Add GFX2_Log() function

src/gfx2log.c

@@ -0,0 +1,67 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+    Copyright 2018 Thomas Bernard
+    Copyright 1996-2001 Sunset Design (Guillaume Dorme & Karl Maritaud)
+
+    Grafx2 is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; version 2
+    of the License.
+
+    Grafx2 is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+
+#if defined(USE_SDL2)
+#include <SDL.h>
+#endif
+#include <stdio.h>
+#include "gfx2log.h"
+
+GFX2_Log_priority_T GFX2_verbosity_level = GFX2_INFO;
+
+extern void GFX2_Log(GFX2_Log_priority_T priority, const char * fmt, ...)
+{
+  va_list ap;
+
+  va_start(ap, fmt);
+  GFX2_LogV(priority, fmt, ap);
+  va_end(ap);
+}
+
+extern void GFX2_LogV(GFX2_Log_priority_T priority, const char * fmt, va_list ap)
+{
+  if ((unsigned)GFX2_verbosity_level < (unsigned)priority)
+    return;
+#if defined(USE_SDL2)
+  {
+    int sdl_priority;
+    switch(priority)
+    {
+      case GFX2_ERROR:
+        sdl_priority = SDL_LOG_PRIORITY_ERROR;
+        break;
+      case GFX2_WARNING:
+        sdl_priority = SDL_LOG_PRIORITY_WARN;
+        break;
+      case GFX2_INFO:
+        sdl_priority = SDL_LOG_PRIORITY_INFO;
+        break;
+      case GFX2_DEBUG:
+        sdl_priority = SDL_LOG_PRIORITY_DEBUG;
+        break;
+      default:
+        sdl_priority = SDL_LOG_PRIORITY_CRITICAL; // unknown
+    }
+    SDL_LogMessageV(SDL_LOG_CATEGORY_APPLICATION, sdl_priority, fmt, ap);
+  }
+#endif
+  vfprintf((unsigned)priority >= GFX2_INFO ? stdout : stderr, fmt, ap);
+}