Added a custom log callback facility to capture log output

common/libmain.cpp

@@ -275,6 +275,10 @@ DLLPUBLIC CapResult Cap_getAutoProperty(CapContext ctx, CapStream stream, CapPro
     return CAPRESULT_ERR;
 }
 
+DLLPUBLIC void Cap_installCustomLogFunction(CapCustomLogFunc logFunc)
+{
+    installCustomLogFunction(logFunc);
+}
 
 DLLPUBLIC const char* Cap_getLibraryVersion()
 {

common/logging.cpp

@@ -28,7 +28,20 @@
 #include <stdarg.h>
 #include "logging.h"
 
+/* In their infinite "wisdom" Microsoft have declared snprintf deprecated
+   and we must therefore resort to a macro to fix something that shouldn't
+   be a problem */
+#ifdef _MSC_VER
+#define snprintf _snprintf
+#endif
+
 static uint32_t gs_logLevel = LOG_NOTICE;
+static customLogFunc gs_logFunc = NULL;
+
+void installCustomLogFunction(customLogFunc logfunc)
+{
+    gs_logFunc = logfunc;
+}
 
 void LOG(uint32_t logLevel, const char *format, ...)
 {
@@ -37,32 +50,51 @@ void LOG(uint32_t logLevel, const char *format, ...)
         return;
     }
 
+    char logbuffer[1024];
+    char *ptr = logbuffer;
+
     switch(logLevel)
     {
     case LOG_CRIT:
-        fprintf(stderr,"[CRIT] ");
+        snprintf(logbuffer,1024,"[CRIT] ");
+        ptr += 7;
         break;        
     case LOG_ERR:
-        fprintf(stderr,"[ERR ] ");
+        snprintf(logbuffer,1024,"[ERR ] ");
+        ptr += 7;
         break;
     case LOG_INFO:
-        fprintf(stderr,"[INFO] ");
+        snprintf(logbuffer,1024,"[INFO] ");
+        ptr += 7;
         break;    
     case LOG_DEBUG:
-        fprintf(stderr,"[DBG ] ");
+        snprintf(logbuffer,1024,"[DBG ] ");
+        ptr += 7;
         break;
     case LOG_VERBOSE:
-        fprintf(stderr,"[VERB] ");
+        snprintf(logbuffer,1024,"[VERB] ");
+        ptr += 7;
         break;
     default:
         break;
     }
-
+    
     va_list args;
 
     va_start(args, format);
-    vfprintf(stderr, format, args);
+    vsnprintf(ptr, 1024-7, format, args);
     va_end(args);
+
+    if (gs_logFunc != nullptr)
+    {
+        // custom log functions to no include the 
+        // prefix.
+        gs_logFunc(logLevel, ptr);
+    }
+    else
+    {
+        fprintf(stderr, logbuffer);
+    }
 }
 
 void setLogLevel(uint32_t logLevel)

common/logging.h

@@ -39,7 +39,22 @@
 #define LOG_DEBUG 7
 #define LOG_VERBOSE 8
 
+/** Log information or an error. The format is the same as printf */
 void LOG(uint32_t logLevel, const char *format, ...);
+
+/** Set the log leveel */
 void setLogLevel(uint32_t logLevel);
+
+/** Get the log level */
 uint32_t getLogLevel();
+
+/** define a custom logging function callback */
+typedef void (*customLogFunc)(uint32_t logLevel, const char *logString);
+
+/** Install a custom callback function for the log.
+    Note: your custom callback function might not be called
+          from the same thead, depending on the platform!
+*/
+void installCustomLogFunction(customLogFunc logfunc);
+
 #endif

include/openpnp-capture.h

@@ -290,6 +290,18 @@ DLLPUBLIC CapResult Cap_getAutoProperty(CapContext ctx, CapStream stream, CapPro
 */
 DLLPUBLIC void Cap_setLogLevel(uint32_t level);
 
+
+typedef void (*CapCustomLogFunc)(uint32_t level, const char *string);
+
+/** install a custom callback for a logging function.
+
+    the callback function must have the following 
+    structure:
+
+        void func(uint32_t level, const char *string);
+*/
+DLLPUBLIC void Cap_installCustomLogFunction(CapCustomLogFunc logFunc);
+
 /** Return the version of the library as a string.
     In addition to a version number, this should 
     contain information on the platform,

win/tests/main.cpp

@@ -13,6 +13,11 @@
 #include "openpnp-capture.h"
 #include "../common/context.h"
 
+void myCustomLogFunction(uint32_t level, const char *string)
+{
+    printf("== %s", string);
+}
+
 std::string FourCCToString(uint32_t fourcc)
 {
     std::string v;
@@ -144,6 +149,8 @@ int main(int argc, char*argv[])
     uint32_t deviceFormatID = 0;
     uint32_t deviceID       = 0;
 
+    Cap_installCustomLogFunction(myCustomLogFunction);
+
     printf("==============================\n");
     printf(" OpenPNP Capture Test Program\n");
     printf(" %s\n", Cap_getLibraryVersion());