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.controlexample; import static org.eclipse.swt.events.SelectionListener.widgetSelectedAdapter; import org.eclipse.swt.SWT; import org.eclipse.swt.events.ControlListener; import org.eclipse.swt.graphics.Color; import org.eclipse.swt.graphics.Font; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Point; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.layout.GridData; import org.eclipse.swt.layout.GridLayout; import org.eclipse.swt.widgets.Button; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Caret; import org.eclipse.swt.widgets.Composite; import org.eclipse.swt.widgets.Group; import org.eclipse.swt.widgets.ScrollBar; import org.eclipse.swt.widgets.TabFolder; import org.eclipse.swt.widgets.Widget; class CanvasTab extends Tab { static final int colors[] = { SWT.COLOR_RED, SWT.COLOR_GREEN, SWT.COLOR_BLUE, SWT.COLOR_MAGENTA, SWT.COLOR_YELLOW, SWT.COLOR_CYAN, SWT.COLOR_DARK_RED, SWT.COLOR_DARK_GREEN, SWT.COLOR_DARK_BLUE, SWT.COLOR_DARK_MAGENTA, SWT.COLOR_DARK_YELLOW, SWT.COLOR_DARK_CYAN }; static final String canvasString = "Canvas"; //$NON-NLS-1$ /* Example widgets and groups that contain them */ Canvas canvas; Group canvasGroup; /* Style widgets added to the "Style" group */ Button horizontalButton, verticalButton, noBackgroundButton, noFocusButton, noMergePaintsButton, noRedrawResizeButton, doubleBufferedButton; /* Other widgets added to the "Other" group */ Button caretButton, fillDamageButton; int paintCount; int cx, cy; int maxX, maxY; /** * Creates the Tab within a given instance of ControlExample. */ CanvasTab(ControlExample instance) { super(instance); } /** * Creates the "Other" group. */ @Override void createOtherGroup() { super.createOtherGroup(); /* Create display controls specific to this example */ caretButton = new Button(otherGroup, SWT.CHECK); caretButton.setText(ControlExample.getResourceString("Caret")); fillDamageButton = new Button(otherGroup, SWT.CHECK); fillDamageButton.setText(ControlExample.getResourceString("FillDamage")); /* Add the listeners */ caretButton.addSelectionListener(widgetSelectedAdapter(event -> setCaret())); } /** * Creates the "Example" group. */ @Override void createExampleGroup() { super.createExampleGroup(); /* Create a group for the canvas widget */ canvasGroup = new Group(exampleGroup, SWT.NONE); canvasGroup.setLayout(new GridLayout()); canvasGroup.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true)); canvasGroup.setText("Canvas"); } /** * Creates the "Example" widgets. */ @Override void createExampleWidgets() { /* Compute the widget style */ int style = getDefaultStyle(); if (horizontalButton.getSelection()) style |= SWT.H_SCROLL; if (verticalButton.getSelection()) style |= SWT.V_SCROLL; if (borderButton.getSelection()) style |= SWT.BORDER; if (noBackgroundButton.getSelection()) style |= SWT.NO_BACKGROUND; if (noFocusButton.getSelection()) style |= SWT.NO_FOCUS; if (noMergePaintsButton.getSelection()) style |= SWT.NO_MERGE_PAINTS; if (noRedrawResizeButton.getSelection()) style |= SWT.NO_REDRAW_RESIZE; if (doubleBufferedButton.getSelection()) style |= SWT.DOUBLE_BUFFERED; /* Create the example widgets */ paintCount = 0; cx = 0; cy = 0; canvas = new Canvas(canvasGroup, style); canvas.addPaintListener(e -> { paintCount++; GC gc = e.gc; if (fillDamageButton.getSelection()) { Color color = e.display.getSystemColor(colors[paintCount % colors.length]); gc.setBackground(color); gc.fillRectangle(e.x, e.y, e.width, e.height); } Point size = canvas.getSize(); gc.drawArc(cx + 1, cy + 1, size.x - 2, size.y - 2, 0, 360); gc.drawRectangle(cx + (size.x - 10) / 2, cy + (size.y - 10) / 2, 10, 10); Point extent = gc.textExtent(canvasString); gc.drawString(canvasString, cx + (size.x - extent.x) / 2, cy - extent.y + (size.y - 10) / 2, true); }); canvas.addControlListener(ControlListener.controlResizedAdapter(e -> { Point size = canvas.getSize(); maxX = size.x * 3 / 2; maxY = size.y * 3 / 2; resizeScrollBars(); })); ScrollBar bar = canvas.getHorizontalBar(); if (bar != null) { hookListeners(bar); bar.addSelectionListener(widgetSelectedAdapter(event -> scrollHorizontal((ScrollBar) event.widget))); } bar = canvas.getVerticalBar(); if (bar != null) { hookListeners(bar); bar.addSelectionListener(widgetSelectedAdapter(event -> scrollVertical((ScrollBar) event.widget))); } } /** * Creates