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how to GUI show data in fraction of seconds for large data sets

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  • SGaistS SGaist

    @Qt-Enthusiast said in how to GUI show data in fraction of seconds for large data sets:

    I have a graph with 20 millon nodes and I have to show the same as squares in QgraphicsView and QgraphicsScence in fraction on seconds . Could you please help

    Hi,

    As my fellow already wrote, trying to render that many point is at best useless.

    You should use the same technique as video games do: use level of details. Group your points together when showing the full extend of the dataset. Then when people start to zoom in, show them a subset of the points for that region, again keep them grouped together in a meaningful way until they are at a sufficient level of details to show the actual points.

    M Offline
    M Offline
    mpergand
    wrote on last edited by
    #12

    Google Maps could be a source a inspiration.

    Q 1 Reply Last reply
    0
    • M mpergand

      Google Maps could be a source a inspiration.

      Q Offline
      Q Offline
      Qt Enthusiast
      wrote on last edited by
      #13

      @mpergand Do we have algorithms for Google maps and Incremental rendering . Any example will help

      1 Reply Last reply
      0
      • jeremy_kJ Offline
        jeremy_kJ Offline
        jeremy_k
        wrote on last edited by
        #14

        The 40000 chips demo might help.

        https://doc.qt.io/qt-6/qtwidgets-graphicsview-chip-example.html

        Chip::paint() is where the level of detail is handled.
        https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/graphicsview/chip/chip.cpp?h=6.6#n33

        Asking a question about code? http://eel.is/iso-c++/testcase/

        Q 1 Reply Last reply
        5
        • jeremy_kJ jeremy_k

          The 40000 chips demo might help.

          https://doc.qt.io/qt-6/qtwidgets-graphicsview-chip-example.html

          Chip::paint() is where the level of detail is handled.
          https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/graphicsview/chip/chip.cpp?h=6.6#n33

          Q Offline
          Q Offline
          Qt Enthusiast
          wrote on last edited by
          #15

          @jeremy_k

          Can we discuss PyQt over here , I have made a prototype

          Q S 2 Replies Last reply
          0
          • Q Qt Enthusiast

            @jeremy_k

            Can we discuss PyQt over here , I have made a prototype

            Q Offline
            Q Offline
            Qt Enthusiast
            wrote on last edited by
            #16

            @Qt-Enthusiast said in how to GUI show data in fraction of seconds for large data sets:

            made

            import sys
            from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QGraphicsRectItem, QApplication, QMainWindow, QVBoxLayout, QWidget, QPushButton
            from PyQt5.QtCore import Qt, QTimer
            from PyQt5.QtGui import QPainter

            Tile class representing a tile in the scene

            class Tile(QGraphicsRectItem):
            def init(self, x, y, size):
            super(Tile, self).init(x, y, size, size)
            self.setBrush(Qt.NoBrush) # Transparent fill for demonstration
            self.macros = []

            def add_macro(self, macro):
                self.macros.append(macro)
                self.addItem(macro)
            

            Base class for both macro types

            class BaseMacroNode(QGraphicsRectItem):
            def init(self, name, x, y, size):
            super(BaseMacroNode, self).init(x, y, size, size)
            self.name = name

            AdaptiveMacroNode class representing a macro with an adaptive level of detail

            class AdaptiveMacroNode(BaseMacroNode):
            def init(self, name, x, y, size, lod):
            super(AdaptiveMacroNode, self).init(name, x, y, size)
            self.lod = lod # Initial level of detail

            def update_lod(self, lod):
                self.lod = lod
                self.update()  # Trigger a repaint when LOD changes
            
            def paint(self, painter, option, widget=None):
                # Custom paint method based on LOD
                painter.setBrush(Qt.blue if self.lod > 0.5 else Qt.red)
                painter.drawRect(self.rect())
                painter.drawText(self.rect(), Qt.AlignCenter, self.name)
            

            AsynchronousMacroNode class representing a macro with asynchronous loading

            class AsynchronousMacroNode(BaseMacroNode):
            def init(self, name, x, y, size):
            super(AsynchronousMacroNode, self).init(name, x, y, size)
            # Simulate asynchronous loading with a timer
            QTimer.singleShot(1000, self.on_loaded)

            def on_loaded(self):
                # Set color after loading
                self.setBrush(Qt.green)
            

