whytofly
/
qt6-bb10
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

tablet example: enable high-DPI rendering 

Change-Id: Ie03867208902fdc9cf794de16d7249c8994351f4
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
bb10
Shawn Rutledge 2017-05-03 14:09:17 +02:00
parent 92a07c6289
commit 8eccd1b0ad
2 changed files with 25 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
examples/widgets/doc/src/tablet.qdoc
View File

@ -206,8 +206,7 @@
\snippet widgets/tablet/tabletcanvas.cpp 0
In the constructor we initialize our class variables. We need
to draw the background of our pixmap, as the default is gray.
In the constructor we initialize most of our class variables.
Here is the implementation of \c saveImage():
@ -247,7 +246,15 @@
\snippet widgets/tablet/tabletcanvas.cpp 4
We simply draw the pixmap to the top left of the widget.
The first time Qt calls paintEvent(), m_pixmap is default-constructed, so
QPixmap::isNull() returns \c true. Now that we know which screen we will be
rendering to, we can create a pixmap with the appropriate resolution.
The size of the pixmap with which we fill the window depends on the screen
resolution, as the example does not support zoom; and it may be that one
screen is \l {High DPI Displays}{high DPI} while another is not. We need to
draw the background too, as the default is gray.
After that, we simply draw the pixmap to the top left of the widget.
Here is the implementation of \c paintPixmap():

28
examples/widgets/widgets/tablet/tabletcanvas.cpp
View File

@ -65,21 +65,9 @@ TabletCanvas::TabletCanvas()
, m_deviceDown(false)
{
resize(500, 500);
initPixmap();
setAutoFillBackground(true);
setAttribute(Qt::WA_TabletTracking);
}
void TabletCanvas::initPixmap()
{
QPixmap newPixmap = QPixmap(width(), height());
newPixmap.fill(Qt::white);
QPainter painter(&newPixmap);
if (!m_pixmap.isNull())
painter.drawPixmap(0, 0, m_pixmap);
painter.end();
m_pixmap = newPixmap;
}
//! [0]
//! [1]
@ -105,7 +93,6 @@ bool TabletCanvas::loadImage(const QString &file)
//! [3]
void TabletCanvas::tabletEvent(QTabletEvent *event)
{
switch (event->type()) {
case QEvent::TabletPress:
if (!m_deviceDown) {
@ -140,8 +127,23 @@ void TabletCanvas::tabletEvent(QTabletEvent *event)
//! [3]
//! [4]
void TabletCanvas::initPixmap()
{
qreal dpr = devicePixelRatioF();
QPixmap newPixmap = QPixmap(width() * dpr, height() * dpr);
newPixmap.setDevicePixelRatio(dpr);
newPixmap.fill(Qt::white);
QPainter painter(&newPixmap);
if (!m_pixmap.isNull())
painter.drawPixmap(0, 0, m_pixmap);
painter.end();
m_pixmap = newPixmap;
}
void TabletCanvas::paintEvent(QPaintEvent *)
{
if (m_pixmap.isNull())
initPixmap();
QPainter painter(this);
painter.drawPixmap(0, 0, m_pixmap);
}