Good progress lately on Gtk#. Got the toggle ref updates into svn, in addition to the Gtk.Object destruction rework. I did a lot of testing on the patch in MonoDevelop, Banshee, F-spot, and some toy apps of mine to feel more confident about such a fundamental change to ref management in the binding.
Having gone through the exercise of building bleeding edge versions of all those apps to test them against bleeding edge Gtk#, I decided it would be good to continue dogfooding like this regularly. I plan to pull the trunk sources of MD, Banshee, and F-spot once a week and run them against Gtk# trunk from now on.
Dogfooding Banshee and F-spot is a simple thing, since I use both applications regularly. MonoDevelop has been something I've only goofed around with every now and then, though. To create a nice dogfooding opportunity I decided to convert my little fitness log application to a MonoDevelop project so I can hack on it in MonoDevelop for an hour or two each week. I wrote a wiki page on my experience of converting the subversion-based autotools project to an MD project. It required surprisingly little manual effort thanks to the nice toys Lluis and folks have been building into MD lately.
Thursday, February 22, 2007
Friday, February 9, 2007
Leaky Documents
Making slow but steady progress on the documentation and auditing for the 2.10 API. Hopefully I'll finish up the Printing API next week. I've been refining some of the tools we use to add boilerplate-ish documentation for things like default signal handler virtual methods, and some of the semi-internal API the binding has to expose for binding purposes.
Since writing documentation doesn't make me feel sexy, I've been mixing in some bugfixing and new development along the way. Today I spent some time hacking toggle ref support into GLib.Object. Toggle refs are a new ref type added in glib-2.8. They are a special ref type which provides notification when transitioning from sole-ownership to shared-ownership of an object.
It's important to account for this with managed subclasses because we have to hold a strong reference to the managed object as long as native-owned refs exist. If Gtk# is the sole owner of a native object, we can allow the managed reference handling to drive garbage collection. However, when any native code takes a native ref on a managed subclass, we need to artificially maintain a managed ref to the object until the native code releases its ref.
Since we maintain a GObject* keyed hashtable of outstanding GLib.Object instances, we can use the toggle ref notification to switch between weak and strong references in the hash. While we have shared ownership, the hash will contain a normal object ref, avoiding garbage collection. When we transition to sole ownership, we'll hold a WeakReference to the object in the hash.
My first pass at toggle ref implementation seems to work well for plain GLib.Object subclasses. Now I just have to make it work within the context of GtkObject destruction and so on. I won't be committing anything until I've done a considerable amount of testing, since ref management changes have historically been a source of pain.
Since writing documentation doesn't make me feel sexy, I've been mixing in some bugfixing and new development along the way. Today I spent some time hacking toggle ref support into GLib.Object. Toggle refs are a new ref type added in glib-2.8. They are a special ref type which provides notification when transitioning from sole-ownership to shared-ownership of an object.
It's important to account for this with managed subclasses because we have to hold a strong reference to the managed object as long as native-owned refs exist. If Gtk# is the sole owner of a native object, we can allow the managed reference handling to drive garbage collection. However, when any native code takes a native ref on a managed subclass, we need to artificially maintain a managed ref to the object until the native code releases its ref.
Since we maintain a GObject* keyed hashtable of outstanding GLib.Object instances, we can use the toggle ref notification to switch between weak and strong references in the hash. While we have shared ownership, the hash will contain a normal object ref, avoiding garbage collection. When we transition to sole ownership, we'll hold a WeakReference to the object in the hash.
My first pass at toggle ref implementation seems to work well for plain GLib.Object subclasses. Now I just have to make it work within the context of GtkObject destruction and so on. I won't be committing anything until I've done a considerable amount of testing, since ref management changes have historically been a source of pain.
Wednesday, January 31, 2007
Good enough
This morning, I committed the ilContrast tool I blogged about on Sunday. It is in the mono-tools product in svn trunk. The tool can compare two individual assemblies which you can provide either by cmdline argument or interactively using the FileChooser.
Some potential features remain for bored hackers and artists to implement:
Update:
In case anyone was actually considering the GtkHtml fallback hack, don't bother. As Miguel pointed out to me, the javascript requirement makes that a non-starter. A more likely hack in that area would be to remove the Gecko# dep by directly rendering the mono-api-diff output with Gtk# itself, perhaps using a TreeView.
Some potential features remain for bored hackers and artists to implement:
- It needs a super-sexy icon. I just copied MonoIcon.png.
- It could probably use some persistence mechanism to recall the last "project".
- Multiple assembly comparisons. The mono-api-info tool looks like it can do it, just needs hooking up.
- Maybe a tabbed view for displaying multiple comparisons.
- The About dialog could use translation to 67 different languages.
- It has a hard dependency on Gecko#. A fallback to GtkHtml like monodoc provides might be useful.
Update:
In case anyone was actually considering the GtkHtml fallback hack, don't bother. As Miguel pointed out to me, the javascript requirement makes that a non-starter. A more likely hack in that area would be to remove the Gecko# dep by directly rendering the mono-api-diff output with Gtk# itself, perhaps using a TreeView.
