This is our 15th interview with Wine developers. Check out the Interviews page for previous ones.
Lionel Ulmer's work was actually the impetus for the original interview series. Last year a significant amount of DirectX work prompted an email to get more information about it. Now it's time to dig into more of his work and find out about Wine's DirectX support. Lionel lives in Toulouse, France and works as a software engineer. You can often find him on irc helping people with various problems. Yet, somehow he still manages to climb, hike, snowboard, or virtually anything else that involves the outdoors.
BV: Do you remember the first work you did on Wine?
Lionel: I started to 'test' Wine pretty early in its development phase, not very long after installing my first Linux distribution (it was Slackware in late 1994 - my current development box is still a derivative of this early install). At that time, it was just "oh a new Wine is out, let's try it" and I was running Solitaire , Winmine , and Notepad on it.
One day just for fun I decided to try two recent games I bought, Fallout and Curse of Monkey Island , to see how far they went ... and I was surprised to see something appearing on screen. I was hooked for the next few years :-)
Basically, Marcus did all of the groundwork to get the games to at least start and display something. The only work remaining was to improve what was already there instead of starting from scratch, which is a LOT more difficult to get around doing.
As to the question that was really asked, my first patch (in late 1998) was about adding mouse support to DInput. It was needed for Fallout as CMI used standard Win32 mouse and not DInput.
BV: What's some of the major stuff that's been added to DirectX over the past year?
Lionel: Well, I can mostly only speak about DDraw and D3D as it's been a long time since I did any real DSound or DInput work.
So, in the D3D case, the biggest recent improvements have been done by Jason, Raphael and Christian on the D3D8/9 code. I really need to find more time, a new GPU and start looking at something else than D3D1/7. :-) For example, the recent hardware shader support patch is a prime example of Wine progressing nicely in this domain. But I cannot really comment more as I do not follow in detail the D3D8/9 code as hacking on D3D1/7 already takes much more free time than I actually have.
On the D3D7 side, it all started by a full rewrite of the COM object code to have a basic framework that ran most games even if nothing was actually displayed on screen. That was the most boring part of the job as it's an all-or-nothing type of job, you cannot progress iteratively. After that, we 'just' had to flesh out all the stubs to get things displayed on screen. Major things added are, for example, framebuffer locking, multi-texturing support and stuff like that.
BV: You brought up some terms people might be familiar with. Could you explain some of them?
Lionel: I won't start to explain what COM is otherwise it would fill a whole interview, and I am not really an expert in that domain.
So to come back to more graphic-oriented terms, what I call framebuffer locking is when an application wants to access directly the 2D framebuffer without doing any 3D processing. In Windows, this only incurs a little performance hit (as the 3D pipeline of the graphic card needs to be flushed), but as this framebuffer is memory-mapped into the application's memory space, the latter can directly write to it.
This is not so in OpenGL for which the framebuffer is 'out of bounds' for the application which cannot access it directly. So basically the only way to have access to the framebuffer is via the 'glReadBuffer' call which is often not really optimized in the drivers as it is frowned upon by any serious GL coder. Moreover, as we often do not run in the BPP asked by the game, there is also some colour conversion to be done. There are some recent extensions that may replace the 'glReadBuffer' call, but to experiment with them, I would need first to replace my old 3D card by a real modern GPU.
In conclusion, compared to Windows which directly writes to the video card memory, we need first to copy from the video card to main memory (possibly with colour conversion). Then we have the application write on the buffer there. Finally, we re-blit this buffer (with again colour conversion) to the graphic card again.
Some people often ask, 'Well, if it slows stuff down, can we disable it to get more speed?' The answer is pretty easy: 90% of all D3D1/7 games use this in some critical part of the games, like drawing the mouse cursor, some in-game 2D stuff like HUDs, etc. You won't be able to play any games without it.
