Hello,
it's nice that you port the new LCD to eGUI and initialize it , but also you have to finish this file: d4dlcd_NT7534.c
At least these function MUST be fill up:
static unsigned char D4DLCD_SetWindow_Nt7534(unsigned short x1, unsigned short y1, unsigned short x2, unsigned short y2)
static unsigned char D4DLCD_Send_PixelColor_Nt7534(unsigned short value)
static void D4DLCD_Delay_ms_Nt7534(unsigned short period)
optionally : static unsigned char D4DLCD_SetOrientation_Nt7534(D4DLCD_ORIENTATION new_orientation)
eGUI is most often call the function set window to set logical window on screen and then fill up the window with new colors by function Send Pixel.
An in this functions you should call your low level SPI functions.
Check for example any other eGUI driver.
Petr