ListView with ImageViews for cells very bugged?

[Kevin Rushforth]

What you have should work, but will create redundant images and 
ImageView ojbects. The recommendation is to create the nodes (ImageView 
in this case) in the constructor of the cell factory and call setGraphic 
with either null or that factory's node.

Having said that, I doubt that this is related to the visual problems 
you are seeing. Maybe Ajit or Andy have some ideas.

-- Kevin


On 7/11/2023 3:50 PM, John Hendrikx wrote:
> I tend to avoid ListView, because for some reason it seems to just 
> never do what I want unless used for its mundane rows of text use 
> case. I so far always just implemented my own skin for ListView that 
> deals with displays that have many images that need to scroll 
> smoothly, but...
>
> Recently, I've again attempted to use ListView, this time for showing 
> (so far) fixed size ImageViews with images exactly 512x512 pixels in 
> size:
>
> The cell factory looks like this, which I think is a correct 
> implementation:
>
>       listView.setCellFactory(lv -> {
>         return new ListCell<>() {
>           protected void updateItem(ImageHandle imageHandle, boolean 
> empty) {
>             if(empty) {
>               setGraphic(null);
>             }
>             else {
>               try {
>                 setGraphic(new ImageView(new Image(new 
> ByteArrayInputStream(imageHandle.getImageData()))));
>               }
>               catch(IOException e) {
>                 e.printStackTrace();
>               }
>             }
>           }
>         };
>       });
>
> Now, this is with JavaFX 21-ea-24 (but also happens on 19).  I spotted 
> the following IMHO bugs:
>
> 1) When the ImageView is so large that a single row is only partially 
> visible, the scrollbar is incorrect (it shows a full bar, even if half 
> of a row is displayed).
>
> 2) The vertical scrollbar doesn't respond to a click in the non-thumb 
> area at all (you'd expect to make it scroll a page up or down that way)
>
> 3) When jerkily resizing the window, I can sometimes have a vertical + 
> horizontal scrollbar when there's a full row visible + anywhere from 0 
> to 10 extra empty pixels (probably the potential height of a 
> horizontal scrollbar) with the vertical scroll bar still visible.  The 
> algorithm to hide the scrollbar apparently is not deterministic and 
> depends on mouse movement speed.
>
> 4) When a row is less than half visible, scrolling the window down to 
> another ImageView will jump the view and hide the first cell that 
> should still be visible for the bottom 0-49% of its height.
>
> 5) It's possible to get the vertical scroll bar in such a state that 
> it doesn't respond to the mouse any more at all, even by dragging the 
> thumb.  Some keyboard action and mouse scrolling sometimes restores it 
> to relatively normal functioning.
>
> 6) Mouse wheel scrolling acts weird.  With one large cell visible and 
> two rows available, scrolling only **down** on the mouse wheel will 
> scroll down, then jump back up, and scroll down again... it's 
> impossible to scroll all the way down to get to a point where it stops 
> scrolling as it keeps jumping back.
>
> This is with ImageView's.  I suppose they're known to have problems... 
> but then I switched to a Region, which contain an ImageView with 
> proper min/pref/max implementations.  This improved the situation 
> somewhat.  The scrollbar was much more reliable, but I still saw 
> almost all of the above issues, but somewhat more reliable than 
> before.  Still rows would disappear when (for the most part) 
> invisible, those and the jumps of the view are just totally unacceptable.
>
> I'm not quite sure what to make of this, it seems the control is not 
> meant for arbitrary graphics.
>
> --John
>
>
>
> package org.int4.sdui.ui;
>
> import hs.mediasystem.util.image.ImageHandle;
> import hs.mediasystem.util.javafx.control.Containers;
>
> import java.io.ByteArrayInputStream;
> import java.io.IOException;
> import java.util.Base64;
> import java.util.List;
>
> import javafx.application.Application;
> import javafx.scene.Scene;
> import javafx.scene.control.Button;
> import javafx.scene.control.ListCell;
> import javafx.scene.control.ListView;
> import javafx.scene.control.TextArea;
> import javafx.scene.image.Image;
> import javafx.scene.image.ImageView;
> import javafx.scene.layout.HBox;
> import javafx.scene.layout.Priority;
> import javafx.stage.Stage;
>
> import kong.unirest.core.Unirest;
>
> public class Main {
>
>   public static void main(String[] args) {
>     Application.launch(UI.class, args);
>   }
>
>   public static class UI extends Application {
>
>     @Override
>     public void start(Stage primaryStage) {
>       TextArea prompt = new TextArea("a flower on Mars");
>       Button button = new Button("Submit");
>       ListView<ImageHandle> listView = new ListView<>();
>
>       listView.setCellFactory(lv -> {
>         return new ListCell<>() {
>           protected void updateItem(ImageHandle imageHandle, boolean 
> empty) {
>             if(empty) {
>               setGraphic(null);
>             }
>             else {
>               try {
>                 setGraphic(new ImageView(new Image(new 
> ByteArrayInputStream(imageHandle.getImageData()))));
>               }
>               catch(IOException e) {
>                 e.printStackTrace();
>               }
>             }
>           }
>         };
>       });
>
>       button.setOnAction(e -> {
>         Txt2ImgResponse response = textToImage(prompt.getText());
>
>         for(String image : response.images) {
>           listView.getItems().add(new 
> InMemoryImageHandle(Base64.getDecoder().decode(image)));
>         }
>       });
>
>       HBox hbox = Containers.hbox(Containers.vbox(prompt, button), 
> listView);
>
>       HBox.setHgrow(listView, Priority.ALWAYS);
>
>       Scene scene = new Scene(hbox);
>
>       primaryStage.setScene(scene);
>       primaryStage.show();
>     }
>
>     private Txt2ImgResponse textToImage(String prompt) {
>       return Unirest.post("http://127.0.0.1:7860/sdapi/v1/txt2img")
>         .body(new Txt2Img(prompt, 5))
>         .contentType("application/json")
>         .asObject(Txt2ImgResponse.class)
>         .getBody();
>     }
>   }
>
>   static class InMemoryImageHandle implements ImageHandle {
>     private final byte[] data;
>
>     public InMemoryImageHandle(byte[] data) {
>       this.data = data;
>     }
>
>     @Override
>     public byte[] getImageData() {
>       return data;
>     }
>
>     @Override
>     public String getKey() {
>       return null;
>     }
>
>     @Override
>     public boolean isFastSource() {
>       return true;
>     }
>   }
>
>   record Txt2Img(String prompt, int steps) {}
>   record Txt2ImgResponse(List<String> images) {}
> }
>
>
>