Multi-texturing is pretty important to get a speed boost as you process your geometry only once to draw multiple textures (instead of drawing the same geometry multiple times). This is nice for Wine considering the fact that we often need to convert D3D's vertex formats into GL's format and thus it prevents us from doing this conversion twice. Of course, support for it in the hardware is needed, but even my TNT2U has it. Another option is to simulate support for it in our driver when the hardware doesn't have it. This might prevent extra processing of the vertices.
For shaders, I am not really the best person to answer this question as they do not exist at all in D3D1/7. This is the realm of Jason, Raphael and Christian. Basically, the idea is to be able to change attributes (like vertices, pixels, etc) via a program that is executed on the graphic card instead of changing them on the CPU and re-loading these to the card. And to get good speed, hardware support is a must. It's a bit like the difference between interpreted and compiled languages.
BV: How do you go about developing this stuff?
Lionel: The methods depend on the developer. In my case, I started first with some demos from Microsoft's DirectX SDK. When I implemented some very tricky cases, like those in the Twist.exe demo, I found out that nobody ever used them in any game. So I switched track and my current way of is to take an application and fix all the bugs I find up until the time I am either blocked or the game runs perfectly.
This means that the code in the D3D1/7 is far from complete according to what it can do in the MSDN, but it implements most of the stuff needed by games.
Jason, on the other hand, developed D3D8 based on MSDN samples. This means that the breadth of the support will be better, but maybe some optimizations may be missing.
As for the hardest game I got to run, it's certainly DungeonSiege . During my last D3D hacking spree, 75 % of all the patches must have come from my work on this game. This does not work anymore in Wine due to a threading issue and which will lead to another set of heavy hacking.
BV: So, once you spend so much time on a game like DungeonSiege getting it to work, do you every get sidetracked playing them?
Lionel: I get less and less side-tracked playing games. I actually have more fun getting games to work in Wine than playing them once they work. This may explain also why Wine gaming is not a very 'streamlined' experience: once it works enough for me, I switch to something else and I do not spend a lot of time polishing it up. I still remember the day I got my first polygons on screen when working on TombRaider2 , it was much better than actually playing the game to completion :-)
To show you how long it has been since I seriously played any game, the last ones I must have finished must be Grim Fandango and Tomb Raider 2 .
As for my favourite game, I think my fondest gaming memories are on adventure games like the Monkey Island series, Day of the Tentacle or Grim Fandango I also have fond memories of Tomb Raider (on my brand new top-of-the-line 3DFx card).
Currently I am sometimes playing with GeneRally (under Wine of course.) It's a nice free racing car game, like SkidMarks for those who remember it. It's exactly the kind of game that I can still play: you start it up and can just play it for 5 minutes. You do not have all the investment that you need to put in other kinds of games just to progress. I once loved roleplaying games like Eye of the Beholder and Dungeon Master but I just do not have the time anymore to play them.
BV: I vowed not to ever own a good video card after losing six months of my life to Diablo. I'm much more productive with my Matrox G200. Given all the different areas of DirectX and Wine, are there parts you like to work on more than others?
Lionel: I've worked on almost all DirectX libraries except DirectPlay and QUARTZ (a.k.a. DirectShow). For some, like DSound, the code has changed so much since I last worked on it that I don't even know how they work anymore. So, basically, the parts of DirectX I prefer is DirectDraw and Direct3D.
As for other parts of Wine, there is, of course OpenGL. But when I see the number of questions we receive on the #WineHQ channel due to Half-Life and CounterStrike I almost regret having ever started doing it. :-)
In 'core' Wine, I've fixed some bugs here and there but nothing fundamental. I am currently trying to work on the Edit control to get a bit more knowledge of real Win32 programming. The BIG advantage of working on the various DirectX APIs is that you only need a very limited knowledge of Win32.
BV: What are the problems with Half-Life ?
