To reproduce:

1) run the test program below on Linux with the DISPLAY variable set to the empty string as follows:

DISPLAY= java -Djavafx.verbose=true -Dprism.verbose=true

Prism pipeline init order: es2 sw
Using platform text rasterizer
Using java-based Pisces rasterizer
Using dirty region optimizations
Not using texture mask for primitives
Not forcing power of 2 sizes for textures
Using hardware CLAMP_TO_ZERO mode
Opting in for HiDPI pixel scaling
Prism pipeline name = com.sun.prism.es2.ES2Pipeline
Loading ES2 native library ... prism_es2
Loaded /localhome/kcr/javafx/8u-kcr/jfx/artifacts/sdk/rt/lib/ext/../amd64/libprism_es2.so from relative path
    succeeded.
GLFactory using com.sun.prism.es2.X11GLFactory
Failed in XOpenDisplay
(X) Got class = class com.sun.prism.es2.ES2Pipeline
GraphicsPipeline.createPipeline: error initializing pipeline com.sun.prism.es2.ES2Pipeline
*** Fallback to Prism SW pipeline
Prism pipeline name = com.sun.prism.sw.SWPipeline
Loaded /localhome/kcr/javafx/8u-kcr/jfx/artifacts/sdk/rt/lib/ext/../amd64/libprism_sw.so from relative path
(X) Got class = class com.sun.prism.sw.SWPipeline
Initialized prism pipeline: com.sun.prism.sw.SWPipeline
JavaFX: using com.sun.javafx.tk.quantum.QuantumToolkit

(java:21288): Gtk-WARNING **: cannot open display: