[harbour-barcode] Tweaked detection of torch support

The torch doesn't work more often that it does, let's only show the
torch button when we know that it actually works.

The button can be forced by setting HARBOUR_BARCODE_ENABLE_TORCH
environment variable to 1 or /apps/harbour-barcode/enableTorch
DConf value to true

src/Settings.cpp

@@ -28,7 +28,7 @@ THE SOFTWARE.
 
 #include <MGConfItem>
 
-#define DCONF_PATH_(x)                 "/apps/harbour-barcode/" x
+#define DCONF_PATH_(x)                 SETTINGS_DCONF_PATH_(x)
 
 // New keys (the ones that have only been in dconf)
 #define KEY_BUZZ_ON_SCAN               "buzz_on_scan"

src/Settings.h

@@ -30,6 +30,8 @@ THE SOFTWARE.
 
 #include <QtQml>
 
+#define SETTINGS_DCONF_PATH_(x)     "/apps/harbour-barcode/" x
+
 // Old keys (the ones that may need to be imported from the database)
 
 #define KEY_SOUND                   "sound"

src/harbour-barcode.cpp

@@ -104,10 +104,15 @@ int main(int argc, char *argv[])
     QScopedPointer<QGuiApplication> app(SailfishApp::application(argc, argv));
     bool torchSupported = false;
 
-    // Parse Qt version to find out what's supported and what's not
     const char* qver = qVersion();
     HDEBUG("Qt version" << qver);
-    if (qver) {
+
+    if (qgetenv("HARBOUR_BARCODE_ENABLE_TORCH").toInt() > 0 ||
+        MGConfItem(SETTINGS_DCONF_PATH_("enableTorch")).value().toBool()) {
+        torchSupported = true;
+        HDEBUG("Torch support is enabled");
+    } else if (qver) {
+        // Figure out what's supported and what's not
         const QStringList s(QString(qver).split('.'));
         if (s.size() >= 3) {
             int v = QT_VERSION_CHECK(s[0].toInt(), s[1].toInt(), s[2].toInt());
@@ -120,6 +125,11 @@ int main(int argc, char *argv[])
                 if (flashValues.size() == 1 &&
                     flashValues.at(0).toInt() == QCameraExposure::FlashOff) {
                     HDEBUG("Flash disabled by" << qPrintable(flashValuesKey));
+                } else if (flashValues.isEmpty()) {
+                    // If this DConf key is missing, assume that the torch
+                    // mode is not supported
+                    HDEBUG("DConf entry" << qPrintable(flashValuesKey) <<
+                        "is missing, disabling the torch");
                 } else {
                     torchSupported = true;
                     HDEBUG("Torch supported");