Things that drive me nuts about OpenGL

Here's a brain dump of the things that sometimes drive me crazy about OpenGL. (Note these are strictly my own opinions, not those of Valve or my coworkers. I'm also in a ranty-type mood today after grappling with OpenGL for several years now..) My major motivation to posting this: the GL API needs a reboot because IMO Mantle/D3D12 are going to most likely eat it for lunch soon, so we should start talking and thinking about this stuff now.

Some are minor issues, and some are specific to tracing the API, but all these issues add up to API "friction" that sometimes make it difficult to encourage other devs to get into the GL API or ecosystem:

1. 20 years of legacy, needs a reboot and major simplification pass
Circle the wagons around a core-style API only with no compatibility mode cruft.
Simplify, KISS principle, "if in doubt throw it out"!
Mantle and D3D12 are going to thoroughly leave GL behind (again!) on the performance and developer "mindshare" axes very soon.
Global context state and the binding pattern sucks. The DSA (direct state access)-style API should be standard/required.

Some bitter medicine/tough love: Most devs will take the easy path and port their PS4/Xbone rendering code to D3D12/Mantle. They will not bother to re-write their entire rendering pipeline to use super-aggressive batching, etc. like the GL community has been recently recommending to get perf up. GL will be treated like a second-class citizen and porting target until the API is modernized and greatly simplified.

2. GL context creation hell:
Creating modern GL contexts can be hair raisingly and mind numbingly tricky and incredibly error prone ("trampoline" contexts anyone?). The process is so error prone, and platform (and occasionally even driver) specific that I would almost always recommend to never go directly to the glX, wgl, etc. API's, and instead always use a library such as SDL or GLFW (and something like GLEW to retrieve the function/extension pointers).

The de-facto requirement to always pick from a small set of large 3rd party libraries just to get a real context rolling sucks. The API should be simplified and standardized so using a 3rd party lib shouldn't be a requirement just to get a real context going.

3. The thread's current context may be an implied "this" pointer:
Function pointers returned by GetProcAddress() cannot (or should not - depending on the platform!) be used globally because they may be strongly tied to the context ("context-dependent" vs. "context-independent" in GL-speak). In other words, calling GetProcAddress() on one context and using the returned func pointer on another is either bad form or just crashes.
So is GL a C API or not?
Can we just simplify and standardize all this cruft?

4. glGet() API deficiencies:
This is probably too tracing specific, but it impacts regular devs indirectly because if the tools suck or are non-existent because the API is hard to trace your life as a developer will be harder.
The glGet() series of API's (glGetIntegerv, glGetTexImage, etc.) don't have a "max_size" parameter, so it's possible for the driver to overwrite the passed in buffer depending on the passed in parameters or even the global context state. These functions should accept a "max_size" parameter and the functions should fail if the supplied max_size is too small, not overwrite memory.
Computing the exact size of texture buffers the driver will read or write depends on various global context state - bad bad bad.
There are hundreds of possible glGet() pname enum's, some accepted by only some drivers. If you're writing a tracer or some sort of debug helper, there is no official way to determine how many values will be written by the driver given a specific pname enum. There are no official tables to determine if the indexed variants of glGet() can be used with a specified enum, or determine the optimal (lossless) type to use given a specific enum.
Also, the behavior of indexed vs. non-indexed gets & sets is not always clear to new users of the API.
Alternately, perhaps just add some glGet() metadeta API's vs. publishing tables.

5. glGetError()
There is no glSetLastError() API like Win32, making tracing needlessly complex.
Some apps never call it, some call it once per frame, some only call it while creating resources. Some call it thousands of times at init, and never again. I've seen major shipped GL apps with per-frame GL errors. (Is this normal? Does the developer even know?)

6. Can't query key things such as texture targets
(I know some of this is being worked on - thanks Cass!) This makes tracing/snapshotting more complex due to shadowing.
Shadowing deeply interacts with glGetError()'s (we can't update our shadow until we know the call succeeded, which involves a call to glGetError(), which absorbs the context's current GL error requiring even more fancy footwork to not diverge the traced app's view of GL errors).

About the recent talk of getting rid of all glGet()'s: IMO either all state should be queryable (which is almost the case today), or the API should be written with maximum perf and scalability in mind like D3D12/Mantle. The value added by the API is clearly understood in either of these extremes.
Getting rid of glGet()'s will make writing tracers & context snapshotters even trickier.

7. DSA (Direct State Access) API variants are still not standard and used/supported everywhere
DSA can make a huge difference to call overhead in some apps (such as Source1's GL backend). Just get rid of the reliance on global state, please, and make DSA standard for once and for all.

