GC#DrawImage(image, destX, destY, destWidth, destHeight) now tries to load images at the requested destination size before drawing

[arunjose696]

The DrawImage API with just destination coordinates now tries to load images at the requested size.
If the requested size is not available, it falls back to the closest available size by calculating the appropriate zoom.
Images are loadable at the target size if the image is created from an SVG stream or filename, or The image is created with an ImageDataProvider that is ImageDataAtSizeProvider.

This commit also introduces the ImageDataAtSizeProvider interface to support dynamic sizing.

With this changes we need to test the following

1. The svgs are rendered at custom sizes without blurry scaling (this can be compared with current commit vs master)
2. Drawing images with targetHeight and targetWidth with ImageDataAtSizeProvider (comparison can be made against ImageDataProvider vs ImageDataAtSizeProvider both at this commit)
   Steps to reproduce:

snippet 1 to check drawing svgs at custom sizes (click to show snippet)

**Step 1**: Copy the eclipse.svg to same path where the snippets are and run the below snippet. **Step 2**: Run the snippet

package org.eclipse.swt.snippets;

package org.eclipse.swt.snippets;

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

public class Snippet386 {

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

        Image[] images = new Image[] {

            new Image(display, createImageFileNameProvider("src/org/eclipse/swt/snippets/eclipse.svg")),

        };

        String[] descriptions = new String[] {

            "ImageFileNameProvider with SVGs scaled by SVG rasterization"
        };

        Slice[] slices = {
        		 new Slice("Full", 0.0, 0.0, 1.0, 1.0),
                 new Slice("Top Half", 0.0, 0.0, 1.0, 0.5)
        };

        createShellWithImages(display, images, descriptions, slices, "Snippet 386 - Flipped Layout");
    }

    private static ImageFileNameProvider createImageFileNameProvider(String fileName) {
        return zoom -> {
        	if(zoom==100)
        	return fileName;
        	return null;};
    }

    static class Slice {
        String name;
        double xFrac, yFrac, wFrac, hFrac;
        Slice(String name, double x, double y, double w, double h) {
            this.name = name;
            this.xFrac = x;
            this.yFrac = y;
            this.wFrac = w;
            this.hFrac = h;
        }
    }

    private static void createShellWithImages(Display display, Image[] images, String[] descriptions, Slice[] slices, String title) {
        Shell shell = new Shell(display, SWT.SHELL_TRIM | SWT.MAX | SWT.RESIZE);
        shell.setText(title);
        shell.setLayout(new FillLayout());

        ScrolledComposite scrolledComposite = new ScrolledComposite(shell, SWT.V_SCROLL | SWT.H_SCROLL | SWT.BORDER);
        Canvas canvas = new Canvas(scrolledComposite, SWT.DOUBLE_BUFFERED);
        scrolledComposite.setContent(canvas);
        scrolledComposite.setExpandHorizontal(true);
        scrolledComposite.setExpandVertical(true);

        int boxW = 1500, boxH = 1500, gap = 20;
        int titleHeight = 20, descHeight = 40, sliceHeaderHeight = 30;

        int rows = images.length;
        int cols = slices.length;

        int canvasWidth = (boxW + gap) * cols + gap;
        int canvasHeight = (boxH + titleHeight + gap) * rows + descHeight + sliceHeaderHeight;
        canvas.setSize(canvasWidth, canvasHeight);
        scrolledComposite.setMinSize(canvasWidth, canvasHeight);

        canvas.addListener(SWT.Paint, e -> {
            // Column headers
            for (int col = 0; col < cols; col++) {
                int x = col * (boxW + gap) + gap;
                Font font = new Font(display, "Arial", 18, SWT.NORMAL);
                e.gc.setFont(font);
                e.gc.drawText(slices[col].name, x, 0, true);
                font.dispose();

            }

            // Rows
            for (int row = 0; row < rows; row++) {
                Image image = images[row];
                Rectangle rect = image.getBounds();
                int y = row * (boxH + titleHeight + gap) + descHeight + sliceHeaderHeight;

