add libosmscout patch 1

backend/CMakeLists.txt

@@ -188,6 +188,7 @@ set(libosmscout_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/libosmscout")
 
 # First apply our patches in the source of lib
 list(APPEND libosmscout_patches
+    libosmscout.patch.1
 )
 foreach(patch IN LISTS libosmscout_patches)
     execute_process(

backend/libosmscout.patch.1

@@ -0,0 +1,23 @@
+diff --git a/libosmscout-client-qt/src/osmscoutclientqt/TiledRenderingHelper.cpp b/libosmscout-client-qt/src/osmscoutclientqt/TiledRenderingHelper.cpp
+index 9f6b45b9d..f8dd8776d 100644
+--- a/libosmscout-client-qt/src/osmscoutclientqt/TiledRenderingHelper.cpp
++++ b/libosmscout-client-qt/src/osmscoutclientqt/TiledRenderingHelper.cpp
+@@ -65,10 +65,16 @@ bool TiledRenderingHelper::RenderTiles(QPainter &painter,
+     }
+   }
+
++  // enable subpixel rendering so that magnification up to 2x remains
++  // as smooth as possible
++  static constexpr double pitchFactor = 1.5;
++  // the magnification level is adjusted taking into account the pixel
++  // ratio of the request and the fixed dpi of the OSM tile
+   projection.Set(request.coord,
+                  0,
+-                 request.magnification,
+-                 request.dpi,
++                 Magnification(request.magnification.GetMagnification()
++                               * pitchFactor * request.dpi / OSMTile::tileDPI()),
++                 OSMTile::tileDPI() / pitchFactor,
+                  width,
+                  height);
+