Fix compatibility with Qt < 5.6

Signed-off-by: falkTX <falktx@falktx.com>

resources/ui/carla_about.ui

@@ -371,7 +371,10 @@
             <enum>Qt::PlainText</enum>
            </property>
            <property name="pixmap">
-            <pixmap resource="../resources.qrc">:/48x48/folder.png</pixmap>
+            <pixmap resource="../resources.qrc">:/scalable/folder.svgz</pixmap>
+           </property>
+           <property name="scaledContents">
+            <bool>true</bool>
            </property>
           </widget>
          </item>
@@ -396,7 +399,10 @@
             <enum>Qt::PlainText</enum>
            </property>
            <property name="pixmap">
-            <pixmap resource="../resources.qrc">:/48x48/warning.png</pixmap>
+            <pixmap resource="../resources.qrc">:/scalable/warning.svgz</pixmap>
+           </property>
+           <property name="scaledContents">
+            <bool>true</bool>
            </property>
           </widget>
          </item>
@@ -421,7 +427,10 @@
             <enum>Qt::PlainText</enum>
            </property>
            <property name="pixmap">
-            <pixmap resource="../resources.qrc">:/48x48/wine.png</pixmap>
+            <pixmap resource="../resources.qrc">:/scalable/wine.svgz</pixmap>
+           </property>
+           <property name="scaledContents">
+            <bool>true</bool>
            </property>
           </widget>
          </item>
@@ -498,6 +507,9 @@
            <property name="pixmap">
             <pixmap resource="../resources.qrc">:/scalable/carla.svg</pixmap>
            </property>
+           <property name="scaledContents">
+            <bool>true</bool>
+           </property>
           </widget>
          </item>
          <item>
@@ -523,6 +535,9 @@
            <property name="pixmap">
             <pixmap resource="../resources.qrc">:/scalable/carla-control.svg</pixmap>
            </property>
+           <property name="scaledContents">
+            <bool>true</bool>
+           </property>
           </widget>
          </item>
          <item>

source/frontend/carla_host.py

@@ -22,7 +22,7 @@
 import json
 
 from PyQt5.Qt import PYQT_VERSION
-from PyQt5.QtCore import qCritical, QEventLoop, QFileInfo, QModelIndex, QPointF, QTimer, QEvent
+from PyQt5.QtCore import QT_VERSION, qCritical, QEventLoop, QFileInfo, QModelIndex, QPointF, QTimer, QEvent
 from PyQt5.QtGui import QImage, QPalette, QBrush
 from PyQt5.QtWidgets import QAction, QApplication, QInputDialog, QFileSystemModel, QListWidgetItem, QGraphicsView, QMainWindow
 
@@ -2329,7 +2329,8 @@ class HostWindow(QMainWindow):
         self.refreshTransport(True)
         QMainWindow.showEvent(self, event)
 
-        self.host.set_engine_option(ENGINE_OPTION_FRONTEND_UI_SCALE, int(self.devicePixelRatioF() * 1000), "")
+        if QT_VERSION >= 0x50600:
+            self.host.set_engine_option(ENGINE_OPTION_FRONTEND_UI_SCALE, int(self.devicePixelRatioF() * 1000), "")
 
         # set our gui as parent for all plugins UIs
         if self.host.manageUIs and not (self.host.isControl or self.host.isPlugin):

source/frontend/patchcanvas/scene.py

@@ -21,7 +21,7 @@
 
 from math import floor
 
-from PyQt5.QtCore import pyqtSignal, pyqtSlot, qFatal, Qt, QPointF, QRectF
+from PyQt5.QtCore import QT_VERSION, pyqtSignal, pyqtSlot, qFatal, Qt, QPointF, QRectF
 from PyQt5.QtGui import QCursor, QPixmap, QPolygonF
 from PyQt5.QtWidgets import QGraphicsRectItem, QGraphicsScene
 
@@ -86,6 +86,9 @@ class PatchScene(QGraphicsScene):
         self.selectionChanged.connect(self.slot_selectionChanged)
 
     def getDevicePixelRatioF(self):
+        if QT_VERSION < 0x50600:
+            return 1.0
+
         return self.m_view.devicePixelRatioF()
 
     def getScaleFactor(self):

source/theme/CarlaStyle.cpp

@@ -1934,8 +1934,8 @@ void CarlaStyle::drawControl(ControlElement element, const QStyleOption *option,
                     pixmap = menuItem->icon.pixmap(iconSize, mode);
 
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
-                const qreal pixw = static_cast<qreal>(pixmap.width()) / pixmap.devicePixelRatioF();
-                const qreal pixh = static_cast<qreal>(pixmap.height()) / pixmap.devicePixelRatioF();
+                const int pixw = pixmap.width() / pixmap.devicePixelRatioF();
+                const int pixh = pixmap.height() / pixmap.devicePixelRatioF();
 #else
                 const int pixw = pixmap.width();
                 const int pixh = pixmap.height();
@@ -2086,6 +2086,7 @@ void CarlaStyle::drawControl(ControlElement element, const QStyleOption *option,
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
                 w = pixmap.width() / pixmap.devicePixelRatio();
 #else
+                w = pixmap.width();
 #endif
 
                 if (button->direction == Qt::RightToLeft)