Assertion in Caret.setIMEFont

[tmssngr]

Describe the bug
A couple of users reported an exception for SWT R4_36 which was not reported for R4_35:

org.eclipse.swt.SWTException: Graphic is disposed
	at org.eclipse.swt.SWT.error(SourceFile:4945)
	at org.eclipse.swt.SWT.error(SourceFile:4860)
	at org.eclipse.swt.SWT.error(SourceFile:4831)
	at org.eclipse.swt.graphics.Resource.getDevice(SourceFile:167)
	at org.eclipse.swt.internal.SWTFontProvider.getFontHandle(SourceFile:77)
	at org.eclipse.swt.widgets.Caret.setIMEFont(SourceFile:512)
	at org.eclipse.swt.widgets.Caret.setFocus(SourceFile:457)
	at org.eclipse.swt.widgets.Canvas.setCaret(SourceFile:286)
	at org.eclipse.swt.custom.StyledText.setCaret(SourceFile:8391)
... our code
	at org.eclipse.swt.widgets.EventTable.sendEvent(SourceFile:91)
	at org.eclipse.swt.widgets.Display.sendEvent(SourceFile:4344)
	at org.eclipse.swt.widgets.Widget.sendEvent(SourceFile:1214)
	at org.eclipse.swt.widgets.Widget.sendEvent(SourceFile:1238)
	at org.eclipse.swt.widgets.Widget.sendEvent(SourceFile:1219)
	at org.eclipse.swt.widgets.Control.sendFocusEvent(SourceFile:2926)
	at org.eclipse.swt.widgets.Widget.wmSetFocus(SourceFile:2475)
	at org.eclipse.swt.widgets.Control.WM_SETFOCUS(SourceFile:5493)
	at org.eclipse.swt.widgets.Canvas.WM_SETFOCUS(SourceFile:433)
	at org.eclipse.swt.widgets.Control.windowProc(SourceFile:4859)
	at org.eclipse.swt.widgets.Canvas.windowProc(SourceFile:336)
	at org.eclipse.swt.widgets.Display.windowProc(SourceFile:5115)
	at org.eclipse.swt.internal.win32.OS.SetFocus
	at org.eclipse.swt.widgets.Control.forceFocus(SourceFile:1054)
	at org.eclipse.swt.widgets.Control.setFocus(SourceFile:3423)
	at org.eclipse.swt.widgets.Composite.setFocus(SourceFile:1086)
	at org.eclipse.swt.custom.StyledText.setFocus(SourceFile:8759)
	at org.eclipse.swt.widgets.Composite.WM_LBUTTONDOWN(SourceFile:1433)
	at org.eclipse.swt.widgets.Canvas.WM_LBUTTONDOWN(SourceFile:428)
	at org.eclipse.swt.widgets.Control.windowProc(SourceFile:4823)
	at org.eclipse.swt.widgets.Canvas.windowProc(SourceFile:336)
	at org.eclipse.swt.widgets.Display.windowProc(SourceFile:5115)
	at org.eclipse.swt.internal.win32.OS.DispatchMessage
	at org.eclipse.swt.widgets.Display.readAndDispatch(SourceFile:3728)

To Reproduce
Unfortunately, I don't know how to reproduce.

Expected behavior
No exception.

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   Windows 11

Version since
Latest R4_36 release.

[fedejeanne]

Adding the tag "regression" until the cause is known. It may be removed later. @arunjose696 is working on it

[arunjose696]

Here is snippet to reproduce the issue

package org.eclipse.swt.snippets;
import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class CanvasCaretFocus {
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setSize(300, 200);
        shell.setText("Canvas Caret Focus");
        Canvas canvas = new Canvas(shell, SWT.BORDER);

        shell.open();
        Caret caret = new Caret(canvas, SWT.NONE);
        Font font = new Font(display, "Default", 10, SWT.BOLD);
    	caret.setFont(font );
    	font.dispose();

    	canvas.setFocus();
        canvas.setCaret(caret);



    }
}