Fix cursor loading incorrect image size when ImageData is unavailable at requested zoom

[arunjose696]

Description

Before this change, the cursor used DPIUtil.validateAndGetImageDataAtZoom() to get image data. However, this method could return image data at a different zoom level if the exact match wasn't available from the ImageDataProvider. As a result, the cursor could be scaled incorrectly, since the returned image data was assumed to match the requested zoom.

With this change, a temporary Image is created, and Image.getImageData(zoom) is called to get properly scaled image data for the requested zoom level.

Steps to reproduce:

Run the below snippet at 150% monitor zoom. The ImageDataProvider in the snippet returns image data only for zoom levels 100 and 200.

Without this change
When run without any swt.autoScale VM argument, the cursor size was incorrectly scaled to 60×60.
When run with -Dswt.autoScale=quarter, the cursor is 30x30.

With this current fix applied
The cursor is now correctly sized (e.g., 45×45 at 150% zoom).

package org.eclipse.swt.snippets;

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

public class Snippet118 {

   public static void main(String[] args) {

      final Display display = new Display();
      final Shell shell = new Shell(display);
      Rectangle bounds = shell.getBounds();

      shell.setLocation((int) (bounds.width * 0.9f), 100);
      shell.setText("Snippet 118");
      shell.setSize(1000, 1000);

      final Cursor[] cursor = new Cursor[1];
      final ImageData[] imageData = new ImageData[1];



      shell.addPaintListener(event -> {

         GC gc = event.gc;

         ImageData oneImageData = imageData[0];
         if (oneImageData != null) {

            gc.drawText("Cursor width %d  - height %d".formatted(
                  oneImageData.width,
                  oneImageData.height), 10, 50, true);
         }

         int i = 1;


         int monitorZoom = DPIUtil.getNativeDeviceZoom();
         int deviceZoom = DPIUtil.getDeviceZoom();
         float devScale = deviceZoom / 100f;

         gc.drawText("Monitor zoom = %d".formatted(monitorZoom), 10, 140);

         int yPos = 400;
         int tickHeight = 10;

         for (int tickIndex = 0; tickIndex < 11; tickIndex++) {

            int xPos = 100 + tickIndex * 10;
            int yOffset = 0;

            if (tickIndex % 3 == 1) {
               yOffset = 20;
            } else if (tickIndex % 3 == 2) {
               yOffset = 40;
            }

            int xPosUnscaled = (int) (xPos / devScale);
            int YPosUnscaled = (int) (yPos / devScale);

            gc.drawLine(xPosUnscaled, YPosUnscaled, xPosUnscaled, YPosUnscaled + tickHeight);
            gc.drawText(Integer.toString(tickIndex * 10), xPosUnscaled - 5, YPosUnscaled + 12 + yOffset);
         }
      });


      ImageDataProvider imageDataProvider = zoom -> {
  		if(zoom==100)
  			return new ImageData(30, 30, 1, new PaletteData(new RGB(255, 0, 0)));
  		else if(zoom==200)
  			return new ImageData(60, 60, 1, new PaletteData(new RGB(255, 0, 0)));
  		else
  			return null;
  	};


      cursor[0] = new Cursor(display, imageDataProvider, 0, 0);
      shell.setCursor(cursor[0]);


      shell.redraw();

      shell.open();
      while (!shell.isDisposed()) {
         if (!display.readAndDispatch())
            display.sleep();
      }

      if (cursor[0] != null)
         cursor[0].dispose();
      display.dispose();
   }
}

Note : This snippet is adapted from [issue #2057](#2057 (comment) to get the scales

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Test Results

   546 files  ±0     546 suites  ±0   31m 0s ⏱️ -1s
 4 407 tests ±0   4 390 ✅ ±0   17 💤 ±0  0 ❌ ±0 
16 713 runs  ±0  16 586 ✅ ±0  127 💤 ±0  0 ❌ ±0 

Results for commit 5a39650. ± Comparison against base commit 95b46b6.