Added preview image to print cluster monitor

CL-894

cura/PrintJobPreviewImageProvider.py

@@ -0,0 +1,27 @@
+from PyQt5.QtGui import QImage
+from PyQt5.QtQuick import QQuickImageProvider
+from PyQt5.QtCore import QSize
+
+from UM.Application import Application
+
+
+class PrintJobPreviewImageProvider(QQuickImageProvider):
+    def __init__(self):
+        super().__init__(QQuickImageProvider.Image)
+
+    ##  Request a new image.
+    def requestImage(self, id, size):
+        # The id will have an uuid and an increment separated by a slash. As we don't care about the value of the
+        # increment, we need to strip that first.
+        uuid = id[id.find("/") + 1:]
+        for output_device in Application.getInstance().getOutputDeviceManager().getOutputDevices():
+            if not hasattr(output_device, "printJobs"):
+                continue
+
+            for print_job in output_device.printJobs:
+                if print_job.key == uuid:
+                    if print_job.getPreviewImage():
+                        return print_job.getPreviewImage(), QSize(15, 15)
+                    else:
+                        return QImage(), QSize(15, 15)
+        return QImage(), QSize(15,15)