Fix Windows console setup so it works in an MSYS2 window.

This change adds checks to see if a console is already attached
and avoids reopening stdout & stderr if so. This allows console
logging to work properly in the typical MSYS2 bash window. For
some reason the freopen() calls in the old code cause console
printing to stop working.

App/NatronApp_main.cpp

@@ -71,17 +71,28 @@ int main(int argc, char *argv[])
 
 #ifdef Q_OS_WIN
     // Setup Windows console output
-    bool hasConsole = false;
     QSettings settings( QString::fromUtf8(NATRON_ORGANIZATION_NAME), QString::fromUtf8(NATRON_APPLICATION_NAME) );
     bool enableConsoleWindow = settings.value( QString::fromUtf8("enableConsoleWindow"), false ).toBool();
-    if (enableConsoleWindow) { // output to console window
-        hasConsole = ( AttachConsole(ATTACH_PARENT_PROCESS) || AllocConsole() );
-    } else { // output to parent console
-        hasConsole = AttachConsole(ATTACH_PARENT_PROCESS);
+    HANDLE stdOutHandle = GetStdHandle(STD_OUTPUT_HANDLE);
+    if (stdOutHandle == INVALID_HANDLE_VALUE) {
+        // Already having an invalid handle when starting likely means something is terribly wrong.
+        OutputDebugStringA("Invalid STD_OUTPUT_HANDLE.");
+        return 1;
     }
-    if (hasConsole) {
-        freopen("CONOUT$", "w", stdout);
-        freopen("CONOUT$", "w", stderr);
+    if (stdOutHandle == NULL) {
+        // A console is not already attached to this process. Try attaching to our parent's console.
+        bool hasConsole = AttachConsole(ATTACH_PARENT_PROCESS);
+        if (!hasConsole && enableConsoleWindow) {
+            // Failed to attach to the parent console. Try creating a console window.
+            hasConsole = AllocConsole();
+        }
+
+        if (hasConsole) {
+            // Reopen stdout & stderr streams so that writing to
+            // them will display on the attached/allocated console.
+            freopen("CONOUT$", "w", stdout);
+            freopen("CONOUT$", "w", stderr);
+        }
     }
 #endif