[Details mode] Allow to fill the column size of directories with actual size

Summary:
Allow to compute the recursive size of directories to fill the details view size column.
A setting allow to set a limit to the recursive level, allowing the user to have some power over the setting.

When sorting by size and the feature is on, we get progressive ordering as the directory size are gathered.

KDirectoryContentsCounter uses a cache internally to keep results so that it can display directory size faster, but counts the dir size of directories each time it is asked to count the size a directory nevertheless and when the size has changed, it is updated.
KDirectoryContentsCounter uses one worker per instance only, meaning one process per view makes the disk spin.

FIXED-IN: 20.08
BUG: 190580
BUG: 158090

Test Plan:
With some recursion allowed:
{F8267580}

Without any recursion allowed (default):
{F8267581}

Reviewers: elvisangelaccio, ngraham, #dolphin

Reviewed By: elvisangelaccio, ngraham, #dolphin

Subscribers: feverfew, anthonyfieroni, iasensio, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D25335

1 files changed, 11 insertions, 3 deletions

diff --git a/src/kitemviews/private/kdirectorycontentscounterworker.h b/src/kitemviews/private/kdirectorycontentscounterworker.h
index b40da6e87..fac9978d5 100644
--- a/src/kitemviews/private/kdirectorycontentscounterworker.h
+++ b/src/kitemviews/private/kdirectorycontentscounterworker.h
@@ -37,6 +37,14 @@ public:
     };
     Q_DECLARE_FLAGS(Options, Option)
 
+    struct CountResult {
+        /// number of elements in the directory
+        int count;
+        /// Recursive sum of the size of the directory content files and folders
+        /// Calculation depends on DetailsModeSettings::recursiveDirectorySizeLimit
+        long size;
+    };
+
     explicit KDirectoryContentsCounterWorker(QObject* parent = nullptr);
 
     /**
@@ -45,13 +53,13 @@ public:
      *
      * @return The number of items.
      */
-    static int subItemsCount(const QString& path, Options options);
+    static CountResult subItemsCount(const QString& path, Options options);
 
 signals:
     /**
-     * Signals that the directory \a path contains \a count items.
+     * Signals that the directory \a path contains \a count items and optionally the size of its content.
      */
-    void result(const QString& path, int count);
+    void result(const QString& path, int count, long size);
 
 public slots:
     /**