ESP32/components/u8g2/doc/u8g2.txt

U8glib V2: Name and project goals

https://github.com/olikraus/u8g2

U8g2 = Universal 8bit Graphics

[U]niversal: Support for many displays ans development platforms
[8]bit: Initial focus had been 8 bit microcontroller systems
[g]raphics": U8g2 is a graphics library with focus on monochrome graphics displays
[2]: Second generation and successor of u8glib


U8glib V2 Goals

- Support for monochrome LCDs and OLEDs 
- Focus on "monochrome"
- Low memory footprint


U8glib V2: Features and Limitations

- Full Memory Buffer 
- 3-wire-SPI
- Support for Arduino Libraries SPI and TWI

- Unicode Support
  Unicode plane 0 (Basic Multilingual Plane, BMP, glyphs with 0x0000-0xffff) 
  is fully supported.
	Limitation: Unicode planes > 0 are not supported
- UTF-8 Support
  2 and 3 byte sequences are detected and handled.
  Limitation:  
	Behavior for sequences with more than 3 bytes is unknown.

- Large number of fonts

- Compilation speed improved (font data)

- "Text only" sub library: U8x8

- Hardware supported display flip

- Better hardware support: Tested with avr, esp8266 and sam architectures.


u8g vs. u8g2

Major Changes (Code rework required)

- The name of the include file has changed: Use 
    #include "U8g2lib.h"
- The native type for pixel coordinates has changed to u8g2_uint_t
  Use the following line to redefine this at the beginning of your code
    typedef u8g2_uint_t u8g_uint_t;

- Old Arduino IDE 00xx (before 1.00) is not supported any more.
	ARDUINO macro must be >= 100
- begin() must be called (this was optional in U8glib)
- constructor contains name of communicaton interface and 
    also contains the display orientation as first argument
- u8g2.drawStr90 does not exist any more, use
      void u8g2_SetFontDirection(u8g2_t *u8g2, uint8_t dir);
- "P" versions of the string functions are not yet implemented.
	This includes drawStrP(), getStrWidthP(), etc
	Use the print function with the F() macro instead.
- In U8glib font transparency was defined in the .begin() statement. This is now
      handled by setFontMode(). 
- Screen rotation is handled by the constructor in u8g2
	The functions undoRotation, setRot90, setRot180 and setRot270 are
	replaced by the first argument of the constructor
- Screen scaling is not there in u8g2
	It is completly removed, there are no corresponding function in u8g2 
	for undoScale() and setScale2x2().
- setColorEntry(), setHiColor(), setHiColorByRGB(), setRGB: Not supported any more
	(u8g2 focus are monochrome displays, use Ucglib instead)
- getMode(): Is not available any more because there is only one monochrome mode.	
- setDefaultForegroundColor(), setDefaultBackgroundColor() and 
	setDefaultMidColor() are not required any more. These functions do not
	exist in U8g2. Use setDrawColor() instead.
- getFontLineSpacing() and setFontLineSpacingFactor() are not supported any more. 
- getStrPixelWidth() is replaced by getStrWidth() 
- setHardwareBackup() not supported any more. Might be implemented later
- Cursor functions are not available. This includes:
	setCursorFont(), setCursorStyle(), setCursorPos(), setCursorColor(),
	enableCursor(), disableCursor(), drawCursor()
- Virtual screen handling is not supported:
	setVirtualScreenDimension(), addToVirtualScreen()
	
Minor Changes (Code update might be required)

- U8g2 drawTriangle() expects signed arguments (u8glib expects unsigned arguments)
- U8g2 has different font names. Some of the old font names are known to u8g2 and are
	mapped automatically. If the font name is unknown, please choose a different font from the font list.

Change Notes (No code change required)

- sleepOn(), sleepOff(): supported, but better user setPowerSave()
- setColorIndex() and getColorIndex() are renamed to setDrawColor() and 
	getDrawColor(). The old names are still supported.
- getFontAscent() and getFontDescent() are renamed to getAscent() and getDescent()
	The old names are still supported.
- Signal names are renamed in the constructor calls:
	U8glib sck == U8g2 clock
	U8glib mosi == U8g2 data
	U8glib a0 == U8g2 dc
- getHeight() renamed to getDisplayHeight(), old name still exists
- getWidth() renamed to getDisplayWidth(), old name still exists