doc clarifications, code alignment with esp32

app/modules/u8g2.c

@@ -12,6 +12,7 @@
 #include "u8g2_fonts.h"
 
 #ifdef ESP_PLATFORM
+// ESP32
 #include "spi_common.h"
 
 #include "sdkconfig.h"
@@ -659,12 +660,14 @@ static int ldisplay_spi( lua_State *L, display_setup_fn_t setup_fn )
   int stack = 0;
 
 #ifndef ESP_PLATFORM
+  // ESP8266
   typedef struct {
     int host;
   } lspi_host_t;
   lspi_host_t host_elem;
   lspi_host_t *host = &host_elem;
 #else
+  // ESP32
   lspi_host_t *host = NULL;
 #endif
   int host_ref = LUA_NOREF;
@@ -680,12 +683,12 @@ static int ldisplay_spi( lua_State *L, display_setup_fn_t setup_fn )
     /* reference host object to avoid automatic gc */
     lua_pushvalue( L, stack );
     host_ref = luaL_ref( L, LUA_REGISTRYINDEX );
-    get_spi_pins = TRUE;
+    get_spi_pins = 1;
   } else if (lua_type( L, stack ) == LUA_TNUMBER) {
     host->host = luaL_checkint( L, stack );
-    get_spi_pins = TRUE;
+    get_spi_pins = 1;
   } else {
-    get_spi_pins = FALSE;
+    get_spi_pins = 0;
     stack--;
   }
 

docs/en/modules/u8g2.md

@@ -3,7 +3,7 @@
 | :----- | :-------------------- | :---------- | :------ |
 | 2017-06-02 | [Oli Kraus](https://github.com/olikraus/u8glib), [Arnim Läuger](https://github.com/devsaurus) | [Arnim Läuger](https://github.com/devsaurus) | [u8g2.c](../../../apps/modules/u8g2.c)|
 
-U8g2 is a graphics library developed at [olikraus/u8g2](https://github.com/olikraus/u8g2) with support for many different displays. It is the successor of [U8glib](https://github.com/olikraus/u8glib) which is not developed any further.
+U8g2 is a graphics library developed at [olikraus/u8g2](https://github.com/olikraus/u8g2) with support for many different displays. It is the successor of [U8glib](https://github.com/olikraus/u8glib) which is not developed any further. Please see [How to port U8g code](https://github.com/olikraus/u8g2/wiki/u8gvsu8g2) for generic porting instructions.
 
 The NodeMCU firmware supports the following displays in I²C and SPI mode:
 
@@ -40,7 +40,7 @@ SPI only:
 - st75256 - jlx172104 and jlx256128 variants
 - uc1701 - dogs102 and mini12864 variants
 
-This integration is based on [v2.19.8](https://github.com/olikraus/U8g2_Arduino/releases/tag/2.19.8).
+This integration uses full "RAM" memory buffer without picture loop and calls u8g2's `begin()` internally when creating a display object. It is based on [v2.19.8](https://github.com/olikraus/U8g2_Arduino/releases/tag/2.19.8).
 
 ## Overview