            ChipDesignScene class with tile-based rendering and dynamic addition of macros

            class ChipDesignScene(QGraphicsScene):
            def init(self):
            super(ChipDesignScene, self).init()
            self.tile_size = 10000
            self.tiles = {}

            def add_tile(self, x, y):
                tile = Tile(x, y, self.tile_size)
                self.addItem(tile)
                self.tiles[(x, y)] = tile
            
            def remove_tile(self, x, y):
                if (x, y) in self.tiles:
                    tile = self.tiles[(x, y)]
                    self.removeItem(tile)
                    del self.tiles[(x, y)]
            
            def add_macro_to_tile(self, x, y, macro):
                tile = self.tiles.get((x, y))
                if tile:
                    tile.add_macro(macro)
            
            def update_tiles(self, lod):
                # For simplicity, consider a fixed-size scene
                scene_width = 1000
                scene_height = 1000
            
                # Calculate visible tiles based on LOD
                visible_tiles = [
                    (x, y)
                    for x in range(0, scene_width, self.tile_size)
                    for y in range(0, scene_height, self.tile_size)
                ]
            
                # Add new tiles and macros
                for tile_pos in visible_tiles:
                    if tile_pos not in self.tiles:
                        self.add_tile(*tile_pos)
            
                        # Add AdaptiveMacroNodes to the newly visible tile during zoom-out
                        for i in range(3):
                            adaptive_macro = AdaptiveMacroNode(f"AdaptiveMacro{i}", tile_pos[0] + i * 50, tile_pos[1] + i * 50, 30, 0.8)
                            self.add_macro_to_tile(*tile_pos, adaptive_macro)
            
                        # Add AsynchronousMacroNodes to the newly visible tile during zoom-out
                        asynchronous_macro = AsynchronousMacroNode("AsynchronousMacro", tile_pos[0] + 150, tile_pos[1] + 150, 30)
                        self.add_macro_to_tile(*tile_pos, asynchronous_macro)
            
                # Remove tiles that are no longer visible
                for tile_pos in list(self.tiles.keys()):
                    if tile_pos not in visible_tiles:
                        self.remove_tile(*tile_pos)
            

            ChipDesignView class with zoom features

            class ChipDesignView(QGraphicsView):
            def init(self, scene):
            super(ChipDesignView, self).init(scene)
            self.setRenderHint(QPainter.Antialiasing, True)
            self.setSceneRect(0, 0, 1000, 1000)
            self.setRenderHint(QPainter.Antialiasing)

            def zoom_in(self):
                zoom_factor = 1.2
                self.scale(zoom_factor, zoom_factor)
                self.update_zoom()
            
            def zoom_out(self):
                zoom_factor = 1 / 1.2
                self.scale(zoom_factor, zoom_factor)
                self.update_zoom()
            
            def update_zoom(self):
                zoom_factor = self.transform().m11()
                lod_value = zoom_factor
                self.scene().update_lod(lod_value)
                self.scene().update_tiles(lod=lod_value)
            

            MainWindow class with zoom buttons

            class MainWindow(QMainWindow):
            def init(self):
            super(MainWindow, self).init()

                self.scene = ChipDesignScene()
                self.view = ChipDesignView(self.scene)
            
                self.zoom_in_button = QPushButton("Zoom In")
                self.zoom_in_button.clicked.connect(self.view.zoom_in)
            
                self.zoom_out_button = QPushButton("Zoom Out")
                self.zoom_out_button.clicked.connect(self.view.zoom_out)
            
                layout = QVBoxLayout()
                layout.addWidget(self.view)
                layout.addWidget(self.zoom_in_button)
                layout.addWidget(self.zoom_out_button)
            
                widget = QWidget()
                widget.setLayout(layout)
                self.setCentralWidget(widget)
            

            Run the application

            def main():
            app = QApplication(sys.argv)
            window = MainWindow()

            # Add an initial AdaptiveMacroNode and AsynchronousMacroNode
            initial_adaptive_macro = AdaptiveMacroNode("InitialAdaptiveMacro", 300, 300, 30, 1.0)
            initial_asynchronous_macro = AsynchronousMacroNode("InitialAsynchronousMacro", 450, 450, 30)
            window.scene.add_macro_to_tile(300, 300, initial_adaptive_macro)
            window.scene.add_macro_to_tile(450, 450, initial_asynchronous_macro)
            
            window.setGeometry(100, 100, 800, 600)
            window.show()
            sys.exit(app.exec_())
            

            if name == "main":
            main()

