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Create system cursors using Display getSystemCursor method #286 (#288)
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Creating the static standard platform cursors may lead to a potential
memory leak, if the Cursors class ever happens to be unloaded, before
the application is terminated (e.g. when the bundle is stopped), because
this process won't free up the allocated resources.

To avoid this issue, we use Display.getSystemCursor, similar to what is
done to get the standard platform colors.

Given that those factory methods are technically API, they have also
been documented, with a large part taken from the getSystemCursor() and
getSystemColor() JavaDoc.
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@ptziegler
ptziegler committed Nov 14, 2023
1 parent f09b6c2 commit 376465f
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35 changes: 21 additions & 14 deletions org.eclipse.draw2d/src/org/eclipse/draw2d/ColorConstants.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*******************************************************************************
* Copyright (c) 2000, 2010 IBM Corporation and others.
* Copyright (c) 2000, 2023 IBM Corporation and others.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
Expand All @@ -23,27 +23,34 @@
*/
public interface ColorConstants {

/**
* This utility class is used to create a system {@link Color} using any of the
* supported {@link SWT} constants. The {@link Color} is created using the
* {@link Display} bound to the current thread.
*
* @since 3.13
*/
class SystemColorFactory {
/**
* Returns the matching standard {@link Color} for the given constant, which
* should be one of the color constants specified in class {@link SWT}. Any
* value other than one of the {@link SWT} color constants which is passed in
* will result in the {@link Color} black. This {@link Color} should not be
* free'd because it was allocated by the system, not the application. Note:
* This method should be invoked from within the UI thread if possible, as it
* will attempt to create a new Display instance, if not!
*
* @since 3.13
* @param which the {@link SWT} {@link Color} constant
* @return the corresponding {@link Color} or the {@link Color} {@code black}
*/
public static Color getColor(final int which) {
Display display = Display.getCurrent();
if (display != null)
if (display != null) {
return display.getSystemColor(which);
display = Display.getDefault();
final Color result[] = new Color[1];
display.syncExec(new Runnable() {
@Override
public void run() {
synchronized (result) {
result[0] = Display.getCurrent().getSystemColor(which);
}
}
});
synchronized (result) {
return result[0];
}
display = Display.getDefault();
return display.syncCall(() -> Display.getCurrent().getSystemColor(which));
}
}

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78 changes: 55 additions & 23 deletions org.eclipse.draw2d/src/org/eclipse/draw2d/Cursors.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*******************************************************************************
* Copyright (c) 2000, 2010 IBM Corporation and others.
* Copyright (c) 2000, 2023 IBM Corporation and others.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
Expand All @@ -14,12 +14,44 @@

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Cursor;
import org.eclipse.swt.widgets.Display;

/**
* A collection of cursors.
*/
public class Cursors {

/**
* This utility class is used to create a system {@link Cursor} using any of the
* supported {@link SWT} constants. The {@link Cursor} is created using the
* {@link Display} bound to the current thread.
*
* @since 3.14
*/
private static class SystemCursorFactory {
/**
* Returns the matching standard platform {@link Cursor} for the given constant,
* which should be one of the {@link Cursor} constants specified in class
* {@link SWT}. This {@link Cursor} should not be free'd because it was
* allocated by the system, not the application. A value of {@code null} will be
* returned if the supplied constant is not an {@link SWT} cursor constant.
* Note: This method should be invoked from within the UI thread if possible, as
* it will attempt to create a new Display instance, if not!
*
* @since 3.14
* @param which the {@link SWT} {@link Cursor} constant
* @return the corresponding {@link Cursor} or {@code null}
*/
public static Cursor getCursor(final int which) {
Display display = Display.getCurrent();
if (display != null) {
return display.getSystemCursor(which);
}
display = Display.getDefault();
return display.syncCall(() -> Display.getCurrent().getSystemCursor(which));
}
}

