Add option to completely disable directory size counting

Dolphin shows the size of directories by listing their contents, which
for some users might cause unwanted load on the file system.
Depending on the size of the subdirectories in question and how the
storage is accessed, this might cause noticeable delays and even
freezing.

This commit adds a new option under "View -> Content Display" that
enables users to set "Folder size:" to "No size", completely disabling
directory size counting. Directory size counting is still enabled by
default.

As a third option for "Folder size" is added, the DirectorySizeCount
boolean setting is replaced with a DirectorySizeMode enum setting. The
old setting is migrated using a kconf_update script.

FEATURE: 477187
GUI:

1 files changed, 4 insertions, 1 deletions

diff --git a/doc/index.docbook b/doc/index.docbook
index a337c14a8..43ee0db44 100644
--- a/doc/index.docbook
+++ b/doc/index.docbook
@@ -1308,7 +1308,10 @@ are displayed in a tree view, where the sub items can be expanded by &LMB; click
 <guiicon>&gt;</guiicon> icon and collapsed by clicking the <guiicon>v</guiicon> icon.
 </para>
 <para>
-<guilabel>Folder size displays</guilabel> allows defining the property to use then sorting folders by their size. It is possible to sort folders by <guilabel>Number of items</guilabel> or <guilabel>Size of contents</guilabel> and choose a limit to the recursive level (can be useful to constrain unneeded iterations in the deep folder structures or on the slow file systems).
+<guilabel>Folder size</guilabel> allows defining the property to use for sorting folders by their size.
+It is possible to sort folders by number of items by choosing <guilabel>Show number of items</guilabel> or by the size of the contents by choosing <guilabel>Show size of contents</guilabel>.
+The recursion level can be limited, which can be useful to constrain unneeded iterations in deep folder structures or on slow file systems.
+It is also possible to disable displaying folder size by choosing <guilabel>Show no size</guilabel> (which might improve performance in rare cases, however impacts other features like sorting).
 </para>
 <para>
 The <guilabel>Date style</guilabel> option can be used to configure the mode to display dates in &dolphin;. It is possible to choose between <guilabel>Relative</guilabel> (&eg;, <quote>Yesterday, 3:00pm</quote>) or <guilabel>Absolute</guilabel> (&eg;, <quote>2020-12-23 15:00</quote>).