Merge lp:~widelands-dev/widelands/opengl_debug into lp:widelands

[SirVer]

- Fixes a bug: We never created zero sized textures, but sometimes we tried to render on them. This is uncritical, theoretically, but I fixed it anyways.
- Added a new undocumented command line argument --debug_gl_trace which will log every OpenGL call that is made, together with arguments, return values and glError status. This requires that Widelands is build using -DOPTION_USE_GLBINDING:BOOL=ON. It is a NoOp for GLEW. This will help debugging non-reproducible OpenGL errors that are reported. Tested with glbinding 1.1.0.
- More logging when OpenGL is initialized.
- Pulls out OpenGL initialization into a separate unit.

Small bug fixes and better debug potential for OpenGL - but only if glbinding is used.

[bunnybot (widelandsofficial)]

Hi, I am bunnybot (https://github.com/widelands/bunnybot).

I am keeping the source branch lp:~widelands-dev/widelands/opengl_debug mirrored to https://github.com/widelands/widelands/tree/_widelands_dev_widelands_opengl_debug

You can give me commands by starting a line with @bunnybot <command>. I understand:
 merge: Merges the source branch into the target branch, closing the merge proposal. I will use the proposed commit message if it is set.

[GunChleoc (gunchleoc)]

Not compiled or tested yet, but code LGTM - just 2 nits.

I think the option and build requirement should be documented somewhere in the code, because we won't find it in this commit message down the road. I think copying the commit message to src/graphic/gl/initialize.cc should be enough for now.

[kaputtnik (franku)]

This is what i get with this branch:

Set home directory: /home/kaputtnik/.widelands
Widelands executable directory: /home/kaputtnik/widelands-repo/opengl_debug/
Adding directory: /home/kaputtnik/widelands-repo/opengl_debug/.
selected language: (system language)
using locale de_DE.UTF-8
Graphics: Try to set Videomode 800x600
Graphics: OpenGL: Version "3.0 Mesa 11.1.1"
Graphics: SDL_GL_RED_SIZE is 8
Graphics: SDL_GL_GREEN_SIZE is 8
Graphics: SDL_GL_BLUE_SIZE is 8
Graphics: SDL_GL_ALPHA_SIZE is 0
Graphics: SDL_GL_BUFFER_SIZE is 24
Graphics: SDL_GL_DOUBLEBUFFER is 1
Graphics: SDL_GL_DEPTH_SIZE is 24
Graphics: SDL_GL_STENCIL_SIZE is 8
Graphics: SDL_GL_ACCUM_RED_SIZE is 0
Graphics: SDL_GL_ACCUM_GREEN_SIZE is 0
Graphics: SDL_GL_ACCUM_BLUE_SIZE is 0
Graphics: SDL_GL_ACCUM_ALPHA_SIZE is 0
Graphics: SDL_GL_STEREO is 0
Graphics: SDL_GL_MULTISAMPLEBUFFERS is 0
Graphics: SDL_GL_MULTISAMPLESAMPLES is 0
Graphics: SDL_GL_ACCELERATED_VISUAL is 1
Graphics: SDL_GL_CONTEXT_MAJOR_VERSION is 2
Graphics: SDL_GL_CONTEXT_MINOR_VERSION is 1
Graphics: SDL_GL_CONTEXT_FLAGS is 0
Graphics: SDL_GL_CONTEXT_PROFILE_MASK is 2
Graphics: SDL_GL_SHARE_WITH_CURRENT_CONTEXT is 0
Graphics: SDL_GL_FRAMEBUFFER_SRGB_CAPABLE is 0
Graphics: OpenGL: Double buffering enabled
Graphics: OpenGL: Max texture size: 8192
Graphics: OpenGL: ShadingLanguage: "1.30"
**** GRAPHICS REPORT ****
 VIDEO DRIVER x11
 pixel fmt 370546692
 size 800 600
**** END GRAPHICS REPORT ****

[SirVer (sirver)]

Adresed all comments and copied an explanative text into initialize.cc

[GunChleoc (gunchleoc)]

Compiler warning:

[ 11%] Building CXX object src/graphic/CMakeFiles/graphic_gl_utils.dir/gl/initialize.cc.o
/home/bratzbert/sources/widelands/opengl_debug/src/graphic/gl/initialize.cc:32:1: warning: unused parameter ‘trace’ [-Wunused-parameter]
 initialize(const Trace& trace, SDL_Window* sdl_window, GLint* max_texture_size) {
 ^

[SirVer (sirver)]

fixed the unused variable.

[GunChleoc (gunchleoc)]

Here's my output - it complains about "debug_gl_trace" not being Boolean, both before and after the commit regarding trace. I simply called ./compile.sh for the compilation, is the switch in CMake set?

