For your first question, I refer you to the Nextion Instruction Set #GUI Designing Commands
- Text Components and Picture Components are usually placed by the Nextion Editor at design time
- the .x and .y attributes for their placement becomes static and fixed at runtime.
- The xpic, pic, picq commands will place pictures and the xstr command will place text at runtime
- when using these gui designing commands, there is no component attributes
- changing their location dynamically at runtime will be the result of crafty coding techniques.
For your second question, Arabic letters are possible, but limited
- the font generator can produce Arabic letters when the project is set to iso-8859-6
- If the font is less than desired, you may need to use the ZI Font Editor v -0.08
- the zi font format is limited to 1/2 width of font height and height in multiples of 8.
- there is no character rendering engine for joining letters in this embedded format
- many times for better quality, the wording is statically included in your project via pictures
- your favorite graphics program will assist in creating nicer quality text.
For the final question
- Using the Rx/Tx wires to upload your completed and compiled TFT file
- requires a FOCA or USB to TTL cable, the upload button from inside the Nextion Editor
- The firmware is limited in that the microSD onboard the Nextion has "no real filesystem"
- therefore there is only one TFT file permitted on the Nextion microSD
- If you MCU has a microSD, then your MCU program could include a filesystem
- the specifications for uploading the TFT are https://www.itead.cc/blog/nextion-hmi-upload-protocol
- The IteadLib Arduino library also includes NexUpload coding for this purpose