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Added scroll line method #1086

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merged 1 commit into from Feb 11, 2022
Merged

Added scroll line method #1086

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38 changes: 37 additions & 1 deletion richtextfx/src/main/java/org/fxmisc/richtext/GenericStyledArea.java
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Expand Up @@ -1371,6 +1371,34 @@ else if ( lineHighlighter != null ) {
}
}

/**
* Scrolls the text one line UP while maintaining the caret's
* position on screen, so that it is now on the NEXT line.
* <i>Note: If the caret isn't visible then this is a noop.</i>
*/
public void nextLine(SelectionPolicy selectionPolicy) {
scrollLine( +1, selectionPolicy );
}

/**
* Scrolls the text one line DOWN while maintaining the caret's
* position on screen, so that it is now on the PREVIOUS line.
* <i>Note: If the caret isn't visible then this is a noop.</i>
*/
public void prevLine(SelectionPolicy selectionPolicy) {
scrollLine( -1, selectionPolicy );
}

/**
* Scrolls the text (direction*caretHeight) while maintaining the caret's current
* position on screen. <i>Note: If the caret isn't visible then this is a noop.</i>
*/
private void scrollLine(int direction, SelectionPolicy selectionPolicy) {
getCaretBoundsOnScreen( getCaretSelectionBind().getUnderlyingCaret() )
.map( caretBounds -> (caretBounds.getHeight()-2) * direction )
.ifPresent( deltaY -> scrollText(deltaY, selectionPolicy) );
}

@Override
public void prevPage(SelectionPolicy selectionPolicy) {
// Paging up and we're in the first frame then move/select to start.
Expand All @@ -1394,12 +1422,20 @@ public void nextPage(SelectionPolicy selectionPolicy) {
* <br>Negative numbers for paging up and positive for down.
*/
private void page(int pgCount, SelectionPolicy selectionPolicy)
{
scrollText( pgCount * getViewportHeight(), selectionPolicy );
}

/**
* Scrolls the text by deltaY while maintaining the caret's current position on screen.
*/
private void scrollText(double deltaY, SelectionPolicy selectionPolicy)
{
// Use underlying caret to get the same behaviour as navigating up/down a line where the x position is sticky
Optional<Bounds> cb = caretSelectionBind.getUnderlyingCaret().getCaretBounds();

paging = true; // Prevent scroll from reverting back to the current caret position
scrollYBy( pgCount * getViewportHeight() );
suspendVisibleParsWhile( () -> virtualFlow.scrollYBy( deltaY ) );

cb.map( this::screenToLocal ) // Place caret near the same on screen position as before
.map( b -> hit( b.getMinX(), b.getMinY()+b.getHeight()/2.0 ).getInsertionIndex() )
Expand Down