n\nThis\ is\ a\ small\ but\ complete\ program\ in\ Tcl/Tk\ that\ puts\ a\ button\ on\ the\ screen\ and\ exits\ when\ the\ button\ is\ pushed,\ with\ proper\ behavior\ for\ iconifying,\ clicking,\ and\ other\ GUI\ conventions.\n\n\nThis\ economy\ of\ expression\ has\ two\ aspects.\ One\ is\ its\ realization\ in\ a\ scripted\ binding.\ All\ GUI\ toolkits\ look\ powerful\ in\ a\ good\ binding\ with\ a\ scripting\ language.\ Typical\ lessons\ in\ Motif\ programming\ require\ explanation\ of\ compilation,\ .h\ headers,\ string\ representations,\ and\ memory\ management\ before\ a\ beginner\ even\ attempts\ to\ create\ a\ working\ application.\ This\ mainly\ reflects\ the\ difference\ between\ C's\ tedium\ and\ other\ scripting\ languages.\n\n\nThe\ second\ aspect\ is\ that\ even\ apart\ from\ its\ usual\ exposure\ through\ a\ scripting\ language,\ Tk\ is\ remarkably\ concise.\ Ousterhout\ deliberately\ defined\ Tk\ to\ behave\ reasonably\ with\ default\ values.\ Tk\ programmers\ often\ write\ skeletal\ implementations\ and\ fill\ in\ details\ as\ requirements\ emerge.\ Tk\ encourages\ this\ style\ more\ than\ any\ other\ toolkit.\ This\ complements\ the\ scripting\ language\ bindings\ nicely,\ because\ these\ languages\ are\ more\ flexible\ than\ C,\ which\ has\ defined\ sequences\ of\ formal\ parameters.\ Scripting\ languages\ are\ comfortable\ with\ variable\ numbers\ of\ arguments,\ default\ arguments,\ and\ arguments\ of\ variable\ type.\ Tk\ uses\ this\ freedom\ wisely.\n\n\nOne\ testimony\ to\ the\ power\ of\ this\ incrementalism\ is\ the\ number\ of\ programmers\ who\ use\ Tk\ by\ accident.\ We\ hear\ many\ anecdotes\ of\ developers\ who\ choose\ Tk\ as\ a\ quick\ prototyping\ tool,\ then\ discover\ they're\ able\ to\ complete\ a\ full-blown\ application\ by\ refinement\ of\ the\ prototype.\n\n***\ Getting\ the\ most\ from\ Tk\ ***\n\nEffective\ Tk\ programming\ depends\ on\ several\ specific\ technical\ concepts:\n\n\ \ \ *\ The\ power\ of\ the\ text\ and\ canvas\ widgets\n\ \ \ *\ Geometry\ management\n\ \ \ *\ Event\ binding\n\n\nTk\ has\ a\ modest\ complement\ of\ widgets.\ The\ core\ Tk\ distribution\ lacks\ widgets\ for\ tree\ display,\ SpinBox,\ ComboBox,\ graphing,\ and\ several\ others\ that\ are\ now\ commonplace.\ One\ frequent\ complaint\ about\ Tk\ is\ that\ it\ has\ \"become\ rather\ lackluster\ in\ the\ age\ in\ terms\ of\ core\ features,\"\ according\ to\ Jeffrey\ Hobbs\ of\ Ajuba\ Solutions.\ However,\ the\ Tk\ text\ and\ canvas\ are\ so\ powerful,\ and\ Tk\ so\ extensible,\ that\ developers\ have\ lived\ without\ new\ features\ by\ relying\ on\ free\ extensions.\n\n***\ text\ and\ canvas\ powerhouses\ ***\n\n`text's`\ capabilities\ lie\ somewhere\ between\ those\ of\ Java's\ `TextArea`\ and\ `JEditorPane`.\ Text\ embeds\ both\ a\ compact\ visual\ editor\ and\ an\ HTMLv2\ display\ engine,\ and\ defines\ sophisticated\ tag\ programming,\ making\ visual\ effects\ easy.\ text's\ full\ Unicode\ capabilities\ helped\ internationalize\ it\ a\ couple\ of\ years\ ago\ with\ the\ 8.1\ release.\n\n\nIt's\ important\ to\ distinguish\ between\ different\ notions\ of\ \"graphical\"\ when\ discussing\ GUIs.