[] [/home/bratzbert/sources/widelands/opengl_debug/src/profile/profile.cc:167] debug_gl_trace: '' is not a boolean value
Graphics: Try to set Videomode 800x600
Graphics: OpenGL: Version "2.1 Mesa 10.1.3"
Graphics: SDL_GL_RED_SIZE is 8
Graphics: SDL_GL_GREEN_SIZE is 8
Graphics: SDL_GL_BLUE_SIZE is 8
Graphics: SDL_GL_ALPHA_SIZE is 8
Graphics: SDL_GL_BUFFER_SIZE is 32
Graphics: SDL_GL_DOUBLEBUFFER is 1
Graphics: SDL_GL_DEPTH_SIZE is 24
Graphics: SDL_GL_STENCIL_SIZE is 8
Graphics: SDL_GL_ACCUM_RED_SIZE is 0
Graphics: SDL_GL_ACCUM_GREEN_SIZE is 0
Graphics: SDL_GL_ACCUM_BLUE_SIZE is 0
Graphics: SDL_GL_ACCUM_ALPHA_SIZE is 0
Graphics: SDL_GL_STEREO is 0
Graphics: SDL_GL_MULTISAMPLEBUFFERS is 0
Graphics: SDL_GL_MULTISAMPLESAMPLES is 0
Graphics: SDL_GL_ACCELERATED_VISUAL is 1
Graphics: SDL_GL_CONTEXT_MAJOR_VERSION is 2
Graphics: SDL_GL_CONTEXT_MINOR_VERSION is 1
Graphics: SDL_GL_CONTEXT_FLAGS is 0
Graphics: SDL_GL_CONTEXT_PROFILE_MASK is 2
Graphics: SDL_GL_SHARE_WITH_CURRENT_CONTEXT is 0
Graphics: SDL_GL_FRAMEBUFFER_SRGB_CAPABLE is 0
Graphics: OpenGL: Double buffering enabled
Graphics: OpenGL: Max texture size: 8192
Graphics: OpenGL: ShadingLanguage: "1.20"
**** GRAPHICS REPORT ****
 VIDEO DRIVER x11
 pixel fmt 370546692
 size 800 600
**** END GRAPHICS REPORT ****

[SirVer (sirver)]

> [] [/home/bratzbert/sources/widelands/opengl_debug/src/profile/profile.cc:167] debug_gl_trace: '' is not a boolean value

Seems like you have it already set in your ~/.widelands/config? strange.

> is the switch in CMake set?

No, we default to using GLEW for compilation since it is mature and packaged and available. You need to set the flag yourself and install glbinding[1] to test this.

cmake -G Ninja -DOPTION_USE_GLBINDING:BOOL=ON -DCMAKE_BUILD_TYPE:STRING="Debug" ..

should do the trick.

[1] https://github.com/cginternals/glbinding

[GunChleoc (gunchleoc)]

My fault, I passed --debug_gl_trace instead of --debug_gl_trace=yes

My system can't handle ninja, so I tried now:

mkdir build
cd build
cmake -DOPTION_USE_GLBINDING:BOOL=ON -DCMAKE_BUILD_TYPE:STRING="Debug" ..

Which gives me:

CMake Error at CMakeLists.txt:60 (find_package):
  By not providing "Findglbinding.cmake" in CMAKE_MODULE_PATH this project
  has asked CMake to find a package configuration file provided by
  "glbinding", but CMake did not find one.

  Could not find a package configuration file provided by "glbinding" with
  any of the following names:

    glbindingConfig.cmake
    glbinding-config.cmake

  Add the installation prefix of "glbinding" to CMAKE_PREFIX_PATH or set
  "glbinding_DIR" to a directory containing one of the above files. If
  "glbinding" provides a separate development package or SDK, be sure it has
  been installed.

[GunChleoc (gunchleoc)]

Duh, I need to install glbinding first... compiling now.

[GunChleoc (gunchleoc)]

OK, next problem:

bratzbert@museum:~/sources/widelands/opengl_debug$ cd build
bratzbert@museum:~/sources/widelands/opengl_debug/build$ cmake -DOPTION_USE_GLBINDING:BOOL=ON -DCMAKE_BUILD_TYPE:STRING="Debug" .
-- Boost version: 1.54.0
-- Found the following Boost libraries:
-- unit_test_framework
-- regex
-- SDL2_INCLUDE_DIR is /usr/include/SDL2
-- SDL2MAIN_LIBRARY is /usr/lib/x86_64-linux-gnu/libSDL2main.a
-- Found GLBINDING: /usr/local/lib/libglbinding.so
-- Version of Widelands Build is bzr7737[opengl_debug](Debug)
-- Found Doxygen: /usr/bin/doxygen (found version "1.8.6")
-- Configuring done
-- Generating done
-- Build files have been written to: /home/bratzbert/sources/widelands/opengl_debug/build

bratzbert@museum:~/sources/widelands/opengl_debug/build$ make
Scanning dependencies of target BzrRevision
-- Version of Widelands Build is bzr7737[opengl_debug](Debug)
[ 0%] Built target BzrRevision
Scanning dependencies of target third_party_eris

