Java tutorial
/******************************************************************************* * Copyright (c) 2006, 2016 IBM Corporation and others. * * This program and the accompanying materials * are made available under the terms of the Eclipse Public License 2.0 * which accompanies this distribution, and is available at * https://www.eclipse.org/legal/epl-2.0/ * * SPDX-License-Identifier: EPL-2.0 * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.swt.examples.graphics; import org.eclipse.swt.SWT; import org.eclipse.swt.events.MouseEvent; import org.eclipse.swt.events.MouseListener; import org.eclipse.swt.events.MouseMoveListener; import org.eclipse.swt.graphics.Cursor; import org.eclipse.swt.graphics.Device; import org.eclipse.swt.graphics.Font; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Path; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.graphics.Transform; import org.eclipse.swt.widgets.Composite; /** * This tab presents cubic and quadratic curves that can be drawn. * The user may reposition the cubic and quadratic handles. */ public class CurvesTab extends GraphicsTab { /** These rectangles represent the handles on the curves. */ private Rectangle quadHndl, quadEndHndl, cubHndl1, cubHndl2, cubEndHndl; /** These values represent the positions of the curves. */ private float quadXPos, quadYPos, cubXPos, cubYPos; /** These values represent the x and y displacement of each handle. */ private float quadDiffX, quadDiffY, quadEndDiffX, quadEndDiffY; private float cubDiffX1, cubDiffY1, cubDiffX2, cubDiffY2, cubEndDiffX, cubEndDiffY; /** These are flags that indicate whether or not a handle has been moved. */ private boolean quadPtMoved, quadEndPtMoved, cubPt1Moved, cubPt2Moved, cubEndPtMoved; private MouseMoveListener mouseMoveListener; private MouseListener mouseListener; private Cursor cursor; /** true if hovering over a handle, false otherwise */ private boolean hovering = false; /** true if left mouse button is held down, false otherwise */ private boolean mouseDown = false; public CurvesTab(GraphicsExample example) { super(example); quadHndl = new Rectangle(200, 150, 5, 5); quadEndHndl = new Rectangle(400, 0, 5, 5); quadDiffX = quadDiffY = quadEndDiffX = quadEndDiffY = 0; cubHndl1 = new Rectangle(133, -60, 5, 5); cubHndl2 = new Rectangle(266, 60, 5, 5); cubDiffX1 = cubDiffY1 = cubDiffX2 = cubDiffY2 = 0; cubEndHndl = new Rectangle(400, 0, 5, 5); cubEndDiffX = cubEndDiffY = 0; } @Override public String getCategory() { return GraphicsExample.getResourceString("Curves"); //$NON-NLS-1$ } @Override public String getText() { return GraphicsExample.getResourceString("Curves"); //$NON-NLS-1$ } @Override public String getDescription() { return GraphicsExample.getResourceString("CurvesDescription"); //$NON-NLS-1$ } @Override public boolean getDoubleBuffered() { return true; } @Override public void dispose() { if (mouseListener != null) example.canvas.removeMouseListener(mouseListener); if (mouseMoveListener != null) example.canvas.removeMouseMoveListener(mouseMoveListener); cursor = null; } /** * This helper method determines whether or not the cursor is positioned * over a handle. * * @param e * A MouseEvent * @return true if cursor is positioned over a handle; false otherwise */ private boolean isHovering(MouseEvent e) { Rectangle quad = new Rectangle(quadHndl.x + (int) quadXPos - 1, quadHndl.y + (int) quadYPos - 1, quadHndl.width + 2, quadHndl.height + 2); Rectangle quadEnd = new Rectangle(quadEndHndl.x + (int) quadXPos - 1, quadEndHndl.y + (int) quadYPos - 1, quadEndHndl.width + 2, quadEndHndl.height + 2); Rectangle cub1 = new Rectangle(cubHndl1.x + (int) cubXPos - 1, cubHndl1.y + (int) cubYPos - 1, cubHndl1.width + 2, cubHndl1.height + 2); Rectangle cub2 = new Rectangle(cubHndl2.x + (int) cubXPos - 1, cubHndl2.y + (int) cubYPos - 1, cubHndl2.width + 2, cubHndl2.height + 2); Rectangle cubEnd = new Rectangle(cubEndHndl.x + (int) cubXPos - 1, cubEndHndl.y + (int) cubYPos - 1, cubEndHndl.width + 2, cubEndHndl.height + 2); return (quad.contains(e.x, e.y) || quadEnd.contains(e.x, e.y) || cub1.contains(e.x, e.y) || cub2.contains(e.x, e.y) || cubEnd.contains(e.x, e.y)); } /** * Creates the widgets used to control the drawing. */ @Override public void createControlPanel(Composite parent) { if (cursor == null) { cursor = parent.getDisplay().getSystemCursor(SWT.CURSOR_HAND); } mouseMoveListener = e -> { if (hovering && mouseDown) { example.canvas.setCursor(cursor); } else if (isHovering(e)) { example.canvas.setCursor(cursor); hovering = true; } else { example.canvas.setCursor(null); hovering = false; } if (quadPtMoved) { quadDiffX = quadDiffX + e.x - (int) quadXPos - quadHndl.x; quadDiffY = quadDiffY + e.y - (int) quadYPos - quadHndl.y; quadHndl.x = e.x - (int) quadXPos; quadHndl.y = e.y - (int) quadYPos; } else if (quadEndPtMoved) { quadEndDiffX = quadEndDiffX + e.x - (int) quadXPos - quadEndHndl.x; quadEndDiffY = quadEndDiffY + e.y - (int) quadYPos - quadEndHndl.y; quadEndHndl.x = e.x - (int) quadXPos; quadEndHndl.y = e.y - (int) quadYPos; } else if (cubPt1Moved) { cubDiffX1 = cubDiffX1 + e.x - (int) cubXPos - cubHndl1.x; cubDiffY1 = cubDiffY1 + e.y - (int) cubYPos - cubHndl1.y; cubHndl1.x = e.x - (int) cubXPos; cubHndl1.y = e.y - (int) cubYPos; } else if (cubPt2Moved) { cubDiffX2 = cubDiffX2 + e.x - (int) cubXPos - cubHndl2.x; cubDiffY2 = cubDiffY2 + e.y - (int) cubYPos - cubHndl2.y; cubHndl2.x = e.x - (int) cubXPos; cubHndl2.y = e.y - (int) cubYPos; } else if (cubEndPtMoved) { cubEndDiffX = cubEndDiffX + e.x - (int) cubXPos - cubEndHndl.x; cubEndDiffY = cubEndDiffY + e.y - (int) cubYPos - cubEndHndl.y; cubEndHndl.x = e.x - (int) cubXPos; cubEndHndl.y = e.y - (int) cubYPos; } example.redraw(); }; mouseListener = new MouseListener() { @Override public void mouseDoubleClick(MouseEvent e) { } /** * Sent when a mouse button is pressed. * * @param e an event containing information about the mouse button press */ @Override public void mouseDown(MouseEvent e) { Rectangle quad = new Rectangle(quadHndl.x + (int) quadXPos - 1, quadHndl.y + (int) quadYPos - 1, quadHndl.width + 2, quadHndl.height + 2); Rectangle quadEnd = new Rectangle(quadEndHndl.x + (int) quadXPos - 1, quadEndHndl.y + (int) quadYPos - 1, quadEndHndl.width + 2, quadEndHndl.height + 2); Rectangle cub1 = new Rectangle(cubHndl1.x + (int) cubXPos - 1, cubHndl1.y + (int) cubYPos - 1, cubHndl1.width + 2, cubHndl1.height + 2); Rectangle cub2 = new Rectangle(cubHndl2.x + (int) cubXPos - 1, cubHndl2.y + (int) cubYPos - 1, cubHndl2.width + 2, cubHndl2.height + 2); Rectangle cubEnd = new Rectangle(cubEndHndl.x + (int) cubXPos - 1, cubEndHndl.y + (int) cubYPos - 1, cubEndHndl.width + 2, cubEndHndl.height + 2); if (quad.contains(e.x, e.y)) { quadPtMoved = true; mouseDown = true; } else if (quadEnd.contains(e.x, e.y)) { quadEndPtMoved = true; mouseDown = true; } else if (cub1.contains(e.x, e.y)) { cubPt1Moved = true; mouseDown = true; } else if (cub2.contains(e.x, e.y)) { cubPt2Moved = true; mouseDown = true; } else if (cubEnd.contains(e.x, e.y)) { cubEndPtMoved = true; mouseDown = true; } } /** * Sent when a mouse button is released. * * @param e an event containing information about the mouse button release */ @Override public void mouseUp(MouseEvent e) { mouseDown = false; if (isHovering(e)) { example.canvas.setCursor(cursor); } else { example.canvas.setCursor(null); } if (quadPtMoved) quadPtMoved = false; if (quadEndPtMoved) quadEndPtMoved = false; if (cubPt1Moved) cubPt1Moved = false; if (cubPt2Moved) cubPt2Moved = false; if (cubEndPtMoved) cubEndPtMoved = false; example.redraw(); } }; example.canvas.addMouseMoveListener(mouseMoveListener); example.canvas.addMouseListener(mouseListener); } @Override public void paint(GC gc, int width, int height) { if (!example.checkAdvancedGraphics()) return; Device device = gc.getDevice(); Font font = new Font(device, getPlatformFont(), 16, SWT.ITALIC); gc.setFont(font); gc.setLineWidth(5); Transform transform; // ----- cubic curve ----- cubXPos = width / 5; cubYPos = height / 3; transform = new Transform(device); transform.translate(cubXPos, cubYPos); gc.setTransform(transform); transform.dispose(); gc.setForeground(device.getSystemColor(SWT.COLOR_RED)); gc.drawString(GraphicsExample.getResourceString("Cubic"), 25, -70, true); Path path = new Path(device); path.cubicTo(133 + cubDiffX1, -60 + cubDiffY1, 266 + cubDiffX2, 60 + cubDiffY2, 400 + cubEndDiffX, 0 + cubEndDiffY); gc.drawPath(path); path.dispose(); gc.setTransform(null); gc.setForeground(device.getSystemColor(SWT.COLOR_DARK_BLUE)); gc.drawRectangle(cubHndl1.x + (int) cubXPos, cubHndl1.y + (int) cubYPos, cubHndl1.width, cubHndl1.height); gc.drawRectangle(cubHndl2.x + (int) cubXPos, cubHndl2.y + (int) cubYPos, cubHndl2.width, cubHndl2.height); gc.drawRectangle(cubEndHndl.x + (int) cubXPos, cubEndHndl.y + (int) cubYPos, cubEndHndl.width, cubEndHndl.height); // ----- quadratic curve ----- quadXPos = width / 5; quadYPos = 2 * height / 3; transform = new Transform(device); transform.translate(quadXPos, quadYPos); gc.setTransform(transform); transform.dispose(); gc.setForeground(device.getSystemColor(SWT.COLOR_GREEN)); gc.drawString(GraphicsExample.getResourceString("Quadratic"), 0, -50, true); path = new Path(device); path.quadTo(200 + quadDiffX, 150 + quadDiffY, 400 + quadEndDiffX, 0 + quadEndDiffY); gc.drawPath(path); path.dispose(); gc.setTransform(null); gc.setForeground(device.getSystemColor(SWT.COLOR_GRAY)); gc.drawRectangle(quadHndl.x + (int) quadXPos, quadHndl.y + (int) quadYPos, quadHndl.width, quadHndl.height); gc.drawRectangle(quadEndHndl.x + (int) quadXPos, quadEndHndl.y + (int) quadYPos, quadEndHndl.width, quadEndHndl.height); font.dispose(); } /** * Returns the name of a valid font for the resident platform. */ static String getPlatformFont() { if (SWT.getPlatform() == "win32") { return "Arial"; } else if (SWT.getPlatform() == "gtk") { return "Baekmuk Batang"; } else { return "Verdana"; } } }