To replace the QGraphicsScene, we need the possibility of
showing and hiding items.
Turns out, the QSG API is completely insane.
Whether an item should be shown is queried by the virtual
function isSubtreeBlocked(), which is supposed to be
overriden by the derived classes.
However, the common nodes for rectangles and pixmaps are
supposed to be created by QQuickWindow, for hardware
optimization. This gives nodes that cannot be derived
from and therefore whether the item is shown or not cannot
be controlled.
There are therefore two distinct cases to consider: The
node is allocated by the code directly or indirectly by
QQuickWindow.
In the latter case, we use a proxy node with the only
purpose of having a "visible" flag and add the obtained
node as a child.
This madness is performed with template trickery to get
unified code.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
It turns out that the wrong base class was used for the chart.
QQuickWidget can only be used on desktop, not in a mobile UI.
Therefore, turn this into a QQuickItem and move the container
QQuickWidget into desktop-only code.
Currently, this code is insane: The chart is rendered onto a
QGraphicsScene (as it was before), which is then rendered into
a QImage, which is transformed into a QSGTexture, which is then
projected onto the device. This is performed on every mouse
move event, since these events in general change the position
of the info-box.
The plan is to slowly convert elements such as the info-box into
QQuickItems. Browsing the QtQuick documentation, this will
not be much fun.
Also note that the rendering currently tears, flickers and has
antialiasing artifacts, most likely owing to integer (QImage)
to floating point (QGraphicsScene, QQuickItem) conversion
problems. The data flow is
QGraphicsScene (float) -> QImage (int) -> QQuickItem (float).
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