8. Official spec is still not complete in 2014:
The XML spec still lacks strongly typed param information everywhere. For example:

 <command>
    <proto>void <name>glBindVertexArray</name></proto>
    <param><ptype>GLuint</ptype> <name>array</name></param>
    <glx type="render" opcode="350"/>
  </command>

apitrace's glapi.py is still the only known public, reliable source of this information that I know of:

  GlFunction(Void, "glBindVertexArray", [(GLarray, "array")]),

Notice how glapi.py defines the type as "GLarray", while the official spec just has the nondescript "GLuint" type.

Add glGet info() to official spec: Mentioned above. How many values does the pname enum return? What are the optimal types to use to losslessly retrieve the driver's shadow of this state? Is the pname ok to use with the indexed variants?

9. GLSL version of the week hell:
For early versions, the GLSL version may not sync up with the GL version it was first defined in, making things even more needlessly confusing. And this is before you add in things like GLSL extensions (*not* GL extensions). Can be overwhelming to beginners.

10. No equivalent of standard/official D3DX lib+tools for GL:
Texture/pixel format conversion helpers that don't rely on using the driver or a GL context
KTX format interchange hell: The few tools that read/write the KTX format (GL's equivalent of DDS) can't always read/write eachother's files.
Devs just need the equivalent of Direct3D's DXTEX tool, with source.
The KTX examples just show how to load a KTX file into a GL texture. We need tools to convert KTX files to/from other standard formats, such as DDS, PNG, etc.
A GLSL compiler should be part of this lib (just like you can compile HLSL shaders with D3DX).

11. GL extensions are written as diffs vs the official spec
So if you're not a OpenGL Specification Expert it can be extremely difficult to understand some/many extensions.

Related: The official spec is written for too many audiences. Most consumers of the spec will not be experts in parsing it. The spec should be divided up into a developer-friendly spec vs a deeper spec for the driver writers. Extensions should not be pure delta's vs. the spec - who can really understand that?

12. Documentation hell
We've got 20 years of GL API cruft out there that adds noise to Google searching for GL API information, and beginners can get easily tripped up by bad/legacy documentation/examples.

13. MakeCurrent() hell
Can be extremely expensive, hidden extra variable cost with some extensions (I'm looking at you NV bindless texturing!), can crash drivers (or even the GPU!) if called within a glBegin/glEnd bracket, etc.
The behavior and performance of this call needs to be better specified and communicated to devs.

14. Drivers should not crash the GPU or CPU, or lock up when called in undefined ways via the API
Should be obvious by now. Please hire real testers and bang on your drivers!
Better yet: Structure the API to minimize the # of undefined or unsafe patterns that are even possible to express via the API.

15. Object deletion with multiple contexts, cross-context refcounting rules, "zombie" objects:
Good luck if the object being deleted is currently bound on another context.
Trying to call glGet()'s on a deleted object (that is still partially "live" because it's bound or attached somewhere) - behavior can differ between drivers.
All of this is needless overhead/complexity IMO.
Makes 100% reliable snapshotting and restoring GL context state very, very difficult.
I see world-class developers screw this up without knowing it, which is a clear sign that the API and/or tool ecosystem is broken.

16. Shader compiling/program linking hell
Major performance implications to shader compiling/linking.
Tokenized shader programs work. Direct3D is the existence proof that this approach works. The overall amount of pain GLSL has caused developers porting from D3D and end users (due to slow load times) is incredible, yet GL still only accepts textual GLSL shaders.
Performance drastically varies between drivers. Shader compiling can be effectively a no-op on some drivers, but extremely expensive on others.
Program linking can take *huge* amounts of time.
Some drivers cache linked programs, some don't.
Program linking time can be unpredictable: fast if the program is cached, but there's no way to query if the program is already cached or not. Also no way to query if the driver even supports caching.
Some drivers support threaded compilation, some don't. No way to query if the driver supports threaded compilation.
Some drivers just deadlock or have race conditions when you try to exploit threaded compilation.
Just a bad API, making it hard to trace and snapshot: Shaders can be detached after linking. Lots of linked program state is just not queryable at all, requiring link time shadowing by tracers.
Just copy & paste what D3D is doing (again, it works and devs understand it).