<snip>

[ 11%] Building CXX object src/graphic/CMakeFiles/graphic_gl_utils.dir/gl/initialize.cc.o
/home/bratzbert/sources/widelands/opengl_debug/src/graphic/gl/initialize.cc: In lambda function:
/home/bratzbert/sources/widelands/opengl_debug/src/graphic/gl/initialize.cc:62:29: error: request for member ‘name’ in ‘call.glbinding::FunctionCall::function’, which is of pointer type ‘const glbinding::AbstractFunction* const’ (maybe you meant to use ‘->’ ?)
    log("%s(", call.function.name());
                             ^
make[2]: *** [src/graphic/CMakeFiles/graphic_gl_utils.dir/gl/initialize.cc.o] Error 1
make[1]: *** [src/graphic/CMakeFiles/graphic_gl_utils.dir/all] Error 2
make: *** [all] Error 2

[wl-zocker (wl-zocker)]

Is this branch to find the problems I encounter? If so, will there be an appveyor build of this branch that will be built with the needed parameters? (I have no building environment on Windows.)

[TiborB (tiborb95)]

The problem is gone. The code also LGTM.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 377. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/104463853.
Appveyor build 284. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-284.

[SirVer (sirver)]

> The problem is gone. The code also LGTM.

Tibor, Which problem are you referring to?

> [ 11%] Building CXX object src/graphic/CMakeFiles/graphic_gl_utils.dir/gl/initialize.cc.o
...

I used a older version of glbinding, apparently they changed the interface. I updated to 1.1.0 and got the same error. Fixed now.

> Is this branch to find the problems I encounter?

There are 3 lurking issues with OpenGL right now: bug 1536377, bug 1535732 and a dynamic drawing problem that was reported on Facebook: http://www.youtube.com/watch?v=v8JG1qjZQ9o. I hope this branch gets us closer to fixing all of them.

> If so, will there be an appveyor build of this branch that will be built with the needed parameters?

That is the intention. Tino managed to build this branch on his local machine already and he was trying to make it work on appveyor too. The debug code will also be in release builds, so a build from appveyor will have it.

We should also switch our PPA away from glew and to glbinding, IMHO. It is a much superior gl loader.

[TiborB (tiborb95)]

@SirVer,

Please ignore my comment, it belongs to other merge request...

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 382. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/104561461.
Appveyor build 289. State: success. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-289.

[Tino (tino79)]

I did not succeed in compiling the glbindings library for now. It does seem to depend on posix threads and does not detect the correct version on my system with mingw-w64.
But i'll continue to try...

I've created a github branch for this branch with a changed appveyor.yml wich enables glbinding: https://ci.appveyor.com/project/widelands-dev/widelands/build/opengl_binding-290

Let's wait if appveyor does manage to build it at some point without a timeout...

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 382. State: errored. Details: https://travis-ci.org/widelands/widelands/builds/104561461.
Appveyor build 289. State: success. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-289.

[GunChleoc (gunchleoc)]

I can compile and run Widelands now.

review: Approve

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 382. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/104561461.
Appveyor build 289. State: success. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-289.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 385. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/104601532.
Appveyor build 293. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-293.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 385. State: canceled. Details: https://travis-ci.org/widelands/widelands/builds/104601532.
Appveyor build 293. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-293.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 386. State: failed. Details: https://travis-ci.org/widelands/widelands/builds/104617324.
Appveyor build 294. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_opengl_debug-294.

[Tino (tino79)]

Ok, i've changed both appveyor and travis scripts to use glbindings:
- Appveyor does fail because it seems at some point GLEW is still included
- Travis fails because no glbindings debian package is installed

I would really like to get both CI systems to build with GLBindings before merging.

review: Needs Fixing

[wl-zocker (wl-zocker)]

Please ping me once you have something I can try. I will not read all comments in this request in detail.

[SirVer (sirver)]

> c I would really like to get both CI systems to build with GLBindings before merging.

As discussed in chat, I reverted the CI changes. I'd like to get the code in as it is approved, we can figure out CI in separate branches after that.

> - Appveyor does fail because it seems at some point GLEW is still included

Fixed in 7744.

> - Travis fails because no glbindings debian package is installed

We need to wire up a PPA I guess. More important than travis is our own PPA though - having the trace feature in the PPA would make debugging OpenGL issues on other Linux computers much easier.

