On Thu, 15 Jan 2026 20:07:43 GMT, Michael Strauß <[email protected]> wrote:
>> In the following program, resizing the window to be smaller than 300px
>> should start a transition for `-fx-scale-x` from 2 to 1, but instead the
>> value sometimes snaps back to 1 instantly:
>>
>>
>> public class InterruptedTransitionBug extends Application {
>> @Override
>> public void start(Stage stage) throws Exception {
>> var root = new StackPane(new Button("My Button"));
>> var scene = new Scene(root, 600, 200);
>> scene.getStylesheets().add("data:text/css;base64," +
>> Base64.getEncoder().encodeToString("""
>> .button {
>> transition: -fx-scale-x 2s;
>> }
>>
>> @media (width > 300px) {
>> .button {
>> -fx-scale-x: 2;
>> }
>> }
>> """.getBytes(StandardCharsets.UTF_8)));
>> stage.setScene(scene);
>> stage.show();
>> }
>> }
>>
>>
>> ### Problem
>> First, let's look at how `CssStyleHelper` works when the cascading style map
>> for a node changes:
>> 1. When the style map for a node has changed,
>> `StyleHelper.createStyleHelper(Node)` determines that the style helper is no
>> longer any good, and a new `CssStyleHelper` for the new style map is created.
>> 2. Before the old style helper is discarded, it calls
>> `CssStyleHelper.resetToInitialValues(Styleable)` and resets all properties
>> that were set by this style helper back to their initial values. This
>> ensures that the new style helper has a "clean slate" to work from.
>> 3. The next `Node.applyCss()` pass will now set the properties that are
>> specified in the new style map to their new values.
>>
>> However, when transitions come into play, this mechanism can break:
>> 1. In our example, the `Button` starts with a style map that contains two
>> properties:
>> * `transition: -fx-scale-x 2s`
>> * `-fx-scale-x: 2`
>> 2. Due to a changing media query, this is replaced with a style map that
>> only contains a single entry:
>> * `transition: -fx-scale-x 2s`
>> 3. Before the new style map is applied, all properties affected by the old
>> style map are reset to their initial values. That means:
>> * `-fx-scale-x` is reset to `1`
>> * `transition` is reset to `null`
>>
>> This is where it breaks: if `transition` is reset before `-fx-scale-x`, the
>> latter will see no transition when its value is set back to `1`.
>>
>> ### Solution
>> Simply resetting all properties back to their initial values when a style
>> map is changed is not necessary. We only need to reset the properties that
>> ar...
>
> Michael Strauß has updated the pull request incrementally with one additional
> commit since the last revision:
>
> private equalsEndValue() implementation
Thank you, it's better to keep related logic closer together.
-------------
Marked as reviewed by angorya (Reviewer).
PR Review: https://git.openjdk.org/jfx/pull/2038#pullrequestreview-3667375162
