Create GTK + applet for LXPanel

An article on how to write your applet for LXPanel. The developers have not yet written the documentation, so you have to learn from the sources, which are, on the contrary, rich in comments.

I decided to make out clearly one example and the easiest way to build into a ready * .so plugin.









Build comes under Ubuntu, requires minimal knowledge of C and GTK +.

Training

1. Get the sources of lxpanel:
   
   

   echo "deb-src http://mirror.yandex.ru/ubuntu maverick main restricted universe multiverse" >> / etc / apt / sources.list
   
   apt-get update && apt-get source lxpanel
   
   cd lxpanel-0.5.6

   
   
   
2. Install the necessary build packages:
   
   

   apt-get build-dep lxpanel

   
   
   
3. Check:
   
   

   LIBS = "-lX11" . / configure --prefix = / usr --with-plugins = cpufreq
   
   make
   
   ls src / plugins / cpufreq / .libs / cpufreq.so

   
   
   

The plugin cpufreq was selected as a victim, later I'll tell you why. And we will write a plugin to switch the performance <-> ondemand processor modes.

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Writing

vim src / plugins / cpufreq / my_plugin.c

Actually, all the code with comments:

1. / **
2. * My_plugin
3. * Habrahabr
4. * /
6. #include <sys / types.h>
7. #include <stdio.h>
8. #include <stdlib.h>
9. #include <glib / gi18n.h>
11. #include <string.h>
13. #include "panel.h"
14. #include "misc.h"
15. #include "plugin.h"
17. // To compare strings
18. #define STREQV (a, b) (* (a) == * (b) && strcmp ((a), (b)) == 0)
20. // Declare the structure of our plugin
21. typedef struct {
22. // Widget that will contain all the icon and menu
23. GtkWidget * namew ;
24. } my_plugin ;
26. // Create an object
27. static my_plugin * mp ;
29. // Plugin structure is declared in src / plugin.h
30. // * mp_p - now plugin class
31. // Which at least sets the parent container mp_p-> pwid
32. // Our mp-> namew widget is "inserted" into it
33. // And the icon, for example, is contained in mp-> namew
34. // Long death hide
35. static Plugin * mp_p ;
37. // An announcement speaks for itself
38. static char get_governor ( ) {
39. FILE * fpipe ;
40. const char governor [ 16 ] ;
41. char line [ 16 ] ;
43. // Problem with recognizing cpufreq-info output
44. // Script / usr / local / bin / cpufreq-gov returns the name of the current mode
45. fpipe = ( FILE * ) popen ( "/ usr / local / bin / cpufreq-gov" , "r" ) ;
46. fgets ( line , sizeof ( line ) , fpipe ) ;
47. pclose ( fpipe ) ;
49. return line ;
50. }
52. // An announcement speaks for itself
53. static char get_frequency ( ) {
54. FILE * fpipe ;
55. const char governor [ 16 ] ;
56. char line [ 16 ] ;
58. // Problem with recognizing cpufreq-info output
59. // Script / usr / local / bin / cpufreq-gov returns the name of the current mode
60. fpipe = ( FILE * ) popen ( "cpufreq-info -f -m" , "r" ) ;
61. fgets ( line , sizeof ( line ) , fpipe ) ;
62. pclose ( fpipe ) ;
63. line [ strlen ( line ) - 1 ] = ' \ 0 ' ;
65. return line ;
66. }
68. // Make the function update the icons when changing the mode
69. static void refresh_icon ( ) {
70. // Find out the current mode
71. const char governor [ 16 ] ;
72. char line [ 16 ] = get_governor ( ) ;
73. sprintf ( governor , "% s" , line ) ;
75. // mp_p-> pwid is the parent container of type GTKWidget, which contains mp-> namew
76. // Remove the mp-> namew widget and change the icon
77. gtk_container_remove ( GTK_CONTAINER ( mp_p -> pwid ) , mp -> namew ) ;
79. // If the mode is "ondemand"
80. if ( STREQV ( governor , "ondemand" ) )
81. {
82. // One badge
83. mp -> namew = gtk_image_new_from_file ( "/usr/share/lxpanel/images/cpufreq_ond.png" ) ;
84. }
85. else
86. {
87. // Otherwise, another
88. mp -> namew = gtk_image_new_from_file ( "/usr/share/lxpanel/images/cpufreq_perf.png" ) ;
89. }
90. // Insert the mp-> namew widget back into the mp_p-> pwid parent container
91. gtk_container_add ( GTK_CONTAINER ( mp_p -> pwid ) , mp -> namew ) ;
92. gtk_widget_show_all ( mp_p -> pwid ) ;
93. }
95. // Mode change function
96. static void set_governor ( GtkWidget * widget , char * p ) {
97. const char exec [ 32 ] ;
98. sprintf ( exec , "cpufreq-set -g% s" , p ) ;
99. system ( exec ) ;
100. refresh_icon ( ) ;
101. }
103. // Create a menu
104. static GtkWidget * mp_menu ( ) {
105. GtkMenu * menu = gtk_menu_new ( ) ;
106. GSList * group = NULL ;
