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Add an explanation of primary instance.

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Toshio Sekiya 2021-01-16 00:43:48 +09:00
parent 79f53d08c7
commit 9267b68030
3 changed files with 76 additions and 2 deletions
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36
gfm/sec14.md
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@ -38,7 +38,7 @@ It connects the command line given by the user and GTK application.
## statup signal handler
"startup" signal is emitted just after the application is generated.
Startup signal is emitted just after the application is generated.
What the signal handler needs to do is initialization of the application.
- Build the widgets using ui file.
@ -213,6 +213,40 @@ They just generate a new GtkNotebookPage.
These codes have become really simple thanks to tfenotebook.c and tfetextview.c.
## Primary instance
Only one GApplication instance can be run at a time per session.
The session is a bit diffcult concept and also platform-dependent, but roughly speaking, it corresponds to a graphical desktop login.
When you use your PC, you probably login first, then your desktop appears until you log off.
This is the session.
However, linux is multi process OS and you can run two or more instances of the same application.
Isn't it a contradiction?
When first instance is launched, then it register itself with its application ID (for example, `com.github.ToshioCP.tfe`).
Just after the registration, startup signal is emitted, then activate or open signal is emitted and the instance's main loop runs.
I wrote "startup signal is emitted just after the application is generated" in the prior subsection.
More precisely, it is emitted just after registration.
If another instance which has the same application ID is invoked after that, it also tries to register itself.
Because this is the second instance, the registration of the ID has already done, so it fails.
Because of the failure startup signal isn't emitted.
After that, activate or open signal is emitted in the primary instance, not the second instance.
The primary instance receives the signal and its handler is invoked.
On the other hand, the second instance doesn't receive the signal and it immediately quits.
Try to run two instances in a row.
$ ./_build/tfe &
[1] 84453
$ ./build/tfe tfeapplication.c
$
First, the primary instance opens a window.
Then, after the second instance is run, a new notebook page with the contents of `tfeapplication.c` appears in the primary instance's window.
This is because the open signal is emitted in the primary instance.
The second instance immediately quits so shell prompt soon appears.
## a series of handlers correspond to the button signals
1 static void

6
gfm/sec2.md
View file

@ -65,6 +65,8 @@ Make a text file below and save it as `env.sh`
LD_LIBRARY_PATH="$HOME/local/lib/x86_64-linux-gnu/"
PATH="$HOME/local/bin:$PATH"
export LD_LIBRARY_PATH PATH
# gsetting
export GSETTINGS_SCHEMA_DIR=$HOME/local/share/glib-2.0/schemas
Then, use . (dot) or source command to include these commands to the current bash.
@ -148,6 +150,10 @@ Modify `env.sh`.
# gir
XDG_DATA_DIRS=$HOME/local/share:$XDG_DATA_DIRS
export XDG_DATA_DIRS
# gsetting
export GSETTINGS_SCHEMA_DIR=$HOME/local/share/glib-2.0/schemas
# girepository-1.0
export GI_TYPELIB_PATH=$HOME/local/lib/x86_64-linux-gnu/girepository-1.0
Include this file by . (dot) command before using gtk4 libraries.

36
src/sec14.src.md
View file

@ -22,7 +22,7 @@ It connects the command line given by the user and GTK application.
## statup signal handler
"startup" signal is emitted just after the application is generated.
Startup signal is emitted just after the application is generated.
What the signal handler needs to do is initialization of the application.
- Build the widgets using ui file.
@ -134,6 +134,40 @@ They just generate a new GtkNotebookPage.
These codes have become really simple thanks to tfenotebook.c and tfetextview.c.
## Primary instance
Only one GApplication instance can be run at a time per session.
The session is a bit diffcult concept and also platform-dependent, but roughly speaking, it corresponds to a graphical desktop login.
When you use your PC, you probably login first, then your desktop appears until you log off.
This is the session.
However, linux is multi process OS and you can run two or more instances of the same application.
Isn't it a contradiction?
When first instance is launched, then it register itself with its application ID (for example, `com.github.ToshioCP.tfe`).
Just after the registration, startup signal is emitted, then activate or open signal is emitted and the instance's main loop runs.
I wrote "startup signal is emitted just after the application is generated" in the prior subsection.
More precisely, it is emitted just after registration.
If another instance which has the same application ID is invoked after that, it also tries to register itself.
Because this is the second instance, the registration of the ID has already done, so it fails.
Because of the failure startup signal isn't emitted.
After that, activate or open signal is emitted in the primary instance, not the second instance.
The primary instance receives the signal and its handler is invoked.
On the other hand, the second instance doesn't receive the signal and it immediately quits.
Try to run two instances in a row.
$ ./_build/tfe &
[1] 84453
$ ./build/tfe tfeapplication.c
$
First, the primary instance opens a window.
Then, after the second instance is run, a new notebook page with the contents of `tfeapplication.c` appears in the primary instance's window.
This is because the open signal is emitted in the primary instance.
The second instance immediately quits so shell prompt soon appears.
## a series of handlers correspond to the button signals
@@@ tfe5/tfeapplication.c open_clicked new_clicked save_clicked close_clicked