> Please ping me once you have something I can try. I will not read all comments in this request in detail.

I will update the bugs and reach out to once this is all figured out. Still a chunk of work to do though.

@bunnybot merge

=== modified file 'cmake/WlFunctions.cmake'
--- cmake/WlFunctions.cmake	2015-09-19 12:19:37 +0000
+++ cmake/WlFunctions.cmake	2016-01-25 20:17:39 +0000
@@ -85,18 +85,23 @@
   endif()
 
   # OpenGL and GLEW are one thing for us. If you use the one, you also use the
-  # other.
+  # other. We always add definitions, because add_definition() is not
+  # transitive and therefore some dependent targets do not set them properly.
+  # And a few -D do not hurt anything.
+  if(OPTION_USE_GLBINDING)
+    add_definitions("-DUSE_GLBINDING")
+  else()
+    add_definitions(${GLEW_EXTRA_DEFINITIONS})
+  endif()
   if(ARG_USES_OPENGL)
     if(OPTION_USE_GLBINDING)
       wl_include_system_directories(${NAME} ${GLBINDING_INCLUDES})
       target_link_libraries(${NAME} ${GLBINDING_LIBRARIES})
       target_link_libraries(${NAME} ${OPENGL_gl_LIBRARY})
-      add_definitions("-DUSE_GLBINDING")
     else()
       wl_include_system_directories(${NAME} ${GLEW_INCLUDE_DIR})
       target_link_libraries(${NAME} ${GLEW_LIBRARY})
       target_link_libraries(${NAME} ${OPENGL_gl_LIBRARY})
-      add_definitions(${GLEW_EXTRA_DEFINITIONS})
     endif()
   endif()
 

=== modified file 'src/graphic/CMakeLists.txt'
--- src/graphic/CMakeLists.txt	2016-01-19 07:33:34 +0000
+++ src/graphic/CMakeLists.txt	2016-01-25 20:17:39 +0000
@@ -87,6 +87,8 @@
   SRCS
     gl/blit_data.h
     gl/coordinate_conversion.h
+    gl/initialize.cc
+    gl/initialize.h
     gl/system_headers.h
     gl/utils.cc
     gl/utils.h

