Keep the "free space" information updated in all visible views

The old code would watch the free space on a mount point, i.e.,
determine the free space again, in 10-second intervals, only until the
view became invisible once (even if it was invisible only for a very
short moment, i.e., while splitting the view).

This commit ensures that the mount point is watched again as soon as
the corresponding view becomes visible again.

Moreover, the object that watches the free space for a mount point is
shared among all views that show URLs that belong to this mount point.
To achieve this, there is a central cache which can be used to obtain
an existing MountPointObserver for a certain path. If necessary, a new
MountPointObserver is created and added to the cache.

The MountPointObserver is removed from the cache and destroyed only if
no views use it any more, and no new users appear until the next update
(which happens every 10 seconds). This prevents that the free space is
measured repeatedly when changing the current directory on the same
mount point.

Many thanks to Emmanuel Pescosta for the initial ideas to factor out
the "free space" code and to establish a central storage for the
"observer" objects, and for providing many good suggestions how to
improve the code!

BUG: 327708
REVIEW: 118208
FIXED-IN: 4.14.0

1 files changed, 19 insertions, 38 deletions

diff --git a/src/statusbar/statusbarspaceinfo.cpp b/src/statusbar/statusbarspaceinfo.cpp
index 61b28334a..3692947b1 100644
--- a/src/statusbar/statusbarspaceinfo.cpp
+++ b/src/statusbar/statusbarspaceinfo.cpp
@@ -20,22 +20,17 @@
 
 #include "statusbarspaceinfo.h"
 
-#include <KDiskFreeSpaceInfo>
+#include "spaceinfoobserver.h"
+
 #include <KLocale>
 #include <KIO/Job>
 
-#include <QTimer>
 #include <QKeyEvent>
 
 StatusBarSpaceInfo::StatusBarSpaceInfo(QWidget* parent) :
     KCapacityBar(KCapacityBar::DrawTextInline, parent),
-    m_kBSize(0),
-    m_timer(0)
+    m_observer(0)
 {
-    // Use a timer to update the space information. Polling is useful
-    // here, as files can be deleted/added outside the scope of Dolphin.
-    m_timer = new QTimer(this);
-    connect(m_timer, SIGNAL(timeout()), this, SLOT(calculateSpaceInfo()));
 }
 
 StatusBarSpaceInfo::~StatusBarSpaceInfo()
@@ -46,8 +41,8 @@ void StatusBarSpaceInfo::setUrl(const KUrl& url)
 {
     if (m_url != url) {
         m_url = url;
-        if (isVisible()) {
-            calculateSpaceInfo();
+        if (m_observer) {
+            m_observer->setUrl(url);
         }
     }
 }
@@ -60,47 +55,33 @@ KUrl StatusBarSpaceInfo::url() const
 void StatusBarSpaceInfo::showEvent(QShowEvent* event)
 {
     KCapacityBar::showEvent(event);
-    if (!event->spontaneous()) {
-        calculateSpaceInfo();
-        m_timer->start(10000);
-    }
+    m_observer.reset(new SpaceInfoObserver(m_url, this));
+    slotValuesChanged();
+    connect(m_observer.data(), SIGNAL(valuesChanged()), this, SLOT(slotValuesChanged()));
 }
 
 void StatusBarSpaceInfo::hideEvent(QHideEvent* event)
 {
-    m_timer->stop();
+    m_observer.reset();
     KCapacityBar::hideEvent(event);
 }
 
-void StatusBarSpaceInfo::calculateSpaceInfo()
+void StatusBarSpaceInfo::slotValuesChanged()
 {
-    // KDiskFreeSpace is for local paths only
-    if (!m_url.isLocalFile()) {
-        setText(i18nc("@info:status", "Unknown size"));
-        setValue(0);
-        update();
-        return;
-    }
-
-    KDiskFreeSpaceInfo job = KDiskFreeSpaceInfo::freeSpaceInfo(m_url.toLocalFile());
-    if (!job.isValid()) {
+    Q_ASSERT(m_observer);
+    const quint64 size = m_observer->size();
+    if (size == 0) {
         setText(i18nc("@info:status", "Unknown size"));
         setValue(0);
         update();
-        return;
-    }
-
-    KIO::filesize_t kBSize = job.size() / 1024;
-    KIO::filesize_t kBUsed = job.used() / 1024;
-
-    const bool valuesChanged = (kBUsed != static_cast<quint64>(value())) || (kBSize != m_kBSize);
-    if (valuesChanged) {
-        setText(i18nc("@info:status Free disk space", "%1 free",
-                KIO::convertSize(job.available())));
+    } else {
+        const quint64 available = m_observer->available();
+        const quint64 used = size - available;
+        const int percentUsed = qRound(100.0 * qreal(used) / qreal(size));
 
+        setText(i18nc("@info:status Free disk space", "%1 free", KIO::convertSize(available)));
         setUpdatesEnabled(false);
-        m_kBSize = kBSize;
-        setValue(kBSize > 0 ? (kBUsed * 100) / kBSize : 0);
+        setValue(percentUsed);
         setUpdatesEnabled(true);
         update();
     }