[PATCH] SDL2: Atlas fails to start on Linux

[historic_bruno]

This is an OpenGL context initialization problem, yashi has been debugging it and made a patch on #2041.

#7  0x0000000000a7ddc7 in ogl_Init () at ../../../source/lib/ogl.cpp:479
#8  0x00000000009b3e31 in AtlasMessage::fInitGraphics (msg=0x168ade0)
    at ../../../source/tools/atlas/GameInterface/Handlers/GraphicsSetupHandlers.cpp:84
#9  0x00000000009b3de7 in AtlasMessage::fInitGraphics_wrapper (msg=0x168ade0)
    at ../../../source/tools/atlas/GameInterface/Handlers/GraphicsSetupHandlers.cpp:64
#10 0x0000000000979714 in RunEngine (data=0x7fffffffe100)
    at ../../../source/tools/atlas/GameInterface/GameLoop.cpp:174
#11 0x00007ffff3c7f0a4 in start_thread (arg=0x7fffe077f700) at pthread_create.c:309
#12 0x00007ffff39b4c2d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
(gdb) f 7
#7  0x0000000000a7ddc7 in ogl_Init () at ../../../source/lib/ogl.cpp:479
479		ENSURE(exts);	// else: called before OpenGL is ready for use
(gdb) p exts
$1 = 0x0
(gdb) 

[trompetin17]

Atlas use wxGLCanvas, it create opengl context, if you look in the code for linux ​https://github.com/wxWidgets/wxWidgets/blob/master/src/unix/glx11.cpp#L119

if ( gc->GetGLXContextAttribs()[0] != 0 ) // OpenGL 3 context creation

so by default use opengl version 3 if you already can use in linux. and glGetString(GL_EXTENSIONS) is obsolete as of OpenGL 3.0. most drivers seem to be tolerant of its continued use, but at least some cases on Linux are NOT, and this call returns NULL, thus causing an actual crash in the code.

One way to fix this is to set in atlas.

int glAttribList[] = {
		0, //this 0 make the difference from opengl 3
		WX_GL_RGBA,
		WX_GL_DOUBLEBUFFER,
		WX_GL_DEPTH_SIZE, 24, // TODO: wx documentation doesn't say 24 is valid
		WX_GL_STENCIL_SIZE, 8,
		WX_GL_BUFFER_SIZE, 24, // colour bits
		WX_GL_MIN_ALPHA, 8, // alpha bits
		WX_GL_MAJOR_VERSION, 2,
		0
	};
	Canvas* canvas = new GameCanvas(*this, m_SectionLayout.GetCanvasParent(), glAttribList);

but i need someone who has linux that help me to test,

[historic_bruno]

I haven't tested that the patch works, it should definitely be a Linux-only patch as it breaks on Windows. But looking at the wxWidgets source code, it seems the hack that makes this possible requires wxWidgets 3.0.2? At least on my Ubuntu 14.04 VM, the latest I have is 3.0.0, so to test I need a custom wxWidgets build.

[historic_bruno]

There was some discussion and testing in IRC on ​2015-02-17.

I built wxWidgets 3.0.2 on my Ubuntu VM and tested the above patch, unfortunately the error still occurred.

OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on SVGA3D; build: RELEASE;  
OpenGL version string: 2.1 Mesa 10.1.3
OpenGL shading language version string: 1.20

[historic_bruno]

cleaned up version of yashi's patch from #2041

[historic_bruno]

Finally got around to testing yashi's patch from #2041 and it solves the main problem. I cleaned it up slightly and added a new InitSDL message. So the Atlas init order is now: 1) Init 2) InitSDL 3) SetCanvas 4) InitGraphics

So far I have tested it on Ubuntu 14.04 with both SDL 1.2.15 and SDL 2.0.2, as well as wxWidgets 2.8.12 and 3.0.2, and on Windows (SDL 2.0.3/wxWidgets 3.0.2). Please test on as many systems as possible to help get this into A18!

The ​OpenGL 3+ GL_EXTENSIONS issue is not addressed by the patch, and I don't have a system that can reproduce that problem. I'm going to consider it a separate issue for now. If anyone has a Linux system w/ OpenGL 3+ and can test Atlas with wxWidgets 3.0.2, that would be great.

[trompetin17]

Tested with Yosemite and everything looks ok from atlas

Replying to historic_bruno:

Finally got around to testing yashi's patch from #2041 and it solves the main problem. I cleaned it up slightly and added a new InitSDL message. So the Atlas init order is now: 1) Init 2) InitSDL 3) SetCanvas 4) InitGraphics

So far I have tested it on Ubuntu 14.04 with both SDL 1.2.15 and SDL 2.0.2, as well as wxWidgets 2.8.12 and 3.0.2, and on Windows (SDL 2.0.3/wxWidgets 3.0.2). Please test on as many systems as possible to help get this into A18!

The ​OpenGL 3+ GL_EXTENSIONS issue is not addressed by the patch, and I don't have a system that can reproduce that problem. I'm going to consider it a separate issue for now. If anyone has a Linux system w/ OpenGL 3+ and can test Atlas with wxWidgets 3.0.2, that would be great.

[elexis]

The patch (​http://trac.wildfiregames.com/attachment/ticket/2847/fix-atlas-sdl2.diff) works on my system and Atlas doesn't crash & works as expected.

System Info: -Ubuntu 14.10 -OpenGL version string: 4.4.12968 Compatibility Profile Context 14.501.1003 -AMD Graphics card with fglrx driver from the repository -compiled 0ad against SDL2

[Stan]

It breaks the windows build though. VS reports an access violation and breaks line 495 in HWDETECT.cpp

System Info :

• Windows 8.1.1 64Bits

[historic_bruno]

updated patch to fix crash on Windows

[Stan]

Works for me, with the first patch, the problem was the way I was building atlas.

[ben]

In 16356:

Fixes Atlas on Linux with SDL2 by reordering OpenGL init, based on patch by yashi, fixes #2847