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Check for GLX vblank extensions more properly.

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Previously, the code checked for an extension by checking if the pointer returned from
glXGetProcAddress was NULL or not.

But in truth, you can get a non-NULL pointer even if that extension is not supported.
Now, we parse the glXQueryExtensionsString() results.

GLFW code that does similar checks, for reference: 51bb76c7c3/src/glx_context.c (L208)

fixes #1367
This commit is contained in:
JW
2020-01-24 14:12:38 -08:00
committed by Бранимир Караџић
parent aae3f238e1
commit 97bafaa7b8
1 changed files with 48 additions and 14 deletions
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62
src/glcontext_glx.cpp
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@@ -57,6 +57,32 @@ namespace bgfx { namespace gl
GLXContext m_context;
};
static bool haveGlxExtension(const char* _ext, const char* _extList)
{
// _extList is assumed to be a space-separated, null-terminated list of
// extension names, and no extension name ever contains a space.
const char* end = _extList + bx::strLen(_extList);
const char* searchStart = _extList;
for(;;)
{
bx::StringView found = bx::strFind(searchStart, _ext);
if (found.isEmpty())
{
return false;
}
// We found the substring, but need an exact match, with a word
// boundary at both the front and back of the found spot.
if ((found.getPtr() == _extList || *(found.getPtr() - 1) == ' ')
&& (found.getTerm() == end || *found.getTerm() == ' '))
{
return true;
}
// else, keep searching
searchStart = found.getTerm();
}
}
void GlContext::create(uint32_t _width, uint32_t _height)
{
BX_UNUSED(_width, _height);
@@ -196,27 +222,35 @@ namespace bgfx { namespace gl
glXMakeCurrent(m_display, (::Window)g_platformData.nwh, m_context);
m_current = NULL;
glXSwapIntervalEXT = (PFNGLXSWAPINTERVALEXTPROC)glXGetProcAddress( (const GLubyte*)"glXSwapIntervalEXT");
if (NULL != glXSwapIntervalEXT)
const char* extensions = glXQueryExtensionsString(m_display, DefaultScreen(m_display));
if (NULL != extensions)
{
BX_TRACE("Using glXSwapIntervalEXT.");
glXSwapIntervalEXT(m_display, (::Window)g_platformData.nwh, 0);
}
else
{
glXSwapIntervalMESA = (PFNGLXSWAPINTERVALMESAPROC)glXGetProcAddress( (const GLubyte*)"glXSwapIntervalMESA");
if (NULL != glXSwapIntervalMESA)
{
BX_TRACE("Using glXSwapIntervalMESA.");
glXSwapIntervalMESA(0);
bool foundSwapControl = false;
if (haveGlxExtension("GLX_EXT_swap_control", extensions)) {
glXSwapIntervalEXT = (PFNGLXSWAPINTERVALEXTPROC)glXGetProcAddress( (const GLubyte*)"glXSwapIntervalEXT");
if (NULL != glXSwapIntervalEXT)
{
BX_TRACE("Using glXSwapIntervalEXT.");
glXSwapIntervalEXT(m_display, (::Window)g_platformData.nwh, 0);
foundSwapControl = true;
}
}
else
{
if (!foundSwapControl && haveGlxExtension("GLX_MESA_swap_control", extensions)) {
glXSwapIntervalMESA = (PFNGLXSWAPINTERVALMESAPROC)glXGetProcAddress( (const GLubyte*)"glXSwapIntervalMESA");
if (NULL != glXSwapIntervalMESA)
{
BX_TRACE("Using glXSwapIntervalMESA.");
glXSwapIntervalMESA(0);
foundSwapControl = true;
}
}
if (!foundSwapControl && haveGlxExtension("GLX_SGI_swap_control", extensions)) {
glXSwapIntervalSGI = (PFNGLXSWAPINTERVALSGIPROC)glXGetProcAddress( (const GLubyte*)"glXSwapIntervalSGI");
if (NULL != glXSwapIntervalSGI)
{
BX_TRACE("Using glXSwapIntervalSGI.");
glXSwapIntervalSGI(0);
foundSwapControl = true;
}
}
}