Visualization of quadrature functions

CHANGELOG

@@ -25,6 +25,16 @@ Version 4.2.1 (development)
 
 - Added a compilation parameter for the default font size.
 
+- Added visualization of quadrature data (QuadratureFunction in MFEM). Both
+  loading from file, with the new command line argument '-q', or from a socket
+  stream, with the keyword 'quadrature', are supported. Three visualization
+  options are provided: piece-wise constants on a refined mesh (LOR), L2 field
+  with DOFs collocated (interpolation), or projection to discontinuous elements
+  (L2 projection). Use 'Q' to switch between them. High-order quadrature data is
+  supported only for tensor finite elements with the first two options. With the
+  first option, only the mesh lines of the original mesh are visualized. This
+  feature is also supported for the element-wise cutting plane (cplane=2).
+
 
 Version 4.2 released on May 23, 2022
 ====================================

README.md

@@ -144,6 +144,10 @@ Key commands
 - <kbd>Ctrl</kbd> + <kbd>p</kbd> – Print to a PDF file using `gl2ps`. Other
   vector formats (SVG, EPS) are also possible, but keep in mind that the
   printing takes a while and the generated files are big.
+- <kbd>Q</kbd> – Cycle between representations of the visualized *quadrature data*. The options are:
+  - piece-wise constant refined (LOR)
+  - L2 element dof collocation (interpolation)
+  - L2 element projection (L2 projection)
 - <kbd>q</kbd> – Exit
 
 ## Advanced