\ One\ usage\ implies\ form-based\ GUI\ programming\ and\ expresses\ the\ difference\ between\ old\ curses\ or\ IBM\ 3270-based\ applications\ and\ typical\ Web\ browsers.\ Browsers\ depend\ on\ cursor\ movement\ and\ selection\ by\ clicking.\ Tk's\ text\ and\ related\ widgets\ such\ as\ button\ and\ label\ suffice\ for\ most\ form-based\ GUI\ programming.\n\n\nApplications\ in\ geographic\ information\ systems,\ electronic\ design\ automation,\ and\ complex\ visualization\ require\ a\ second\ level\ of\ graphics\ to\ display\ and\ manage\ arbitrary\ drawings\ such\ as\ maps,\ engineering\ diagrams,\ and\ images.\ Many\ successful\ programmers\ work\ only\ on\ form-based\ office\ automation\ tasks.\ However,\ Tk's\ canvas\ can\ help\ those\ with\ more\ general\ needs.\n\n\ncanvas\ is\ like\ text\ in\ that\ it\ embeds\ much\ functionality,\ unified\ by\ analogous\ programmability\ in\ terms\ of\ tags\ and\ configuration\ attributes.\ Tk\ is\ the\ established\ basis\ for\ successful\ commercial\ GUI\ applications,\ many\ of\ which\ have\ stringent\ requirements\ for\ scale\ and\ performance.\ One\ is\ Red\ Hat's\ Source-Navigator\ IDE\ (integrated\ development\ environment),\ used\ with\ all\ programming\ languages.\ Red\ Hat\ engineer\ Mo\ DeJong\ recently\ wrote,\ \"We\ are\ really\ pushing\ to\ make\ it\ the\ default\ IDE\ for\ Linux.\"\n\n***\ Geometry\ ***\n\nTk's\ fans\ also\ laud\ the\ toolkit\ for\ its\ geometry\ management.\ Geometry\ is\ the\ positioning\ of\ widgets\ on\ the\ visual\ screen.\ Windows's\ Visual\ Basic\ is\ reputedly\ easy\ for\ beginners\ because\ of\ its\ IDE's\ facility\ for\ dragging\ and\ dropping\ widgets\ into\ a\ form.\ However,\ due\ to\ its\ inflexibility\ in\ managing\ windows\ of\ variable\ sizes,\ this\ approach\ is\ severely\ limited\ in\ building\ professional\ applications.\n\n\nTk,\ by\ contrast,\ offers\ a\ variety\ of\ geometry\ managers,\ most\ of\ which\ can\ intelligently\ handle\ window\ resizing.\ It's\ typical\ in\ Tk\ to\ code\ such\ elements\ as:\n\n======\npack\ \$save_button\ \$cancel_button\ \$help_button\ \\\n\ \ \ \ -side\ left\ -fill\ both\ -expand\ yes\n======\n\nThis\ places\ three\ buttons\ in\ a\ sequence\ from\ left\ to\ right.\ Tk\ makes\ sure\ that\ the\ buttons\ are\ symmetrical\ and\ that\ they\ adjust\ properly\ to\ size\ changes.\n\n\nTk's\ geometry\ management\ is\ so\ widely\ admired,\ one\ common\ complaint\ heard\ about\ Java\ is\ that\ it\ still\ doesn't\ do\ geometry\ well,\ even\ though\ it's\ had\ at\ least\ five\ years\ to\ learn\ from\ Tk.\n\n***\ Events\ ***\n\nEvent\ handling\ distinguishes\ between\ different\ GUI\ toolkits.\ The\ programming\ model\ for\ all\ GUI\ systems\ has\ them\ wait\ for,\ receive,\ and\ communicate\ events\ to\ small\ pieces\ of\ code,\ or\ callbacks.\ Tk's\ event\ handling\ resembles\ its\ other\ programming\ constructs:\ its\ concisely\ expressed\ default\ actions\ are\ adequate\ for\ many\ situations,\ and\ more\ flexibility\ is\ available\ if\ necessary.\ In\ the\ one-line\ program\ near\ the\ top\ of\ this\ article,\ the\ -command\ exit\ phrase\ says,\ \"When\ someone\ pushes\ the\ button,\ perform\ the\ Tcl\ procedure\ named\ 'exit.'