Lionel: Basic Half-Life , the game itself, runs fine in Wine and has for a long time now. The problems we have are either:
I do not follow the HL story at all, so I have no idea what the status on #2 and #3 are currently. But if I had a nickel each time we got a 'Please help me, HL is the only application which still makes me use Windows' plea on #WineHQ, I would now sport a better graphic card.
(and, no, I do not code on Wine for you to be able to ditch Windows, I code on it because it's fun, so you are free to use Windows if it runs your games fine :-) )
BV: You brought up OpenGL. Why is that such a problem? It seems like any time someone touches the headers everything starts to break.
Lionel: Well, the problem with OpenGL headers is that there are too many sources for them. Basically, NVIDIA ships one set of headers with their drivers, then you have the XFree headers, the Mesa headers, the ones you can download on SGI's OpenGL site, etc.
After that, the problem we face is that we do not want to check at 'configure' time for the presence of all the extensions we plan to use. Otherwise the code would be even more of an #ifdef mess than it is currently. And this is perfectly fine with OpenGL as you have all the tools to detect at run-time the features that are actually available (and you know that the constants you use are 'normalized' in the extension and won't change from one implementation to the other).
So our half-assed solution for now is to add in Wine's internal GL header files all the constants / prototypes for the list of (recent) extensions we use in the code. A clean, but overkill, solution would have been to ship in Wine our own private version of gl_ext.h - the reference file with all GL extensions defined.
Note that this problem is only relevant to Wine's D3D and D3D8 code as our GL thunking layer does not need any problematic OpenGL headers.
As for Wine's GL headers, we do not ship any (except for wgl.h).
BV: Everyone involved in Wine's DirectX seems fairly distributed. Is there anything special you do to keep in touch?
Lionel: Well, the distribution is not that widespread for DDraw / D3D as you have three Frenchies and a Brit'.
To be more serious, at the time we wanted to resurrect the D3D code in Wine, I created a private mailing list called wine-d3d to be able to discuss a bit less formally than on wine-devel. The list is pretty quiet now, but it still helped us some times to share ideas, pre-versions of patches and to do some self-motivation.
So there is not really any formal coordination between people. Usually, I work on D3D1/7, with Christian chiming in sometimes to add some features and fixes. On D3D8/9, it's Raphael, Jason and Christian who manage it between themselves. As is the case for the vertex shader patch : started by Jason, sent to wine-d3d and finished by Christian. On DSound, we have Robert working on it.
But it's still in my goals to try to do a DirectX Wine summit in Europe (we are not that far one from the other).
BV: Rok Mandeljc did some DSound work too, right?
Lionel: Well, since the DirectSound code has changed so much since last I hacked on it, I did not follow all the changes... But yeah, Rok also worked on DSound recently and now on DMusic with Raphael.
BV: Have you met any of these guys in person?
Lionel: Actually no. I was the only DirectX guy at the last WineConf and I missed the first one. I had to choose between WineConf and a week of snowboarding and I choose the latter.
BV: You've been working on the same areas as the TransGaming guys. Do you have any contact with them? Is there any tension there?
Lionel: Well, we often interact on IRC, but we do not speak that often of Wine-related subjects :-). We sometimes discuss tricky points, like possible solutions for the aforementioned multi-threading problem or about some debugging sessions on some games.
As for tensions, except when we go down the classical licensing flame war, I never did really feel any. And they perfectly know my opinion on all this: that it's perfectly OK for them to do what they do and the only thing that I resent somewhat is the 'free' WineX CVS that could lure potential developers from our tree.
BV: From what I understand, their approach is quite a bit different than Wine's. However, you've talked of redesigning everything to use a middle layer to consolidate OpenGL calls between the different versions of Direct3D. Are you still planning on doing that?
Lionel: Yes, it's still in our plans to create this layer. At least it's in Raphael's plans as I am not very motivated right now to work on it.
The goal of this layer would be multiple:
Then, the obstacles... The biggest one we have is derived from goal #2. We have basically a choice: do the separation as Windows does it (this is how TransGaming is doing it) or devise our own API. The pros and cons of the two options...