Sunday, January 28, 2007
ilContrast
After helping Miguel with a corcompare run on IRC Friday afternoon, we decided it would be nice to have a GUI tool that would hook it all up for you. Running the three cmdline tools in the current manner is not the most user-friendly experience.
I threw a few hours at the problem this weekend and have a little Gecko# frontend sort of working. It has a few warts, but it's at least to the point of rendering recognizable information. Look for it to hit the mono-tools module some time this week, hopefully.
I threw a few hours at the problem this weekend and have a little Gecko# frontend sort of working. It has a few warts, but it's at least to the point of rendering recognizable information. Look for it to hit the mono-tools module some time this week, hopefully.
Friday, January 26, 2007
Hang on
Delegate persistence is an interesting challenge in a pinvoke binding like Gtk#. Hang on to delegates too long and you tie up the delegate instance memory and keep objects alive which are providing the delegate's invocation target. Release the delegate too soon and you get crashes when the native code tries to invoke it posthumously.
Most of the callback parameters in Gtk+ are destroy notified, taking away the guesswork of when to release the delegate. We have supported notified delegate release for a while now.
Of the non-notified callbacks, most only need to persist for the duration of the method to which they are passed. Foreach methods are a common user of this style of delegate scope. I refer to this as "call" scope. You may have noticed warnings for method parameters defaulted to call scope. The generator treats all callback parameters as call scope if the method signature doesn't contain destroy notification and a scope attribute isn't explicitly provided via metadata.
The challenge appears when a callback parameter doesn't fit into either of these paradigms. There are callbacks which persist until removed by another method. Some of these luckily also provide destroy notification, but not all of them. There is also another class of callbacks that I will call "async" since they are typically provided to allow non-blocking implementations of functionality. The task is queued up by the method call and control returns before the task is actually completed.
Often these async methods take a delegate parameter that is invoked at the completion of the operation to notify the caller the operation is finished. I ran across an example of this method type while documenting the new Gtk printing API from 2.10. Since I was bored of writing documentation, I decided to take a crack at implementing async scope callbacks in the generator.
If you have any async callback delegates in your bindings, you can now add the scope="async" attribute to the parameter with metadata to automatically handle the persistence for this new scope.
Most of the callback parameters in Gtk+ are destroy notified, taking away the guesswork of when to release the delegate. We have supported notified delegate release for a while now.
Of the non-notified callbacks, most only need to persist for the duration of the method to which they are passed. Foreach methods are a common user of this style of delegate scope. I refer to this as "call" scope. You may have noticed warnings for method parameters defaulted to call scope. The generator treats all callback parameters as call scope if the method signature doesn't contain destroy notification and a scope attribute isn't explicitly provided via metadata.
The challenge appears when a callback parameter doesn't fit into either of these paradigms. There are callbacks which persist until removed by another method. Some of these luckily also provide destroy notification, but not all of them. There is also another class of callbacks that I will call "async" since they are typically provided to allow non-blocking implementations of functionality. The task is queued up by the method call and control returns before the task is actually completed.
Often these async methods take a delegate parameter that is invoked at the completion of the operation to notify the caller the operation is finished. I ran across an example of this method type while documenting the new Gtk printing API from 2.10. Since I was bored of writing documentation, I decided to take a crack at implementing async scope callbacks in the generator.
If you have any async callback delegates in your bindings, you can now add the scope="async" attribute to the parameter with metadata to automatically handle the persistence for this new scope.
Wednesday, January 24, 2007
Back in the Saddle
After a lengthier than expected hiatus, I've been turned loose again to dedicate most of my time to Gtk#. I'm looking forward to adding some new features and improving the memory management of the existing bindings.
I've completed an initial triage of outstanding bugs, along with some work bringing the documentation up to speed with current monodoc updater. I use the monodoc update as a first check for API stability, in addition to the CorCompare-based audit mechanism in svn, so it's important to me to have the docs updating with as little noise as possible.
My initial focus will be working on the higher priority bugs, while also documenting and auditing the remainder of the new types added in the Gtk# 2.10 release. While I document the new types, I'll be auditing the API for correctness and making any adjustments for members the automated code generator bound incorrectly. Hopefully within a couple of weeks I'll be able to move on to new features like GInterface Registration.
I've completed an initial triage of outstanding bugs, along with some work bringing the documentation up to speed with current monodoc updater. I use the monodoc update as a first check for API stability, in addition to the CorCompare-based audit mechanism in svn, so it's important to me to have the docs updating with as little noise as possible.
My initial focus will be working on the higher priority bugs, while also documenting and auditing the remainder of the new types added in the Gtk# 2.10 release. While I document the new types, I'll be auditing the API for correctness and making any adjustments for members the automated code generator bound incorrectly. Hopefully within a couple of weeks I'll be able to move on to new features like GInterface Registration.
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