Scalar bar is not visible with GLES context
When VTK is compiled for GLES contexts (ex: webassembly), the scalar bar actor shows values with text but doesn't display the scalar bar itself.
The developer console shows the following error:
SelectionTest.js:1360 ERROR: In vtkShaderProgram.cxx, line 454
SelectionTest.js:1360 vtkShaderProgram (0x1fec88): ERROR: 0:79: 'gl_PrimitiveID' : undeclared identifier
SelectionTest.js:1360 ERROR: 0:79: '+' : wrong operand types - no operation '+' exists that takes a left-hand operand of type 'const highp float' and a right operand of type 'uniform mediump int' (or there is no acceptable conversion)
SelectionTest.js:1360 ERROR: 0:79: 'texelFetch' : no matching overloaded function found
SelectionTest.js:1360 ERROR: 0:79: '=' : dimension mismatch
SelectionTest.js:1360 ERROR: 0:79: 'assign' : cannot convert from 'const mediump float' to 'out highp 4-component vector of float'