            Q JonBJ 2 Replies Last reply
            0
            • Q Qt Enthusiast

              @Qt-Enthusiast said in how to GUI show data in fraction of seconds for large data sets:

              made

              import sys
              from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QGraphicsRectItem, QApplication, QMainWindow, QVBoxLayout, QWidget, QPushButton
              from PyQt5.QtCore import Qt, QTimer
              from PyQt5.QtGui import QPainter

              Tile class representing a tile in the scene

              class Tile(QGraphicsRectItem):
              def init(self, x, y, size):
              super(Tile, self).init(x, y, size, size)
              self.setBrush(Qt.NoBrush) # Transparent fill for demonstration
              self.macros = []

              def add_macro(self, macro):
                  self.macros.append(macro)
                  self.addItem(macro)
              

              Base class for both macro types

              class BaseMacroNode(QGraphicsRectItem):
              def init(self, name, x, y, size):
              super(BaseMacroNode, self).init(x, y, size, size)
              self.name = name

              AdaptiveMacroNode class representing a macro with an adaptive level of detail

              class AdaptiveMacroNode(BaseMacroNode):
              def init(self, name, x, y, size, lod):
              super(AdaptiveMacroNode, self).init(name, x, y, size)
              self.lod = lod # Initial level of detail

              def update_lod(self, lod):
                  self.lod = lod
                  self.update()  # Trigger a repaint when LOD changes
              
              def paint(self, painter, option, widget=None):
                  # Custom paint method based on LOD
                  painter.setBrush(Qt.blue if self.lod > 0.5 else Qt.red)
                  painter.drawRect(self.rect())
                  painter.drawText(self.rect(), Qt.AlignCenter, self.name)
              

              AsynchronousMacroNode class representing a macro with asynchronous loading

              class AsynchronousMacroNode(BaseMacroNode):
              def init(self, name, x, y, size):
              super(AsynchronousMacroNode, self).init(name, x, y, size)
              # Simulate asynchronous loading with a timer
              QTimer.singleShot(1000, self.on_loaded)

              def on_loaded(self):
                  # Set color after loading
                  self.setBrush(Qt.green)
              

              ChipDesignScene class with tile-based rendering and dynamic addition of macros

              class ChipDesignScene(QGraphicsScene):
              def init(self):
              super(ChipDesignScene, self).init()
              self.tile_size = 10000
              self.tiles = {}

              def add_tile(self, x, y):
                  tile = Tile(x, y, self.tile_size)
                  self.addItem(tile)
                  self.tiles[(x, y)] = tile
              
              def remove_tile(self, x, y):
                  if (x, y) in self.tiles:
                      tile = self.tiles[(x, y)]
                      self.removeItem(tile)
                      del self.tiles[(x, y)]
              
              def add_macro_to_tile(self, x, y, macro):
                  tile = self.tiles.get((x, y))
                  if tile:
                      tile.add_macro(macro)
              
              def update_tiles(self, lod):
                  # For simplicity, consider a fixed-size scene
                  scene_width = 1000
                  scene_height = 1000
              
                  # Calculate visible tiles based on LOD
                  visible_tiles = [
                      (x, y)
                      for x in range(0, scene_width, self.tile_size)
                      for y in range(0, scene_height, self.tile_size)
                  ]
              
                  # Add new tiles and macros
                  for tile_pos in visible_tiles:
                      if tile_pos not in self.tiles:
                          self.add_tile(*tile_pos)
              
                          # Add AdaptiveMacroNodes to the newly visible tile during zoom-out
                          for i in range(3):
                              adaptive_macro = AdaptiveMacroNode(f"AdaptiveMacro{i}", tile_pos[0] + i * 50, tile_pos[1] + i * 50, 30, 0.8)
                              self.add_macro_to_tile(*tile_pos, adaptive_macro)
              
                          # Add AsynchronousMacroNodes to the newly visible tile during zoom-out
                          asynchronous_macro = AsynchronousMacroNode("AsynchronousMacro", tile_pos[0] + 150, tile_pos[1] + 150, 30)
                          self.add_macro_to_tile(*tile_pos, asynchronous_macro)
              
