[locale] Expand test to check zones-overlap

- Document index and find methods,
- Check that each location is claimed by only one image (e.g. by
  one zone). This is currently false.

src/modules/locale/Tests.cpp

@@ -112,12 +112,34 @@ LocaleTests::testTZImages()
     using namespace CalamaresUtils::Locale;
     const CStringPairList& regions = TZRegion::fromZoneTab();
 
+    int overlapcount = 0;
     for ( const auto* pr : regions )
     {
         const TZRegion* region = dynamic_cast< const TZRegion* >( pr );
-        if ( region )
-        {
+        QVERIFY( region );
+
         cDebug() << "Region" << region->region() << "zones #" << region->zones().count();
+        Logger::setupLogLevel( Logger::LOGERROR );
+
+        const auto zones = region->zones();
+        for ( const auto* pz : zones )
+        {
+            const TZZone* zone = dynamic_cast< const TZZone* >( pz );
+            QVERIFY( zone );
+
+            int overlap = 0;
+            auto pos = images.getLocationPosition( zone->longitude(), zone->latitude() );
+            QVERIFY( images.index( pos, overlap ) >= 0 );
+            if ( overlap > 1 )
+            {
+                Logger::setupLogLevel( Logger::LOGDEBUG );
+                cDebug() << Logger::SubEntry << "Zone" << zone->zone() << pos;
+                (void)images.index( pos, overlap );
+                Logger::setupLogLevel( Logger::LOGERROR );
+                overlapcount++;
             }
         }
     }
+
+    QCOMPARE( overlapcount, 0 );
+}

src/modules/locale/timezonewidget/TimeZoneImage.cpp

@@ -144,12 +144,11 @@ TimeZoneImageList::getLocationPosition( double longitude, double latitude )
 static constexpr const int RGB_TRANSPARENT = 0;
 
 int
-TimeZoneImageList::index( QPoint pos, int& overlap ) const
+TimeZoneImageList::index( QPoint pos, int& count ) const
 {
-    overlap = 0;
+    count = 0;
 
 #ifdef DEBUG_TIMEZONES
-    bool found = false;
     for ( int i = 0; i < size(); ++i )
     {
         const QImage& zone = at( i );
@@ -159,19 +158,18 @@ TimeZoneImageList::index( QPoint pos, int& overlap ) const
         {
             // Log *all* the zones that contain this point,
             // but only pick the first.
-            if ( !found )
+            if ( !count )
             {
-                found = true;
                 cDebug() << Logger::SubEntry << "First zone found" << i << zone.text( ZONE_NAME );
             }
             else
             {
                 cDebug() << Logger::SubEntry << "Also in zone" << i << zone.text( ZONE_NAME );
-                overlap++;
+            }
+            count++;
         }
     }
-    }
-    if ( !found )
+    if ( !count )
     {
         return -1;
     }

src/modules/locale/timezonewidget/TimeZoneImage.h

@@ -56,8 +56,24 @@ public:
      */
     static QPoint getLocationPosition( double longitude, double latitude );
 
+    /** @brief Find the index of the image claiming point @p p
+     *
+     * This maps a point (presumably from getLocationPosition(), so
+     * originating from a longitude and latitude) to a specific zone
+     * image index. Returns -1 if no image claims the point (e.g. if
+     * it is out of bounds).
+     */
     int index( QPoint p ) const;
-    int index( QPoint p, int& overlap ) const;
+    /** @brief Find the index of the image claiming point @p p
+     *
+     * As `index(p)`, but also fills in @p count with the number of
+     * zones that claim the point.
+     */
+    int index( QPoint p, int& count ) const;
+    /** @brief Get image of the zone claiming @p p
+     *
+     * Can return a null image, if the point is unclaimed or invalid.
+     */
     QImage find( QPoint p ) const;
 
     /// @brief The **expected** number of zones in the list.