From 6a991f9cce9da6057c4a053e52e5956284805eea Mon Sep 17 00:00:00 2001 From: Shawn Rutledge Date: Mon, 27 Jul 2015 12:02:06 +0200 Subject: Tablet example: smoother, rotation stylus, better airbrush MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The drawing is antialiased and with rounded caps and joins. Rotation stylus acts like a felt marker. Airbrush sprays a radial gradient of color, and its alpha can depend on the tangential pressure if so chosen. Task-number: QTBUG-46694 Change-Id: I4fb16eb621707e3c56a75aa302dd0d3bf418a745 Reviewed-by: Laszlo Agocs Reviewed-by: Topi Reiniö --- examples/widgets/doc/src/tablet.qdoc | 24 ++--- examples/widgets/widgets/tablet/mainwindow.cpp | 11 ++- examples/widgets/widgets/tablet/mainwindow.h | 1 + examples/widgets/widgets/tablet/tabletcanvas.cpp | 107 +++++++++++------------ examples/widgets/widgets/tablet/tabletcanvas.h | 8 +- 5 files changed, 77 insertions(+), 74 deletions(-) (limited to 'examples') diff --git a/examples/widgets/doc/src/tablet.qdoc b/examples/widgets/doc/src/tablet.qdoc index 1ab2917b7e..bc03d46332 100644 --- a/examples/widgets/doc/src/tablet.qdoc +++ b/examples/widgets/doc/src/tablet.qdoc @@ -259,24 +259,18 @@ \snippet widgets/tablet/tabletcanvas.cpp 5 - In this function we draw on the pixmap based on the movement of the - device. If the device used on the tablet is a stylus we want to draw a - line between the positions of the stylus recorded in \c polyLine. We - also assume that this is a reasonable handling of any unknown device, - but update the statusbar with a warning so that the user can see that - for his tablet he might have to implement special handling. - If it is an airbrush we want to draw a circle of points with a - point density based on the tangential pressure, which is the position - of the finger wheel on the airbrush. We use the Qt::BrushStyle to - draw the points as it has styles that draw points with different - density; we select the style based on the tangential pressure in - \c brushPattern(). + In this function we draw on the pixmap based on the movement of the device. + If the device used on the tablet is a stylus, we want to draw a line from + the last-known position to the current position. We also assume that this + is a reasonable handling of any unknown device, but update the status bar + with a warning. If it is an airbrush, we want to draw a circle filled with + a soft gradient, whose density can depend on various event parameters. + By default it depends on the tangential pressure, which is the position of + the finger wheel on the airbrush. If it is a rotation stylus, we simulate + a felt marker by drawing trapezoidal strokes. \snippet widgets/tablet/tabletcanvas.cpp 6 - We return a brush style with a point density that increases with - the tangential pressure. - In \c updateBrush() we set the pen and brush used for drawing to match \c alphaChannelType, \c lineWidthType, \c colorSaturationType, and \c myColor. We will examine the code to diff --git a/examples/widgets/widgets/tablet/mainwindow.cpp b/examples/widgets/widgets/tablet/mainwindow.cpp index aed84c50df..5e84f5b6a2 100644 --- a/examples/widgets/widgets/tablet/mainwindow.cpp +++ b/examples/widgets/widgets/tablet/mainwindow.cpp @@ -52,7 +52,7 @@ MainWindow::MainWindow(TabletCanvas *canvas) myCanvas->setColor(Qt::red); myCanvas->setLineWidthType(TabletCanvas::LineWidthPressure); - myCanvas->setAlphaChannelType(TabletCanvas::NoAlpha); + myCanvas->setAlphaChannelType(TabletCanvas::AlphaTangentialPressure); myCanvas->setColorSaturationType(TabletCanvas::NoSaturation); setWindowTitle(tr("Tablet Example")); @@ -75,6 +75,8 @@ void MainWindow::alphaActionTriggered(QAction *action) { if (action == alphaChannelPressureAction) { myCanvas->setAlphaChannelType(TabletCanvas::AlphaPressure); + } else if (action == alphaChannelTangentialPressureAction) { + myCanvas->setAlphaChannelType(TabletCanvas::AlphaTangentialPressure); } else if (action == alphaChannelTiltAction) { myCanvas->setAlphaChannelType(TabletCanvas::AlphaTilt); } else { @@ -157,15 +159,19 @@ void MainWindow::createActions() alphaChannelPressureAction = new QAction(tr("&Pressure"), this); alphaChannelPressureAction->setCheckable(true); + alphaChannelTangentialPressureAction = new QAction(tr("T&angential Pressure"), this); + alphaChannelTangentialPressureAction->setCheckable(true); + alphaChannelTangentialPressureAction->setChecked(true); + alphaChannelTiltAction = new QAction(tr("&Tilt"), this); alphaChannelTiltAction->setCheckable(true); noAlphaChannelAction = new QAction(tr("No Alpha Channel"), this); noAlphaChannelAction->setCheckable(true); - noAlphaChannelAction->setChecked(true); alphaChannelGroup = new QActionGroup(this); alphaChannelGroup->addAction(alphaChannelPressureAction); + alphaChannelGroup->addAction(alphaChannelTangentialPressureAction); alphaChannelGroup->addAction(alphaChannelTiltAction); alphaChannelGroup->addAction(noAlphaChannelAction); connect(alphaChannelGroup, SIGNAL(triggered(QAction*)), @@ -259,6 +265,7 @@ void MainWindow::createMenus() alphaChannelMenu = tabletMenu->addMenu(tr("&Alpha Channel")); alphaChannelMenu->addAction(alphaChannelPressureAction); + alphaChannelMenu->addAction(alphaChannelTangentialPressureAction); alphaChannelMenu->addAction(alphaChannelTiltAction); alphaChannelMenu->addAction(noAlphaChannelAction); diff --git a/examples/widgets/widgets/tablet/mainwindow.h b/examples/widgets/widgets/tablet/mainwindow.h index 5e77ea1acf..c6ac2e6026 100644 --- a/examples/widgets/widgets/tablet/mainwindow.h +++ b/examples/widgets/widgets/tablet/mainwindow.h @@ -79,6 +79,7 @@ private: QActionGroup *alphaChannelGroup; QAction *alphaChannelPressureAction; + QAction *alphaChannelTangentialPressureAction; QAction *alphaChannelTiltAction; QAction *noAlphaChannelAction; diff --git a/examples/widgets/widgets/tablet/tabletcanvas.cpp b/examples/widgets/widgets/tablet/tabletcanvas.cpp index 20d6291292..bf98a6d621 100644 --- a/examples/widgets/widgets/tablet/tabletcanvas.cpp +++ b/examples/widgets/widgets/tablet/tabletcanvas.cpp @@ -47,14 +47,13 @@ TabletCanvas::TabletCanvas() { resize(500, 500); - myBrush = QBrush(); - myPen = QPen(); + myColor = Qt::red; + myBrush = QBrush(myColor); + myPen = QPen(myBrush, 1.0, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin); initPixmap(); setAutoFillBackground(true); deviceDown = false; - myColor = Qt::red; - myTabletDevice = QTabletEvent::Stylus; - alphaChannelType = NoAlpha; + alphaChannelType = AlphaTangentialPressure; colorSaturationType = NoSaturation; lineWidthType = LineWidthPressure; } @@ -99,24 +98,23 @@ void TabletCanvas::tabletEvent(QTabletEvent *event) case QEvent::TabletPress: if (!deviceDown) { deviceDown = true; - polyLine[0] = polyLine[1] = polyLine[2] = event->pos(); + lastPoint.pos = event->posF(); + lastPoint.rotation = event->rotation(); } break; - case QEvent::TabletRelease: - if (deviceDown) - deviceDown = false; - break; case QEvent::TabletMove: - polyLine[2] = polyLine[1]; - polyLine[1] = polyLine[0]; - polyLine[0] = event->pos(); - if (deviceDown) { updateBrush(event); QPainter painter(&pixmap); paintPixmap(painter, event); + lastPoint.pos = event->posF(); + lastPoint.rotation = event->rotation(); } break; + case QEvent::TabletRelease: + if (deviceDown && event->buttons() == Qt::NoButton) + deviceDown = false; + break; default: break; } @@ -135,23 +133,44 @@ void TabletCanvas::paintEvent(QPaintEvent *) //! [5] void TabletCanvas::paintPixmap(QPainter &painter, QTabletEvent *event) { - QPoint brushAdjust(10, 10); + painter.setRenderHint(QPainter::Antialiasing); - switch (myTabletDevice) { + switch (event->device()) { +//! [6] case QTabletEvent::Airbrush: - myBrush.setColor(myColor); - myBrush.setStyle(brushPattern(event->pressure())); - painter.setPen(Qt::NoPen); - painter.setBrush(myBrush); - - for (int i = 0; i < 3; ++i) { - painter.drawEllipse(QRect(polyLine[i] - brushAdjust, - polyLine[i] + brushAdjust)); + { + painter.setPen(Qt::NoPen); + QRadialGradient grad(lastPoint.pos, myPen.widthF() * 10.0); + QColor color = myBrush.color(); + color.setAlphaF(color.alphaF() * 0.25); + grad.setColorAt(0, myBrush.color()); + grad.setColorAt(0.5, Qt::transparent); + painter.setBrush(grad); + qreal radius = grad.radius(); + painter.drawEllipse(event->posF(), radius, radius); } break; + case QTabletEvent::RotationStylus: + { + myBrush.setStyle(Qt::SolidPattern); + painter.setPen(Qt::NoPen); + painter.setBrush(myBrush); + QPolygonF poly; + qreal halfWidth = myPen.widthF(); + QPointF brushAdjust(qSin(qDegreesToRadians(lastPoint.rotation)) * halfWidth, + qCos(qDegreesToRadians(lastPoint.rotation)) * halfWidth); + poly << lastPoint.pos + brushAdjust; + poly << lastPoint.pos - brushAdjust; + brushAdjust = QPointF(qSin(qDegreesToRadians(event->rotation())) * halfWidth, + qCos(qDegreesToRadians(event->rotation())) * halfWidth); + poly << event->posF() - brushAdjust; + poly << event->posF() + brushAdjust; + painter.drawConvexPolygon(poly); + } + break; +//! [6] case QTabletEvent::Puck: case QTabletEvent::FourDMouse: - case QTabletEvent::RotationStylus: { const QString error(tr("This input device is not supported by the example.")); #ifndef QT_NO_STATUSTIP @@ -174,40 +193,13 @@ void TabletCanvas::paintPixmap(QPainter &painter, QTabletEvent *event) } // FALL-THROUGH case QTabletEvent::Stylus: - painter.setBrush(myBrush); painter.setPen(myPen); - painter.drawLine(polyLine[1], event->pos()); + painter.drawLine(lastPoint.pos, event->posF()); break; } } //! [5] -//! [6] -Qt::BrushStyle TabletCanvas::brushPattern(qreal value) -{ - int pattern = int((value) * 100.0) % 7; - - switch (pattern) { - case 0: - return Qt::SolidPattern; - case 1: - return Qt::Dense1Pattern; - case 2: - return Qt::Dense2Pattern; - case 3: - return Qt::Dense3Pattern; - case 4: - return Qt::Dense4Pattern; - case 5: - return Qt::Dense5Pattern; - case 6: - return Qt::Dense6Pattern; - default: - return Qt::Dense7Pattern; - } -} -//! [6] - //! [7] void TabletCanvas::updateBrush(QTabletEvent *event) { @@ -220,7 +212,13 @@ void TabletCanvas::updateBrush(QTabletEvent *event) switch (alphaChannelType) { case AlphaPressure: - myColor.setAlpha(int(event->pressure() * 255.0)); + myColor.setAlphaF(event->pressure()); + break; + case AlphaTangentialPressure: + if (event->device() == QTabletEvent::Airbrush) + myColor.setAlphaF(qMax(0.01, (event->tangentialPressure() + 1.0) / 2.0)); + else + myColor.setAlpha(255); break; case AlphaTilt: myColor.setAlpha(maximum(abs(vValue - 127), abs(hValue - 127))); @@ -271,5 +269,4 @@ void TabletCanvas::updateBrush(QTabletEvent *event) void TabletCanvas::resizeEvent(QResizeEvent *) { initPixmap(); - polyLine[0] = polyLine[1] = polyLine[2] = QPoint(); } diff --git a/examples/widgets/widgets/tablet/tabletcanvas.h b/examples/widgets/widgets/tablet/tabletcanvas.h index 873f3a7ab0..06090a9052 100644 --- a/examples/widgets/widgets/tablet/tabletcanvas.h +++ b/examples/widgets/widgets/tablet/tabletcanvas.h @@ -61,7 +61,7 @@ class TabletCanvas : public QWidget Q_OBJECT public: - enum AlphaChannelType { AlphaPressure, AlphaTilt, NoAlpha }; + enum AlphaChannelType { AlphaPressure, AlphaTangentialPressure, AlphaTilt, NoAlpha }; enum ColorSaturationType { SaturationVTilt, SaturationHTilt, SaturationPressure, NoSaturation }; enum LineWidthType { LineWidthPressure, LineWidthTilt, NoLineWidth }; @@ -107,7 +107,11 @@ private: QBrush myBrush; QPen myPen; bool deviceDown; - QPoint polyLine[3]; + + struct Point { + QPointF pos; + qreal rotation; + } lastPoint; }; //! 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