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Added VScrollCtl and VScrollBubble for easier VScroll handling (#10).
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‎CHANGES.md

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## [Unreleased]
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### Added
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- `CoatMux.Layer` now exposes its root `Control` instance ([#12](https://github.com/diffplug/durian-swt/issues/12)).
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- `VScrollCtl` and `VScrollBubble` for easier VScroll handling ([#10](https://github.com/diffplug/durian-swt/issues/10)).
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### Removed
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- **BREAKING** Removed `ColorPool.getSystemColor()` ([#8](https://github.com/diffplug/durian-swt/issues/8)).
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- **BREAKING** Switched type arguments of `TypedDataField` ([#3](https://github.com/diffplug/durian-swt/issues/3)).

‎durian-swt/src/main/java/com/diffplug/common/swt/VScrollBubble.java

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/*
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* Copyright (C) 2020-2021 DiffPlug, LLC - All Rights Reserved
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* Unauthorized copying of this file via any medium is strictly prohibited.
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* Proprietary and confidential.
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* Please send any inquiries to Ned Twigg <[email protected]>
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*/
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package com.diffplug.common.swt;
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import java.util.Optional;
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import org.eclipse.swt.SWT;
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import org.eclipse.swt.custom.ScrolledComposite;
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import org.eclipse.swt.graphics.Point;
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import org.eclipse.swt.graphics.Rectangle;
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import org.eclipse.swt.widgets.Composite;
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import org.eclipse.swt.widgets.Display;
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import org.eclipse.swt.widgets.Event;
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import org.eclipse.swt.widgets.ScrollBar;
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import org.eclipse.swt.widgets.Scrollable;
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import org.eclipse.swt.widgets.Tree;
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import org.eclipse.swt.widgets.TreeItem;
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import com.diffplug.common.swt.SwtMisc;
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import com.diffplug.common.tree.TreeStream;
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/**
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* Bubbles vertical scroll events up to a parent container, so that you don't get stuck.
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* Doesn't work great on mac due to rubber-banding.
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*/
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public class VScrollBubble {
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private static Display appliedTo;
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/** Returns true iff the given scrollable is maxed out for scrolling in the direction of the given event. */
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private static boolean isMaxed(Event e, Scrollable scrollable) {
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ScrollBar scrollBar = scrollable.getVerticalBar();
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if (scrollBar == null) {
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return true;
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} else {
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boolean isMaxed;
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// System.out.println("[" + scrollBar.getMinimum() + " " + scrollBar.getMaximum() + "] " + scrollBar.getSelection() + " thumb=" + scrollBar.getThumb());
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if (e.count > 0) {
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// scrolling up
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isMaxed = scrollBar.getSelection() <= 0;
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} else {
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// scrolling down
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isMaxed = scrollBar.getSelection() >= scrollBar.getMaximum() - scrollBar.getThumb();
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if (!isMaxed) {
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// special case for trees & tables which have all their items visible, where scrolling down gives
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// scrollBar.getMinimum()/getMaximum=[0 100] scrollBar.getSelection()=0 scrollBar.getThumb()=10
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if (scrollable instanceof Tree) {
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Tree tree = (Tree) scrollable;
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int itemCount = tree.getItemCount();
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if (itemCount == 0) {
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return true;
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}
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TreeItem lastItem = tree.getItem(itemCount - 1);
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while (lastItem.getItemCount() > 0) {
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lastItem = lastItem.getItem(lastItem.getItemCount() - 1);
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}
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Rectangle itemBounds = lastItem.getBounds();
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Rectangle clientArea = tree.getClientArea();
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return itemBounds.y + itemBounds.height < clientArea.height;
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}
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}
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}
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return isMaxed;
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}
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}
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/** Applies the necessary display filter, don't worry about calling it more than once. */
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public static void applyTo(Display display) {
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// prevent double-apply
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if (display == appliedTo) {
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return;
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}
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appliedTo = display;
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display.addFilter(SWT.MouseVerticalWheel, e -> {
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if (!(e.widget instanceof Scrollable)) {
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return;
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}
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// find the parent two levels up
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Composite parentOfScrollable = ((Scrollable) e.widget).getParent();
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if (parentOfScrollable == null) {
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return;
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}
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parentOfScrollable = parentOfScrollable.getParent();
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if (parentOfScrollable == null) {
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return;
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}
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boolean isMaxed = isMaxed(e, (Scrollable) e.widget);
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if (!isMaxed) {
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return;
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}
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Optional<ScrolledComposite> firstNotMaxed = TreeStream.toParent(SwtMisc.treeDefComposite(), parentOfScrollable)
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.filter(c -> c instanceof ScrolledComposite && SwtMisc.flagIsSet(SWT.V_SCROLL, c))
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.map(ScrolledComposite.class::cast)
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.filter(sc -> !isMaxed(e, sc))
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.findFirst();
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if (!firstNotMaxed.isPresent()) {
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// there isn't a parent which we can bubble the scroll to
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return;
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}
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ScrolledComposite toScroll = firstNotMaxed.get();
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Point origin = toScroll.getOrigin();
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origin.y -= e.count * toScroll.getVerticalBar().getIncrement();
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toScroll.setOrigin(origin);
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// copy the event
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Event copy = SwtMisc.copyEvent(e);
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// cancel the old one
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e.doit = false;
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// and send the copy to the parent
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copy.widget = toScroll;
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Point d = ((Scrollable) e.widget).toDisplay(e.x, e.y);
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Point mapped = toScroll.toControl(d);
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copy.x = mapped.x;
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copy.y = mapped.y;
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copy.widget.notifyListeners(SWT.MouseVerticalWheel, copy);
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});
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}
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}

