QGIS - control of expansion and rotation of multiple Map-Windows in Layout

Question

I created a polygon layer ('Blattschnitt') with two sections of a route of interest, with a certain expansion and rotation. The rotation has been calculated, if needed.

In the Layout I set up two Map-Windows (f.e. Map1 & Map2) wich I would like to link to the sections from the layer 'Blattschnitt'. Is there a possibility? I assume the Atlas function does not apply with two Maps in one layout?

Answer 1

You can use an expression in the data defined override of the map rotation in each map to reference the "rotate" attribute in the Blattschnitt layer.

For example, for the rotation of 'Map 1':

Either get the feature using the Blatt nr attribute:

attribute(
    get_feature(
        layer:='Blattschnitt',
        attribute:='Blatt nr',
        value:='Blatt 1'
    ), 
    'rotate'
)

Or simply by the feature id:

attribute(
    get_feature_by_id(
        layer:='Blattschnitt',
        feature_id:=1
    ),
    'rotate'
)

Both of these expressions will return -51,262. Use the expression again for 'Map 2' but alter the Blatt nr attribute value, or feature_id accordingly.

A dynamic solution

Alternatively, in the following example on my layer called sections, I use the main_angle function on the polygons to get the rotation angle dynamically. The section number is referenced automatically by substringing the Map id (in my case, the 5th character of the id is the number following Map). In this case, the same expression can be used on each map, provided the map id number matches the section number - no need to change anything.

with_variable('angle',
    main_angle(
        geometry(
            get_feature('sections', 'section', 'section ' || substr(@map_id, 5, 5))
        )
    ),
    
    case 
        when @angle >= 90 and @angle < 180
        then -@angle + 90
        when @angle >= 0 and @angle < 90
        then 90 - @angle
    end
)

Answer 2

To have both the Rotation and the Extent adapt automatically, you need to do the following:

• apply the geometry rotation to the Map item Rotation (via the rotation field or the main_angle). You might want to use main_angle as it will ensure better consistency when the angle changes from quadrant to quadrant

• set the Map item Extents based on the polygon geometry, and there's a trick as the polygon geometry (Xmin/Xmax/Ymin/Ymax don't work)

In my example, the layer containing the reference polygons is called ref, and polygons have an id field.

Set the Map item Rotation to :

90-main_angle(geometry(get_feature('ref','id',1))) where 1 is the id of the polygon you refer to in this case

Set the Map item Extents to:

Xmin field formula:

x_min(
       rotate(
              geometry(get_feature('ref','id',1)),
              90-main_angle(geometry(get_feature('ref','id',1)))))

Apply the same formula for Xmax, Ymin, Ymax, replacing the first x_min(...) by x_max(...) and so on.

Replace the id number according to the targeted polygon (or use the suggested dynamic index)

Xmin setup for Map2 / polygin id = 2:

Example 1:

Example 2:

---

The key part for the Extents is to rotate the polygon $geometry before extracting the min/max extents. If you just take the extent of the geometry itself, you don't get a suitable result: