magnum/doc/troubleshooting.dox

/*
    This file is part of Magnum.

    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018
              Vladimír Vondruš <mosra@centrum.cz>

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*/

namespace Magnum {
/** @page troubleshooting Troubleshooting
@brief Various tricks to overcome common building and rendering issues.

@m_footernavigation

@section troubleshooting-building Building issues

If your project suddenly stops building after Magnum upgrade, check these
things:

-   If the building fails on CMake step, be sure that you have up-to-date
    `FindCorrade.cmake`, `FindMagnum.cmake` and other CMake modules in your
    project (`FindSDL2.cmake`). They are contained in `modules/` directory of
    Magnum sources (and sources of other projects) also are installed into
    `share/cmake/Magnum`.
-   In some cases when the changes done to build system are too drastic,
    recreating the build dir or clearing CMake cache is needed, but this is
    a very rare occasion.
-   The library is constantly evolving, thus some API might get deprecated over
    time (and later removed). Either build the libraries with `BUILD_DEPRECATED`
    or switch to non-deprecated features. See @ref building for more
    information.

@section troubleshooting-rendering Rendering issues

If you are experiencing so-called "black screen of death", weird behavior or
crashes on GL calls, you might want to try these things:

-   Verify that @ref Renderer::error() "no OpenGL error was emitted".
-   Check that you use only extensions that are
    @ref Context::isExtensionSupported() "available on your system".
-   Check that you didn't exceed any implementation-defined limit (see
    @ref magnum-info output for list of all of them).
-   Enable @ref DebugMessage "debug output" to see more detailed errors,
    warnings and performance hints.
-   If using framebuffer objects, @ref Framebuffer::checkStatus() "check that they are complete".
-   Change @ref Renderer::setClearColor() "framebuffer clear color" to
    something else than black to verify that at least something is drawn.
-   If nothing is drawn, use @ref PrimitiveQuery to check that at least some
    primitives were generated. Use @ref SampleQuery to check whether fragments
    were drawn.
-   Verify that the mesh is properly set up --- nonzero vertex/index count,
    matching type in buffer and @ref Mesh::addVertexBuffer() "vertex specification",
    properly set up @ref Mesh::setIndexBuffer() "index buffer" and index count
    for indexed mesh. If you specified index range, be sure that all indices
    fall into it, otherwise you would get undefined behavior.
-   Try disabling @ref Renderer::Feature::DepthTest "depth test",
    @ref Renderer::Feature::FaceCulling "face culling" and other renderer
    features that might affect the fragments.
-   Verify that your projection and transformation matrix is properly set up ---
    try drawing points instead of triangles, to see if they are at least at
    proper places.
-   @ref AbstractShaderProgram::validate() "Validate the shader", check that
    all used uniforms and attributes have proper locations. Try reducing it
    until it is able to draw something, possibly also with some simpler mesh.
-   Magnum tracks the OpenGL state to improve performance, but the tracker can
    get confused if you or any other library are doing OpenGL calls outside of
    Magnum. You can use @ref Context::resetState() to reset the internal state
    tracker. The other library also needs to be aware of this fact (either
    setting all state explicitly every time or having similar ability to reset
    its state tracker), otherwise you may need to save and restore GL state
    manually for that library to work.

@section troubleshooting-debugging Debugging rendering

-   Enable @ref DebugMessage "debug output" to see additional performance hints
    and implementation-dependent information.
-   Use @ref TimeQuery to find hot spots in the rendering code.
-   @ref DebugMessage::insert() "Mark relevant parts of code" to find them
    easier in the debugger.
-   Use ApiTrace to trace the program call by call, verify buffer and texture
    contents, vertex binding and count of generated primitives, rendered
    fragments and time spent in various calls.
*/
}