the "Style" group. */ @Override void createStyleGroup() { super.createStyleGroup(); /* Create the extra widgets */ horizontalButton = new Button(styleGroup, SWT.CHECK); horizontalButton.setText("SWT.H_SCROLL"); horizontalButton.setSelection(true); verticalButton = new Button(styleGroup, SWT.CHECK); verticalButton.setText("SWT.V_SCROLL"); verticalButton.setSelection(true); borderButton = new Button(styleGroup, SWT.CHECK); borderButton.setText("SWT.BORDER"); noBackgroundButton = new Button(styleGroup, SWT.CHECK); noBackgroundButton.setText("SWT.NO_BACKGROUND"); noFocusButton = new Button(styleGroup, SWT.CHECK); noFocusButton.setText("SWT.NO_FOCUS"); noMergePaintsButton = new Button(styleGroup, SWT.CHECK); noMergePaintsButton.setText("SWT.NO_MERGE_PAINTS"); noRedrawResizeButton = new Button(styleGroup, SWT.CHECK); noRedrawResizeButton.setText("SWT.NO_REDRAW_RESIZE"); doubleBufferedButton = new Button(styleGroup, SWT.CHECK); doubleBufferedButton.setText("SWT.DOUBLE_BUFFERED"); } /** * Creates the tab folder page. * * @param tabFolder org.eclipse.swt.widgets.TabFolder * @return the new page for the tab folder */ @Override Composite createTabFolderPage(TabFolder tabFolder) { super.createTabFolderPage(tabFolder); /* * Add a resize listener to the tabFolderPage so that * if the user types into the example widget to change * its preferred size, and then resizes the shell, we * recalculate the preferred size correctly. */ tabFolderPage.addControlListener(ControlListener.controlResizedAdapter(e -> setExampleWidgetSize())); return tabFolderPage; } /** * Gets the "Example" widget children. */ @Override Widget[] getExampleWidgets() { return new Widget[] { canvas }; } /** * Returns a list of set/get API method names (without the set/get prefix) * that can be used to set/get values in the example control(s). */ @Override String[] getMethodNames() { return new String[] { "ToolTipText" }; } /** * Gets the text for the tab folder item. */ @Override String getTabText() { return "Canvas"; } /** * Resizes the maximum and thumb of both scrollbars. */ void resizeScrollBars() { Rectangle clientArea = canvas.getClientArea(); ScrollBar bar = canvas.getHorizontalBar(); if (bar != null) { bar.setMaximum(maxX); bar.setThumb(clientArea.width); bar.setPageIncrement(clientArea.width); } bar = canvas.getVerticalBar(); if (bar != null) { bar.setMaximum(maxY); bar.setThumb(clientArea.height); bar.setPageIncrement(clientArea.height); } } /** * Scrolls the canvas horizontally. * * @param scrollBar */ void scrollHorizontal(ScrollBar scrollBar) { Rectangle bounds = canvas.getClientArea(); int x = -scrollBar.getSelection(); if (x + maxX < bounds.width) { x = bounds.width - maxX; } canvas.scroll(x, cy, cx, cy, maxX, maxY, false); cx = x; } /** * Scrolls the canvas vertically. * * @param scrollBar */ void scrollVertical(ScrollBar scrollBar) { Rectangle bounds = canvas.getClientArea(); int y = -scrollBar.getSelection(); if (y + maxY < bounds.height) { y = bounds.height - maxY; } canvas.scroll(cx, y, cx, cy, maxX, maxY, false); cy = y; } /** * Sets or clears the caret in the "Example" widget. */ void setCaret() { Caret oldCaret = canvas.getCaret(); if (caretButton.getSelection()) { Caret newCaret = new Caret(canvas, SWT.NONE); Font font = canvas.getFont(); newCaret.setFont(font); GC gc = new GC(canvas); gc.setFont(font); newCaret.setBounds(1, 1, 1, gc.getFontMetrics().getHeight()); gc.dispose(); canvas.setCaret(newCaret); canvas.setFocus(); } else { canvas.setCaret(null); } if (oldCaret != null) oldCaret.dispose(); } /** * Sets the state of the "Example" widgets. */ @Override void setExampleWidgetState() { super.setExampleWidgetState(); horizontalButton.setSelection((canvas.getStyle() & SWT.H_SCROLL) != 0); verticalButton.setSelection((canvas.getStyle() & SWT.V_SCROLL) != 0); borderButton.setSelection((canvas.getStyle() & SWT.BORDER) != 0); noBackgroundButton.setSelection((canvas.getStyle() & SWT.NO_BACKGROUND) != 0); noFocusButton.setSelection((canvas.getStyle() & SWT.NO_FOCUS) != 0); noMergePaintsButton.setSelection((canvas.getStyle() & SWT.NO_MERGE_PAINTS) != 0); noRedrawResizeButton.setSelection((canvas.getStyle() & SWT.NO_REDRAW_RESIZE) != 0); doubleBufferedButton.setSelection((canvas.getStyle() & SWT.DOUBLE_BUFFERED) != 0); if (!instance.startup) setCaret(); } }