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129 | .\" ======================================================================== | |
130 | .\" | |
131 | .IX Title "INTERNALS 1" | |
132 | .TH INTERNALS 1 "2000-12-30" "perl v5.8.0" "User Contributed Perl Documentation" | |
133 | .SH "NAME" | |
134 | CallingTk \- what is Perl Tk interface doing when you call Tk functions. | |
135 | .PP | |
136 | This information is worse than useless for \f(CW\*(C`perlTk\*(C'\fR users, but can of | |
137 | some help for people interested in using modified Tk source with | |
138 | \&\f(CW\*(C`perlTk\*(C'\fR. | |
139 | .PP | |
140 | \&\fIThis document is under construction. The information is believed to | |
141 | be pertinent to the version of\fR \f(CW\*(C`portableTk\*(C'\fR \fIavailable when it was | |
142 | created. All the details are subject to change.\fR | |
143 | .SH "DESCRIPTION" | |
144 | .IX Header "DESCRIPTION" | |
145 | .IP "PreCompiling" 4 | |
146 | .IX Item "PreCompiling" | |
147 | Before the actual compilation stage a script scans the source | |
148 | and extracts the subcommands of different commands. This information | |
149 | resides in the file \f(CW\*(C`pTk/Methods.def\*(C'\fR. | |
150 | .IP "Compilation" 4 | |
151 | .IX Item "Compilation" | |
152 | During compilation the above file is included in the source of booting | |
153 | routine of dynamic (or static) library. More precisely, the booting | |
154 | code of module \f(CW\*(C`Tk\*(C'\fR calls the subroutine \fIBoot_Glue()\fR from the module | |
155 | \&\f(CW\*(C`tkGlue.c\*(C'\fR, and this subroutine includes the file (with appropriate | |
156 | macro definitions). | |
157 | .ie n .IP "Inside ""use Tk;""" 4 | |
158 | .el .IP "Inside \f(CWuse Tk;\fR" 4 | |
159 | .IX Item "Inside use Tk;" | |
160 | The module bootstraps the C code, then loads the Perl libraries. The | |
161 | heart of the Perl code is contained in the \f(CW\*(C`Tk::Widget\*(C'\fR library, all the | |
162 | widgets inherit from this module. Code for toplevels is loaded from | |
163 | \&\f(CW\*(C`Tk::MainWindow\*(C'\fR. | |
164 | .Sp | |
165 | During bootstrap of the C glue code the \f(CW\*(C`Xevent::?\*(C'\fR codes and a | |
166 | handful of \f(CW\*(C`Tk::Widget\*(C'\fR and \f(CW\*(C`Tk::Image\*(C'\fR routines are defined. (Much | |
167 | more XSUBs are created from \f(CW\*(C`Tk.xs\*(C'\fR code.) The widget subcommands are | |
168 | glued to Perl basing on the list included from \f(CW\*(C`pTk/Methods.def\*(C'\fR. In | |
169 | fact all the subcommands are glued to XSUBs that are related to the | |
170 | same C subroutine \fIXStoWidget()\fR, but have different data parts. | |
171 | .Sp | |
172 | During the Perl code bootstrap the method \f(CW\*(C`Tk::Widget::import\*(C'\fR is | |
173 | called. This call requires all the code from particular widget | |
174 | packages. | |
175 | .Sp | |
176 | Code from the widget packages calls an obscure command like | |
177 | .Sp | |
178 | .Vb 1 | |
179 | \& (bless \e"Text")->WidgetClass; | |
180 | .Ve | |
181 | .Sp | |
182 | This command (actually \fITk::Widget::WidgetClass()\fR) creates three | |
183 | routines: \fITk::Widget::Text()\fR, \fITk::Widget::isText()\fR, and | |
184 | \&\fITk::Text::isText()\fR. The first one is basically \f(CW\*(C`new\*(C'\fR of \f(CW\*(C`Tk::Text\*(C'\fR, | |
185 | the other two return constants. It also puts the class into | |
186 | depository. | |
187 | .ie n .IP "Inside ""$top = MainWindow\->new;""" 4 | |
188 | .el .IP "Inside \f(CW$top = MainWindow\->new;\fR" 4 | |
189 | .IX Item "Inside $top = MainWindow->new;" | |
190 | This is quite intuitive. This call goes direct to | |
191 | \&\f(CW\*(C`Tk::MainWindow::new\*(C'\fR, that calls \s-1XSUB\s0 | |
192 | \&\f(CW\*(C`Tk::MainWindow::CreateMainWindow\*(C'\fR, that calls C subroutine | |
193 | \&\fITk_CreateMainWindow()\fR. It is a \f(CW\*(C`Tk\*(C'\fR subroutine, so here black magic | |
194 | ends (almost). | |
195 | .Sp | |
196 | The only remaining black magic is that the \f(CW\*(C`Tk\*(C'\fR initialization | |
197 | routine creates a lot of commands, but the subroutine for creation is | |
198 | usurped by \fBportableTk\fR and the commands are created in the package | |
199 | \&\f(CW\*(C`Tk\*(C'\fR. They are associated to XSUBs that are related to one of three C | |
200 | subroutines \fIXStoSubCmd()\fR, \fIXStoBind()\fR, or \fIXStoTk()\fR, but have different | |
201 | data parts. | |
202 | .Sp | |
203 | The result of the call is blessed into \f(CW\*(C`Tk::MainWindow\*(C'\fR, as it should. | |
