Insaturé

You need a wayland compositor library to create a wayland server. Wayland is a protocol, itself, cannot do much, long time ago I used to think the server-side wl_resource represents some structure you can operate on, well it turned out all you do with it is handling messages between client and server. All the logic you need to implement yourself.

There were a few attempts to wayland compositing library created. The first sucessful one is wlc. I think its existence is that weston (the twin of the wayland project, now maintained by Pekka Paalanen). was a monolith application for a long time. Weston looks pretty and quite fast and beautiful but not very useful to anyone else. The developers maybe realized that they want to get more people to use weston, so they managed to strip libweston out of weston itself. It was a good attempt, although I doubt their true intention was to creating a reusable compositing library. Nonetheless, to some extent, it helped the birth of the third library by Drew Devault, the wlroots.

wl_data_device interface in the base wayland protocol is the most complex one, in my opinion, wayland.xml explains it fairly well, but every pieces are scattered in the file, here I serialize it together, give you quick run through.

In brief, data device in wayland consists of four interfaces: The first is wl_data_device_manager, it is the global. The second is wl_data_device, can be created from wl_data_device_manager for a given seat, it is used to set selection(ctrl-c ctrl-v) and drag-n-drop. The 3rd is wl_data_source, also created from wl_data_device_manager, this source will be either a selection source or drag-n-drop source. The last is wl_data_offer, which is used for copying data from wl_data_source.

Forcing a monthly blog update seems to be a good idea, giving myself a reason to keep paying for this Domain. Also, I don’t usually has a topic to address specifically, a monthly update can fill this role. Anyway, time passes rapidly in quarantine my friends. I hope a few years forward when I look back at this moment, I would not feel I wasted so much time. I don’t actually feel I made much progress through this month. I would say, I am digging into my memory right now, it is hard to recall much in detail. yeah, that is life in quarantine, “stagnation”, like the blackwater.

I update this blog less frequent than once per year, which sometimes makes me question why do I keep paying for this site. Be able to update blogs is always my pursuit, unfortunately there were always more code to write. It has been more than one year, last time I was still on how to MSAA on OpenGL 4, somehow it felt like a decade ago. The peaceful developing world took an interesting turn. A long run bull market is killed and NYSE triggered circuit break 4 times in 10 days. People are joking they now have 75% of Warren Buffet’s experience. Will this gonna be the story we told our grand children born after 2020? “You know back in 2020, it was a crazy year…”. We just saw the quarter of it, I am kind of expecting the crazier in the rest, will it be massive unemployment and a scary recession will be waiting? This week the market has recovered a bit of its confidence somehow, despite the Covid-19 cases are surging. A friend used to tell me, it would be a point where many will be killed by the virus and people just don’t care anymore, looks like the market is at that point.

Deferred MSAA, always has been a good problem. In the spatial anti-aliasing domain, MSAA is still the swiss-army knife, handle almost all the case.

Some other post-processing methods like nvidia’s FXAA, AMDs MLAA, or DLAA. FXAA is rather pleasing in many cases as well, especially if you are a video game developer, as long as your rasterization implementation does not screwed up. But for the case like grass rendering, fur rendering, when you have many layers of thin line, FXAA will fail you. Just like the pixels annotated in the image below.

The last post I laid out the story of me with wayland. Technology is fascinating isn’t it? Every once a while, there are plenty of new projects that aim to start an revolution, getting people excited. Projects like systemd, Wayland, Vulkan make us think how come we did not think of those before, they seemed perfect at the moment. Technologies always work like a rush of hot wave, our sights are limited at the moment we are in, maybe 5 years from now, even vulkan is not sexy anymore. For ten years, community has been urging everyone to jump on the boat of wayland. Some major platform adopted it, just there is no money in it. Major platforms like GNOME and KDE are not even mature yet, KDE developers also worries about the future of the wayland, will it last 30 years like X window?

It was a good will.

5 years ago, I read a blog about the future of linux desktop, I was using a window manager called Awesome (one of my friend introduced it to me, I was enchanted by how he opened two terminals side-by-side, one for coding and one for compiling). A voice about next generation desktop was just raised in the linux community , a group of hackers demod the weston project, where you can rotate the application windows. They also pointed out the existing problems in the x server architecture(basically it is too old, let us just replace it). It is cumbersome, too many components, easily dead after package upgrade.

Rotation, combined with translation and scaling, are the three affin transforms we do every day in the 3D nutshell universe. The rotation itself, however, is somehow much more complicated than the other two transform, it is one really needs a matrix representation among all three. Representations and computation of it has been developed for years. We have systems like Axis-angle representation, matrix representation, euler angles and quaternions. Despite I have known them for a long time, when I forgot, the rotation is still complicated. Here I am writing this again, as easily understanding as possible, for my future-self (or I can just travel through time to ask myself now).

I have been trying to create a animation system for my OpenGL Project for a long time, one of the reason is I have limited amount of time after starting the full-time job. Another problem was that, I mean, if I intend to keep it a clean project rather than just a school project, building a animation system is like a rabbit hole, 30 lines of code got me another 100 lines of work, it only leaded me deeper and deeper. Well, it is a perfect opportunity for me to explain the story here. The amount of skeletal animation that I found online, especially good blogs are less than a dozen. Gladly, I would like to point it out here, there is a good youtube video series you can follow, it is in Java, the author provided the source code for reference. Khronos has a shader example here and there are a few others.

Template is a confusing and hard features in C++ if you want use it well, and I think it is also one of the reason which causes c++ programmers cannot understand each other. Sometimes the Deduction rule for c++ is really confusing, you don’t understand why you code doesn’t work or why it works. And Since STL heavily uses nesting Templates, both your compiler and your mind suffers from that.