17. Difficult API to trace, replay, and snapshot/restore
Hurts tool ecosystem, ultimately impacts all users of API.
API should either be written to be easily traced/replayed/snapshotted, or incredibly performant/scalable like Mantle/D3D12. Right now GL has none of these properties, putting it in a bad spot from a value proposition perspective.
API authors should focus more on VALUE ADDED and less on how things should work, or how we are different from D3D because we're smarter.

18. Endless maze of GL functions (thousands of them!)
Hey - do we really need dozens of glVertexAttrib variants? Who really even uses this API?
API needs a reboot/simplification pass. Boost the "signal to noise" ratio, please.

19. Legacy complexities around v3.x API transition:
"Forward compatible", "compatibility" vs. "core" profiles etc. etc. etc.
Devs should not have to master this stuff to just use the API to render shaded triangles.
"Core" should not even be in the lexicon.

20. Reliably locking a buffer with DISCARD-semantics on all drivers without stalling the pipeline:
Do you use a map flag? BufferData() with NULL? Both, either, etc.?
What lock flag or flags do you use? Or does the driver just completely ignore the flag?
Trivial in D3D, difficult to do reliably in GL without being an expert or having direct access to driver developers.
This stuff is incredibly important!
Special note to driver developers: What separates the REAL driver devs from wannabees is how well you implement and test stuff like this. Pipeline stalling is not an option in 2014!

21. BufferSubData() stalls when called with "too much" data on threaded drivers
No way to query what "too much" data is. Is it 4k? 8k? 256k?

22. Pipeline stalling
No official (or any) way to get a callback or debug message when the driver decides to throw up its hands and insert a giant pipeline stall into your rendering thread
This can be the #1 source of rendering bottlenecks, yet we still have almost zero tools (or API's to help us build these tools) to track them down

23. Threaded drivers hell
Some manufacturers decide to forceably auto-enable their buggy multithreaded drivers months after titles have been shipped & thoroughly tested by the developer. (And to make matters worse, they do this without informing the developer of the "app profile" change or additions.)
Some multithreaded drivers have buggy glGet()'s when threading is enabled - makes snapshotting a nightmare.
No official way to query or control whether or not the driver will use multithreading.
No way to specify to the driver that a tracer is active which may issue a lot of glGet()'s (that the app would not normally do)
Bone headed threaded drivers that slow to an absolute crawl and stay there when an app or tracer constantly issues glGet()'s (just use a heuristic and automatically turn threading off!)

24. Timestamp queries can stall the pipeline on some drivers
Makes them useless for cross platform, reliable GPU profiling. GL spec should strongly define when the driver is allowed to stall on these queries. Unnecessary stalling should be redefined as a driver bug (by sometimes lazy/incompetent driver developers who don't understand how key these little API's can be).
For reference, NVidia does this stuff correctly. If you are a driver writer working on pipeline query code, please measure your implementation vs. NVidia's driver before bothering to release it.

25. GL is really X different API's (one per driver, sometimes per platform!) masquerading as a single API.
You can't/shouldn't ship a GL product until after you've thoroughly tested for correctness and performance on all drivers (in both threaded and non-threaded modes). You will be surprised at the driver differences. This came as a big shock to me after working for so long with D3D.
This indicates to me that Khronos needs to be more proactive at testing and validating the drivers. GL needs the equivalent of the WHQL process.

26. Extension hell
One of the touted advantages of GL is its support for extensions. I argue that extensions actually harm the API overall, not help it.

I've been through a large amount of major and minor GL callstreams (intricately!) over the previous ~1.5 years. (Before that I was the dev actually making togl work and be shippable on all the drivers. I can't even begin to communicate how difficult and stressful that process was 2+ years ago.) Excluding the driver devs I've probably worked with more real GL callstreams than most GL devs out there. Sadly, in many cases, some to many of the most advanced "modern" extensions barely work yet (and sometimes vendors will even admit this fact publicly). Or, if you try to use a cool-sounding extension you quickly discover that you're pushing a little-used (and tested) path down the driver and the thing is useless for all practical purposes.

From studying and working with the callstreams, it's apparent that devs do a massive MIN() operation across the functionality implemented on the available/targeted drivers. This typically means core profile v3.x, maybe also a 4.x backend with very simple/safe operations. (Or it's a small title that just uses compatiblity GL like it was still 1998 or 2003 - because that's all they need.) They don't bother with most extensions (especially the "modern" ones) because they either don't work reliably (because the driver paths that implement them are not tested on real apps at all - the classic chicken and egg problem), or they are only supported (sometimes barely) by 1 driver, or the value add just isn't there to justify expanding the product testing matrix even more.

