opengl shaders

cpp/experiments/opengl_shaders/README.md

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+# Link GLEW and SDL
+
+An experiment to link GLEW and SDL.
+
+## How to run
+
+I downloaded .dll and .lib files for 64-bit processor on Windows operating system. I checked the licences for SDL and GLEW and as I understood they allow redistribution. In case I would like to run this experiment on other machine, I would need it to be 64-bit and I would need the binaries.
+
+I don't know of more convenient way to distribute them so I can download the binaries on other machine.
+
+## Important
+
+**DYNAMIC LIBRARIES MUST BE PLACED IN THE LOCATION OF EXECUTABLE!!!**
+
+An alternative approach is to add it to wherever the executable searches for dynamic libraries on the system.
+
+It seems it is common approach to deliver dynamic libraries in the directory of the executable. For example, World of Warcraft has dynamic libraries located next to the executable.
+
+## Notes
+
+Notes about problems I encountered when performing this experiment.
+
+### Linking order is important
+
+The following command to link SDL2, causes the error below the command:
+
+```cmd
+clang++ main.cpp -L./ -lSDL2 -lSDL2main -o main
+```
+
+```cmd
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0x84): undefined reference to `SDL_wcslen'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0xa2): undefined reference to `SDL_iconv_string'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0xb6): undefined reference to `SDL_strlen'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0xf3): undefined reference to `SDL_memcpy'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0xfb): undefined reference to `SDL_free'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0x122): undefined reference to `SDL_SetMainReady'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0x12e): undefined reference to `SDL_main'
+C:/msys64/ucrt64/bin/ld: .//SDL2main.lib(x64/Release/SDL_windows_main.obj):(.text$mn+0x18e): undefined reference to `SDL_ShowSimpleMessageBox'
+```
+
+However, the following command linked without problems:
+
+```cmd
+clang++ main.cpp -L./ -lSDL2main -lSDL2 -o main
+```
+
+### SDL requires specific signature for main function
+
+SDL2 requires the following signature:
+
+```cpp
+int main(int argv, char** args) {
+  // ...
+}
+```
+
+Without signature like this, SDL2 causes an error:
+
+```txt
+undefined reference to `SDL_main`
+```
+
+[Here is stackoverflow answer.](https://stackoverflow.com/questions/10803918/undefined-reference-to-sdl-main)
+
+### Linking against `opengl32.lib`
+
+This library `opengl32.lib` is delivered with operating system. GLEW allows us to use latest OpenGL functions. Therefore we have to against `opengl32.lib` because we are using the code from there as well.
+
+### Linking against dynamic libraries for GLEW and SDL
+
+The reason dynamic libraries are linked without any code provided in this example is that the compiled binary is using dynamic libraries relative to the executable. An alternative would be to place dynamic libraries in `C:\Windows\System32`, but that is bad practice because any program can run them. If there is any vulnerability within them it can be exploited.
+
+### Using better includes
+
+I would like to include glew and SDL2 libraries as follows:
+
+```cpp
+#include "GL/glew.h"
+#include "SDL2/SDL.h"
+```
+
+I had to tell the compiler where to search for included files.
+
+The full command:
+
+```cmd
+clang++ main.cpp -L./ -lSDL2main -lSDL2 -lglew32 -lopengl32 -I./deps/GLEW-2.2.0/include -I./deps/SDL2-2.26.2/include -o main
+```
+
+One directory to search for includes:
+
+```txt
+-I./deps/GLEW-2.2.0/include
+```
+
+Another directory to search for includes:
+
+```txt
+-I./deps/SDL2-2.26.2/include
+```
+
+The reason i said _one and another directory_ is because it tells where to search for included files. Imagine the compiler as a person who has a list of places to visit in town. But we suggest one or more places to visit. This flag tells the compiler exactly that.
+
+### Explanation of the compilation command
+
+- Search for lib files in: `-L./deps/GLEW-2.2.0/lib`
+- Search for lib files in: `-L./deps/SDL2-2.26.2/lib`
+- Link SDL2main.lib: `-lSDL2main`
+- Link SDL2.lib: `-lSDL2`
+- Link glew32.lib: `-lglew32`
+- The `opengl32.lib` file is distributed with operating system. There is no need to add it to the project, link flag: `-lopengl32`
+- Tell the compiler where to search for included glew headers: `-I./deps/GLEW-2.2.0/include`
+- Tell the compiler where to search for included SDL2 headers: `-I./deps/SDL2-2.26.2/include`

cpp/experiments/opengl_shaders/compile.bat

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+@ECHO OFF
+
+@REM LINKER SEARCH PATHS
+SET link_search_flag=-L
+SET link_search_path_sdl=%link_search_flag%./deps/SDL2-2.26.2/lib
+SET link_search_path_glew=%link_search_flag%./deps/GLEW-2.2.0/lib
+SET link_search_paths=%link_search_path_sdl% %link_search_path_glew%
+
+@REM LINKER INCLUDES
+SET link_flag=-l
+SET link_sdl=%link_flag%SDL2main %link_flag%SDL2
+SET link_glew=%link_flag%glew32
+SET link_opengl=%link_flag%opengl32
+SET link_libs=%link_sdl% %link_glew% %link_opengl%
+
+@REM COMPILER INCLUDE PATHS
+SET include_flag=-I
+SET include_glew=%include_flag%./deps/GLEW-2.2.0/include
+SET include_sdl=%include_flag%./deps/SDL2-2.26.2/include
+SET include_paths=%include_glew% %include_sdl%
+
+@REM SOURCE FILES
+SET file_name=main
+SET file_extension=.cpp
+SET file=%file_name%%file_extension%
+
+@REM OUTPUT
+SET out_name=%file_name%
+SET out_extension=.exe
+SET out=%out_name%%out_extension%
+
+ECHO Compiling %file%...
+
+clang++ %file% %link_search_paths% %link_libs% %include_paths% -o %out%
+
+@REM Check if compilation succeeded
+IF %ERRORLEVEL% EQU 0 (
+  ECHO Compilation succeeded! Type ./%out% to run.
+)
+@REM Let compiler handle failure

cpp/experiments/opengl_shaders/deps/GLEW-2.2.0/LICENSE.txt

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+The OpenGL Extension Wrangler Library
+Copyright (C) 2002-2007, Milan Ikits <milan ikits[]ieee org>
+Copyright (C) 2002-2007, Marcelo E. Magallon <mmagallo[]debian org>
+Copyright (C) 2002, Lev Povalahev
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without 
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, 
+  this list of conditions and the following disclaimer.
+* Redistributions in binary form must reproduce the above copyright notice, 
+  this list of conditions and the following disclaimer in the documentation 
+  and/or other materials provided with the distribution.
+* The name of the author may be used to endorse or promote products 
+  derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+THE POSSIBILITY OF SUCH DAMAGE.
+
+
+Mesa 3-D graphics library
+Version:  7.0
+
+Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+
+Copyright (c) 2007 The Khronos Group Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and/or associated documentation files (the
+"Materials"), to deal in the Materials without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Materials, and to
+permit persons to whom the Materials are furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Materials.
+
+THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.