[vlc-devel] [PATCH 1/2] qt: improve time tooltip for hidpi

[Romain Vimont]

On Thu, May 03, 2018 at 10:49:10AM +0200, Hugo Beauzée-Luyssen wrote:
> Hi,
> 
> On Thu, May 3, 2018, at 10:21 AM, Romain Vimont wrote:
> > The time tooltip (for the seek slider) was pixelated on hidpi screens.
> > 
> > Both the polygon to draw the tooltip and the widget mask had low
> > definition.
> > 
> > Replace QPolygon by QPolygonF to fix the tooltip drawing.
> > 
> > Currently, Qt does not support hidpi masks. Instead, disable the mask,
> > set a translucent background and make the widget transparent for mouse
> > events.
> > 
> 
> Could you clarify the implication of setting WA_TransparentForMouseEvents?

When setting a mask to a widget, it receives mouse events only on its
visible portions: <http://doc.qt.io/qt-5/qwidget.html#setMask>
If you click outside the mask, then the events are generated on the
widget "below" (as if the current widget were not present).

Here, we don't set a custom mask anymore, so the whole rectangle around
the tooltip captures mouse events. Since it is partially over the
seekbar, it prevents to seek correctly (cf video in #20011).

We never need to capture mouse events on the tooltip itself, so we can
make it completely "transparent" so that all mouse events pass through
it.

> 
> Otherwise LGTM
> 
> > It also fixes #20011 as a side effect.
> > ---
> >  modules/gui/qt/util/timetooltip.cpp | 15 +++------------
> >  modules/gui/qt/util/timetooltip.hpp |  2 --
> >  2 files changed, 3 insertions(+), 14 deletions(-)
> > 
> > diff --git a/modules/gui/qt/util/timetooltip.cpp b/modules/gui/qt/util/
> > timetooltip.cpp
> > index 2e7e97d987..1314b520ea 100644
> > --- a/modules/gui/qt/util/timetooltip.cpp
> > +++ b/modules/gui/qt/util/timetooltip.cpp
> > @@ -40,6 +40,8 @@ TimeTooltip::TimeTooltip( QWidget *parent ) :
> >      // Tell Qt that it doesn't need to erase the background before
> >      // a paintEvent occurs. This should save some CPU cycles.
> >      setAttribute( Qt::WA_OpaquePaintEvent );
> > +    setAttribute( Qt::WA_TranslucentBackground );
> > +    setAttribute( Qt::WA_TransparentForMouseEvents );
> >  
> >      // Inherit from the system default font size -5
> >      mFont = QFont( "Verdana", qMax( qApp->font().pointSize() - 5, 7 ) );
> > @@ -91,7 +93,6 @@ void TimeTooltip::adjustPosition()
> >  
> >          resize( size );
> >          buildPath();
> > -        setMask( mMask );
> >      }
> >  }
> >  
> > @@ -105,7 +106,7 @@ void TimeTooltip::buildPath()
> >      mPainterPath.addRect( mBox );
> >  
> >      // Draw the tip
> > -    QPolygon polygon;
> > +    QPolygonF polygon;
> >      polygon << QPoint( qMax( 0, mTipX - 3 ), mBox.height() )
> >              << QPoint( mTipX, mBox.height() + TIP_HEIGHT )
> >              << QPoint( qMin( mTipX + 3, mBox.width() ), mBox.height() );
> > @@ -113,16 +114,6 @@ void TimeTooltip::buildPath()
> >  
> >      // Store the simplified version of the path
> >      mPainterPath = mPainterPath.simplified();
> > -
> > -    // Create the mask used to erase the background
> > -    // Note: this is a binary bitmap (black & white)
> > -    mMask = QBitmap( size() );
> > -    QPainter painter( &mMask );
> > -    painter.fillRect( mMask.rect(), Qt::white );
> > -    painter.setPen( Qt::black );
> > -    painter.setBrush( Qt::black );
> > -    painter.drawPath( mPainterPath );
> > -    painter.end();
> >  }
> >  
> >  void TimeTooltip::setTip( const QPoint& target, const QString& time, 
> > const QString& text )
> > diff --git a/modules/gui/qt/util/timetooltip.hpp b/modules/gui/qt/util/
> > timetooltip.hpp
> > index d239d9984b..e7e57f622a 100644
> > --- a/modules/gui/qt/util/timetooltip.hpp
> > +++ b/modules/gui/qt/util/timetooltip.hpp
> > @@ -25,7 +25,6 @@
> >  #include "qt.hpp"
> >  
> >  #include <QWidget>
> > -#include <QBitmap>
> >  
> >  class QPaintEvent;
> >  class QString;
> > @@ -54,7 +53,6 @@ private:
> >      QFont mFont;
> >      QRect mBox;
> >      QPainterPath mPainterPath;
> > -    QBitmap mMask;
> >      int mTipX;
> >  };
> >  
> > -- 
> > 2.17.0
> > 
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> 
> 
> -- 
>   Hugo Beauzée-Luyssen
>   hugo at beauzee.fr
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