mesa: if MESA_DEBUG=context, create a debug context

A number of drivers report useful debug/perf information accessible
through GL_ARB_debug_output and with debug contexts (i.e. setting the
GLX_CONTEXT_DEBUG_BIT_ARB flag).  But few applications actually use
the GL_ARB_debug_output extension.

This change lets one set the MESA_DEBUG env var to "context" to force-set
a debug context and report debug/perf messages to stderr (or whatever
file MESA_LOG_FILE is set to).  This is a useful debugging tool.

The small change in st_api_create_context() is needed so that
st_update_debug_callback() gets called to hook up the driver debug
callbacks when ST_CONTEXT_FLAG_DEBUG was not set, but MESA_DEBUG=context.

v2: use %.*s format string instead of allocating temporary buffer.

Reviewed-by: Nicolai Hähnle <[email protected]>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/mesa/main/debug.c b/src/mesa/main/debug.c
index 5ca7d5ce500..3471b26aad8 100644
--- a/src/mesa/main/debug.c
+++ b/src/mesa/main/debug.c
@@ -189,7 +189,8 @@ set_debug_flags(const char *str)
       { "silent", DEBUG_SILENT }, /* turn off debug messages */
       { "flush", DEBUG_ALWAYS_FLUSH }, /* flush after each drawing command */
       { "incomplete_tex", DEBUG_INCOMPLETE_TEXTURE },
-      { "incomplete_fbo", DEBUG_INCOMPLETE_FBO }
+      { "incomplete_fbo", DEBUG_INCOMPLETE_FBO },
+      { "context", DEBUG_CONTEXT } /* force set GL_CONTEXT_FLAG_DEBUG_BIT flag */
    };
    GLuint i;