core: fixed strange black areas at small display

In certain cases the main UI window when opened
at the small resolution display has some strange
black areas at the top and right.
When the UI window is repainted by "Qt", the issue is solved:
1. Minimize and maximize.
2. Move the UI window to the large display
and then back to the small display.
3. Switch to another application that partially
hides the dashboard's window and then switch back.

Several root causes related to UI were identified and fixed:
1. Fixed window and content dimension mismatch: the main window
is set to 1117x636 pixels, while background label is set to
1111x651 pixels, that's 15 pixels taller than the main window
(this caused content to be drawn outside the visible area,
creating overflow areas that appeared black).
After the fix the background perfectly matches the main window size.
To avoid such problem in the future, the magic numbers were
refactored into the class-level constants.
2. Added DPI awareness and automatic high DPI scaling support
to properly handle different display DPI settings and scaling
factors, which caused rendering issues when moving between displays.
3. Added automatic window centering on the primary screen.
This ensures consistent positioning regardless of monitor setup.
4. Also disabled the window context help button (the "?" button
that appears in window title bars on some platforms).

The solution was tested on both small and large displays
to ensure black areas are eliminated.

Co-authored-by: Cursor AI

Signed-off-by: Pavel Bar <pbar@redhat.com>

Author: barpavel

app.py

@@ -32,21 +32,25 @@
 
 
 class Ui_MainWindow(object):
+    # Main window dimensions constants
+    WINDOW_WIDTH = 1117
+    WINDOW_HEIGHT = 636
+
     # Webcam widget dimensions constants
     WEBCAM_WIDTH = 321
     WEBCAM_HEIGHT = 331
-    
+
     def __init__(self, video_path=None):
         self.video_path = video_path
-    
+
     def setupUi(self, MainWindow):
         MainWindow.setObjectName("MainWindow")
-        MainWindow.setFixedSize(1117, 636)
+        MainWindow.setFixedSize(Ui_MainWindow.WINDOW_WIDTH, Ui_MainWindow.WINDOW_HEIGHT)
         MainWindow.setStyleSheet("background-color: rgb(30, 31, 40);")
         self.centralwidget = QWidget(MainWindow)
         self.centralwidget.setObjectName("centralwidget")
         self.label = QLabel(self.centralwidget)
-        self.label.setGeometry(QRect(0, 0, 1111, 651))
+        self.label.setGeometry(QRect(0, 0, Ui_MainWindow.WINDOW_WIDTH, Ui_MainWindow.WINDOW_HEIGHT))
         self.label.setText("")
         self.label.setPixmap(QPixmap(":/bg/Untitled (1).png"))
         self.label.setScaledContents(True)
@@ -921,10 +925,26 @@ def progress(self):
     parser = argparse.ArgumentParser(description='Smart Car Dashboard GUI')
     parser.add_argument('--play-video', metavar='path', type=str, help='[Optional] path to video file to play instead of camera')
     args = parser.parse_args()
-    
+
+    # Enable automatic high DPI scaling
+    QApplication.setAttribute(Qt.AA_EnableHighDpiScaling, True)
+    # Enable crisp rendering on high DPI displays
+    QApplication.setAttribute(Qt.AA_UseHighDpiPixmaps, True)
+    # Disable window context help button
+    QApplication.setAttribute(Qt.AA_DisableWindowContextHelpButton, True)
+
     app = QApplication(sys.argv)
     main_app_window = QMainWindow()
     ui = Ui_MainWindow(video_path=args.play_video)
     ui.setupUi(main_app_window)
+
+    # Center window on screen
+    screen = app.primaryScreen()
+    screen_geometry = screen.geometry()
+    window_geometry = main_app_window.frameGeometry()
+    center_point = screen_geometry.center()
+    window_geometry.moveCenter(center_point)
+    main_app_window.move(window_geometry.topLeft())
+
     main_app_window.show()
     sys.exit(app.exec_())