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Add a new snippet to demonstrate drawing to different devices
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  • examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets

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‎examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet391.java‎

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/*******************************************************************************
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* Copyright (c) 2026 Eclipse Platform Contributors and others.
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*
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* This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License 2.0
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* which accompanies this distribution, and is available at
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* https://www.eclipse.org/legal/epl-2.0/
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*
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* SPDX-License-Identifier: EPL-2.0
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*
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* Contributors:
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* Eclipse Platform Contributors - initial API and implementation
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*******************************************************************************/
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package org.eclipse.swt.snippets;
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/*
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* Drawing operations test snippet: compare drawing on Display, Printer and PDF
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*
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* This snippet demonstrates drawing operations across different devices (Display, Printer, PDF)
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* to verify that drawing is consistent. It draws a test pattern with borders, crosses, and
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* a reference box of a specific physical size (in centimeters).
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*
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* For a list of all SWT example snippets see
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* http://www.eclipse.org/swt/snippets/
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*/
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import org.eclipse.swt.*;
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import org.eclipse.swt.graphics.*;
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import org.eclipse.swt.layout.*;
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import org.eclipse.swt.printing.*;
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import org.eclipse.swt.program.*;
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import org.eclipse.swt.widgets.*;
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public class Snippet391 {
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private static int boxSizeCm = 10;
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private static boolean considerMonitorZoom = false;
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public static void main(String[] args) {
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Display display = new Display();
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Shell shell = new Shell(display);
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shell.setText("Drawing Operations Test - Snippet 391");
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shell.setLayout(new GridLayout(2, false));
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// Canvas on the left
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Canvas canvas = new Canvas(shell, SWT.BORDER | SWT.DOUBLE_BUFFERED);
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GridData canvasData = new GridData(SWT.FILL, SWT.FILL, true, true);
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canvasData.minimumWidth = 400;
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canvasData.minimumHeight = 400;
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canvas.setLayoutData(canvasData);
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canvas.setBackground(display.getSystemColor(SWT.COLOR_WHITE));
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canvas.addListener(SWT.Paint, e -> {
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Monitor monitor = canvas.getMonitor();
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Rectangle clientArea = canvas.getClientArea();
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drawTestPattern(e.gc, display, clientArea, monitor);
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});
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// Controls on the right
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Composite controlPanel = new Composite(shell, SWT.NONE);
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controlPanel.setLayout(new GridLayout(2, false));
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controlPanel.setLayoutData(new GridData(SWT.FILL, SWT.TOP, false, false));
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// Box size spinner
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Label sizeLabel = new Label(controlPanel, SWT.NONE);
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sizeLabel.setText("Box size (cm):");
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Spinner sizeSpinner = new Spinner(controlPanel, SWT.BORDER);
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sizeSpinner.setMinimum(1);
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sizeSpinner.setMaximum(50);
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sizeSpinner.setSelection(boxSizeCm);
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sizeSpinner.addListener(SWT.Selection, e -> {
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boxSizeCm = sizeSpinner.getSelection();
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canvas.redraw();
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});
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// Monitor zoom checkbox
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Button zoomCheckbox = new Button(controlPanel, SWT.CHECK);
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zoomCheckbox.setText("Consider Monitor zoom");
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GridData checkboxData = new GridData();
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checkboxData.horizontalSpan = 2;
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zoomCheckbox.setLayoutData(checkboxData);
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zoomCheckbox.addListener(SWT.Selection, e -> {
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considerMonitorZoom = zoomCheckbox.getSelection();
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canvas.redraw();
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});
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// Separator
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Label separator = new Label(controlPanel, SWT.SEPARATOR | SWT.HORIZONTAL);
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GridData sepData = new GridData(SWT.FILL, SWT.CENTER, true, false);
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sepData.horizontalSpan = 2;
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separator.setLayoutData(sepData);
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// Print button
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Button printButton = new Button(controlPanel, SWT.PUSH);
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printButton.setText("Print");
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GridData printData = new GridData(SWT.FILL, SWT.CENTER, true, false);
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printData.horizontalSpan = 2;
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printButton.setLayoutData(printData);
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printButton.addListener(SWT.Selection, e -> printToPrinter(shell));
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// Create PDF button
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Button pdfButton = new Button(controlPanel, SWT.PUSH);
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pdfButton.setText("Create PDF");
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GridData pdfData = new GridData(SWT.FILL, SWT.CENTER, true, false);
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pdfData.horizontalSpan = 2;
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pdfButton.setLayoutData(pdfData);
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pdfButton.addListener(SWT.Selection, e -> createPdf(shell, canvas));
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shell.setSize(800, 600);
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shell.open();
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while (!shell.isDisposed()) {
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if (!display.readAndDispatch()) {
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display.sleep();
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}
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}
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display.dispose();
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}
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/**
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* Draws a test pattern on the given GC.
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*
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* @param gc the graphics context to draw on
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* @param device the device (Display, Printer, or PDFDocument)
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* @param rect the rectangle defining the drawing area
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* @param monitor optional monitor for zoom information (can be null)
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*/