                Font font = new Font(display, "Arial", 18, SWT.NORMAL);
                e.gc.setFont(font);
                e.gc.drawText(descriptions[row], 0, y - 10, true);
                font.dispose();

                for (int col = 0; col < cols; col++) {
                    Slice s = slices[col];
                    int x = col * (boxW + gap) + gap;

                    int boxTop = y + titleHeight;
                    e.gc.drawRectangle(x, boxTop, (int) Math.round(boxW / s.wFrac), (int) Math.round(boxH / s.hFrac));

                    e.gc.drawImage(image, x, boxTop, (int) Math.round(boxW / s.wFrac), (int) Math.round(boxH / s.hFrac));
                }
            }
        });

        shell.setMaximized(true);
        shell.open();

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

        for (Image img : images) img.dispose();
        display.dispose();
    }
}

before

after

**snippet 2** Drawing images with ImageDataAtSizeProvider

package org.eclipse.swt.snippets;

package org.eclipse.swt.snippets;

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

public class Snippet386 {

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

        Image[] images = new Image[] {
            new Image(display, createImageDataProvider()),
            new Image(display, createImageDataAtSizeProvider())
        };

        String[] descriptions = new String[] {

            "ImageDataProvider with fixed font size for a given zoom",
            "ImageDataAtSizeProvider which scales font size based on target height and width"
        };

        Slice[] slices = {
            new Slice("Full", 0.0, 0.0, 1.0, 1.0),
            new Slice("Top Half", 0.0, 0.0, 1.0, 0.5),
            new Slice("Bottom Half", 0.0, 0.5, 1.0, 0.5),
            new Slice("Left Half", 0.0, 0.0, 0.5, 1.0),
            new Slice("Right Half", 0.5, 0.0, 0.5, 1.0),
            new Slice("Top-Left Quarter", 0.0, 0.0, 0.5, 0.5)
        };

        createShellWithImages(display, images, descriptions, slices, "Snippet 386 - Flipped Layout");
    }



    private static ImageDataProvider createImageDataProvider() {
        return new ImageDataProvider() {
            @Override
            public ImageData getImageData(int zoomLevel) {
                int scaleFactor = zoomLevel / 100;
                return createScaledTextImageData(100 * scaleFactor, 100 * scaleFactor);
            }
        };
    }

    private static ImageDataProvider createImageDataAtSizeProvider() {
        return new ImageDataAtSizeProvider() {
            @Override
            public ImageData getImageData(int zoomLevel) {
                int scaleFactor = zoomLevel / 100;
                return createScaledTextImageData(100 * scaleFactor, 100 * scaleFactor);
            }

            @Override
            public ImageData getImageData(int width, int height) {
                return createScaledTextImageData(width, height);
            }
        };
    }

    private static ImageData createScaledTextImageData(int width, int height) {
        Display display = Display.getDefault();
        String text = "abcd";

        int fontSize = Math.max(1, height / 100);
        Font font = new Font(display, "Arial", fontSize, SWT.NORMAL);

        Image tmp = new Image(display, 1, 1);
        GC measureGC = new GC(tmp);
        measureGC.setFont(font);
        Point textExtent = measureGC.textExtent(text);
        measureGC.dispose();
        tmp.dispose();

        double scale = Math.min((double) width / textExtent.x, (double) height / textExtent.y);
        font.dispose();
        font = new Font(display, "Arial", Math.max(1, (int) (fontSize * scale)), SWT.NORMAL);

        Image image = new Image(display, width, height);
        GC gc = new GC(image);
        gc.setFont(font);
        gc.setForeground(display.getSystemColor(SWT.COLOR_BLACK));
        gc.setBackground(display.getSystemColor(SWT.COLOR_WHITE));
        gc.fillRectangle(image.getBounds());

        gc.setLineWidth(Math.max(1, width / 20));
        gc.drawLine(0, 0, width / 2, height);

