true for techniques that drive the renderer's thick-line
path (currently ThickLinesDrawColorTechnique). The
_draw switch in the base technique uses this to route
through gl.drawArrays(gl.TRIANGLES, …, n × 6) instead of
gl.drawElements(gl.LINES, …), and the vertex shader
derives quad-corner positions from gl_VertexID.
Number of vertices emitted per primitive: 3 for
triangles, 2 for legacy GL_LINES, 6 for the new
thick-line quad expansion, 1 for points. Pulled
directly from the technique's public field.
Compile-time configuration captured from a DrawTechnique — surfaced alongside the shader source so introspection tools (the shaders panel, batch dumps) can tell at a glance which slots use, e.g., the thick-line 6-vertex quad-expansion path vs. the legacy 2-vertex GL_LINES path.