Support map zooms relative to the Viking zoom level (e.g. 2×)

[vinc17fr]

In the Default Map → Properties dialog box, one can set Zoom Level either to some fixed value (a power of 2) or to "Use Viking Zoom Level". A fixed value consists in scaling the viewport on a fixed image, meaning that when zooming in, the image can be pixelized, and when zooming out, the text from the map can become unreadable. So "Use Viking Zoom Level" is normally much more interesting, as the selected image (set of tiles) depends on the zoom level, thus with the most possible details on the map, but on very high DPI screens, the fonts can be too small, making text almost unreadable. So a value relative to the Viking zoom level would be useful to keep text readable though some details would be lost (a map type with big fonts for HDPI screens would be the best solution, but such maps do not seem to be available); just a value of 2× may actually be sufficient, so that this would need only one additional line in the Zoom Level menu.

Note: setting viewport_scale=2 in the ~/.viking/viking.ini file almost achieves the above feature, but

• this unnecessarily affects the scaling of some other things (not related to text);
• changing its value needs a restart of Viking.

[vinc17fr]

The use of viewport_scale is mentioned in the related issue #97.

[rnorris]

Apologies for lateness of the reply, just to clarify my understanding of the request...

You would like an additional scale factor to apply solely to the map images (unlike the viewport_scale). I will ponder on how best to achieve this.