Additionally, some of these modern extensions are very difficult to trace, which means that whatever debugging tools employed by the developer aren't compatible with them. So you need a fallback anyway, and if the devs must implement a fallback they might as well just ship the fallback (which works everywhere) and not worry about the extension (unless it adds a significant amount of value to the product).

So unless it's non-extended GL it might as well not be there to a large number of devs who just want to ship a reliable/working product.

Replay Divergence Hell

We've had a handful of traces in vogl that don't replay correctly hanging around in our regression test suite. One g-truc sample (gl-320-fbo-blit) was randomly failing -- turns out it wasn't clearing the backbuffer every frame. It was rendering a checkerboard of quads, so half the pixels in the backbuffer were not being written. Sometimes it would play back seemingly correctly (black pixels where quads weren't being rendered), and sometimes we would see random-looking bits in there.

Anyhow, I'm now trying to figure out why the g-truc sample gl-330-blend-rtt diverges when replayed with vogl. It's also randomly failing. Beyond Compare's image comparison mode can be pretty helpful in cases like this.

Update: OK, I found the problem. The sample uses a FBO with 3 texture attachments, but it was only clearing the first one in display(). The fix is simple:

for (int i = 0; i < 3; i++)
  glClearBufferfv(GL_COLOR, i, &glm::vec4(1.0f)[0]);

vogl Windows port, new regression test system, new vogl_chroot repo

Windows Port Progress

John McDonald has officially begun the Windows port of vogl. The voglcore lib and voglgen (our code generator tool) are now running on Windows as of this morning!

New Regression Test System

vogl has a shiny new tracing/replaying/trimming regression and smoke test system written by Mike Sartain that runs the following steps on a library of traces:

• Plays back either an apitrace or a vogl trace, captures its output using the libvogltrace SO, and records the backbuffer CRC's (or per-component checksums on traces with multisampling) to a text file.
• Plays back this trace and diffs the backbuffer CRC's vs. the CRC's seen during tracing.
• Finally, we trim the test trace, then play back the trimmed trace and compare the backbuffer CRC's vs. the original trace's CRC's. Trimming involves playing back the test trace up to a predetermined point, capturing the entire GL state vector to memory and serializing it out, so we get a lot of good coverage in this step.

The system is located in the test directory of vogl's chroot repository, here. The script that runs the test is run_tests.sh. (This little script actually compiles and launches a small .C file that contains the entire test system.) The file tests.json configures which traces are tested and the parameters to the various test steps. 

Currently, only our smallest traces (from the g-truc 3.x suite) are pushed up to vogl_chroot. We also have many GB's of game traces (please drop me a message if you would like these traces). It's pretty easy to add your own traces - I'll be documenting how on vogl's wiki this afternoon.

Here are some shots of it in action on our dual Xeon (20 core/40 HW thread) test machine, using "/run_tests.sh -j 6" - to spawn up to 6 parallel processes at a time vs. the default 4:

Interestingly, the limiting scaling factor on this system seems to primarily be GPU video memory, not raw CPU or GPU performance. Metro Last Light, TF2, and DotA2 each can use ~1 GB of VRAM (and we only have a 3GB 780 Ti on this system). We don't try to order the trace replay order in any particular way to optimize overall throughput, which would be a nice addition.

vogl_src and vogl_chroot repos

Thanks to Carl Worth (Intel OTC) and Sir Anthony for submitting some patches to help us break up the previously huge vogl repo into two smaller repos. The primary one on github contains only the (buildable) source:

https://github.com/ValveSoftware/vogl

And vogl_chroot is the optional portion we use internally to simplify building and testing vogl:

https://bitbucket.org/raddebugger/vogl_chroot

You don't strictly need vogl_chroot, but beware you'll need to manually figure out the build dependencies if you don't. Building both 32-bit and 64-bit vogl without using the chroot approach can be a huge pain due to sometimes unresolvable/obscure i386 vs. amd64 system dependency issues. (If you disagree, I claim you haven't tried to actually do it. And no, gcc-multilib is not enough.)

Next Steps

We've been supplied with more test traces from various teams working on titles that will be released later this year on Steam Linux. (Hey - if you're working on a new GL game or port, feel free to send us more traces!) Also, Rad Game Tools just provided us with a fresh drop of Bink video, which now supports using compute shaders to massively accelerate video decoding. I'll be adding support for its GL 4.x callstream next week.

vogl support for Unreal Engine 4

We're extremely excited that Epic is porting Unreal Engine 4 to Linux -- see the official announcement or some press here and here. Once we heard UE4 Linux was coming we pretty much dropped everything to ensure vogl can handle UE4 callstreams. The latest code on github now supports full-stream tracing/replaying and trimming of UE4 callstreams in either GL3 or GL4 mode. UI support for UE4 is still in the early stages, but now that we can snapshot/restore UE4 and continue to play back the callstream without diverging it's only matter of time before the UI comes up to speed.

