I'm working on my first patch to the Qt framework which I hope to get into Qt 6.9. It's currently rejected, but there's a chance I can fix issues and get it approved.
There's an important question that I don't know the answer to: Does anyone see modifying vertex counts in a QSGGeometryNode while animating as valuable? If no one else wants this, I'm wasting reviewers' time and this contribution is worth little to the community. The patch enables resizing geometries in a QSGGeometry node without invalidating existing geometries. Normally, resizing to add vertices requires updating all existing geometry vertices as well as the new ones. Resizing to remove vertices requires updating the remaining vertices. Suppose a geometry node has 1000 vertices and 10 more are added. Currently, resizing the geometry invalidates the entire buffer and all previous 1000 vertices must be updated as well as the 10 new vertices. With this change, it is only necessary to update the 10 new vertices. That's 100X less work. If getting data to populate vertices is slow, like when scaling data, the need to update every vertex after calling allocate() can have an impact on performance, i.e., dropped frames. My review was rightfully rejected. I believe this is a valuable change but am I the only one who will use this? I have a second question. No reviewer commented on this so I don't know the answer: In a patch review, is it okay to touch documentation on functions that are not modified? Specifically, I want to change vertexCount()'s documentation <https://doc.qt.io/qt-5/qsggeometry.html#vertexCount>to read: "Returns the number of vertices that can be rendered, or if indices are used, it returns the number of vertices that can be accessed through indices." The description should change because it no longer returns the capacity of the buffer -- the capacity may be much higher. Mentioning *indices* is out-of-scope, but IMO sorely needed for this function. It may help others, or me in 6 months if I finally find a use case for indexed drawing. /Stan
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