Information Panel: show early icons for folders

Summary:
Folders previews can be long to generate.
This can be noticeable by the user.

This diff displays folder icons after a 100ms timer.

BUG: 420340
FIXED-IN: 20.08

Test Plan:
rm -r ~/.cache/thumbnails/
In dolphin open trash
Click on download (or any directory with a long to generate preview).

Reviewers: #dolphin, ngraham

Reviewed By: #dolphin, ngraham

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D29204

1 files changed, 15 insertions, 12 deletions

diff --git a/src/panels/information/informationpanelcontent.cpp b/src/panels/information/informationpanelcontent.cpp
index 1161ea694..a0c872560 100644
--- a/src/panels/information/informationpanelcontent.cpp
+++ b/src/panels/information/informationpanelcontent.cpp
@@ -78,7 +78,7 @@ InformationPanelContent::InformationPanelContent(QWidget* parent) :
     // delay. This prevents flickering if the new preview can be generated
     // within a very small timeframe.
     m_outdatedPreviewTimer = new QTimer(this);
-    m_outdatedPreviewTimer->setInterval(300);
+    m_outdatedPreviewTimer->setInterval(100);
     m_outdatedPreviewTimer->setSingleShot(true);
     connect(m_outdatedPreviewTimer, &QTimer::timeout,
             this, &InformationPanelContent::markOutdatedPreview);
@@ -189,12 +189,8 @@ void InformationPanelContent::refreshPixmapView()
 
     // Mark the currently shown preview as outdated. This is done
     // with a small delay to prevent a flickering when the next preview
-    // can be shown within a short timeframe. This timer is not started
-    // for directories, as directory previews might fail and return the
-    // same icon.
-    if (!m_item.isDir()) {
-        m_outdatedPreviewTimer->start();
-    }
+    // can be shown within a short timeframe.
+    m_outdatedPreviewTimer->start();
 
     QStringList plugins = KIO::PreviewJob::availablePlugins();
     m_previewJob = new KIO::PreviewJob(KFileItemList() << m_item,
@@ -411,11 +407,18 @@ void InformationPanelContent::showPreview(const KFileItem& item,
 
 void InformationPanelContent::markOutdatedPreview()
 {
-    KIconEffect *iconEffect = KIconLoader::global()->iconEffect();
-    QPixmap disabledPixmap = iconEffect->apply(m_preview->pixmap(),
-                                               KIconLoader::Desktop,
-                                               KIconLoader::DisabledState);
-    m_preview->setPixmap(disabledPixmap);
+    if (m_item.isDir()) {
+        // directory preview can be long
+        // but since we always have icons to display
+        // use it until the preview is done
+        showIcon(m_item);
+    } else {
+        KIconEffect *iconEffect = KIconLoader::global()->iconEffect();
+        QPixmap disabledPixmap = iconEffect->apply(m_preview->pixmap(),
+                                                   KIconLoader::Desktop,
+                                                   KIconLoader::DisabledState);
+        m_preview->setPixmap(disabledPixmap);
+    }
 }
 
 KFileItemList InformationPanelContent::items()