107. GtkWidget * menuitem , * radio1 , * radio2 ;
109. FILE * fpipe ;
110. const char governor [ 16 ] ;
111. const char frequency [ 16 ] ;
112. char line [ 16 ] ;
114. line = get_governor ( ) ;
115. sprintf ( governor , "% s" , line ) ;
117. line = get_frequency ( ) ;
118. sprintf ( frequency , "% s" , line ) ;
120. // 1) Add the current frequency to the menu, make the item inactive
121. menuitem = gtk_menu_item_new_with_label ( frequency ) ;
122. gtk_menu_append ( menu , menuitem ) ;
123. gtk_widget_set_sensitive ( menuitem , FALSE ) ;
124. gtk_widget_show ( menuitem ) ;
126. // 2) Add a separator
127. menuitem = gtk_separator_menu_item_new ( ) ;
128. gtk_menu_append ( menu , menuitem ) ;
129. gtk_widget_show ( menuitem ) ;
131. // 3) 2 radio buttons for switching between modes
132. radio1 = gtk_radio_menu_item_new_with_label ( group , "Savings" ) ;
133. group = gtk_radio_menu_item_get_group ( GTK_RADIO_MENU_ITEM ( radio1 ) ) ;
134. if ( STREQV ( governor , "ondemand" ) )
135. {
136. gtk_check_menu_item_set_active ( GTK_CHECK_MENU_ITEM ( radio1 ) , TRUE ) ;
137. }
138. gtk_menu_append ( menu , radio1 ) ;
139. gtk_widget_show ( radio1 ) ;
141. // 4) The second button
142. radio2 = gtk_radio_menu_item_new_with_label ( group , "Performance" ) ;
143. if ( STREQV ( governor , "performance" ) )
144. {
145. gtk_check_menu_item_set_active ( GTK_CHECK_MENU_ITEM ( radio2 ) , TRUE ) ;
146. }
147. gtk_menu_append ( menu , radio2 ) ;
148. gtk_widget_show ( radio2 ) ;
150. // When you click on the radio buttons, the modes switch
151. g_signal_connect ( G_OBJECT ( radio1 ) , "toggled" , G_CALLBACK ( set_governor ) , "ondemand" ) ;
152. g_signal_connect ( G_OBJECT ( radio2 ) , "toggled" , G_CALLBACK ( set_governor ) , "performance" ) ;
154. return menu ;
155. }
157. // Event handler for clicking on the plugin icon
158. static gboolean clicked ( GtkWidget * widget , GdkEventButton * evt , Plugin * plugin ) {
159. gtk_menu_popup ( mp_menu ( ) , NULL , NULL , NULL , NULL , evt -> button , evt -> time ) ;
160. return TRUE ;
161. }
163. // Object constructor proper
164. static int constructor ( Plugin * p ) {
165. // Create an object
166. mechanism_mp = g_new0 ( my_plugin , 1 ) ;
167. p -> priv = mechanism_mp ;
169. // Make the parent widget sensitive (we follow the events)
170. // And remove the window decoration from it
171. p -> pwid = gtk_event_box_new ( ) ;
172. GTK_WIDGET_SET_FLAGS ( p -> pwid , GTK_NO_WINDOW ) ;
173. gtk_container_set_border_width ( GTK_CONTAINER ( p -> pwid ) , 0 ) ;
175. // Set the initial icon
176. refresh_icon ( ) ;
178. // When clicked, the clicked () handler function is triggered.
179. g_signal_connect ( G_OBJECT ( p -> pwid ) , "button_press_event" , G_CALLBACK ( clicked ) , ( gpointer ) p ) ;
181. gtk_widget_show ( mechanism_mp -> namew ) ;
182. }
184. // Destructor
185. static void destructor ( Plugin * p ) {
186. my_plugin * mechanism_mp = ( my_plugin * ) p -> priv ;
187. g_free ( mechanism_mp ) ;
188. }
190. // And here we specify information about our plugin
191. PluginClass mp_plugin_class = {
192. PLUGINCLASS_VERSIONING ,
194. type : "my_plugin" ,
195. name : N_ ( "My super plugin" ) ,
196. version : "1.0" ,
197. description : N_ ( "Habrahabr" ) ,
199. constructor : constructor ,
200. destructor : destructor ,
201. // In our plugin are not used,
202. // but you can assign handlers for the configuration, save the configuration
203. // And widget redrawing, when changing configuration
204. config : NULL ,
205. save : NULL ,
206. panel_configuration_changed : NULL
207. } ;

Compilation

You can add our plugin to the build scripts, but this is not necessary and it is extremely dreary. Therefore, just take the cpufreq victim plugin and replace its source src / plugins / cpufreq / cpufreq.c with ours.

We collect:

LIBS = "-lX11" . / configure --prefix = / usr --with-plugins = cpufreq

make

Ready * .so is in src / plugins / cpufreq / .libs / , you need to drop it into the folder with the other plugins, only under a different name, for example /usr/lib/lxpanel/plugins/my_plugin.so



The contents of / usr / local / bin / cpufreq-gov :

1. #! / bin / sh
3. echo ` cpufreq-info -p | awk '{print $ 3}' `

2 icons in / usr / share / lxpanel / images / :

Finally

For greater clarity, I advise you to read the files, they are rich in comments.

• src / plugin.c
• src / plugin.h
• src / panel.c
• src / panel.h

Good luck! Example source : my_plugin.c