I slightly changed Your library by adding the initialization code of the ILI9331 display that displays the serial port
TFT LCD test
Using Adafruit 2.8" TFT Breakout Board Pinout
TFT size is 240x320
Found ILI9331 LCD driver
Benchmark Time (microseconds)
Screen fill 1717572
Text 366476
Lines 2297612
Horiz/Vert Lines 177060
Rectangles (outline) 142544
Rectangles (filled) 3574852
Circles (filled) 2359488
Circles (outline) 1002960
Triangles (outline) 728860
Triangles (filled) 2385364
Rounded rects are (outline) 409180
Rounded rects are (filled) 4459388
Done!
Don't know how to attach Your modified source code.