=== added file 'src/graphic/gl/initialize.cc'
--- src/graphic/gl/initialize.cc	1970-01-01 00:00:00 +0000
+++ src/graphic/gl/initialize.cc	2016-01-25 20:17:39 +0000
@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2006-2016 by the Widelands Development Team
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include "graphic/gl/initialize.h"
+
+#include <csignal>
+
+#include <SDL.h>
+
+#include "base/macros.h"
+#include "graphic/gl/utils.h"
+
+namespace Gl {
+
+SDL_GLContext initialize(
+#ifdef USE_GLBINDING
+   const Trace& trace,
+#else
+   const Trace&,
+#endif
+   SDL_Window* sdl_window,
+   GLint* max_texture_size) {
+	// Request an OpenGL 2 context with double buffering.
+	SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
+	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
+	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
+	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY);
+	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 16);
+	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
+
+	SDL_GLContext gl_context = SDL_GL_CreateContext(sdl_window);
+	SDL_GL_MakeCurrent(sdl_window, gl_context);
+
+#ifdef USE_GLBINDING
+	glbinding::Binding::initialize();
+
+	// The undocumented command line argument --debug_gl_trace will set
+	// Trace::kYes. This will log every OpenGL call that is made, together with
+	// arguments, return values and glError status. This requires that Widelands
+	// is built using -DOPTION_USE_GLBINDING:BOOL=ON. It is a NoOp for GLEW.
+	if (trace == Trace::kYes) {
+		setCallbackMaskExcept(
+				glbinding::CallbackMask::After | glbinding::CallbackMask::ParametersAndReturnValue,
+				{"glGetError"});
+		glbinding::setAfterCallback([](const glbinding::FunctionCall& call) {
+			log("%s(", call.function->name());
+			for (size_t i = 0; i < call.parameters.size(); ++i) {
+				log("%s", call.parameters[i]->asString().c_str());
+				if (i < call.parameters.size() - 1)
+					log(", ");
+			}
+			log(")");
+			if (call.returnValue) {
+				log(" -> %s", call.returnValue->asString().c_str());
+			}
+			const auto error = glGetError();
+			log(" [%s]\n", gl_error_to_string(error));
+			// The next few lines will terminate Widelands if there was any OpenGL
+			// error. This is useful for super aggressive debugging, but probably
+			// not for regular builds. Comment it in if you need to understand
+			// OpenGL problems.
+			// if (error != GL_NO_ERROR) {
+			// std::raise(SIGINT);
+			// }
+		});
+	}
+#else
+	// See graphic/gl/system_headers.h for an explanation of the next line.
+	glewExperimental = GL_TRUE;
+	GLenum err = glewInit();
+	if (err != GLEW_OK) {
+		log("glewInit returns %i\nYour OpenGL installation must be __very__ broken. %s\n", err,
+		    glewGetErrorString(err));
+		throw wexception("glewInit returns %i: Broken OpenGL installation.", err);
+	}
+#endif
+
+	log(
+	   "Graphics: OpenGL: Version \"%s\"\n", reinterpret_cast<const char*>(glGetString(GL_VERSION)));
+
+#define LOG_SDL_GL_ATTRIBUTE(x)                                                                        \
+	{                                                                                               \
+		int value;                                                                                   \
+		SDL_GL_GetAttribute(x, &value);                                                              \
+		log("Graphics: %s is %d\n", #x, value);                                                      \
+	}
+
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_RED_SIZE)
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_GREEN_SIZE)
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_BLUE_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_ALPHA_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_BUFFER_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_DOUBLEBUFFER);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_DEPTH_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_STENCIL_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_ACCUM_RED_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_ACCUM_GREEN_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_ACCUM_BLUE_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_ACCUM_ALPHA_SIZE);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_STEREO);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_MULTISAMPLEBUFFERS);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_MULTISAMPLESAMPLES);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_ACCELERATED_VISUAL);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_CONTEXT_MAJOR_VERSION);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_CONTEXT_MINOR_VERSION);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_CONTEXT_FLAGS);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_CONTEXT_PROFILE_MASK);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_SHARE_WITH_CURRENT_CONTEXT);
+	LOG_SDL_GL_ATTRIBUTE(SDL_GL_FRAMEBUFFER_SRGB_CAPABLE);
+#undef LOG_SDL_GL_ATTRIBUTE
+
+	GLboolean glBool;
+	glGetBooleanv(GL_DOUBLEBUFFER, &glBool);
+	log("Graphics: OpenGL: Double buffering %s\n", (glBool == GL_TRUE) ? "enabled" : "disabled");
+
+	glGetIntegerv(GL_MAX_TEXTURE_SIZE, max_texture_size);
+	log("Graphics: OpenGL: Max texture size: %u\n", *max_texture_size);
+
+	log("Graphics: OpenGL: ShadingLanguage: \"%s\"\n",
+	    reinterpret_cast<const char*>(glGetString(GL_SHADING_LANGUAGE_VERSION)));
+
+	glDrawBuffer(GL_BACK);
+
+	glDisable(GL_DEPTH_TEST);
+	glDepthFunc(GL_LEQUAL);
+
+	glEnable(GL_BLEND);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	return gl_context;
+}
+
+}  // namespace Gl

=== added file 'src/graphic/gl/initialize.h'
--- src/graphic/gl/initialize.h	1970-01-01 00:00:00 +0000
+++ src/graphic/gl/initialize.h	2016-01-25 20:17:39 +0000
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2006-2016 by the Widelands Development Team
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#ifndef WL_GRAPHIC_GL_INITIALIZE_H
+#define WL_GRAPHIC_GL_INITIALIZE_H
+
+#include <SDL.h>
+
+#include "graphic/gl/system_headers.h"
+
+namespace Gl {
+
+// Initializes OpenGL. Creates a context for 'window' using SDL and loads the
+// GL library. Fills in 'max_texture_size' and returns the created SDL_Context
+// which must be closed by the caller.
+// If we are built against glbinding, 'trace' will set up tracing for
+// OpenGL and output every single opengl call ever made, together with it's
+// arguments, return values and the result from glGetError.
+enum class Trace {
+	kYes,
+	kNo,
+};
+SDL_GLContext
+initialize(const Trace& trace, SDL_Window* window, GLint* max_texture_size);
+
+}  // namespace Gl
+
+#endif  // end of include guard: WL_GRAPHIC_GL_INITIALIZE_H

=== modified file 'src/graphic/gl/system_headers.h'
--- src/graphic/gl/system_headers.h	2016-01-23 15:44:29 +0000
+++ src/graphic/gl/system_headers.h	2016-01-25 20:17:39 +0000
@@ -32,10 +32,7 @@
 // http://stackoverflow.com/questions/13558073/program-crash-on-glgenvertexarrays-call.
 //
 // TODO(sirver): glbinding seems to be a sane solution to the GL
-// loading problem. (https://github.com/hpicgs/glbinding).
-
-// GLEW must be first. Do not include any other GL headers, it
-// should define all functions.
+// loading problem. Switch to it everywhere. (https://github.com/hpicgs/glbinding).
 
 #ifdef USE_GLBINDING
 #   include <glbinding/gl/gl.h>
@@ -45,6 +42,8 @@
 using namespace gl;
 CLANG_DIAG_ON("-Wheader-hygiene")
 #else
+// GLEW must be first. Do not include any other GL headers, it
+// should define all functions.
 #   include <GL/glew.h>
 #endif
 

=== modified file 'src/graphic/gl/utils.cc'
--- src/graphic/gl/utils.cc	2016-01-23 15:44:29 +0000
+++ src/graphic/gl/utils.cc	2016-01-25 20:17:39 +0000
@@ -18,6 +18,7 @@
 
 #include "graphic/gl/utils.h"
 
+#include <cassert>
 #include <memory>
 #include <string>
 
@@ -43,41 +44,24 @@
 
 }  // namespace
 
-GLenum _handle_glerror(const char * file, unsigned int line)
-{
-	GLenum err = glGetError();
-	if (err == GL_NO_ERROR)
-		return err;
-
-	log("%s:%d: OpenGL ERROR: ", file, line);
-
-	switch (err)
-	{
-	case GL_INVALID_VALUE:
-		log("invalid value\n");
-		break;
-	case GL_INVALID_ENUM:
-		log("invalid enum\n");
-		break;
-	case GL_INVALID_OPERATION:
-		log("invalid operation\n");
-		break;
-	case GL_STACK_OVERFLOW:
-		log("stack overflow\n");
-		break;
-	case GL_STACK_UNDERFLOW:
-		log("stack undeflow\n");
-		break;
-	case GL_OUT_OF_MEMORY:
-		log("out of memory\n");
-		break;
-	case GL_TABLE_TOO_LARGE:
-		log("table too large\n");
-		break;
+const char* gl_error_to_string(const GLenum err) {
+	CLANG_DIAG_OFF("-Wswitch-enum");
+#define LOG(a) case a: return #a
+	switch (err) {
+		LOG(GL_INVALID_ENUM);
+		LOG(GL_INVALID_OPERATION);
+		LOG(GL_INVALID_VALUE);
+		LOG(GL_NO_ERROR);
+		LOG(GL_OUT_OF_MEMORY);
+		LOG(GL_STACK_OVERFLOW);
+		LOG(GL_STACK_UNDERFLOW);
+		LOG(GL_TABLE_TOO_LARGE);
 	default:
-		log("unknown\n");
+		break;
 	}
-	return err;
+#undef LOG
+	CLANG_DIAG_ON("-Wswitch-enum");
+	return "unknown";
 }
 
 // Thin wrapper around a Shader object to ensure proper cleanup.
@@ -214,6 +198,7 @@
 	if (framebuffer != 0) {
 		unbind_texture_if_bound(texture);
 		glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
+		assert(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
 	}
 	current_framebuffer_ = framebuffer;
 	current_framebuffer_texture_ = texture;

=== modified file 'src/graphic/gl/utils.h'
--- src/graphic/gl/utils.h	2016-01-09 20:33:51 +0000
+++ src/graphic/gl/utils.h	2016-01-25 20:17:39 +0000
@@ -20,6 +20,7 @@
 #define WL_GRAPHIC_GL_UTILS_H
 
 #include <memory>
+#include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
@@ -35,7 +36,8 @@
 
 class Shader;
 
-GLenum _handle_glerror(const char * file, unsigned int line);
+// Returns the name of the 'error'.
+const char* gl_error_to_string(GLenum error);
 
 // Thin wrapper around a OpenGL program object to ensure proper cleanup. Throws
 // on all errors.
@@ -147,10 +149,4 @@
 
 }  // namespace Gl
 
-/**
- * handle_glerror() is intended to make debugging of OpenGL easier. It logs the
- * error code returned by glGetError and returns the error code.
- */
-#define handle_glerror() Gl::_handle_glerror(__FILE__, __LINE__)
-
 #endif  // end of include guard: WL_GRAPHIC_GL_UTILS_H

=== modified file 'src/graphic/graphic.cc'
--- src/graphic/graphic.cc	2016-01-23 15:44:29 +0000
+++ src/graphic/graphic.cc	2016-01-25 20:17:39 +0000
@@ -31,6 +31,7 @@
 #include "graphic/font.h"
 #include "graphic/font_handler.h"
 #include "graphic/font_handler1.h"
+#include "graphic/gl/initialize.h"
 #include "graphic/gl/system_headers.h"
 #include "graphic/image.h"
 #include "graphic/image_io.h"
@@ -69,70 +70,30 @@
 /**
  * Initialize the SDL video mode.
  */
-void Graphic::initialize(int window_mode_w, int window_mode_h, bool init_fullscreen) {
+void Graphic::initialize(const TraceGl& trace_gl,
+                         int window_mode_w,
+                         int window_mode_h,
+                         bool init_fullscreen) {
 	window_mode_width_ = window_mode_w;
 	window_mode_height_ = window_mode_h;
 	requires_update_ = true;
 
