Patch is basically something like:

//////////

@@ -216,7 +217,7 @@ qt5_add_dbus_adaptor(kdenlive_SRCS

mainwindow.h
MainWindow

)
-qt5_add_resources(kdenlive_SRCS ui/resources.qrc uiresources.qrc)
+qt5_add_resources(kdenlive_SRCS ui/resources.qrc uiresources.qrc iconresources.qrc)
add_executable(kdenlive

${kdenlive_SRCS}
${kdenlive_UIS}

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index bf8cf21..7834870 100644

• a/src/mainwindow.cpp

+++ b/src/mainwindow.cpp
@@ -143,6 +143,8 @@ MainWindow::MainWindow(const QString &MltPath, const QUrl &Url, const QString &

qRegisterMetaType<audioByteArray> ("audioByteArray");
qRegisterMetaType< QVector <int> > ();
qRegisterMetaType<requestClipInfo> ("requestClipInfo");

+
+ QIcon::setThemeName("kbreeze");

Core::build(this);
KActionMenu *themeAction= new KActionMenu(i18n("Theme"), this);

@@ -461,6 +463,10 @@ void MainWindow::slotThemeChanged(const QString &theme)

QPalette plt = palette();
 
KdenliveSettings::setColortheme(theme);

+ QColor background = qApp->palette().window().color();
+ bool useDarkIcons = background.value() < 100;
+ QIcon::setThemeName(useDarkIcons ? "kbreeze-dark" : "kbreeze");
+

if (m_effectStack) {
    m_effectStack->updatePalette()

///////////

Then we can use the official QIcon::fromTheme function to create icons. The 2 custom icon themes are called "kbreeze" and "kbreeze-dark", and contain the following index.theme file:

////
[Icon Theme]
Name=kbreeze

DisplayDepth=32

Inherits=breeze

1. Directories
2. ordered by category and alphabetically

Directories=actions/22

[actions/22]
Size=22
Context=Actions
Type=Fixed

EOF

//////////

The icon theme resources file, iconresources.qrc is like this:

//

<RCC>

<qresource>
  <file>icons/kbreeze/index.theme</file>
  <file>icons/kbreeze/actions/22/audio-volume-muted.svg</file>

  <file>icons/kbreeze-dark/index.theme</file>
  <file>icons/kbreeze-dark/actions/22/audio-volume-muted.svg</file>
  </qresource>

</RCC>

/////

Since KDE Frameworks 5.23, icons automatically adjust to text's color, making things much easier.
We just need to put our icons in a qrc resource, and add some style info (see breeze icons for reference).
Currently implemented for a few icons in git master

More infos about KDE framework's icon auto color:
http://notmart.org/blog/2016/05/icon-colors/

I think Farid brought this up in one of the bugs, recently (or maybe the mailing list). It looks like the oxygen-icons package is required (at least, in Ubuntu-based distros) for Kdenlive, otherwise there's no icons in the layout interface.

Does Kdenlive need oxygen? Shouldn't Breeze suffice? I'm asking because getting rid of another dependency that Kdenlive doesn't always install by default would probably be a good step towards better stability.

I recently did a fresh install of archlinux and kdenlive didn't have icons in the interface... so i had to install oxygen-icons. There should be at least a guideline od dependencies for packagers so we can guarantee a similar experience across all distros.

Farid, which KDE Frameworks version ? When using KDE Frameworks 5.23, it is normal to have no icons using git master because I am currently reviewing our icon handling to use new features

It is 5.22 and kdenlive 16.04.1.

In Kdenlive 16.08.2 on Ubuntu 16.10 (Unity 7.5.0 desktop), the layout and interface looks 90% uniform to Kdenlive in its native KDE environment. There are still icons in the "Open" dialog box, the "Render" dialog box, and a few text fields that are still showing the light-theme icons in Breeze dark theme.