UE4's OpenGL renderer is the most advanced we've worked with so far. It has provided us with valuable real-world test cases for several modern GPU features we've not had traces to validate our code against, such as compute shaders and cubemap arrays. We'll be making UE4 GL callstreams part of our regression test suite going forward.

Here are some shots of a trace of UE4's test game being replayed in voglreplay64's --interactive mode (which relies on state snapshotting/restoring):

Here's a trimmed trace loaded in the editor:

Known problems:

• UI: Peter Lohrmann just added a dropdown that lets you select which context's state to view. This code is hot off the presses and is a bit fiddly at the moment. Also, UE4 uses several texture formats that the vogl UI can't display right now (LunarG is helping us fix this, see below.)
• Snapshotting UE4 during tracing is currently unsupported (but snapshotting during replaying works), because the tracer can't snapshot state while any buffers are mapped. (We also have this problem with the Steam Big Picture renderer.) We have a fix in the works.
• We're seeing several query related warnings/errors while snapshotting and replaying UE4 callstreams. (This problem is in vogl's replayer, not UE4.) These need to be investigated, but they don't seem to cause the replayer to diverge.
• There are several "zombie" buffer objects that have been deleted on one context but remain bound on another, which causes the snapshot system to report handle remapping errors on these objects during snapshotting. These buffers don't appear to be actually referenced after they are deleted, so this doesn't cause the replay to diverge. We've got some ideas on how to improve vogl's handling of this scenario (which is unfortunately very easy to do by accident in GL).

Other news:

LunarG has provided us with the first drop of their universal OpenGL texture format converter/transformer module, which will be going open source soon. This module allows us to convert any type of OpenGL/KTX texture data to various canonical formats (such as 8-bit or float RGBA) in a driver independent manner, with the optional transforms we need to build a good texture/framebuffer viewer UI. The current vogl UI uses some temporary and very incomplete stand-in code to convert textures to formats Qt accepts, so we're really looking forward to switching to LunarG's solution.

Finally, John McDonald recently joined Valve and the SteamOS team and is currently getting up to speed on the vogl codebase.

couple vogl debugger/editor UI screenshots

vogl's UI (being worked on by Peter Lohrmann) has come far in the past month. I used it today while debugging what seemed to be a replay bug in Xonotic (reported by a dev named blackout24 on github). I first trimmed a single frame that clearly showed the problem, then played back this trimmed trace in a endless loop to verify the issue still showed up in the trim. I manually trimmed the source trace using voglreplay64, but I think initial support for doing all this directly from the UI just went in.

The UI helped me quickly pinpoint the first draw affected by the rendering problem. I then drilled down and examined all the GL state, textures, shaders, etc. on and around this draw. Clicking on a GL command that already had a snapshot was fast, only around a second in debug, and around 3-4 seconds on commands without snapshots. I still dumped the trimmed trace to JSON+loose files, more out of habit than anything, but using the UI was much faster than doing things the old way (which involved dumping massive amounts of PNG's on each major event, then using voglreplay -find and/or grep on huge JSON files).

Here's the pinpointed draw showing the problem (a completely opaque foliage billboard that should have been rendered transparently):

Depth and stencil buffers are currently displayed by mapping their individual bytes directly to image components - we're working on that.

Here's the foliage texture. I enabled alpha blending in the UI to double check the texture's alpha channel was reasonable:

Xonotic replay showing the problem, with the powerful QtCreator IDE in the background:

Turns out the problem was caused by Xonotic's usage of alpha to coverage on a multisampled default framebuffer. We don't currently support automatically enabling multisampling on default framebuffers during replaying. (We do of course support MSAA renderbuffers/textures/FBO's, but not on the default framebuffer yet.)

For now, I added a "-msaa X" command line option to the replayer to enable MSAA on the default framebuffer until we address this. This is crappy, but the vast majority of GL apps just don't enable MSAA this way and we have bigger fish to fry at the moment. (Also, I don't want to touch vogl's GLX/X-Windows related code until we abstract it away into SDL or something.)

vogl's tracer/replayer now supports the Steam Linux client

Steam's Big Picture mode is one of the last remaining Valve OpenGL apps that vogl didn't support until now. (The desktop client's GL callstream has worked for months.) The fixes for Big Picture are now all pushed to our github repo.

