magnum/doc/troubleshooting.dox

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

-   Enable @ref GL::DebugOutput "debug output" to see more detailed errors,
    warnings and performance hints. You can do that easily through the
    `--magnum-gpu-validation` @ref GL-Context-usage-command-line "command-line option"
    or an environment variable.
    -   If you are on Mac, the native OpenGL implementation doesn't support
        this. Instead you can manually verify that
        @ref GL::Renderer::error() "no OpenGL error was emitted".
-   Check that you use only extensions that are
    @ref GL::Context::isExtensionSupported() "available on your system".
-   Check that you didn't exceed any implementation-defined limit (see
    @ref magnum-gl-info output for a list of all of them).
-   If using framebuffer objects,
    @ref GL::Framebuffer::checkStatus() "check that they are complete".
    -   Rendering to three-component @ref GL::TextureFormat works on some GPUs
        but not others. TO avoid platform-dependent issues, always use one-,
        two- or four-component formats.
-   Change @ref GL::Renderer::setClearColor() "framebuffer clear color" to
    something else than black to verify that at least something is drawn. The
    engine sets it to @cpp 0x1f1f1f_rgbf @ce by default to help you a bit in
    this regard.
-   If nothing is drawn, use @ref GL::PrimitiveQuery to check that at least
    some primitives were generated. Use @ref GL::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 GL::Mesh::addVertexBuffer() "vertex specification",
    properly set up @ref GL::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 the @ref GL::Renderer::Feature::DepthTest "depth test",
    @ref GL::Renderer::Feature::FaceCulling "face culling" and other renderer
    features that might cause fragments to be discarded.
-   Verify that your projection and transformation matrix is properly set up
    --- try drawing points instead of triangles, to see if they are in proper
    places at least.
-   For custom shaders you can @ref GL::AbstractShaderProgram::validate() "Validate them".
    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. For that to work, you need to
    @ref opengl-state-tracking "reset the state tracker" on boundaries between
    3rd party and Magnum calls into GL. 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

-   Use @ref GL::TimeQuery to find hot spots in the rendering code.
-   @ref GL::DebugMessage::insert() "Mark relevant parts of code" to find them
    easier in the debugger.
-   Use ApiTrace or RenderDoc 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.
*/
}