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2021-01-20statistics: convert QuartileMarkers to QSGNodesGravatar Berthold Stoeger
Slowly converting the QGraphicsScene items to QSGNodes to avoid full replot of the scene. This adds a new abstraction for line-nodes. Since the render() function here is fundamentally different from the pixmap-nodes we had so far, this has to be made virtual. Also, move the quartile markers to their own source file, since the StatsView source file is quite huge already. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
2021-01-20statistics: add notion of Z-value to chart itemsGravatar Berthold Stoeger
The chart items were drawn in order of creation. To control this, add a notion of Z-value. In contrast to QGraphicsScene, make this a small integer value. To controll order of drawing, a plain QSGNode is created for every possible Z-Value and items are added to these nodes. Thus, items are rendered by Z-value and if the Z-value is equal by order of creation. Likewise split the list of chart-items into Z-values, so that items can be quickly unregistered: The items that will be removed individually will usuall be part of Z-levels with only few items (e.g. legend, infobox). Z-levels with many items (notably the series) will always be fully rebuilt. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
2021-01-20statistics: draw legend as a QSGNodeGravatar Berthold Stoeger
In order not to waste CPU by constantly rerendering the chart, we must use these weird OpenGL QSGNode things. The interface is appallingly low-level and unfriendly. As a first test, try to convert the legend. Create a wrapper class that represents a rectangular item with a texture and that will certainly need some (lots of) optimization. Make sure that all low-level QSG-objects are only accessed in the rendering thread. This means that the wrapper has to maintain a notion of "dirtiness" of the state. I.e. which part of the QSG-objects have to be modified. From the low-level wrapper derive a class that draws a rounded rectangle for every resize. The child class of that must then paint on the rectangle after every resize. That looks all not very fortunate, but it displays a legend and will make it possible to move the legend without and drawing operations, only shifting around an OpenGL surface. The render thread goes through all chart-items and rerenders them if dirty. Currently, on deletion of these items, this list is not reset. I.e. currently it is not supported to remove individual items. Only the full scene can be cleared! Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>