\"\ This\ command\ callback\ can\ hold\ arbitrarily\ complex\ instructions.\ A\ PerlTk\ program\ might\ read:\n\n======perl\n\$window->Button(-command\ =>\ sub\ \{\n\ \ \ \ sub1()\;\n\ \ \ \ sub2()\;\n\ \ \ \ #\ Do\ still\ other\ things.\n\ \ \ \ subn()\;\n\})->pack\n======\n\n\nThe\ flexibility\ is\ dual,\ which\ means\ one\ can\ associate\ arbitrary\ callbacks\ to\ standard\ events,\ as\ well\ as\ precisely\ manage\ the\ events\ an\ application\ recognizes.\ Tk's\ bind\ command\ can\ program\ the\ Enter\ key\ to\ duplicate\ an\ on-screen\ button\ click:\n\n======\nbind\ \$my_button\ <Key-Return>\ \"\$my_button\ invoke\"\n======\n\nThis\ precise,\ programmatic\ control\ gives\ Tk\ a\ great\ advantage\ in\ constructing\ highly\ responsive\ GUIs.\ Tk\ makes\ it\ easy\ to\ \"gray\ out\"\ buttons\ for\ actions\ that\ temporarily\ don't\ make\ sense,\ program\ hot\ spots\ on\ a\ screen,\ and\ generally\ implement\ what\ Bell\ Labs\ researcher\ Brian\ Kernighan\ calls\ intelligent\ GUIs,\ which\ are\ sensitive\ to\ context.\n\nState\ of\ the\ toolkit\ 2000\n\nHobbs's\ own\ history\ with\ Tk\ is\ typical.\ \"I\ was\ originally\ a\ C/Motif\ programmer.\ Once\ I\ learned\ Tk,\ I\ never\ did\ another\ project\ in\ Motif,\"\ he\ said.\ In\ fact,\ one\ Tcl\ insider\ claims\ to\ have\ once\ overheard\ Tim\ O'Reilly\ of\ O'Reilly\ &\ Associates\ (ORA)\ saying\ that\ Tk's\ introduction\ cut\ the\ sales\ of\ ORA\ Motif\ manuals.\n\n\nThe\ future\ of\ Tk\ is\ uncertain,\ though.\ Recent\ generations\ of\ programmers,\ based\ in\ Windows\ and\ Linux,\ tend\ to\ regard\ Tk\ applications\ as\ old-fashioned\ in\ appearance.\ The\ absence\ of\ an\ officially\ supported\ drag-and-drop\ visual\ builder\ for\ Tk\ is\ a\ barrier\ for\ many.\ Tk's\ commitment\ to\ Mac\ OS\ support\ seems\ tentative,\ and\ other\ toolkits\ are\ improving\ their\ portability.\ Where\ does\ this\ leave\ Tk\ in\ the\ year\ 2000?\n\n\nHobbs\ said:\n===\n\ \ \ \ Tk\ has\ a\ rich\ set\ of\ extensions\ that\ expand\ the\ widget\ set\ considerably\ ...\ Many\ of\ the\ complaints\ that\ Tk\ hasn't\ aged\ well\ are\ fairly\ near-sighted,\ because\ they\ never\ take\ account\ of\ the\ wealth\ of\ widget\ extensions\ available.\ Hopefully\ the\ new\ sumo\ Tcl\ distribution\ will\ finally\ address\ those\ concerns,\ along\ with\ fostering\ a\ more\ open\ development\ community\ that\ is\ interested\ in\ working\ with\ a\ larger\ Tcl\ distribution.\ \n===\n\nSo\ the\ Tcl\ development\ community\ is\ reorganizing\ itself\ to\ accelerate\ release\ cycles.\ Moreover,\ Hobbs\ and\ his\ colleagues\ are\ repackaging\ Tcl\ distributions\ to\ make\ popular\ extensions\ more\ accessible\ to\ nonexperts.\ \"8.4\ should\ be\ the\ first\ distribution\ that\ has\ a\ coexisting\ 'batteries\ included'\ release,\"\ said\ Hobbs.\ \"Major\ extensions\ that\ work\ with\ TEA\ (Tcl\ Extension\ Architecture)\ would\ be\ gathered\ together\ and\ all\ released.\"\n\n\nThose\ aren't\ the\ only\ structural\ changes.\ Tk's\ stewards\ are\ working\ to\ capture\ more\ of\ the\ open\ source\ buzz\ competing\ toolkits\ now\ receive.