seperated library by into header and source file since changes in the implementation part force a complete recompile

demo/nanovg.c

@@ -32,7 +32,6 @@
 #define LEN(a)      (sizeof(a)/sizeof(a)[0])
 #define UNUSED(a)   ((void)(a))
 
-#define GUI_IMPLEMENTATION
 #include "../gui.h"
 #include "demo.c"
 

demo/opengl.c

@@ -33,7 +33,6 @@
 #define LEN(a)      (sizeof(a)/sizeof(a)[0])
 #define UNUSED(a)   ((void)(a))
 
-#define GUI_IMPLEMENTATION
 #define GUI_USE_FIXED_TYPES
 #include "../gui.h"
 #include "demo.c"

demo/win32.c

@@ -20,7 +20,6 @@
 #define LEN(a)      (sizeof(a)/sizeof(a)[0])
 #define UNUSED(a)   ((void)(a))
 
-#define GUI_IMPLEMENTATION
 #include "gui.h"
 #include "demo.c"