Once we decide how we do it, the work after is to first write the code in the driver (which would mostly be a copy paste of what is in the various code already present in Wine) and then rewrite all the current code using the API. Which is why I am not really motivated to do it as it's something that is not sexy to do.
Anyway, at the moment we are still in the 'let's try to decide what to do' phase of stuff.
BV: It seems like OpenGL adds some overhead to the whole process. Or am I wrong?
Lionel: Well, the overhead when going through OpenGL is mostly when we cannot directly use the data sent by the application and we need to first translate it into something usable by OpenGL. Like, for example, projected vertices. This can incur significant overhead, especially because applications are not written with Wine's limitations in mind.
Apart from that, in my opinion, as the granularity of the API is getting more and more coarse, the overhead is starting to get smaller. What I mean by that is, before one API call would be done pretty fast by the driver (basically, just draw one triangle). Now, with shaders, vertex buffers and all that, one API call sends a lot more work to the driver. So I think the part spent in Wine is less and less important in time compared to the part spent in the driver and graphic card itself.
I may be wrong though as I never measured anything :-)
BV: You demoed 3DMark2000 at WineConf. Does that give any insight on Wine's performance versus Windows?
Lionel: For this too I have no idea. On my main development box, I do not have a version of Windows anymore so I cannot compare. The problem of the laptop I demoed 3DMark2000 on is that the GL driver on the Linux side is not really stable so I was not able to do any real measurements. Moreover, we would not be able to separate what is due to Wine's code and what is due to a sub-optimal OpenGL driver. The best would be to test on an NVIDIA hardware where the core driver is supposedly the same between Windows and Linux.
As for optimizations, I have some ideas for them - mostly on some games who do surface locking. But there are so many problems to fix first, like the dreaded multi-threaded D3D games issue, that I never find the motivation to hack on them.
BV: Recently there's been some people who have performed tests by taking a ton of games and trying to run them. The results have been somewhat mediocre. What's the single biggest problem that prevents Wine from playing games?
Lionel: Well, I think it's still as explained in my slides during WineConf 2004:
So when you ask, 'Will EverQuest work as it uses DX9?' I would answer, 'Does EverQuest really crash due to the missing DX9 support or due to other non-DirectX related problems?'
To be more serious, the current plan is to not start on DX9 support as long as the 'wined3d' layer is not finalized. If it really takes too long, the back-up plan is to copy the complete D3D8 code in the D3D9 library and to modify it to add D3D9. It would be messy but would have a chance to work pretty fast.
BV: Is there any special combination of hardware that seems to work better than others for games?
Lionel: Most of the people (except Jason) use NVIDIA hardware for their 3D card. Despite the fact that it's closed source, it's still one of the most stable and feature-full OpenGL driver out there. On the audio / input side, actual hardware is a bit less important. Except, of course, if you have a SB16 and are hit by the kernel bug that leads to a nice kernel freeze when using Wine.
In my case, I have an old TNT2U as my graphic card and an Emu10k1 audio card.
As for driver issues, an example that comes to mind are problems I had on my laptop using DRI drivers. For example, problems with alpha channel in 32 bit RGB textures. On the other hand, these 'bugs' are often problems in Wine for which I use a special Mesa library built with debugging on. It's REALLY slow on my box, but is a must for debugging any OpenGL errors lurking in the code.
BV: Thanks for taking the time for this interview.
Lionel: While I am under the spotlights right now thanks to my work on DirectX, all this would be for nothing if the rest of Wine did not work. Basically, you can have the best DirectX implementation in the world, if the rest of Wine does not get you the game at least starting and up until the point where it actually uses DirectX, it's all for nothing. So we are just standing on the shoulders of giants (who are doing jobs that are less 'sexy' and 'glamorous' than DirectX but absolutely necessary).