        Point newTextExtent = gc.textExtent(text);
        gc.drawText(text, (width - newTextExtent.x) / 2, (height - newTextExtent.y) / 2, true);

        gc.dispose();
        ImageData data = image.getImageData();

        image.dispose();
        font.dispose();

        return data;
    }

    static class Slice {
        String name;
        double xFrac, yFrac, wFrac, hFrac;
        Slice(String name, double x, double y, double w, double h) {
            this.name = name;
            this.xFrac = x;
            this.yFrac = y;
            this.wFrac = w;
            this.hFrac = h;
        }
    }

    private static void createShellWithImages(Display display, Image[] images, String[] descriptions, Slice[] slices, String title) {
        Shell shell = new Shell(display, SWT.SHELL_TRIM | SWT.MAX | SWT.RESIZE);
        shell.setText(title);
        shell.setLayout(new FillLayout());

        ScrolledComposite scrolledComposite = new ScrolledComposite(shell, SWT.V_SCROLL | SWT.H_SCROLL | SWT.BORDER);
        Canvas canvas = new Canvas(scrolledComposite, SWT.DOUBLE_BUFFERED);
        scrolledComposite.setContent(canvas);
        scrolledComposite.setExpandHorizontal(true);
        scrolledComposite.setExpandVertical(true);

        int boxW = 500, boxH = 500, gap = 20;
        int titleHeight = 20, descHeight = 40, sliceHeaderHeight = 30;

        int rows = images.length;
        int cols = slices.length;

        int canvasWidth = (boxW + gap) * cols + gap;
        int canvasHeight = (boxH + titleHeight + gap) * rows + descHeight + sliceHeaderHeight;
        canvas.setSize(canvasWidth, canvasHeight);
        scrolledComposite.setMinSize(canvasWidth, canvasHeight);

        canvas.addListener(SWT.Paint, e -> {
            // Column headers
            for (int col = 0; col < cols; col++) {
                int x = col * (boxW + gap) + gap;
                Font font = new Font(display, "Arial", 18, SWT.NORMAL);
                e.gc.setFont(font);
                e.gc.drawText(slices[col].name, x, 0, true);
                font.dispose();

            }

            // Rows
            for (int row = 0; row < rows; row++) {
                Image image = images[row];
                Rectangle rect = image.getBounds();
                int y = row * (boxH + titleHeight + gap) + descHeight + sliceHeaderHeight;

                Font font = new Font(display, "Arial", 18, SWT.NORMAL);
                e.gc.setFont(font);
                e.gc.drawText(descriptions[row], 0, y - 10, true);
                font.dispose();

                for (int col = 0; col < cols; col++) {
                    Slice s = slices[col];
                    int x = col * (boxW + gap) + gap;

                    int srcX = (int) (rect.width * s.xFrac);
                    int srcY = (int) (rect.height * s.yFrac);
                    int srcW = (int) (rect.width * s.wFrac);
                    int srcH = (int) (rect.height * s.hFrac);

                    int boxTop = y + titleHeight;
                    e.gc.drawRectangle(x, boxTop, boxW, boxH);


                    e.gc.drawImage(image, x, boxTop, boxW, boxH);

                }
            }
        });

        shell.setMaximized(true);
        shell.open();

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

        for (Image img : images) img.dispose();
        display.dispose();
    }
}

This depends on #2514 and #2509, Only last commit is relevant to this PR

[github-actions]

Test Results

  118 files  ±0    118 suites  ±0   12m 4s ⏱️ +59s
4 583 tests ±0  4 547 ✅ ±0  36 💤 ±0  0 ❌ ±0 
  330 runs  ±0    307 ✅ ±0  23 💤 ±0  0 ❌ ±0 

Results for commit b238dec. ± Comparison against base commit 749ed1a.

♻️ This comment has been updated with latest results.

[HeikoKlare]

I scanned the PR and commented on some obvious or essential points I came across.

[HeikoKlare]

Thank you for the latest cleanups. They made the code much easier to understand.
Reading the code again I see that, if I am not mistaken, it breaks the existing (implicit) contract for the cache image data, such that it would like lead to a regression. That's why I request changes to avoid that we break existing behavior,
In addition, all the changes related to creating a temporary handle based on zoom for executing a drawing operation on look far more complicated than they need to be to me. I wrote a longer comment trying to explain what in my opinion can/should be done to improve that.

[akoch-yatta]

Changes look good to me and I didn't find any regression testing it with the Runtime or the CustomControlExample that already use the new GC API that triggers the changed logic