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Difference between revisions of "GEF/GEF4/Graphics"

< GEF‎ | GEF4
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(Removed outdated documentation, as initial GEF4 Graphics component was discontinued.)
 
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''Note to non-wiki readers: This documentation is generated from the Eclipse wiki - if you have corrections or additions it would be awesome if you added them in [http://wiki.eclipse.org/GEF/GEF4/Graphics the original wiki page]''.
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The GEF4 Graphics component became obsolete and was replaced by the [[GEF/GEF4/FX|GEF4 FX]] component.
 
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__NOTOC__
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== Introduction ==
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The GEF4 Graphics component provides a level of abstraction over different drawing toolkits (natives). At the moment, SWT and AWT backends are in development. Its goal is to be as complete as possible, i.e. you should have access to all the functionality that you have access to when working directly with one of the natives (SWT or AWT). Of course, this is not always viable. But we aim to provide at least the greatest common divisor of the functionality that is offered by the individual natives and additionally, decent simulations for operations which are not offered by all natives.
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== IGraphics ==
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The heart of the GEF4 Graphics component is the IGraphics interface. Normally, you will be handed over an IGraphics to accomplish your displaying tasks by a surrounding framework, but it can be used stand-alone, too. Thereto, you have to create a specific IGraphics implementation. Let us consider the following SWT example:
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''[Example 001: Simple Graphics]''
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<source lang="java">
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/*******************************************************************************
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* Copyright (c) 2012 itemis AG and others.
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*
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html
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*
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* Contributors:
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*    Matthias Wienand (itemis AG) - initial API and implementation
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*   
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*******************************************************************************/
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package org.eclipse.gef4.graphics.examples.doc;
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import org.eclipse.gef4.geometry.planar.Ellipse;
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import org.eclipse.gef4.geometry.planar.Polygon;
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import org.eclipse.gef4.geometry.planar.Rectangle;
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import org.eclipse.gef4.graphics.IGraphics;
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import org.eclipse.gef4.graphics.LineCap;
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import org.eclipse.gef4.graphics.LineJoin;
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import org.eclipse.gef4.graphics.color.Color;
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import org.eclipse.gef4.graphics.swt.SwtGraphics;
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import org.eclipse.swt.SWT;
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import org.eclipse.swt.events.PaintEvent;
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import org.eclipse.swt.events.PaintListener;
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import org.eclipse.swt.widgets.Display;
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import org.eclipse.swt.widgets.Shell;
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public class Ex001SimpleGraphics implements PaintListener {
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public static void main(String[] args) {
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new Ex001SimpleGraphics("Simple Graphics");
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}
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public Ex001SimpleGraphics(String title) {
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Display display = new Display();
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Shell shell = new Shell(display, SWT.SHELL_TRIM | SWT.DOUBLE_BUFFERED);
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shell.setText(title);
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shell.setBounds(0, 0, 640, 480);
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shell.open();
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shell.addPaintListener(this);
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shell.redraw(); // platform independently triggers a PaintEvent
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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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}
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public void paintControl(PaintEvent e) {
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SwtGraphics g = new SwtGraphics(e.gc);
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renderScene(g);
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g.cleanUp();
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}
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public void renderScene(IGraphics g) {
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// The rendering code goes here. It is independent of the actual
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// IGraphics implementation. Therefore, it is independent of the
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// underlying drawing toolkit, too.
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final Ellipse ellipse = new Ellipse(50, 50, 350, 200);
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final Rectangle rectangle = new Rectangle(100, 160, 125, 220);
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final Polygon triangle = new Polygon(260, 170, 190, 300, 330, 300);
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g.setFill(new Color(255, 0, 0)).setDraw(new Color(128, 0, 0))
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.setDashArray(25, 10);
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g.fill(ellipse).draw(ellipse.getOutline());
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g.setFill(new Color(0, 0, 255)).setLineJoin(LineJoin.ROUND)
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.setLineCap(LineCap.ROUND);
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g.fill(rectangle).draw(rectangle.getOutline());
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g.setFill(new Color(0, 255, 0)).setDraw(new Color(0, 128, 0))
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.setLineJoin(LineJoin.MITER);
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g.fill(triangle).draw(triangle.getOutline());
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}
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}
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</source>
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[[Image:GEF4Graphics-example001.png|Simple GEF4 Graphics example (SWT)]]
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''[Note: You can tryout the examples in your local GEF4 installation. Every example shown in this documentation exists in the org.eclipse.gef4.graphics.examples project under the org.eclipse.gef4.graphics.examples.doc package. The examples are easily found via their identification number which is written atop the source code.]''
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As you can see in this example, the SWTGraphics is an IGraphics implementation. It can be constructed via a SWT GC which is passed-in to the paintControl() event handler. The renderScene() method does not know anything about the actual IGraphics implemention that is used. That's why we do not need to adjust our rendering code when switching to AWT, for example. You may wonder why we have to call the cleanUp() method on the IGraphics. In the case of SWT, this is necessary to fully free the system resources that will be allocated during the rendering process. But let us concentrate on the renderScene() method.