204 | .ie n .IP "Inside ""$top\->title('Text demo');""" 4 | |
205 | .el .IP "Inside \f(CW$top\->title('Text demo');\fR" 4 | |
206 | .IX Item "Inside $top->title('Text demo');" | |
207 | The package \f(CW\*(C`Tk::Toplevel\*(C'\fR defines a lot of subroutines on the fly on | |
208 | some list. All the commands from the list are converted to the | |
209 | corresponding subcommands of \f(CW\*(C`wm\*(C'\fR method of the widget. Here | |
210 | subcommand is a command with some particular second argument (in this | |
211 | case \f(CW"title"\fR). Recall that the first argument is \f(CW$self\fR. | |
212 | .Sp | |
213 | Now \f(CW\*(C`Tk::Toplevel\*(C'\fR \f(CW@ISA\fR \f(CW\*(C`Tk::Widget\*(C'\fR, that in turn \f(CW@ISA\fR \f(CW\*(C`Tk\*(C'\fR. So a | |
214 | call to \f(CW\*(C`$top\->wm('title','Text demo')\*(C'\fR calls \f(CW\*(C`Tk::wm\*(C'\fR, that is | |
215 | defined during call to \fITk_CreateMainWindow()\fR. As it is described | |
216 | above, the \s-1XSUB\s0 associated to \fIXStoSubCmd()\fR is called. | |
217 | .Sp | |
218 | This C routine is defined in \f(CW\*(C`tkGlue.c\*(C'\fR. It gets the data part of | |
219 | \&\s-1XSUB\s0, creates a \f(CW\*(C`SV\*(C'\fR with the name of the command, and calls | |
220 | \&\fICall_Tk()\fR with the \s-1XSUB\s0 data as the first argument, and with the name | |
221 | of \s-1XSUB\s0 stuffed into the Perl stack in the place there \f(CW\*(C`tk\*(C'\fR expects | |
222 | it. (In fact it can also reorder the arguments if it thinks it is | |
223 | what you want). | |
224 | .Sp | |
225 | The latter procedure extracts name of \f(CW\*(C`tk\*(C'\fR procedure and | |
226 | \&\f(CW\*(C`clientData\*(C'\fR from the first argument and makes a call, using Perl | |
227 | stack as \f(CW\*(C`argv\*(C'\fR for the procedure. A lot of black magic is performed | |
228 | afterwards to convert result of the procedure to a Perl array return. | |
229 | .ie n .IP "Inside ""$text = $top\->Text(background => $txtBg);""" 4 | |
230 | .el .IP "Inside \f(CW$text = $top\->Text(background => $txtBg);\fR" 4 | |
231 | .IX Item "Inside $text = $top->Text(background => $txtBg);" | |
232 | Above we discussed how the command \f(CW\*(C`Tk::Widget::Text\*(C'\fR is created. The | |
233 | above command calls it via inheritance. It is translated to | |
234 | .Sp | |
235 | .Vb 1 | |
236 | \& Tk::Text::new($top, background => $txtBg); | |
237 | .Ve | |
238 | .Sp | |
239 | The package \f(CW\*(C`Tk::Text\*(C'\fR has no method \f(CW\*(C`new\*(C'\fR, so the | |
240 | \&\f(CW\*(C`Tk::Widget::new\*(C'\fR is called. In turn it calls | |
241 | \&\f(CW\*(C`Tk::Text\->DoInit($top)\*(C'\fR, that is | |
242 | \&\f(CW\*(C`Tk::Widget::DoInit(Tk::Text,$top)\*(C'\fR, that initializes the bindings if | |
243 | necessary. Then it creates the name for the widget of the form | |
244 | \&\f(CW\*(C`.text0\*(C'\fR, and calls \f(CW\*(C`Tk::text('.text0', background => $txtBg)\*(C'\fR | |
245 | (note lowercase). The result of the call is blessed into \f(CW\*(C`Tk::Text\*(C'\fR, | |
246 | and the method \f(CW\*(C`bindtags\*(C'\fR for this object is called. | |
247 | .Sp | |
248 | Now the only thing to discuss is who defines the methods \f(CW\*(C`text\*(C'\fR and | |
249 | \&\f(CW\*(C`bindtags\*(C'\fR. The answer is that they are defined in \f(CW\*(C`tkWindow.c\*(C'\fR, | |
250 | and these commands are created in the package \f(CW\*(C`Tk\*(C'\fR in the same sweep | |
251 | that created the command \f(CW\*(C`Tk::wm\*(C'\fR discussed above. | |
252 | .Sp | |
253 | So the the same C code that corresponds to the processing of | |
254 | corresponding \s-1TCL\s0 commands is called here as well (this time via | |
255 | \&\f(CW\*(C`XStoTk\*(C'\fR interface). | |
256 | .ie n .IP "Inside ""$text\->insert('insert','Hello, world!');""" 4 | |
257 | .el .IP "Inside \f(CW$text\->insert('insert','Hello, world!');\fR" 4 | |
258 | .IX Item "Inside $text->insert('insert','Hello, world!');" | |
259 | As we discussed above, the subcommands of widget procedures correspond | |
260 | to \s-1XSUB\s0 \f(CW\*(C`XStoWidget\*(C'\fR. This \s-1XSUB\s0 substitutes the first argument \f(CW$text\fR | |
261 | (that is a hash reference) to an appropriate value from this hash, | |
262 | adds the additional argument after the first one that contains the | |
263 | name of the subcommand extracted from the data part of \s-1XSUB\s0, and calls | |
264 | the corresponding Tk C subroutine via \f(CW\*(C`Call_Tk\*(C'\fR. | |
265 | .PP | |
266 | Ilya Zakharevich <ilya@math.ohio\-state.edu> |