-	// Request an OpenGL 2 context with double buffering.
-	SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY);
-	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
-
-
 	log("Graphics: Try to set Videomode %ux%u\n", window_mode_width_, window_mode_height_);
 	sdl_window_ =
 	   SDL_CreateWindow("Widelands Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
 	                    window_mode_width_, window_mode_height_, SDL_WINDOW_OPENGL);
 
+	GLint max_texture_size;
+	gl_context_ = Gl::initialize(
+	   trace_gl == TraceGl::kYes ? Gl::Trace::kYes : Gl::Trace::kNo, sdl_window_,
+	   &max_texture_size);
+
 	resolution_changed();
 	set_fullscreen(init_fullscreen);
 
 	SDL_SetWindowTitle(sdl_window_, ("Widelands " + build_id() + '(' + build_type() + ')').c_str());
 	set_icon(sdl_window_);
 
-	gl_context_ = SDL_GL_CreateContext(sdl_window_);
-	SDL_GL_MakeCurrent(sdl_window_, gl_context_);
-
-#ifdef USE_GLBINDING
-	glbinding::Binding::initialize();
-#else
-	// See graphic/gl/system_headers.h for an explanation of the next line.
-	glewExperimental = GL_TRUE;
-	GLenum err = glewInit();
-	if (err != GLEW_OK) {
-		log("glewInit returns %i\nYour OpenGL installation must be __very__ broken. %s\n", err,
-		    glewGetErrorString(err));
-		throw wexception("glewInit returns %i: Broken OpenGL installation.", err);
-	}
-#endif
-
-	log(
-	   "Graphics: OpenGL: Version \"%s\"\n", reinterpret_cast<const char*>(glGetString(GL_VERSION)));
-
-	GLboolean glBool;
-	glGetBooleanv(GL_DOUBLEBUFFER, &glBool);
-	log("Graphics: OpenGL: Double buffering %s\n", (glBool == GL_TRUE) ? "enabled" : "disabled");
-
-	GLint max_texture_size;
-	glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max_texture_size);
-	log("Graphics: OpenGL: Max texture size: %u\n", max_texture_size);
-
-	log("Graphics: OpenGL: ShadingLanguage: \"%s\"\n",
-	    reinterpret_cast<const char*>(glGetString(GL_SHADING_LANGUAGE_VERSION)));
-
-	glDrawBuffer(GL_BACK);
-
-	glDisable(GL_DEPTH_TEST);
-	glDepthFunc(GL_LEQUAL);
-
-	glEnable(GL_BLEND);
-	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-
-	glClear(GL_COLOR_BUFFER_BIT);
-
 	SDL_GL_SwapWindow(sdl_window_);
 
 	/* Information about the video capabilities. */
@@ -148,7 +109,6 @@
 		assert(SDL_BYTESPERPIXEL(disp_mode.format) == 4);
 	}
 
-
 	std::map<std::string, std::unique_ptr<Texture>> textures_in_atlas;
 	auto texture_atlases = build_texture_atlas(max_texture_size, &textures_in_atlas);
 	image_cache_->fill_with_texture_atlases(

=== modified file 'src/graphic/graphic.h'
--- src/graphic/graphic.h	2016-01-19 07:28:40 +0000
+++ src/graphic/graphic.h	2016-01-25 20:17:39 +0000
@@ -55,8 +55,11 @@
 	~Graphic();
 
 	// Initializes with the given resolution if fullscreen is false, otherwise a
-	// window that fills the screen.
-	void initialize(int window_mode_w, int window_mode_height, bool fullscreen);
+	// window that fills the screen. The 'trace_gl' parameter gets passed on to
+	// 'Gl::initialize'.
+	enum class TraceGl {kNo, kYes};
+	void
+	initialize(const TraceGl& trace_gl, int window_mode_w, int window_mode_height, bool fullscreen);
 
 	// Gets and sets the resolution.
 	void change_resolution(int w, int h);

=== modified file 'src/graphic/text/test/render_richtext.cc'
--- src/graphic/text/test/render_richtext.cc	2016-01-09 15:27:05 +0000
+++ src/graphic/text/test/render_richtext.cc	2016-01-25 20:17:39 +0000
@@ -99,7 +99,7 @@
 	g_fs->add_file_system(&FileSystem::create(INSTALL_DATADIR));
 
 	g_gr = new Graphic();
-	g_gr->initialize(1, 1, false);
+	g_gr->initialize(Graphic::TraceGl::kNo, 1, 1, false);
 }
 