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There are two important things to notice:
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# A set of property groups exists which control the state of the IGraphics. For every drawing operation, a corresponding IGraphicsProperties exists. The properties can be accessed/modified through the IGraphics, such as the fillProperties() calls in the example. The currently active IFillProperties will affect any fill() operation on our IGraphics.
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# The GEF4 Geometry component is integrated into the IGraphics interface, so that we can easily display geometry objects.
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[[Image:GEF4Graphics-IGraphicsProperties.png|IGraphics operations and properties]]
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There are four different drawing operations available on an IGraphics: draw(), fill(), write(), and blit(). Correspondingly, you can get the active drawProperties(), fillProperties(), writeProperties(), and blitProperties() out of an IGraphics. Additionally, the canvasProperties() are used to control global IGraphics settings, such as the current drawing position. Changing the attributes of any of these IGraphicsProperties directly affects the next operation.
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Using the IGraphics#draw(ICurve) and IGraphics#draw(Path) methods, you can display the (contour of the) passed-in geometry object. The operation is affected by the currently active IDrawProperties and ICanvasProperties. For a reference of all available geometry objects, take a look at the GEF4 Geometry component ([[GEF/GEF4/Geometry]]). Analogical, the IGraphics#fill(IShape), IGraphics#fill(IMultiShape), and IGraphics#fill(Path) methods will fill the interior of the passed-in geometry object. The operation is affected by the currently active IFillProperties and ICanvasProperties. Using the IGraphics#blit(Image) method, you can display the passed-in Image object. The operation is affected by the currently active IBlitProperties and ICanvasProperties. Using the IGraphics#write(String) method, you can display the passed-in String object. The operation is affected by the currently active IWriteProperties and ICanvasProperties.
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The currently active IBlitProperties, ICanvasProperties, IDrawProperties, IFillProperties, and IWriteProperties are referred to as the current state of an IGraphics. You can save the current state via the pushState() method. A saved state can be restored later via the popState() method. Using this mechanism has the potential to ease the drawing code by eliminating many accesses to the individual IGraphicsProperties.
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For every IGraphicsProperties you can modify multiple attributes in one method-chain, ...
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=== IBlitProperties ===
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The currently active IBlitProperties do affect every IGraphics#blit(Image) call according to the following setting options:
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* '''InterpolationHint = QUALITY'''<br />When displaying a transformed Image, the InterpolationHint specifies whether to apply a fast and low-quality (InterpolationHint#SPEED) interpolation, or to apply a slower but higher-quality (InterpolationHint#QUALITY) interpolation.
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=== ICanvasProperties ===
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The currently active ICanvasProperties do affect every draw(), fill(), blit(), and write() call according to the following setting options:
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* '''AffineTransform = identity transform'''<br />Transforms the coordinate system before applying any drawing operations.
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* '''ClippingArea = null'''<br />Specifies an IMultiShape which serves as the clipping area for all subsequent drawing operations, i.e. trimming the parts out of the specified IMultiShape.
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=== IDrawProperties ===
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The currently active IDrawProperties do affect every IGraphics#draw(...) call according to the following setting options:
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* '''Color = black'''<br />Specifies the drawing Color.
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* '''DashArray = null'''<br />Specifies a double[] consisting of distance values which alternatingly specify opaque and transparent sections.
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* '''DashBegin = 0'''<br />Specifies the initially assumed covered distance when applying the DashArray.
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* '''LineCap = FLAT'''<br />Specifies how to display unconnected end points of displayed lines. A FLAT LineCap will not extend a drawn line beyond its unconnected end points. A ROUND LineCap will draw a semi-circle at the unconnected end points of a displayed line. A SQUARE LineCap will extend a drawn line beyond its unconnected end points by half the line's width.
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* '''LineJoin = BEVEL'''<br />Specifies how to display the connection point of two displayed lines. A BEVEL LineJoin fills the bent corner triangular. A MITER LineJoin fills the bent corner up to the intersection point of the two outermost lines if its distance to the middle intersection is less than or equal to the MiterLimit. In case of exceeding the MiterLimit, the BEVEL LineJoin is used.
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* '''LineWidth = 1'''<br />Specifies the width of displayed lines.
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* '''MiterLimit = 10'''<br />Restricts the use of the MITER LineJoin, because for low intersection angles, the intersection point may lie far away from the original connection point. Its value is the maximal quotient of the distance between the intersection point and the connection point and the line width.
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* '''Antialiasing = true'''<br />Enables or disables anti-aliasing.
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Example:
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<source lang="java">
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g.drawProperties()
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    .setColor(new Color(128, 128, 0, 255))
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    .setDashArray(30, 10, 5, 10)
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    .setDashBegin(15)
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    .setLineCap(LineCap.ROUND)
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    .setLineWidth(4);
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g.draw(new Line(50, 50, 350, 50));
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</source>
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[[Image:GEF4Graphics-IDrawProperties-example001.png|IDrawProperties example]]
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=== IFillProperties ===
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The currently active IFillProperties do affect every IGraphics#fill(...) call according to the following setting options:
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* '''Color = black'''<br />Specfies the fill Color.
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* '''Antialiasing = true'''<br />Enables or disables anti-aliasing.
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=== IWriteProperties ===
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The currently active IWriteProperties do affect every IGraphics#write(String) call according to the following setting options:
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* '''BackgroundColor = transparent white'''
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* '''ForegroundColor = black'''
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* '''Font = Times New Roman, 14pt'''
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* '''Antialiasing = true'''
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== Extension Mechanisms ==
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[[Category:GEF]]
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Latest revision as of 04:57, 23 May 2015

The GEF4 Graphics component became obsolete and was replaced by the GEF4 FX component.

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