Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2017 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.paint; import static org.eclipse.swt.events.SelectionListener.widgetSelectedAdapter; import org.eclipse.swt.events.ControlListener; import org.eclipse.swt.events.MouseAdapter; import org.eclipse.swt.events.MouseEvent; import org.eclipse.swt.graphics.Color; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Image; import org.eclipse.swt.graphics.Point; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.graphics.Region; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.ScrollBar; import org.eclipse.swt.widgets.Shell; import org.eclipse.swt.widgets.Text; /** * Manages a simple drawing surface. */ public class PaintSurface { private Point currentPosition = new Point(0, 0); private Canvas paintCanvas; private PaintSession paintSession; private Image image; private Image paintImage; // buffer for refresh blits private int imageWidth, imageHeight; private int visibleWidth, visibleHeight; private FigureDrawContext displayFDC = new FigureDrawContext(); private FigureDrawContext imageFDC = new FigureDrawContext(); private FigureDrawContext paintFDC = new FigureDrawContext(); /* Rubberband */ private ContainerFigure rubberband = new ContainerFigure(); // the active rubberband selection private int rubberbandHiddenNestingCount = 0; // always >= 0, if > 0 rubberband has been hidden /* Status */ private Text statusText; private String statusActionInfo, statusMessageInfo, statusCoordInfo; /** * Constructs a PaintSurface. * <p> * paintCanvas must have SWT.NO_REDRAW_RESIZE and SWT.NO_BACKGROUND styles, * and may have SWT.V_SCROLL and/or SWT.H_SCROLL. * </p> * @param paintCanvas the Canvas object in which to render * @param paintStatus the PaintStatus object to use for providing user feedback * @param fillColor the color to fill the canvas with initially */ public PaintSurface(Canvas paintCanvas, Text statusText, Color fillColor) { this.paintCanvas = paintCanvas; this.statusText = statusText; clearStatus(); /* Set up the drawing surface */ Rectangle displayRect = paintCanvas.getDisplay().getClientArea(); imageWidth = displayRect.width; imageHeight = displayRect.height; image = new Image(paintCanvas.getDisplay(), imageWidth, imageHeight); imageFDC.gc = new GC(image); imageFDC.gc.setBackground(fillColor); imageFDC.gc.fillRectangle(0, 0, imageWidth, imageHeight); displayFDC.gc = new GC(paintCanvas); /* Initialize the session */ setPaintSession(null); /* Add our listeners */ paintCanvas.addDisposeListener(e -> displayFDC.gc.dispose()); paintCanvas.addMouseListener(new MouseAdapter() { @Override public void mouseDown(MouseEvent event) { processMouseEventCoordinates(event); if (paintSession != null) paintSession.mouseDown(event); } @Override public void mouseUp(MouseEvent event) { processMouseEventCoordinates(event); if (paintSession != null) paintSession.mouseUp(event); } @Override public void mouseDoubleClick(MouseEvent event) { processMouseEventCoordinates(event); if (paintSession != null) paintSession.mouseDoubleClick(event); } }); paintCanvas.addMouseMoveListener(event -> { processMouseEventCoordinates(event); if (paintSession != null) paintSession.mouseMove(event); }); paintCanvas.addPaintListener(event -> { if (rubberband.isEmpty()) { // Nothing to merge, so we just refresh event.gc.drawImage(image, displayFDC.xOffset + event.x, displayFDC.yOffset + event.y, event.width, event.height, event.x, event.y, event.width, event.height); } else { /* * Avoid flicker when merging overlayed objects by constructing the image on * a backbuffer first, then blitting it to the screen. */ // Check that the backbuffer is large enough if (paintImage != null) { Rectangle rect1 = paintImage.getBounds(); if ((event.width + event.x > rect1.width) || (event.height + event.y > rect1.height)) { paintFDC.gc.dispose(); paintImage.dispose(); paintImage = null; } } if (paintImage == null) { Display display = getDisplay(); Rectangle rect2 = display.getClientArea(); paintImage = new Image(display, Math.max(rect2.width, event.width + event.x), Math.max(rect2.height, event.height + event.y)); paintFDC.gc = new GC(paintImage); } // Setup clipping and the FDC Region clipRegion = new Region(); event.gc.getClipping(clipRegion); paintFDC.gc.setClipping(clipRegion); clipRegion.dispose(); paintFDC.xOffset = displayFDC.xOffset; paintFDC.yOffset = displayFDC.yOffset; paintFDC.xScale = displayFDC.xScale; paintFDC.yScale = displayFDC.yScale; // Merge the overlayed objects into the image, then blit paintFDC.gc.drawImage(image, displayFDC.xOffset + event.x, displayFDC.yOffset + event.y, event.width, event.height, event.x, event.y, event.width, event.height); rubberband.draw(paintFDC); event.gc.drawImage(paintImage, event.x, event.y, event.width, event.height, event.x, event.y, event.width, event.height); } }); paintCanvas.addControlListener(ControlListener.controlResizedAdapter(e -> handleResize())); /* Set up the paint canvas scroll bars */ ScrollBar horizontal = paintCanvas.getHorizontalBar(); horizontal.setVisible(true); horizontal .addSelectionListener(widgetSelectedAdapter(event -> scrollHorizontally((ScrollBar) event.widget))); ScrollBar vertical = paintCanvas.getVerticalBar(); vertical.setVisible(true); vertical.addSelectionListener(widgetSelectedAdapter(event -> scrollVertically((ScrollBar) event.widget))); handleResize(); } /** * Disposes of the PaintSurface's resources. */ public void dispose() { imageFDC.gc.dispose(); image.dispose(); if (paintImage != null) { paintImage.dispose(); paintFDC.gc.dispose(); } currentPosition = null; paintCanvas = null; paintSession = null; image = null; paintImage = null; displayFDC = null; imageFDC = null; paintFDC = null; rubberband = null; statusText = null; statusActionInfo = null; statusMessageInfo = null; statusCoordInfo = null; } /** * Called when we must grab focus. */ public void setFocus() { paintCanvas.setFocus(); } /** * Returns the Display on which the PaintSurface resides. * @return the Display */ public Display getDisplay() { return paintCanvas.getDisplay(); } /** * Returns the Shell in which the PaintSurface resides. * @return the Shell */ public Shell getShell() { return paintCanvas.getShell(); } /** * Sets the current paint session. * <p> * If oldPaintSession != paintSession calls oldPaintSession.end() * and paintSession.begin() * </p> * * @param paintSession the paint session to activate; null to disable all sessions */ public void setPaintSession(PaintSession paintSession) { if (this.paintSession != null) { if (this.paintSession == paintSession) return; this.paintSession.endSession(); } this.paintSession = paintSession; clearStatus(); if (paintSession != null) { setStatusAction(paintSession.getDisplayName()); paintSession.beginSession(); } else { setStatusAction(PaintExample.getResourceString("tool.Null.label")); setStatusMessage(PaintExample.getResourceString("session.Null.message")); } } /** * Returns the current paint session. * * @return the current paint session, null if none is active */ public PaintSession getPaintSession() { return paintSession; } /** * Returns the current paint tool. * * @return the current paint tool, null if none is active (though some other session * might be) */ public PaintTool getPaintTool() { return (paintSession != null && paintSession instanceof PaintTool) ? (PaintTool) paintSession : null; } /** * Returns the current position in an interactive operation. * * @return the last known position of the pointer */ public Point getCurrentPosition() { return currentPosition; } /** * Draws a Figure object to the screen and to the backing store permanently. * * @param object the object to draw onscreen */ public void drawFigure(Figure object) { object.draw(imageFDC); object.draw(displayFDC); } /** * Adds a Figure object to the active rubberband selection. * <p> * This object will be drawn to the screen as a preview and refreshed appropriately * until the selection is either cleared or committed. * </p> * * @param object the object to add to the selection */ public void addRubberbandSelection(Figure object) { rubberband.add(object); if (!isRubberbandHidden()) object.draw(displayFDC); } /** * Clears the active rubberband selection. * <p> * Erases any rubberband objects on the screen then clears the selection. * </p> */ public void clearRubberbandSelection() { if (!isRubberbandHidden()) { Region region = new Region(); rubberband.addDamagedRegion(displayFDC, region); Rectangle r = region.getBounds(); paintCanvas.redraw(r.x, r.y, r.width, r.height, true); region.dispose(); } rubberband.clear(); } /** * Commits the active rubberband selection. * <p> * Redraws any rubberband objects on the screen as permanent objects then clears the selection. * </p> */ public void commitRubberbandSelection() { rubberband.draw(imageFDC); if (isRubberbandHidden()) rubberband.draw(displayFDC); rubberband.clear(); } /** * Hides the rubberband (but does not eliminate it). * <p> * Increments by one the rubberband "hide" nesting count. The rubberband * is hidden from view (but remains active) if it wasn't already hidden. * </p> */ public void hideRubberband() { if (rubberbandHiddenNestingCount++ <= 0) { Region region = new Region(); rubberband.addDamagedRegion(displayFDC, region); Rectangle r = region.getBounds(); paintCanvas.redraw(r.x, r.y, r.width, r.height, true); region.dispose(); } } /** * Shows (un-hides) the rubberband. * <p> * Decrements by one the rubberband "hide" nesting count. The rubberband * is only made visible when showRubberband() has been called once for each * previous hideRubberband(). It is not permitted to call showRubberband() if * the rubber band is not presently hidden. * </p> */ public void showRubberband() { if (rubberbandHiddenNestingCount <= 0) throw new IllegalStateException("rubberbandHiddenNestingCount > 0"); if (--rubberbandHiddenNestingCount == 0) { rubberband.draw(displayFDC); } } /** * Determines if the rubberband is hidden. * * @return true iff the rubber is hidden */ public boolean isRubberbandHidden() { return rubberbandHiddenNestingCount > 0; } /** * Handles a horizontal scroll event * * @param scrollbar the horizontal scroll bar that posted this event */ public void scrollHorizontally(ScrollBar scrollBar) { if (image == null) return; if (imageWidth > visibleWidth) { final int oldOffset = displayFDC.xOffset; final int newOffset = Math.min(scrollBar.getSelection(), imageWidth - visibleWidth); if (oldOffset != newOffset) { paintCanvas.update(); displayFDC.xOffset = newOffset; paintCanvas.scroll(Math.max(oldOffset - newOffset, 0), 0, Math.max(newOffset - oldOffset, 0), 0, visibleWidth, visibleHeight, false); } } } /** * Handles a vertical scroll event * * @param scrollbar the vertical scroll bar that posted this event */ public void scrollVertically(ScrollBar scrollBar) { if (image == null) return; if (imageHeight > visibleHeight) { final int oldOffset = displayFDC.yOffset; final int newOffset = Math.min(scrollBar.getSelection(), imageHeight - visibleHeight); if (oldOffset != newOffset) { paintCanvas.update(); displayFDC.yOffset = newOffset; paintCanvas.scroll(0, Math.max(oldOffset - newOffset, 0), 0, Math.max(newOffset - oldOffset, 0), visibleWidth, visibleHeight, false); } } } /** * Handles resize events */ private void handleResize() { paintCanvas.update(); Rectangle visibleRect = paintCanvas.getClientArea(); visibleWidth = visibleRect.width; visibleHeight = visibleRect.height; ScrollBar horizontal = paintCanvas.getHorizontalBar(); if (horizontal != null) { displayFDC.xOffset = Math.min(horizontal.getSelection(), imageWidth - visibleWidth); if (imageWidth <= visibleWidth) { horizontal.setEnabled(false); horizontal.setSelection(0); } else { horizontal.setEnabled(true); horizontal.setValues(displayFDC.xOffset, 0, imageWidth, visibleWidth, 8, visibleWidth); } } ScrollBar vertical = paintCanvas.getVerticalBar(); if (vertical != null) { displayFDC.yOffset = Math.min(vertical.getSelection(), imageHeight - visibleHeight); if (imageHeight <= visibleHeight) { vertical.setEnabled(false); vertical.setSelection(0); } else { vertical.setEnabled(true); vertical.setValues(displayFDC.yOffset, 0, imageHeight, visibleHeight, 8, visibleHeight); } } } /** * Virtualizes MouseEvent coordinates and stores the current position. */ private void processMouseEventCoordinates(MouseEvent event) { currentPosition.x = event.x = Math.min(Math.max(event.x, 0), visibleWidth - 1) + displayFDC.xOffset; currentPosition.y = event.y = Math.min(Math.max(event.y, 0), visibleHeight - 1) + displayFDC.yOffset; } /** * Clears the status bar. */ public void clearStatus() { statusActionInfo = ""; statusMessageInfo = ""; statusCoordInfo = ""; updateStatus(); } /** * Sets the status bar action text. * * @param action the action in progress, null to clear */ public void setStatusAction(String action) { statusActionInfo = (action != null) ? action : ""; updateStatus(); } /** * Sets the status bar message text. * * @param message the message to display, null to clear */ public void setStatusMessage(String message) { statusMessageInfo = (message != null) ? message : ""; updateStatus(); } /** * Sets the coordinates in the status bar. * * @param coord the coordinates to display, null to clear */ public void setStatusCoord(Point coord) { statusCoordInfo = (coord != null) ? PaintExample.getResourceString("status.Coord.format", new Object[] { Integer.valueOf(coord.x), Integer.valueOf(coord.y) }) : ""; updateStatus(); } /** * Sets the coordinate range in the status bar. * * @param a the "from" coordinate, must not be null * @param b the "to" coordinate, must not be null */ public void setStatusCoordRange(Point a, Point b) { statusCoordInfo = PaintExample.getResourceString("status.CoordRange.format", new Object[] { Integer.valueOf(a.x), Integer.valueOf(a.y), Integer.valueOf(b.x), Integer.valueOf(b.y) }); updateStatus(); } /** * Updates the display. */ private void updateStatus() { statusText.setText(PaintExample.getResourceString("status.Bar.format", new Object[] { statusActionInfo, statusMessageInfo, statusCoordInfo })); } }