                  # Remove tiles that are no longer visible
                  for tile_pos in list(self.tiles.keys()):
                      if tile_pos not in visible_tiles:
                          self.remove_tile(*tile_pos)
              

              ChipDesignView class with zoom features

              class ChipDesignView(QGraphicsView):
              def init(self, scene):
              super(ChipDesignView, self).init(scene)
              self.setRenderHint(QPainter.Antialiasing, True)
              self.setSceneRect(0, 0, 1000, 1000)
              self.setRenderHint(QPainter.Antialiasing)

              def zoom_in(self):
                  zoom_factor = 1.2
                  self.scale(zoom_factor, zoom_factor)
                  self.update_zoom()
              
              def zoom_out(self):
                  zoom_factor = 1 / 1.2
                  self.scale(zoom_factor, zoom_factor)
                  self.update_zoom()
              
              def update_zoom(self):
                  zoom_factor = self.transform().m11()
                  lod_value = zoom_factor
                  self.scene().update_lod(lod_value)
                  self.scene().update_tiles(lod=lod_value)
              

              MainWindow class with zoom buttons

              class MainWindow(QMainWindow):
              def init(self):
              super(MainWindow, self).init()

                  self.scene = ChipDesignScene()
                  self.view = ChipDesignView(self.scene)
              
                  self.zoom_in_button = QPushButton("Zoom In")
                  self.zoom_in_button.clicked.connect(self.view.zoom_in)
              
                  self.zoom_out_button = QPushButton("Zoom Out")
                  self.zoom_out_button.clicked.connect(self.view.zoom_out)
              
                  layout = QVBoxLayout()
                  layout.addWidget(self.view)
                  layout.addWidget(self.zoom_in_button)
                  layout.addWidget(self.zoom_out_button)
              
                  widget = QWidget()
                  widget.setLayout(layout)
                  self.setCentralWidget(widget)
              

              Run the application

              def main():
              app = QApplication(sys.argv)
              window = MainWindow()

              # Add an initial AdaptiveMacroNode and AsynchronousMacroNode
              initial_adaptive_macro = AdaptiveMacroNode("InitialAdaptiveMacro", 300, 300, 30, 1.0)
              initial_asynchronous_macro = AsynchronousMacroNode("InitialAsynchronousMacro", 450, 450, 30)
              window.scene.add_macro_to_tile(300, 300, initial_adaptive_macro)
              window.scene.add_macro_to_tile(450, 450, initial_asynchronous_macro)
              
              window.setGeometry(100, 100, 800, 600)
              window.show()
              sys.exit(app.exec_())
              

              if name == "main":
              main()

              Q Offline
              Q Offline
              Qt Enthusiast
              wrote on last edited by
              #17

              @Qt-Enthusiast

              Can we review the code and let me know if it solves the purpose

              1 Reply Last reply
              0
              • Q Qt Enthusiast

                @Qt-Enthusiast said in how to GUI show data in fraction of seconds for large data sets:

                made

                import sys
                from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QGraphicsRectItem, QApplication, QMainWindow, QVBoxLayout, QWidget, QPushButton
                from PyQt5.QtCore import Qt, QTimer
                from PyQt5.QtGui import QPainter

                Tile class representing a tile in the scene

                class Tile(QGraphicsRectItem):
                def init(self, x, y, size):
                super(Tile, self).init(x, y, size, size)
                self.setBrush(Qt.NoBrush) # Transparent fill for demonstration
                self.macros = []

                def add_macro(self, macro):
                    self.macros.append(macro)
                    self.addItem(macro)
                

                Base class for both macro types

                class BaseMacroNode(QGraphicsRectItem):
                def init(self, name, x, y, size):
                super(BaseMacroNode, self).init(x, y, size, size)
                self.name = name

                AdaptiveMacroNode class representing a macro with an adaptive level of detail

                class AdaptiveMacroNode(BaseMacroNode):
                def init(self, name, x, y, size, lod):
                super(AdaptiveMacroNode, self).init(name, x, y, size)
                self.lod = lod # Initial level of detail

                def update_lod(self, lod):
                    self.lod = lod
                    self.update()  # Trigger a repaint when LOD changes
                
                def paint(self, painter, option, widget=None):
                    # Custom paint method based on LOD
                    painter.setBrush(Qt.blue if self.lod > 0.5 else Qt.red)
                    painter.drawRect(self.rect())
                    painter.drawText(self.rect(), Qt.AlignCenter, self.name)
                