 }  // namespace

=== modified file 'src/graphic/texture.cc'
--- src/graphic/texture.cc	2016-01-13 07:27:55 +0000
+++ src/graphic/texture.cc	2016-01-25 20:17:39 +0000
@@ -103,9 +103,10 @@
 {
 	init(w, h);
 
-	if (width() <= 0 || height() <= 0) {
+	if (m_blit_data.texture_id == 0) {
 		return;
 	}
+
 	glTexImage2D
 		(GL_TEXTURE_2D, 0, static_cast<GLint>(GL_RGBA), width(), height(), 0, GL_RGBA,
 			GL_UNSIGNED_BYTE, nullptr);
@@ -187,7 +188,7 @@
 		w, h,
 		Rect(0, 0, w, h),
 	};
-	if (width() <= 0 || height() <= 0) {
+	if (w * h == 0) {
 		return;
 	}
 
@@ -203,7 +204,7 @@
 }
 
 void Texture::lock() {
-	if (width() <= 0 || height() <= 0) {
+	if (m_blit_data.texture_id == 0) {
 		return;
 	}
 
@@ -263,6 +264,7 @@
 
 
 void Texture::setup_gl() {
+	assert(m_blit_data.texture_id != 0);
 	Gl::State::instance().bind_framebuffer(
 	   GlFramebuffer::instance().id(), m_blit_data.texture_id);
 	glViewport(0, 0, width(), height());
@@ -272,6 +274,9 @@
                      const BlitData& texture,
                      float opacity,
                      BlendMode blend_mode) {
+	if (m_blit_data.texture_id == 0) {
+		return;
+	}
 	setup_gl();
 	BlitProgram::instance().draw(dst_rect, 0.f, texture, BlitData{0, 0, 0, Rect()},
 	                             RGBAColor(0, 0, 0, 255 * opacity), blend_mode);
@@ -282,6 +287,9 @@
                               const BlitData& mask,
                               const RGBColor& blend) {
 
+	if (m_blit_data.texture_id == 0) {
+		return;
+	}
 	setup_gl();
 	BlitProgram::instance().draw(dst_rect, 0.f, texture, mask, blend, BlendMode::UseAlpha);
 }
@@ -289,18 +297,27 @@
 void Texture::do_blit_monochrome(const FloatRect& dst_rect,
                                  const BlitData& texture,
                                  const RGBAColor& blend) {
+	if (m_blit_data.texture_id == 0) {
+		return;
+	}
 	setup_gl();
 	BlitProgram::instance().draw_monochrome(dst_rect, 0.f, texture, blend);
 }
 
 void
 Texture::do_draw_line(const FloatPoint& start, const FloatPoint& end, const RGBColor& color, int line_width) {
+	if (m_blit_data.texture_id == 0) {
+		return;
+	}
 	setup_gl();
 	DrawLineProgram::instance().draw(start, end, 0.f, color, line_width);
 }
 
 void
 Texture::do_fill_rect(const FloatRect& dst_rect, const RGBAColor& color, BlendMode blend_mode) {
+	if (m_blit_data.texture_id == 0) {
+		return;
+	}
 	setup_gl();
 	FillRectProgram::instance().draw(dst_rect, 0.f, color, blend_mode);
 }

=== modified file 'src/logic/map_info.cc'
--- src/logic/map_info.cc	2016-01-09 15:27:05 +0000
+++ src/logic/map_info.cc	2016-01-25 20:17:39 +0000
@@ -49,7 +49,7 @@
 	g_fs->add_file_system(&FileSystem::create(INSTALL_DATADIR));
 
 	g_gr = new Graphic();
-	g_gr->initialize(1, 1, false);
+	g_gr->initialize(Graphic::TraceGl::kNo, 1, 1, false);
 }
 
 }  // namespace

=== modified file 'src/wlapplication.cc'
--- src/wlapplication.cc	2016-01-24 20:11:53 +0000
+++ src/wlapplication.cc	2016-01-25 20:17:39 +0000
@@ -288,9 +288,10 @@
 	   UI::create_fonthandler(&g_gr->images());  // This will create the fontset, so loading it first.
 	UI::g_fh = new UI::FontHandler();
 
-	g_gr->initialize(config.get_int("xres", DEFAULT_RESOLUTION_W),
-	                 config.get_int("yres", DEFAULT_RESOLUTION_H),
-	                 config.get_bool("fullscreen", false));
+	g_gr->initialize(
+	   config.get_bool("debug_gl_trace", false) ? Graphic::TraceGl::kYes : Graphic::TraceGl::kNo,
+	   config.get_int("xres", DEFAULT_RESOLUTION_W), config.get_int("yres", DEFAULT_RESOLUTION_H),
+	   config.get_bool("fullscreen", false));
 	g_sound_handler.init(); //  TODO(unknown): memory leak!