\ Consolidation\ of\ the\ internationalization\ and\ performance\ benefits\ of\ versions\ 8.0\ to\ 8.2\ has\ already\ led\ to\ opportunities\ for\ specific\ new\ features.\ Hobbs\ reported,\ \"More\ recently,\ the\ core\ of\ Tk\ incorporated\ popular\ paths\ that\ enhanced\ the\ existing\ widget\ set.\ The\ entry\ widget\ can\ validate\ input\ easier\ than\ before,\ the\ already\ feature-rich\ canvas\ receives\ even\ more\ features,\ the\ list\ box\ gets\ individualized\ color,\ and\ the\ text\ widget\ can\ now\ have\ hidden\ text\ fields.\"\ The\ official\ 8.4\ release\ is\ scheduled\ to\ include\ a\ new\ megawidget\ system\ \"to\ make\ Tcl-level\ \[graphical\ extensions\]\ easier\ to\ create\ than\ ever\ before.\"\n\n\nHobbs\ concluded,\ \"Tk\ is\ a\ simple\ and\ elegant\ UI\ toolkit\ that\ works\ across\ platforms\ without\ any\ code\ changes.\ Development\ time\ for\ a\ Tk\ app\ is\ significantly\ less\ than\ for\ the\ equivalent\ Java\ or\ C++\ UI\ toolkit\ app.\"\n\n***\ Broader\ context\ ***\n\nTk\ can\ certainly\ hold\ its\ own\ with\ other\ GUI\ toolkits.\ Its\ variety\ of\ available\ language\ bindings\ means\ almost\ anyone\ curious\ about\ Tk\ can\ quickly\ find\ a\ version\ in\ a\ familiar\ language.\ It\ only\ takes\ a\ few\ minutes\ to\ begin\ producing\ meaningful\ applications,\ and\ there\ are\ plenty\ of\ books\ and\ tutorials\ to\ help.\n\n\nHowever,\ there's\ a\ broader\ context\ that,\ at\ least\ temporarily,\ falsifies\ some\ of\ what\ we've\ already\ written\ --\ for\ the\ last\ couple\ of\ years,\ our\ true\ toolkit\ of\ choice\ was\ not\ Tk,\ but\ HTML.\ As\ Tim\ O'Reilly\ told\ us\ about\ the\ aforementioned\ incident\ regarding\ Motif\ book\ sales,\ \"I\ don't\ remember\ saying\ anything\ of\ the\ sort\ ...\ What\ eventually\ wounded\ both\ Tk\ and\ Motif,\ perhaps\ fatally,\ was\ the\ rise\ of\ the\ Web,\ which\ took\ the\ frontier\ of\ application\ development\ away\ from\ the\ desktop\ and\ put\ it\ instead\ in\ the\ browser-server\ interaction.\"\n\n\nThe\ current\ Silicon\ Valley\ rush\ to\ Webification\ is\ as\ silly\ as\ the\ aversion\ to\ the\ same\ architecture\ displayed\ by\ large\ corporations\ just\ a\ few\ years\ ago.\ Plenty\ of\ applications\ require\ the\ rich\ feature\ set\ of\ a\ toolkit\ such\ as\ Tk.\n\n\nThere's\ no\ doubt,\ though,\ that\ fashion\ can\ dominate\ computing\ for\ long\ stretches.\ One\ can\ easily\ conceive\ of\ a\ world\ that\ turns\ its\ back\ on\ Tk.\ The\ toolkit's\ usage\ might\ become\ limited\ to\ a\ core\ of\ developers\ and\ administrators\ who\ realize\ its\ indispensability\ for\ extremely\ rapid\ production\ of\ portable,\ intelligent,\ fully\ internationalized,\ visually\ well-behaved\ GUI\ applications.\n\n\nThere\ are\ at\ least\ a\ couple\ more\ wrinkles\ in\ this\ speculation.\ O'Reilly\ is\ one\ of\ many\ commentators\ to\ foresee\ open\ source\ Mozilla\ as\ the\ basis\ for\ the\ standardized\ toolkit\ of\ the\ future.\ This\ might\ make\ Tk\ more\ popular\ than\ ever,\ because\ Steve\ Ball\ of\ Zveno\ is\ working\ with\ TkGecko\ to\ create\ a\ Tk\ extension\ that\ allows\ the\ NewLayout\ rendering\ engine\ to\ be\ embedded\ in\ a\ Tk\ application\ as\ a\ Tk\ widget.