                AsynchronousMacroNode class representing a macro with asynchronous loading

                class AsynchronousMacroNode(BaseMacroNode):
                def init(self, name, x, y, size):
                super(AsynchronousMacroNode, self).init(name, x, y, size)
                # Simulate asynchronous loading with a timer
                QTimer.singleShot(1000, self.on_loaded)

                def on_loaded(self):
                    # Set color after loading
                    self.setBrush(Qt.green)
                

                ChipDesignScene class with tile-based rendering and dynamic addition of macros

                class ChipDesignScene(QGraphicsScene):
                def init(self):
                super(ChipDesignScene, self).init()
                self.tile_size = 10000
                self.tiles = {}

                def add_tile(self, x, y):
                    tile = Tile(x, y, self.tile_size)
                    self.addItem(tile)
                    self.tiles[(x, y)] = tile
                
                def remove_tile(self, x, y):
                    if (x, y) in self.tiles:
                        tile = self.tiles[(x, y)]
                        self.removeItem(tile)
                        del self.tiles[(x, y)]
                
                def add_macro_to_tile(self, x, y, macro):
                    tile = self.tiles.get((x, y))
                    if tile:
                        tile.add_macro(macro)
                
                def update_tiles(self, lod):
                    # For simplicity, consider a fixed-size scene
                    scene_width = 1000
                    scene_height = 1000
                
                    # Calculate visible tiles based on LOD
                    visible_tiles = [
                        (x, y)
                        for x in range(0, scene_width, self.tile_size)
                        for y in range(0, scene_height, self.tile_size)
                    ]
                
                    # Add new tiles and macros
                    for tile_pos in visible_tiles:
                        if tile_pos not in self.tiles:
                            self.add_tile(*tile_pos)
                
                            # Add AdaptiveMacroNodes to the newly visible tile during zoom-out
                            for i in range(3):
                                adaptive_macro = AdaptiveMacroNode(f"AdaptiveMacro{i}", tile_pos[0] + i * 50, tile_pos[1] + i * 50, 30, 0.8)
                                self.add_macro_to_tile(*tile_pos, adaptive_macro)
                
                            # Add AsynchronousMacroNodes to the newly visible tile during zoom-out
                            asynchronous_macro = AsynchronousMacroNode("AsynchronousMacro", tile_pos[0] + 150, tile_pos[1] + 150, 30)
                            self.add_macro_to_tile(*tile_pos, asynchronous_macro)
                
                    # Remove tiles that are no longer visible
                    for tile_pos in list(self.tiles.keys()):
                        if tile_pos not in visible_tiles:
                            self.remove_tile(*tile_pos)
                

                ChipDesignView class with zoom features

                class ChipDesignView(QGraphicsView):
                def init(self, scene):
                super(ChipDesignView, self).init(scene)
                self.setRenderHint(QPainter.Antialiasing, True)
                self.setSceneRect(0, 0, 1000, 1000)
                self.setRenderHint(QPainter.Antialiasing)

                def zoom_in(self):
                    zoom_factor = 1.2
                    self.scale(zoom_factor, zoom_factor)
                    self.update_zoom()
                
                def zoom_out(self):
                    zoom_factor = 1 / 1.2
                    self.scale(zoom_factor, zoom_factor)
                    self.update_zoom()
                
                def update_zoom(self):
                    zoom_factor = self.transform().m11()
                    lod_value = zoom_factor
                    self.scene().update_lod(lod_value)
                    self.scene().update_tiles(lod=lod_value)
                

                MainWindow class with zoom buttons

                class MainWindow(QMainWindow):
                def init(self):
                super(MainWindow, self).init()

                    self.scene = ChipDesignScene()
                    self.view = ChipDesignView(self.scene)
                
                    self.zoom_in_button = QPushButton("Zoom In")
                    self.zoom_in_button.clicked.connect(self.view.zoom_in)
                
                    self.zoom_out_button = QPushButton("Zoom Out")
                    self.zoom_out_button.clicked.connect(self.view.zoom_out)
                
                    layout = QVBoxLayout()
                    layout.addWidget(self.view)
                    layout.addWidget(self.zoom_in_button)
                    layout.addWidget(self.zoom_out_button)
                
                    widget = QWidget()
                    widget.setLayout(layout)
                    self.setCentralWidget(widget)
                