/**
* Returns the cursor corresponding to the given direction, defined in
* {@link PositionConstants}. Note that
Expand Down Expand Up @@ -172,28 +204,28 @@ public static Cursor getDirectionalCursor(int direction, boolean isMirrored) {
public static final Cursor WAIT;

static {
ARROW = new Cursor(null, SWT.CURSOR_ARROW);
SIZEN = new Cursor(null, SWT.CURSOR_SIZEN);
SIZENE = new Cursor(null, SWT.CURSOR_SIZENE);
SIZEE = new Cursor(null, SWT.CURSOR_SIZEE);
SIZESE = new Cursor(null, SWT.CURSOR_SIZESE);
SIZES = new Cursor(null, SWT.CURSOR_SIZES);
SIZESW = new Cursor(null, SWT.CURSOR_SIZESW);
SIZEW = new Cursor(null, SWT.CURSOR_SIZEW);
SIZENW = new Cursor(null, SWT.CURSOR_SIZENW);
SIZENS = new Cursor(null, SWT.CURSOR_SIZENS);
SIZEWE = new Cursor(null, SWT.CURSOR_SIZEWE);
APPSTARTING = new Cursor(null, SWT.CURSOR_APPSTARTING);
CROSS = new Cursor(null, SWT.CURSOR_CROSS);
HAND = new Cursor(null, SWT.CURSOR_HAND);
HELP = new Cursor(null, SWT.CURSOR_HELP);
IBEAM = new Cursor(null, SWT.CURSOR_IBEAM);
NO = new Cursor(null, SWT.CURSOR_NO);
SIZEALL = new Cursor(null, SWT.CURSOR_SIZEALL);
SIZENESW = new Cursor(null, SWT.CURSOR_SIZENESW);
SIZENWSE = new Cursor(null, SWT.CURSOR_SIZENWSE);
UPARROW = new Cursor(null, SWT.CURSOR_UPARROW);
WAIT = new Cursor(null, SWT.CURSOR_WAIT);
ARROW = SystemCursorFactory.getCursor(SWT.CURSOR_ARROW);
SIZEN = SystemCursorFactory.getCursor(SWT.CURSOR_SIZEN);
SIZENE = SystemCursorFactory.getCursor(SWT.CURSOR_SIZENE);
SIZEE = SystemCursorFactory.getCursor(SWT.CURSOR_SIZEE);
SIZESE = SystemCursorFactory.getCursor(SWT.CURSOR_SIZESE);
SIZES = SystemCursorFactory.getCursor(SWT.CURSOR_SIZES);
SIZESW = SystemCursorFactory.getCursor(SWT.CURSOR_SIZESW);
SIZEW = SystemCursorFactory.getCursor(SWT.CURSOR_SIZEW);
SIZENW = SystemCursorFactory.getCursor(SWT.CURSOR_SIZENW);
SIZENS = SystemCursorFactory.getCursor(SWT.CURSOR_SIZENS);
SIZEWE = SystemCursorFactory.getCursor(SWT.CURSOR_SIZEWE);
APPSTARTING = SystemCursorFactory.getCursor(SWT.CURSOR_APPSTARTING);
CROSS = SystemCursorFactory.getCursor(SWT.CURSOR_CROSS);
HAND = SystemCursorFactory.getCursor(SWT.CURSOR_HAND);
HELP = SystemCursorFactory.getCursor(SWT.CURSOR_HELP);
IBEAM = SystemCursorFactory.getCursor(SWT.CURSOR_IBEAM);
NO = SystemCursorFactory.getCursor(SWT.CURSOR_NO);
SIZEALL = SystemCursorFactory.getCursor(SWT.CURSOR_SIZEALL);
SIZENESW = SystemCursorFactory.getCursor(SWT.CURSOR_SIZENESW);
SIZENWSE = SystemCursorFactory.getCursor(SWT.CURSOR_SIZENWSE);
UPARROW = SystemCursorFactory.getCursor(SWT.CURSOR_UPARROW);
WAIT = SystemCursorFactory.getCursor(SWT.CURSOR_WAIT);
}

}

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