isextensionsupported.cc

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#include "ion/portgfx/isextensionsupported.h"

#include <cctype>
#include <cstring>

#include "ion/base/logging.h"
#include "ion/portgfx/glheaders.h"
#include "ion/portgfx/visual.h"

namespace ion {
namespace portgfx {

ION_API bool IsExtensionSupported(const std::string& unprefixed_extension,
                                  const std::string& extensions_string) {
  if (unprefixed_extension.empty())
    return false;
  if (IsExtensionIncomplete(unprefixed_extension.c_str()))
    return false;

  size_t found = 0;
  while ((found = extensions_string.find(unprefixed_extension, found + 1)) !=
         std::string::npos) {
    size_t found_begin = extensions_string.rfind(' ', found);
    if (found_begin != std::string::npos) {
      ++found_begin;
    } else {
      found_begin = 0;
    }

    for (size_t c = found_begin; c < found; ++c) {
      if (!isupper(extensions_string[c]) && extensions_string[c] != '_')
        goto next;
    }

    if (extensions_string.size() > found + unprefixed_extension.size() &&
        extensions_string[found + unprefixed_extension.size()] != ' ')
      goto next;

    return true;

  next:
    continue;
  }

  return false;
}

ION_API bool IsExtensionSupported(const char* unprefixed_extension) {
  if (!Visual::GetCurrent()) {
    LOG(WARNING) << "IsExtensionSupported(" << unprefixed_extension
                 << ") returning false because there is no OpenGL context.";
    return false;
  }
  const char* extensions =
      reinterpret_cast<const char*>(glGetString(GL_EXTENSIONS));
  if (!extensions) return false;
  const std::string unprefixed(unprefixed_extension);
  return IsExtensionSupported(std::string(unprefixed_extension),
                              std::string(extensions));
}

ION_API bool IsExtensionIncomplete(const char* unprefixed_extension) {
#if defined(ION_PLATFORM_ANDROID) || defined(ION_PLATFORM_GENERIC_ARM)
  if (!strcmp(unprefixed_extension, "vertex_array_object"))
    return true;
#endif
  return false;
}

}  // namespace portgfx
}  // namespace ion