- Snapshot Docker.
- Users should be able to save the current state of document as a snapshot. Use KisDocument::clone() to obtain a (relatively) shallow copy of the document.
- The docker should display a list of snapshots (shallow copies) of the document, and allow users to replace the current document with any of the snapshots taken.
- A user manual should be written on how to use this docker. After finishing the docker, a tutorial video should be recorded.
- Copy-on-Write Vector Layers.
- Current implementations of vector layers:
- Data are stored using d-pointers that are not shared
- Subclasses’ d-pointers are inherited from those of the parent class
- Have at least two constructors for each class to prevent creating multiple data instances
- ChildClass() : ParentClass(new ChildClassPrivate(this))
- ChildClass(ChildClassPrivate * dd) : ParentClass(dd)
- All shapes are descended from KoShape, including KisShapeLayer itself
- Possible implementations:
- Similar implementation to the one in KisTile, which manually calls KisTileData::acquire() when an edit is needed.
- Qt’s implicit sharing, using the Qt class QSharedDataPointer. This class is reentrant (guaranteed to be safe when different threads access different instances). This is the preferred method. However, this is not thread-safe and may cause problems if the same instance is accessed from multiple threads. More work needs to be done to ensure thread-safety.
- C++11’s shared_ptr, as demonstrated by Sean Parent. However, in KDE guidelines, Qt libraries are preferred over std. This should be attempted only if QSharedDataPointer cannot work.
- Current implementations of vector layers:
Week 1-4 (May 27 - June 23)
Write core code to replace the current document with another KisDocument
Unit test for replacing the current document with another KisDocument
This involves emitting signals to GUI
Probably begin writing the snapshot docker
Week 5 (June 24 - June 30)
Write user manuals
Make a tutorial/demo video
Week 6 (July 1 - July 7)
Build a testing release, and collect feedback from the community
Is snapshot taking helpful to your workflow?
Is it efficient?
Other features wanted?
Improve the docker using the feedback
Week 7-8 (July 8 - July 21)
Start working on Copy-on-Write vector layers
The re-written classes should have the same API as the old ones, where possible.
Start using implicit sharing for members of KoShapePrivate
What have been stored using pointers may be now stored using shallow copies, for example, QSharedPointer<KoShapeStrokeModel> stroke could be replaced with KoShapeStrokeModel stroke
Make api documents on how implicit-sharing works for these components, and possibly a “guideline” or example on how to use implicit sharing in other classes.
Week 9-10 (July 22 - August 4)
Implicit sharing for the KoShape hierarchy
According to the discussion above, I may need to replace Qt’s macro with code written by myself in all descendents
Write and run unit tests
Try to merge the changes into master
Week 11 (August 5 - August 11)
Write undo commands that switch between states to replace the original ones that stores actions
Week 12 + Remaining 1 day (August 12 - August 19)
Used for buffering
See also: https://phabricator.kde.org/T11969
Discussions with Dmitry on #krita, Sat 9 Nov 2019. All times in UTC-5.
<tusooa> dmitryK|log: do you mean https://github.com/arximboldi/lager this library? [10:11] <dmitryK|log> tusooa: yes [10:13] <dmitryK|log> tusooa: I didn't look at it deeply <dmitryK|log> tusooa: it is more for GUI controls, but some of its ideas might be useful for shapes as well <tusooa> oh [10:14] <tusooa> what do you mean by "limiting shapes editing to GUI only sounds really wrong."? <tusooa> i think i meant the reverse (gui threads only read shapes) [10:15] <dmitryK|log> tusooa: I mean that shapes editing should be also allowed in the background threads <tusooa> in stroke? <dmitryK|log> tusooa: and gui threads shoul dbe able to read some (old) copy of them <dmitryK|log> tusooa: yes, in stroke <tusooa> that is exactly what i intended to say lol <dmitryK|log> well, sorry :) <tusooa> np -)) [10:16] <tusooa> "access" -> "read" <tusooa> dmitryK|log: and, what do you mean by the "original problem"? <tusooa> btw "KisDescendent<const KoShape>" is inspired by the pattern introduced by Sean Parent [10:17] <dmitryK|log> tusooa: I mean that we don't have a proper general solution to it in Krita at all :) [10:21] <tusooa> thread-safety? [10:22] <tusooa> or what <dmitryK|log> tusooa: yes <dmitryK|log> tusooa: bascially, my recent refactorings of transform tool and move tool can partially address this problem <dmitryK|log> tusooa: but this approach is not applicable to other tools <Animtim> boud: about your question related to the blog post on Qt+android+openssl, it probably is relevant for you, except if you build using KDE's docker image; the article talks only about 5.13.1, but I found out the same applies to 5.12.5 [10:23] <dmitryK|log> tusooa: bascially, if