https://github.com/p3/regal

OpenGL portability layer for OpenGL 2.x, 3.x, 4.x, Core contexts and ES 2.0

Regal is a portable OpenGL layer on top of existing OpenGL implementations. Compile and link an app against Regal and deploy on various OpenGL implementations including compatibility, core and ES 2.0 OpenGL contexts.

• Portability

  Consistent OpenGL API that runs on all major platforms: Windows, Linux, Mac, iOS, and Android

• Compatible

  Immediate mode, fixed function, GL_QUADS work everywhere, emulated as necessary.

• Modern OpenGL API

  Direct State Access (DSA) and Vertex Array Object (VAO), emulated as necessary.

• Open Source

  There is nothing behind the curtain. You can see what Regal is doing and change it if needed.

• Ease of Use

  Set breakpoints on OpenGL functions. Step into the code. Inspect state.

• Efficiency

  If it cannot be implemented efficiently in Regal, it is not universally supported. For example, tessellation support requires tessellation hardware.

• Most code remains unchanged.
• Optionally #include <GL/Regal.h>
• Link with regal32.dll, libRegal.so or libRegal.dylib

From an application developer's perspective, Regal just looks like an OpenGL implementation. You link with it instead of your platform's OpenGL library or framework, and that's really all you have to do to use Regal. The rest of your code can remain unchanged.

• Emulation
  • Fixed function texturing, lighting and fog.

  • Direct State Access extension

    http://www.opengl.org/registry/specs/EXT/direct_state_access.txt

  • GL_EXT_debug_marker extension

    http://www.khronos.org/registry/gles/extensions/EXT/EXT_debug_marker.txt

  • Fixed function and DSA emulation enabled by default.
  • Build-time configuration:
    • REGAL_NO_EMULATION -- Disable the use of emulation
    • REGAL_FORCE_EMULATION -- Force the use of emulation, even for compatibility contexts with DSA
  • Environment variable configuration:
    • REGAL_NO_EMULATION -- Disable the use of emulation
    • REGAL_FORCE_EMULATION -- Force the use of emulation, even for compatibility contexts with DSA
• OpenGL error checking
  • Disabled by default.
  • Build-time configuration: REGAL_ERROR
  • Environment variable configuration: REGAL_ERROR
• Browser-based interface
  • Enabled by default.
  • REGAL_NO_HTTP --- Build-time and environment variable enable/disable.
  • REGAL_HTTP_PORT --- Port for HTTP connections (8080 by default)
  • REGAL_HTTP_LOG_LIMIT --- Number of lines of logging buffered
  • http://127.0.0.1:8080/log --- View log
  • http://127.0.0.1:8080/glEnable?GL_LOG_APP_REGAL --- Enable/disable application logging
  • http://127.0.0.1:8080/glEnable?GL_LOG_DRIVER_REGAL --- Enable/disable driver logging
  • http://127.0.0.1:8080 --- State information

• Logging

  Regal supports detailed logging for development purposes.

  • Error -- Fatal and non-fatal Regal runtime errors.
  • Warning -- Non-fatal Regal warnings.
  • Info -- Informational messages.
  • App -- Application calls into Regal.
  • Driver -- Regal calls into OpenGL.
  • Internal -- Internal Regal calls.
  • Http -- HTTP traffic logging.

  Build-time configuration:

  • REGAL_LOG_ERROR
  • REGAL_LOG_WARNING
  • REGAL_LOG_INFO
  • REGAL_LOG_APP
  • REGAL_LOG_DRIVER
  • REGAL_LOG_INTERNAL
  • REGAL_LOG_HTTP
  • Debug mode: All logging supported with error, warning, info and http logging enabled.
  • Release mode: Support for application, driver and internal logging disabled by default.

  Environment variable configuration:

  • REGAL_LOG_ERROR
  • REGAL_LOG_WARNING
  • REGAL_LOG_INFO
  • REGAL_LOG_APP
  • REGAL_LOG_DRIVER
  • REGAL_LOG_INTERNAL
  • REGAL_LOG_HTTP
  • REGAL_LOG_API --- Application + Driver OpenGL logging
  • REGAL_LOG_NONE --- enable or disable all logging

  Environment variable lookup is globally disabled by defining REGAL_NO_GETENV at compile-time.

  Runtime configuration via GL_REGAL_log extension: (glEnable/glDisable/glIsEnabled)

  • GL_LOG_ERROR_REGAL
  • GL_LOG_WARNING_REGAL
  • GL_LOG_INFO_REGAL
  • GL_LOG_APP_REGAL
  • GL_LOG_DRIVER_REGAL
  • GL_LOG_INTERNAL_REGAL
  • GL_LOG_HTTP_REGAL

• Spoofing OpenGL vendor, renderer, version and extension strings

  Build-time configuration

  • REGAL_GL_VENDOR
  • REGAL_GL_RENDERER
  • REGAL_GL_VERSION
  • REGAL_GL_EXTENSION

  Environment variable configuration:

  • REGAL_GL_VENDOR
  • REGAL_GL_RENDERER
  • REGAL_GL_VERSION
  • REGAL_GL_EXTENSION

  Environment variable lookup is globally disabled by defining REGAL_NO_GETENV at compile-time.

• Regal OpenGL extensions
  • GL_REGAL_error_string for GLU-style GLenum to error string conversion.
  • GL_REGAL_extension_query for GLEW-style extension checking.
  • GL_REGAL_log for Regal logging configuration.

• Debug label.
• Debug output.
• Web browser-based debugging tools.
• Display list emulation.

• Incomplete implementation, so far.
• Limited GLSL language support.
• GL_QUADS only works in immediate mode or with DrawArrays for ES and core profiles.