Map: generate pixmap name in model

Experimentation has shown that the image of a flag will
only be changed after dataChanged() if it is a simple
property. The old code had a complex QML expression and
then - for some reason - it didn't work.

To give us better control over the flags and avoid full
reloads of the map therefore introduce a model-property
pixmap name. The name depends on whether the site is
selected and if not, whether we are in divesite-edit mode.
This makes the code rather convoluted. Firstly, we have
to save whether the site is selected in the map-item.
Secondly we have to access the global map-widget, which
in turn has to go to the map-widget helper (layering
violation!).

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

map-widget/qmlmapwidgethelper.cpp

@@ -11,6 +11,7 @@
 #include "qt-models/divelocationmodel.h"
 #ifndef SUBSURFACE_MOBILE
 #include "qt-models/filtermodels.h"
+#include "desktop-widgets/mapwidget.h"
 #endif
 
 #define SMALL_CIRCLE_RADIUS_PX            26.0
@@ -235,6 +236,11 @@ void MapWidgetHelper::diveSiteChanged(struct dive_site *ds, int field)
 	centerOnDiveSite(ds);
 }
 
+bool MapWidgetHelper::editMode() const
+{
+	return m_editMode;
+}
+
 QString MapWidgetHelper::pluginObject()
 {
 	QString lang = uiLanguage(NULL).replace('_', '-');