On Mon, 25 Jul 2022 09:25:57 GMT, Sai Pradeep Dandem <[email protected]> wrote:
> **Issue:**
> When the `TableView` is set with built-in `CONSTRAINED_RESIZE_POLICY`, the
> horizontal scroll bar keeps flickering when the `TableView` width is reduced.
>
> **Cause:**
> The table columns widths are recalculated only if the difference of the
> `TableView` width and the total columns width is greater than 1px. Because of
> this improper calculations, if the `TableView` width is reduced by 1px, the
> columns widths are not updated. Which results to computing for horizontal
> scroll bar visibility in `VirtualFlow` to improper results and let the
> horizontal scroll bar to be visible.
>
> Where as if the `TableView` width is reduced by more than 1px, the
> calculations are done correctly and the horizontal scroll bar visibility is
> turned off. Because of this behaviour, it looks like the horizontal scroll
> bar is flickering when the `TableView` width is reduced (let’s say by
> dragging).
>
> To confirm this behaviour, please find the below example that showcases the
> issue:
> When the tableView width is reduced/increased by 1px, the column widths are
> recalculated only after every alternate 1px change. Whereas if the tableView
> width is reduced/increased by more than 1px (say 10px), the column widths are
> calculated correctly.
>
>
> import javafx.application.Application;
> import javafx.beans.property.SimpleStringProperty;
> import javafx.beans.property.StringProperty;
> import javafx.collections.FXCollections;
> import javafx.collections.ObservableList;
> import javafx.geometry.Insets;
> import javafx.scene.Group;
> import javafx.scene.Scene;
> import javafx.scene.control.*;
> import javafx.scene.layout.HBox;
> import javafx.scene.layout.VBox;
> import javafx.stage.Stage;
>
> public class ConstrainedResizePolicyIssueDemo extends Application {
> @Override
> public void start(Stage primaryStage) throws Exception {
> TableColumn<Person, String> fnCol = new TableColumn<>("First Name");
> fnCol.setMinWidth(100);
> fnCol.setCellValueFactory(param ->
> param.getValue().firstNameProperty());
>
> TableColumn<Person, String> priceCol = new TableColumn<>("Price");
> priceCol.setMinWidth(100);
> priceCol.setMaxWidth(150);
> priceCol.setCellValueFactory(param ->
> param.getValue().priceProperty());
>
> TableColumn<Person, String> totalCol = new TableColumn<>("Total");
> totalCol.setMinWidth(100);
> totalCol.setMaxWidth(150);
> totalCol.setCellValueFactory(param ->
> param.getValue().totalProperty());
>
> ObservableList<Person> persons = FXCollections.observableArrayList();
> persons.add(new Person("Harry", "200.00", "210.00"));
> persons.add(new Person("Jacob", "260.00", "260.00"));
>
> TableView<Person> tableView = new TableView<>();
> tableView.getColumns().addAll(fnCol, priceCol, totalCol);
> tableView.setItems(persons);
> tableView.setColumnResizePolicy(TableView.CONSTRAINED_RESIZE_POLICY);
> tableView.setMinWidth(500);
> tableView.maxWidthProperty().bind(tableView.minWidthProperty());
>
> Button button1 = new Button("Reduce 1px");
> button1.setOnAction(e ->
> tableView.setMinWidth(tableView.getMinWidth() - 1));
> Button button2 = new Button("Reduce 10px");
> button2.setOnAction(e ->
> tableView.setMinWidth(tableView.getMinWidth() - 10));
> Button button3 = new Button("Reset");
> button3.setOnAction(e -> tableView.setMinWidth(500));
> Button button4 = new Button("Increase 1px");
> button4.setOnAction(e ->
> tableView.setMinWidth(tableView.getMinWidth() + 1));
> Button button5 = new Button("Increase 10px");
> button5.setOnAction(e ->
> tableView.setMinWidth(tableView.getMinWidth() + 10));
>
> HBox row = new HBox(button1, button2, button3, button4, button5);
> row.setSpacing(10);
> TextArea output = new TextArea();
>
> addWidthListeners(tableView, output);
> VBox root = new VBox(row, new Group(tableView), output);
> root.setSpacing(10);
> root.setPadding(new Insets(10));
>
> Scene scene = new Scene(root);
> primaryStage.setScene(scene);
> primaryStage.setTitle("Constrained Resize Policy Issue TableView");
> primaryStage.show();
> }
>
> private void addWidthListeners(TableView<Person> tableView, TextArea
> output) {
> tableView.widthProperty().addListener((obs, old, val) -> {
> String str = "Table width changed :: " + val + "\n";
> output.setText(output.getText() + str);
> output.positionCaret(output.getText().length());
> });
> tableView.getColumns().forEach(column -> {
> column.widthProperty().addListener((obs, old, width) -> {
> String str = " ---> " + column.getText() + " : width changed
> to : " + column.getWidth()+"\n";
> output.setText(output.getText() + str);
> output.positionCaret(output.getText().length());
> });
> });
> }
>
> class Person {
> private StringProperty firstName = new SimpleStringProperty();
> private StringProperty price = new SimpleStringProperty();
> private StringProperty total = new SimpleStringProperty();
>
> public Person(String fn, String price, String total) {
> setFirstName(fn);
> setPrice(price);
> setTotal(total);
> }
>
> public StringProperty firstNameProperty() {
> return firstName;
> }
>
> public void setFirstName(String firstName) {
> this.firstName.set(firstName);
> }
>
> public StringProperty priceProperty() {
> return price;
> }
>
> public void setPrice(String price) {
> this.price.set(price);
> }
>
> public StringProperty totalProperty() {
> return total;
> }
>
> public void setTotal(String total) {
> this.total.set(total);
> }
> }
> }
>
>
> **Fix:**
> On investigating the code, it is noticed that there is an explicit line of
> code to check if the difference in widths is greater than 1px. I think this
> should be greater than 0px. Because we need to recompute the columns widths
> even if the width is increased by 1px.
>
> The part of the code that need to be updated is in TableUtil.java ->
> constrainedResize(..) method -> line 226
>
> `if (Math.abs(colWidth - tableWidth) > 1) {`
>
> If I update the value 1 to 0, the issue is fixed and the horizontal scroll
> bar visibility is computed correctly.
I'll let @aghaisas and @andy-goryachev-oracle review this. I added one comment
based on Andy's first question.
modules/javafx.controls/src/main/java/javafx/scene/control/TableUtil.java line
226:
> 224: }
> 225:
> 226: if (Math.abs(colWidth - tableWidth) > 0) {
Related to Andy's question, shouldn't this be `> EPSILON` (for some small value
of EPSILON), since floating-point arithmetic isn't precise?
-------------
PR: https://git.openjdk.org/jfx/pull/848
