Fix label cutoff

[amartya4256]

This PR contributes to precise scaling of computation of size inside gridLayout by using float precision. This fixes the issue reported in #2166

How to test

package org.eclipse.swt.snippets;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class SnippetLabelCutOff {
	public static void main(String[] args) {
		Display display = new Display();


		/* Provide different resolutions for icons to get
		 * high quality rendering wherever the OS needs
		 * large icons. For example, the ALT+TAB window
		 * on certain systems uses a larger icon.
		 */
		Shell shell = new Shell(display);
		PartView partView = new Snippet138.PartView(display);
		partView.postConstruct(shell);
		shell.open();



		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}
		partView.preDestroy();
		shell.dispose();
		display.dispose();
	}

	public static class PartView
	{
	   public Display aDisplay;

	   private Composite aMidComposite;

	   private Label aRepairLabel;

	   public Font aNormalFont;

	   public PartView(Display display) {
		aDisplay = display;
	}

	   public void postConstruct(Composite pParent)
	   {
	      FormLayout vLayout = new FormLayout();
	      vLayout.marginHeight = 5;
	      vLayout.marginWidth = 6;
	      pParent.setLayout(vLayout);

	      createResources();

	      createMid(pParent);

	      pParent.pack();
	   }

	   private void createResources()
	   {
	      aNormalFont = new Font(
	            aDisplay,
	            new FontData("Arial", 11, SWT.NORMAL));

	   }

	   private void createMid(Composite pParent)
	   {
	      // MID
	      aMidComposite = new Composite(pParent, SWT.NONE);
	      aMidComposite.setBackground(aDisplay.getSystemColor(SWT.COLOR_WHITE));
	      FormData aFormDataMid = new FormData();
	      aFormDataMid.top = new FormAttachment(0, 0);
	      aFormDataMid.bottom = new FormAttachment(100, 0);
	      aFormDataMid.left = new FormAttachment(0, 0);
	      aFormDataMid.right = new FormAttachment(100, 0);
	      aMidComposite.setLayoutData(aFormDataMid);

	      GridLayout vLayout = new GridLayout();
	      aMidComposite.setLayout(vLayout);

	      aRepairLabel = new Label(aMidComposite, SWT.WRAP);
	      aRepairLabel.setFont(aNormalFont);
	      GridData vRepairLabelGridData = new GridData();
	      vRepairLabelGridData.horizontalAlignment = GridData.BEGINNING;
	      vRepairLabelGridData.verticalAlignment = GridData.CENTER;
	      vRepairLabelGridData.grabExcessHorizontalSpace = true;
	      vRepairLabelGridData.verticalIndent = Math.round(32);
	      aRepairLabel.setLayoutData(vRepairLabelGridData);

	      aRepairLabel
	            .setText(
	                  "Rhe erv fhe eovianae tb orao estnffd rniTaa eultoolte i sssube wreco.");
	   }

	   public void preDestroy()
	   {
	      aNormalFont.dispose();
	   }
	}
}

Before:

After:

[github-actions]

Test Results

   546 files  ±0     546 suites  ±0   33m 58s ⏱️ + 4m 25s
 4 425 tests ±0   4 408 ✅ ±0   17 💤 ±0  0 ❌ ±0 
16 746 runs  ±0  16 619 ✅ ±0  127 💤 ±0  0 ❌ ±0 

Results for commit fc7dedf. ± Comparison against base commit 20d18aa.

♻️ This comment has been updated with latest results.

[arunjose696]

Suggested change

	cacheSize = new Point.OfFloat(-1, -1);
	cacheSize = new Point.OfFloat(SWT.DEFAULT, SWT.DEFAULT);

[arunjose696]

I think the -1 in all comparisons in this function should be replaced with SWT.DEFAULT

[arunjose696]

Another option I think is cleaner is to have
public static final OfFloat UNDEFINED = new OfFloat(-1f, -1f);

in the point class so comparisons could be

cacheSize == Point.OfFloat.UNDEFINED;

[amartya4256]

We cannot set UNDEFINED = new OfFloat(-1f, -1f) since -1, -1 can also represent a point in the coordinate system and it's only valid for cacheSize in the case of Grid data. Hence, that should be handled in GridData. I like the idea of checking with SWT.DEFAULT.

[HeikoKlare]

One general question on this: wouldn't it possible or even reasonable to stick to width/height values inside GridData but just make them floats and only use Point.OfFloat for the returns of API methods?
Two reasons for this:

1. SWT is generally lacking some Size object and, unfortunately, at many places Point is used to represent a size (even though that semantically does not make that much sense). Thus, we usually try to stick to width/height when considering sizes.
2. It would be less error prone as now if you accidentally use, e.g., size.x instead of size.getX(), you may calculate with a wrong value.

[amartya4256]

One general question on this: wouldn't it possible or even reasonable to stick to width/height values inside GridData but just make them floats and only use Point.OfFloat for the returns of API methods? Two reasons for this:

1. SWT is generally lacking some Size object and, unfortunately, at many places Point is used to represent a size (even though that semantically does not make that much sense). Thus, we usually try to stick to width/height when considering sizes.
2. It would be less error prone as now if you accidentally use, e.g., size.x instead of size.getX(), you may calculate with a wrong value.

I agree, I'll make the changes.

[fedejeanne]

Would it be ok to simply change the existing point instead of creating a new one?

[fedejeanne]

I mean: to avoid unnecessary object creation. I assume that layout is called pretty often?