                Run the application

                def main():
                app = QApplication(sys.argv)
                window = MainWindow()

                # Add an initial AdaptiveMacroNode and AsynchronousMacroNode
                initial_adaptive_macro = AdaptiveMacroNode("InitialAdaptiveMacro", 300, 300, 30, 1.0)
                initial_asynchronous_macro = AsynchronousMacroNode("InitialAsynchronousMacro", 450, 450, 30)
                window.scene.add_macro_to_tile(300, 300, initial_adaptive_macro)
                window.scene.add_macro_to_tile(450, 450, initial_asynchronous_macro)
                
                window.setGeometry(100, 100, 800, 600)
                window.show()
                sys.exit(app.exec_())
                

                if name == "main":
                main()

                JonBJ Offline
                JonBJ Offline
                JonB
                wrote on last edited by
                #18

                @Qt-Enthusiast
                This is a large listing of code. Is there a question?

                Q 1 Reply Last reply
                0
                • JonBJ JonB

                  @Qt-Enthusiast
                  This is a large listing of code. Is there a question?

                  Q Offline
                  Q Offline
                  Qt Enthusiast
                  wrote on last edited by Qt Enthusiast
                  #19

                  i have made a prototype code for how to make GUI to show large data sets in fraction of second . if someone can review and suggest improvements. Can some one review the code if the changes helps in performance improvement

                  jsulmJ 1 Reply Last reply
                  0
                  • Q Qt Enthusiast

                    i have made a prototype code for how to make GUI to show large data sets in fraction of second . if someone can review and suggest improvements. Can some one review the code if the changes helps in performance improvement

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #20

                    @Qt-Enthusiast You should at least format your code properly...

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                    1 Reply Last reply
                    1
                    • Q Offline
                      Q Offline
                      Qt Enthusiast
                      wrote on last edited by
                      #21

                      https://codeshare.io/ZJYk4o

                      I have put the formatted code in the link . PLease review

                      jeremy_kJ 1 Reply Last reply
                      0
                      • Q Qt Enthusiast

                        @jeremy_k

                        Can we discuss PyQt over here , I have made a prototype

                        S Offline
                        S Offline
                        SimonSchroeder
                        wrote on last edited by
                        #22

                        @Qt-Enthusiast said in how to GUI show data in fraction of seconds for large data sets:

                        Can we discuss PyQt over here

                        If you really want to have good performance for millions of nodes, Python is not the best choice for that. It does help that Qt will handle most of the heavy lifting and is written in C++. You might get lucky with you paint function and it will quickly be optimized by the interpreter, but there is no guarantee. Performance-critical code should not be written in an interpreted language. (That being said: Measure first before optimizing prematurely.)

                        1 Reply Last reply
                        0
                        • Q Qt Enthusiast

                          https://codeshare.io/ZJYk4o

                          I have put the formatted code in the link . PLease review

                          jeremy_kJ Offline
                          jeremy_kJ Offline
                          jeremy_k
                          wrote on last edited by
                          #23

                          @Qt-Enthusiast said in how to GUI show data in fraction of seconds for large data sets:

                          https://codeshare.io/ZJYk4o

                          I have put the formatted code in the link . PLease review

                          Tip 1: Use the forum code button instead of an external website:
                          0d38d28e-38e1-4556-91f0-925da5ed69b8-image.png
                          or format manually:
                          ```
                          code goes here
                          ```

                          Tip 2: For python3, avoid super(Class, object) when super() will work. Can you spot the error? This is valid code, but probably not what is intended.

                          class Base:
                              def __init__(self, *args, **kwargs):
                                  print("Base.__init__")
                          
                          class Mid(Base):
                              def __init__(self, *args, **kwargs):
                                  super(Mid, self).__init__(*args, **kwargs)
                                  print("Mid.__init__")
                          
                          class Derived(Mid):
                              def __init__(self, *args, **kwargs):
                                  super(Mid, self).__init__(*args, **kwargs)
                                  print("Derived.__init__")
                          
                          obj = Derived()
                          

                          As for the general strategy, displaying or hiding visible items based on what is visible is the job of the view. Unless the overhead of non-viewable items in the scene is significant, don't remove them from the scene. One of the points of the chips demo is to alter the details of the visible items as appropriate, rather than removing or adding them.

                          Asking a question about code? http://eel.is/iso-c++/testcase/

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