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public static void drawTestPattern(GC gc, Device device, Rectangle rect, Monitor monitor) {
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Point deviceDpi = device.getDPI();
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int dpi = deviceDpi.x;
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// Calculate effective DPI considering monitor zoom if enabled
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int effectiveDpi = dpi;
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if (monitor != null && considerMonitorZoom) {
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int zoom = monitor.getZoom();
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effectiveDpi = (dpi * zoom) / 100;
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}
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// Save original settings
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int originalLineWidth = gc.getLineWidth();
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Color originalFg = gc.getForeground();
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// Draw red border at 1px distance from edges
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gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_RED));
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gc.setLineWidth(1);
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gc.drawRectangle(rect.x + 1, rect.y + 1, rect.width - 3, rect.height - 3);
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// Draw blue border at 5px distance from edges
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gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_BLUE));
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gc.drawRectangle(rect.x + 5, rect.y + 5, rect.width - 11, rect.height - 11);
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// Draw DPI info in upper left if drawable is a Device
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gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_BLACK));
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gc.drawString("DPI: " + dpi, rect.x + 10, rect.y + 10, true);
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// Draw monitor zoom in upper right if monitor is given
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if (monitor != null) {
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String zoomText = "Zoom: " + monitor.getZoom() + "%";
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Point textExtent = gc.stringExtent(zoomText);
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gc.drawString(zoomText, rect.x + rect.width - textExtent.x - 10, rect.y + 10, true);
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}
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// Draw black cross with 2px line width over full rectangle
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gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_BLACK));
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gc.setLineWidth(2);
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gc.drawLine(rect.x, rect.y, rect.x + rect.width, rect.y + rect.height);
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gc.drawLine(rect.x + rect.width, rect.y, rect.x, rect.y + rect.height);
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// Calculate box size in pixels from centimeters
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// 1 inch = 2.54 cm, so pixels = (cm / 2.54) * DPI
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int boxWidthPx = (int) Math.round((boxSizeCm / 2.54) * effectiveDpi);
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int boxHeightPx = boxWidthPx;
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// Center the box in the rectangle
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int boxX = rect.x + (rect.width - boxWidthPx) / 2;
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int boxY = rect.y + (rect.height - boxHeightPx) / 2;
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// Fill the box with light gray
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gc.setBackground(gc.getDevice().getSystemColor(SWT.COLOR_GRAY));
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gc.fillRectangle(boxX, boxY, boxWidthPx, boxHeightPx);
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// Draw 1px black border around the box
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gc.setForeground(gc.getDevice().getSystemColor(SWT.COLOR_BLACK));
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gc.setLineWidth(1);
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gc.drawRectangle(boxX, boxY, boxWidthPx, boxHeightPx);
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// Show the actual computed pixel dimensions on top/right of the box
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String pixelInfo = boxWidthPx + " x " + boxHeightPx + " px";
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Point infoExtent = gc.stringExtent(pixelInfo);
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int infoX = boxX + boxWidthPx - infoExtent.x;
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int infoY = boxY - infoExtent.y - 2;
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if (infoY < rect.y + 30) {
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infoY = rect.y + 30;
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}
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gc.drawString(pixelInfo, infoX, infoY, true);
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// Show the box size in cm below the pixel info
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String cmInfo = boxSizeCm + " cm (effective DPI: " + effectiveDpi + ")";
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gc.drawString(cmInfo, boxX, boxY + boxHeightPx + 5, true);
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// Restore original settings
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gc.setLineWidth(originalLineWidth);
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gc.setForeground(originalFg);
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}
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private static void printToPrinter(Shell shell) {
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PrintDialog printDialog = new PrintDialog(shell);
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PrinterData data = printDialog.open();
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if (data == null) {
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return; // User cancelled
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}
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Printer printer = new Printer(data);
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if (printer.startJob("Drawing Test - Snippet 391")) {
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GC gc = new GC(printer);
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if (printer.startPage()) {
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Rectangle printArea = printer.getClientArea();
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drawTestPattern(gc, printer, printArea, null);
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printer.endPage();
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}
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gc.dispose();
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printer.endJob();
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}
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printer.dispose();
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MessageBox msgBox = new MessageBox(shell, SWT.ICON_INFORMATION | SWT.OK);
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msgBox.setText("Print Complete");
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msgBox.setMessage("Document sent to printer.");
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msgBox.open();
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}
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private static void createPdf(Shell shell, Canvas canvas) {
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try {
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String tempDir = System.getProperty("java.io.tmpdir");
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String pdfPath = tempDir + "/drawing_test_snippet391.pdf";
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// Use exact canvas size in points (1 point = 1 pixel at 72 DPI)
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Point canvasSize = canvas.getSize();
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double widthPoints = canvasSize.x;
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double heightPoints = canvasSize.y;
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PDFDocument pdf = new PDFDocument(pdfPath, widthPoints, heightPoints);
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GC gc = new GC(pdf);
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Rectangle pdfRect = new Rectangle(0, 0, canvasSize.x, canvasSize.y);
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drawTestPattern(gc, pdf, pdfRect, null);
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gc.dispose();
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pdf.dispose();
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System.out.println("PDF exported to: " + pdfPath);
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Program.launch(pdfPath);
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} catch (Throwable ex) {
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MessageBox errorBox = new MessageBox(shell, SWT.ICON_ERROR | SWT.OK);
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errorBox.setText("Error");
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errorBox.setMessage("Failed to create PDF: " + ex.getMessage());
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errorBox.open();
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ex.printStackTrace();
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}
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}
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}

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