Here's a Big Picture ("10ft") replay in interactive mode after pausing (which involves a full state snapshot, context teardown, and state restore) and continuing playback:

Replaying 10ft traces on NVidia technically works, but there's a driver bug that is causing playback to be extremely slow on my box (that NVidia is checking out). So all tracing and replaying in these shots was done on a AMD 57xx series part using the closed source fglrx driver.

The desktop ("2ft") GL callstream is looking good too, but compared to 10ft I have hardly spent any time looking at it. (I used the "-lock_window_dimensions -width 2560 -height 1600" cmd line options to replay this trace for 10ft, so the window is much bigger than needed for 2ft):

There are some known remaining issues, none of them show stoppers for debugging purposes. I'll be adding this trace to our shiny new regression test system Mike Sartain is working on soon.

- The replayer's auto window resize logic is almost useless on Steam traces because it creates so many trampoline contexts (associated with tiny windows) during startup and mode changes. So you must currently replay using "-lock_window_dimensions -width X -height Y".

- Can't make single/multi-frame snapshots of 10ft during tracing, only replaying. This isn't a big deal, because you can make a full-stream trace and just trim the frames you want to look at.

This problem is caused by the 10ft renderer keeping several buffers mapped all the time. I have a safe and easy fix coming that might address this issue (but it'll only work when the app keeps the entire buffer mapped).

- Can only debug 10ft on AMD until the NVidia driver bug is fixed

- The UI has not been tested on 10ft traces yet. Peter Lohrmann just added better support for debugging traces containing multiple contexts (specifically to help 10ft debugging along) which I'll try soon.

- The 10ft renderer deletes textures while they are still bound to FBO's (and keeps the FBO's around)

This causes various problems for the snapshot code because it can't retrieve the texture attachment handles in these FBO's (we just get 0's for the GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME), and (the last time I checked) we can't reliably retrieve information on these deleted textures on all drivers. This seems to be a very rare pattern (that I've never seen in any game titles, just 10ft). After asking around it turns out this problem is not a showstopper for 10ft because it always rebinds a new texture to the same attachment point before it ever renders to the FBO again.

All that red text in the below screenshot is due to this issue, but the output should still be correct.

You don't need to do anything special to trace steam:

./trace.sh /usr/bin/steam

trace.sh is our example tracing script, see here. The example script causes the tracer to wait for a keypress, but you may not see the "waiting for keypress" message - just press any key if the app appears to stop.

Trying SmartGitHg build v6 preview 4

We've been using Mercurial+TortoiseHg for the previous year (with hosting on Bitbucket), but the open source mainstream uses git so we're now switching vogl over to it exclusively. I gather most Linux devs primarily use command line tools, which is fine and all (I obviously do too when needed) but I want to find good GUI's for this stuff. The last time I had to use CLI tools for version control was 1997 under DOS.

There's an added bonus to being obstinate and pushing to find and use good native Linux GUI's for our major devtools: devs porting from the Windows/OSX/console worlds already have huge piles of solid GUI-based tools, and we need to find reasonably competitive native Linux alternatives. (When I say "native", I mean "not under Wine". I use Wine every day to run some old non-critical Windows programs I just can't find Linux alternatives for that I like, such as the Boxer Text Editor and Paint Shop Pro. Wine seems to run older Win32 apps better than Windows 7/8 itself these days!)

So I'm on the lookout for a git UI that is at least as good as TortoiseHg for doing the basics. I found a good Visual Studio alternative (QtCreator) a year ago after a wide search involving around a half dozen other Linux IDE's. I knew QtCreator was a good product after using its debugger for 20 minutes. It's by no means perfect but I've not had to use gdb/cgdb once since switching to it.

SmartGitHg has been on my radar, so I'm trying it out. It's commercial but has a 30 day trial (and is free for non-commercial use). This thing could be unusable -- I have no idea yet.

http://www.syntevo.com/smartgithg/early-access

It needs openjdk-7-jre to run, which I installed first using the Muon package manager (under Ubuntu 13.10+KDE). The UI seems more complex, but cleaner, than TortoiseHg's. If you're already familiar with Mercurial/thg it seems pretty easy to map over the concepts and accomplish the basics. I just pushed a trivial change up using it (added a link to the vogl wiki). I'll keep trying UI's if necessary until something works for 90% of the things devs do (add files, check in, push, pull, merge, resolve conflicts, browse history, etc).