Add function to update search filter when the user types

Seems to work fine.
The pyqtSignal is not technically necessary unless we display this filter in the interface anywhere. We don't currently. If the signal is not present it would complain about non-notifyable properties. And making it a slot instead of a signal seems a bit unintuitive to me in how the field is being used.

Contributes to issue CURA-8009.

plugins/DigitalLibrary/resources/qml/SelectProjectPage.qml

@@ -48,6 +48,8 @@ Item
             id: searchBar
             Layout.fillWidth: true
             height: createNewProjectButton.height
+
+            onTextEdited: manager.projectFilter = text
         }
 
         Cura.SecondaryButton

plugins/DigitalLibrary/src/DigitalFactoryController.py

@@ -1,4 +1,6 @@
 # Copyright (c) 2021 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
 import json
 import math
 import os
@@ -8,7 +10,7 @@ from enum import IntEnum
 from pathlib import Path
 from typing import Optional, List, Dict, Any, cast
 
-from PyQt5.QtCore import pyqtSignal, QObject, pyqtSlot, pyqtProperty, Q_ENUMS, QUrl
+from PyQt5.QtCore import pyqtSignal, QObject, pyqtSlot, pyqtProperty, Q_ENUMS, QTimer, QUrl
 from PyQt5.QtNetwork import QNetworkReply
 from PyQt5.QtQml import qmlRegisterType, qmlRegisterUncreatableType
 
@@ -116,6 +118,11 @@ class DigitalFactoryController(QObject):
         self._project_model = DigitalFactoryProjectModel()
         self._selected_project_idx = -1
         self._project_creation_error_text = "Something went wrong while creating a new project. Please try again."
+        self._project_filter = ""
+        self._project_filter_change_timer = QTimer()
+        self._project_filter_change_timer.setInterval(1000)
+        self._project_filter_change_timer.setSingleShot(True)
+        self._project_filter_change_timer.timeout.connect(self._applyProjectFilter)
 
         # Initialize the file model
         self._file_model = DigitalFactoryFileModel()
@@ -302,6 +309,36 @@ class DigitalFactoryController(QObject):
             self._selected_file_indices = file_indices
             self.selectedFileIndicesChanged.emit(file_indices)
 
+    def setProjectFilter(self, new_filter) -> None:
+        """
+        Called when the user wants to change the search filter for projects.
+
+        The filter is not immediately applied. There is some delay to allow the user to finish typing.
+        :param new_filter: The new filter that the user wants to apply.
+        """
+        self._project_filter = new_filter
+        self._project_filter_change_timer.start()
+
+    """
+    Signal to notify Qt that the applied filter has changed.
+    """
+    projectFilterChanged = pyqtSignal()
+
+    @pyqtProperty(str, notify = projectFilterChanged, fset = setProjectFilter)
+    def projectFilter(self) -> str:
+        """
+        The current search filter being applied to the project list.
+        :return: The current search filter being applied to the project list.
+        """
+        return self._project_filter
+
+    def _applyProjectFilter(self):
+        """
+        Actually apply the current filter to search for projects with the user-defined search string.
+        :return:
+        """
+        self.projectFilterChanged.emit()
+
     @pyqtProperty(QObject, constant = True)
     def digitalFactoryProjectModel(self) -> "DigitalFactoryProjectModel":
         return self._project_model