Its handy to be able to ask an object to do something for you by
handing it a subcommand. For example if we want to get the value
of an object's private field the object could expose a method that
would return that value. Application level code can then invoke
"$inst get" to perform the method call.
Tk uses this pattern for all of its widgets, so we'd certainly
like to use it for our own mega-widgets that we might develop.
Up until now we haven't needed such functionality, but I'm working
on a new revision picker mega-widget that would benefit from it.
To make this work we have to change the definition of $this to
actually be a procedure within the namespace. By making $this a
procedure any caller that has $this can call subcommands by passing
them as the first argument to $this. That subcommand then needs
to call the proper subroutine.
Placing the dispatch procedure into the object's variable namespace
ensures that it will always be deleted when the object is deleted.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Because Tk does not assure us the order that it will process
children in before it destroys the main toplevel we cannot safely
save our geometry data during a "bind . <Destroy>" event binding.
The geometry may have already changed as a result of a one or
more children being removed from the layout. This was pointed
out in gitk by Mark Levedahl, and patched over there by commit
b6047c5a8166a71e01c6b63ebbb67c6894d95114.
So we now also use "wm protocol . WM_DELETE_WINDOW" to detect when
the window is closed by the user, and forward that close event to
our main do_quit routine.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Earlier git.git applied a large "war on whitespace" patch that was
created using 'apply --whitespace=strip'. Unfortunately a few of
git-gui's own files got caught in the mix and were also cleaned up.
That was a6080a0a44d5ead84db3dabbbc80e82df838533d.
This patch is needed in git-gui.git to reapply those exact same
changes here, otherwise our version generator script is unable to
obtain our version number from git-describe when we are hosted in
the git.git repository.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
If a variable reference to a field is to an array, and it is
the only reference to that field in that method we cannot make
it an inlined [set foo] call as the regexp was converting the
Tcl code wrong. We were producing "[set foo](x)" for "$foo(x)",
and that isn't valid Tcl when foo is an array. So we just punt
if the only occurance has a ( after it.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
As most of the git-gui interface is based upon "meta-widgets"
that need to carry around a good deal of state (e.g. console
windows, browser windows, blame viewer) we have a good deal
of messy code that tries to store this meta-widget state in
global arrays, where keys into the array are formed from a
union of a unique "object instance id" and the field name.
This is a simple class system for Tcl that allows us to
hide much of that mess by making Tcl do what it does best;
process strings to manipulate its own code during startup.
Each object instance is placed into its own namespace. The
namespace is created when the object instance is created and
the namespace is destroyed when the object instance is removed
from the system. Within that namespace we place variables for
each field within the class; these variables can themselves be
scalar values or full-blown Tcl arrays.
A simple class might be defined as:
class map {
field data
field size 0
constructor {} {
return $this
}
method set {name value} {
set data($name) $value
incr size
}
method size {} {
return $size
} ifdeleted { return 0 }
}
All fields must be declared before any constructors or methods. This
allows our class to generate a list of the fields so it can properly
alter the definition of the constructor and method bodies prior to
passing them off to Tcl for definition with proc. A field may optionally
be given a default/initial value. This can only be done for non-array
type fields.
Constructors are given full access to all fields of the class, so they
can initialize the data values. The default values of fields (if any)
are set before the constructor runs, and the implicit local variable
$this is initialized to the instance identifier.
Methods are given access to fields they actually use in their body.
Every method has an implicit "this" argument inserted as its first
parameter; callers of methods must be sure they supply this value.
Some basic optimization tricks are performed (but not much). We
try to only upvar (locally bind) fields that are accessed within a
method, but we err on the side of caution and may upvar more than
we need to. If a variable is accessed only once within a method
and that access is by $foo (read) we avoid the upvar and instead
use [set foo] to obtain the value. This is slightly faster as Tcl
does not need to lookup the variable twice.
We also offer some small syntatic sugar for interacting with Tk and
the fileevent callback system in Tcl. If a field (say "foo") is used
as "@foo" we insert instead the true global variable name of that
variable into the body of the constructor or method. This allows easy
binding to Tk textvariable options, e.g.:
label $w.title -textvariable @title
Proper namespace callbacks can also be setup with the special cb proc
that is defined in each namespace. [cb _foo a] will invoke the method
_foo in the current namespace, passing it $this as the first (implied)
parameter and a as the second parameter. This makes it very simple to
connect an object instance to a -command option for a Tk widget or to
a fileevent readable or writable for a file channel.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