\ Ball\ hopes\ this\ new\ widget\ will\ be\ as\ configurable\ as\ other\ Tk\ widgets,\ with\ all\ configuration\ options\ able\ to\ be\ queried\ and\ changed\ at\ runtime.\n\n\nThere\ are\ several\ interesting\ client-side\ Tk\ Web\ stories.\ The\ Tk\ plug-in\ is\ a\ module\ compatible\ with\ Microsoft's\ Internet\ Explorer\ and\ Netscape\ Navigator,\ which\ allows\ Web\ presentations\ to\ be\ scripted\ in\ Tcl,\ as\ they\ are\ currently\ done\ in\ JavaScript.\ The\ plug-in,\ a\ remarkably\ capable\ extension,\ has\ proved\ itself\ in\ several\ production\ systems.\ Although\ its\ maintenance\ was\ largely\ dormant\ for\ a\ couple\ of\ years,\ Ajuba\ is\ now\ making\ it\ compatible\ with\ the\ latest\ browser\ and\ Tk\ versions.\n\n***\ Summary\ ***\n\nTk's\ prospects\ involve\ so\ many\ free\ variables\ that\ the\ toolkit's\ future\ defies\ predictions.\ What's\ certain\ is\ that\ Tk's\ fans\ find\ the\ toolkit\ exceptionally\ useful\ right\ now,\ and\ that\ new\ widgets,\ books,\ and\ language\ bindings\ are\ making\ it\ easier\ for\ a\ newcomer\ to\ learn\ and\ for\ a\ mature\ programmer\ to\ use\ expertly.\n\n***\ Resources\ ***\n\n\ \ \ *\ Cameron\ Laird's\ personal\ notes\ on\ Tk:\ http://starbase.neosoft.com/~claird/comp.lang.tcl/tk.html\n\ \ \ *\ Cameron\ Laird's\ personal\ notes\ on\ Motif:\ http://starbase.neosoft.com/~claird/comp.windows.x.motif/motif.html\n\ \ \ *\ \"Qt\ 2.x\ and\ Python\ 1.6\ bind\ together\ well,\"\ Boudewijn\ Rempt\ and\ Cameron\ Laird:\ http://www.itworld.com/AppDev/4073/UIR000530qt/\n\ \ \ *\ John\ K.\ Ousterhout:\ http://www.scriptics.com/people/john.ousterhout\n\ \ \ *\ wxWindows\ Home:\ http://www.wxwindows.org\n\ \ \ *\ TkGS\ Specification:\ the\ Tk\ Graphics\ System:\ http://www.multimania.com/fbonnet/Tcl/TkGS/specs.htm\n\ \ \ *\ Cameron\ Laird's\ personal\ notes\ on\ Scriptics\ Corporation\ (or\ Ajuba\ Solutions):\ http://starbase.neosoft.com/~claird/comp.lang.tcl/scriptics.html\n\ \ \ *\ Red\ Hat's\ and\ Cygnus\ Solutions'\ Source-Navigator:\ http://www.cygnus.com/sn\n\ \ \ *\ Zveno\ XML\ tools\ and\ training:\ http://www.zveno.com\n\ \ \ *\ TkGecko:\ http://www.usenix.org/publications/library/proceedings/tcl2k/ball.html} CALL {my revision {Tk Sets The Standard by Cameron Laird and Kathryn Soraiz}} CALL {::oo::Obj6656898 process revision/Tk+Sets+The+Standard+by+Cameron+Laird+and+Kathryn+Soraiz} CALL {::oo::Obj6656896 process}

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Unknow state transition: LINE -> END
    while executing
"error $msg"
    (class "::Wiki" method "render_wikit" line 6)
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"my render_$default_markup $N $C $mkup_rendering_engine"
    (class "::Wiki" method "render" line 8)
    invoked from within
"my render $name $C"
    (class "::Wiki" method "revision" line 31)
    invoked from within
"my revision $page"
    (class "::Wiki" method "process" line 56)
    invoked from within
"$server process [string trim $uri /]"

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4