Ja, als Funktion auslagern habe ich auch schon überlegt.
Ich kapier aber noch nicht so ganz was die da machen.
Z.B.
// Adafruit_GFX has a handy method getTextBounds() to determine the boundary box for a text for the actual font
int16_t tbx, tby; uint16_t tbw, tbh; // boundary box window
display.getTextBounds(text, 0, 0, &tbx, &tby, &tbw, &tbh); // it works for 0, 0, fortunately (negative tby!)
oder
display.setFullWindow();
display.firstPage();
do
{
display.fillScreen(GxEPD_WHITE);
display.setCursor(x, y);
display.print(HelloWorld);
}
while (display.nextPage());
//Serial.println("helloWorld done");
Eigentlich habe die ja extra für Typen wie mich ein Erklärungscode geschrieben:
void helloWorldForDummies()
{
//Serial.println("helloWorld");
const char text[] = "Hello World!";
// most e-papers have width < height (portrait) as native orientation, especially the small ones
// in GxEPD2 rotation 0 is used for native orientation (most TFT libraries use 0 fix for portrait orientation)
// set rotation to 1 (rotate right 90 degrees) to have enough space on small displays (landscape)
display.setRotation(1);
// select a suitable font in Adafruit_GFX
display.setFont(&FreeMonoBold9pt7b);
// on e-papers black on white is more pleasant to read
display.setTextColor(GxEPD_BLACK);
// Adafruit_GFX has a handy method getTextBounds() to determine the boundary box for a text for the actual font
int16_t tbx, tby; uint16_t tbw, tbh; // boundary box window
display.getTextBounds(text, 0, 0, &tbx, &tby, &tbw, &tbh); // it works for 0, 0, fortunately (negative tby!)
// center the boundary box of the text
uint16_t x = (display.width() - tbw) / 2;
uint16_t y = (display.height() + tbh) / 2; // y is base line!
// full window mode is the initial mode, set it anyway
display.setFullWindow();
// here we use paged drawing, even if the processor has enough RAM for full buffer
// so this can be used with any supported processor board.
// the cost in code overhead and execution time penalty is marginal
// tell the graphics class to use paged drawing mode
display.firstPage();
do
{
// this part of code is executed multiple times, as many as needed,
// in case of full buffer it is executed once
// IMPORTANT: each iteration needs to draw the same, to avoid strange effects
// use a copy of values that might change, don't read e.g. from analog or pins in the loop!
display.fillScreen(GxEPD_WHITE); // set the background to white (fill the buffer with value for white)
display.setCursor(x, y); // set the postition to start printing text
display.print(text); // print some text
// end of part executed multiple times
}
// tell the graphics class to transfer the buffer content (page) to the controller buffer
// the graphics class will command the controller to refresh to the screen when the last page has been transferred
// returns true if more pages need be drawn and transferred
// returns false if the last page has been transferred and the screen refreshed for panels without fast partial update
// returns false for panels with fast partial update when the controller buffer has been written once more, to make the differential buffers equal
// (for full buffered with fast partial update the (full) buffer is just transferred again, and false returned)
while (display.nextPage());
//Serial.println("helloWorld done");
}
Aber ehrlich gesagt habe ich ihn noch nicht ganz kapiert. 
Bin ich jetzt schlimmer als ein Dummie....? 