the tool has "options widget" and does something in Kis*Tool::paint(), then it probaly reads from the image in unsafe way. <Wolthera_laptop> Animtim: thanks for mentioning it! <tusooa> ok [10:24] <Animtim> :) <dmitryK|log> tusooa: tiles engine guarantees that this access does not cause any crash, but the data read is still "undefined behavior" <tusooa> i can see the case for DefaultTool <dmitryK|log> tusooa: to fix this problem in MoveTool and TransformTool I had to move tool initialization into the stroke itself [10:25] <dmitryK|log> tusooa: and it is not very possible for Default Tool. <dmitryK|log> tusooa: some other approach should be used for it <tusooa> i mean the Tool Options Widget <tusooa> i locked the canvas in updateActions to prevent it accessing shapes when there might be changes ongoing [10:26] <dmitryK|log> tusooa: yes, everything related to flake is really affected :) <tusooa> but that does not solve the whole problem <dmitryK|log> yes <tusooa> it seems we might need something mediating between tools and shapes [10:27] <dmitryK|log> tusooa: ideally, it needs some higer level solution. Like read-copy-update. But I have no clear idea what exactly <tusooa> especially to provide atomic/pseudo-atomic access <tusooa> dmitryK|log: i think copy-update sounds viable [10:28] <dmitryK|log> tusooa: well, actually, original idea of KoShapeManager could solve this issue :) <dmitryK|log> tusooa: but now we have KoShapeDocumentController and all these weird classes around it [10:29] <tusooa> but doesn't that mean we would introduce "dummies" again? <dmitryK|log> tusooa: well, what I can tell from those c++ talks... <tusooa> um probably not if we just pass everything by value <tusooa> wait i have not really seen KoShapeDocumentController [10:30] <tusooa> i only know KisShapeController, KoShapeController, KoShapeControllerBase [10:31] <tusooa> but that's already a mess -(( <dmitryK|log> tusooa: 1) tools should not use pointers to shapes. Only values; 2) If a tool needs to save a pointer to a shape, it should use some "persistent index" (see QPersistentModelIndex for inspiration). 3) KoShapeManager should be a *the only* point, which is used for accessing shapes by the tools. 4) KoShapeManager can be swapped atomically after any operation; 5) No other controllers will exist [10:32] <dmitryK|log> tusooa: sorry, I didn't remember their name. One of these classes was name KoShapeDocumentBase, and then was renamed into something like KoShapeControllerBase or somehting [10:33] <tusooa> ha, i see why one of the classes has the weird documentBase() function [10:34] <tusooa> ok <tusooa> (1)(2) makes sense to me <dmitryK|log> tusooa: but all this "persistent index" idea is rather complicated. And that is why I was suggesting to look into Lager library <tusooa> yea [10:35] <dmitryK|log> tusooa: Lager is supposed to track changed in such objects and emit notifications properly <tusooa> ok <dmitryK|log> tusooa: all this talk gradualy comes down to a "functional programming" thing... [10:36] <tusooa> dmitryK|log: what do you mean by (4) *** slangkamp (~email@example.com) has joined channel #krita <dmitryK|log> tusooa: is RCU paradigm you need to swap something in the end of update operation <dmitryK|log> tusooa: KoShapeManager (or its internals) is a good candidate for that <dmitryK|log> *in RCU... <tusooa> but don't see why we would want to swap KoShapeManager [10:37] <tusooa> isn't it just a controller class? <tusooa> that persists? <dmitryK|log> tusooa: well, I have no strong opinion about this <tusooa> i mean we need to be able to swap things atomacally, that's true [10:38] <dmitryK|log> tusooa: perhaps, if we swap into Lager library, then KoShapeManager will just stop to exist <tusooa> um <dmitryK|log> tusooa: because Lager is bascially an entity that updates tracking [10:39] <tusooa> i haven't finished reading its documentation <dmitryK|log> tusooa: and KoShapeManager also does updates tracking :) <raghukamath> sometimes convrting colors crashes krita <dmitryK|log> tusooa: watch videos of the author, he is really a nice guy :) <tusooa> sure will do <dmitryK|log> raghukamath: in master? or in 4. [10:40] <raghukamath> master <raghukamath> but it can't be reproduced <raghukamath> i have only encountered it twice <Wolthera_laptop> race condition, maybe? <dmitryK|log> raghukamath: report a backtrace, I've merged the this week <dmitryK|log> raghukamath: which sha1 <dmitryK|log> ? <tusooa> dmitryK|log: it monitors changes in shapes and forwards them to the canvas right? <raghukamath> 7104885 [10:41] <dmitryK|log> tusooa: KoShapeManager, yes <dmitryK|log> tusooa: Lager does the same thing. And it can also aggregate the updates <raghukamath> 7104885cf0904dbfe03cd04346a3b46d2547effb <raghukamath> i'll update <tusooa> shapes notice KoShapeManager that they have been modified --> shape manager compresses it and make the canvas do updates <tusooa> i will read the doc [10:42] <tusooa> dmitryK|log: thank you for the insights