‎durian-swt/src/main/java/com/diffplug/common/swt/widgets/VScrollCtl.java

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/*
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* Copyright (C) 2018-2020 DiffPlug, LLC - All Rights Reserved
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* Unauthorized copying of this file via any medium is strictly prohibited.
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* Proprietary and confidential.
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* Please send any inquiries to Ned Twigg <[email protected]>
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*/
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package com.diffplug.common.swt.widgets;
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import com.diffplug.common.swt.VScrollBubble;
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import org.eclipse.swt.SWT;
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import org.eclipse.swt.custom.ScrolledComposite;
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import org.eclipse.swt.graphics.Point;
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import org.eclipse.swt.widgets.Composite;
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import org.eclipse.swt.widgets.Control;
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import com.diffplug.common.swt.ControlWrapper;
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/**
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* SWT provides {@link ScrolledComposite} which provides a wealth of
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* scrolling behavior ([google](https://www.google.com/search?q=SWT+ScrolledComposite)).
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* However, the most common case is that you only want to scroll vertically. This class
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* makes that easy. Just create your content with {@link #getParentForContent()} as the
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* parent, and then set it to be the content with {@link #setContent(Control)}. Easy!
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*/
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public class VScrollCtl extends ControlWrapper.AroundControl<ScrolledComposite> {
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public VScrollCtl(Composite parent, int style) {
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super(new ScrolledComposite(parent, SWT.VERTICAL | style));
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VScrollBubble.applyTo(parent.getDisplay());
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}
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public ScrolledComposite getParentForContent() {
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return wrapped;
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}
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public void setContent(ControlWrapper wrapper) {
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setContent(wrapper.getRootControl());
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}
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public void setContent(Control content) {
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wrapped.setContent(content);
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wrapped.setExpandHorizontal(true);
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wrapped.setExpandVertical(true);
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wrapped.addListener(SWT.Resize, e -> {
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int scrollWidth = wrapped.getVerticalBar().getSize().x;
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Point size = wrapped.getSize();
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Point contentSize = content.computeSize(size.x - scrollWidth, SWT.DEFAULT);
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content.setSize(contentSize);
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wrapped.setMinSize(contentSize);
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});
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}
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}

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