#include <nano_gfx.h>
#include <ssd1306.h>

// BG driver IC SSD1306, 0.91 inch OLED, 128x32, IIC, white, Vcc 3.3-5V, 
// SSD1306 by Alexey Dynda Arduino library

#define W 128
#define H 32

uint8_t d_buffer[W*H/8];

void setup() {
    ssd1306_128x32_i2c_init();
    // ssd1306_displayOn();
}

void loop() {
    NanoCanvas d_canvas(W,H, d_buffer);
    ssd1306_clearScreen();
    d_canvas.clear();
    d_canvas.drawRect(0,0, W-1, H-1);

    // putPixel is OK:
    for(int x = 0; x<W; x++) {
        int y = x%32;
        d_canvas.putPixel(x,y);
        d_canvas.blt(0,0);
    }

    float x = 10;
    float y = 2;
    float dy = 0.1; // slightly descending line    1 : 0.1   dx:dy ratio

    for (x = 10; x < W; x++) {
        y += dy;
// slightly descending line made from 2x2 filled rects (in slow motion) : NanoCanvas::fillRect is broken
        d_canvas.fillRect( x, y, x + 1, y + 1,0xFF);
// the same but 15 pixels below, fixed fillRect
        xfillRect( x, y+15, x + 1, y+15 + 1,0xFF);
        //d_canvas.putPixel( x, y); // check the proper line

        d_canvas.blt(0,0);
        delay(300);
    }
}

// simple re-defines for @128x32 xfillRect() acting as NanoCanvas member function
#define M_P 7
#define YADDR(y) (((y) >> 3) << M_P)
#define BADDR(b) ((b) << M_P)
uint8_t m_invertByte = 0;
uint8_t m_w = W;
uint8_t m_h = H;
uint8_t *m_bytes = d_buffer;

void xfillRect(uint8_t x1, uint8_t y1, uint8_t x2, uint8_t y2, uint8_t templ)
{
    templ ^= m_invertByte;
    if ((x1 < x2) && (x1 >= m_w)) return;
    if ((y1 < y2) && (y1 >= m_h)) return;
    if (x1 > x2) x1 = 0;
    if (y1 > y2) y1 = 0;
    if (x2 >= m_w) x2 = m_w -1;
    if (y2 >= m_h) y2 = m_h -1;
    uint8_t bank1 = (y1 >> 3);
    uint8_t bank2 = (y2 >> 3);
    for (uint8_t bank = bank1; bank<=bank2; bank++)
    {
        uint8_t mask = 0xFF;
        if (bank1 == bank2)
        {
            //mask = (mask >> ((y1 & 7) + 7 - (y2 & 7))) << (7 - (y2 & 7));     // <---  nano_gfx.cpp line #92
// here comes the fixed mask
            mask = (mask >> ((y1 & 7) + 7 - (y2 & 7))) << (y1 & 7); 
        }
        else if (bank1 == bank)
        {
            mask = (mask << (y1 & 7));
        }
        else if (bank2 == bank)
        {
            mask = (mask >> (7 - (y2 & 7)));
        }
        for (uint8_t x=x1; x<x2; x++)
        {
            m_bytes[BADDR(bank) + x] &= ~mask;
            m_bytes[BADDR(bank) + x] |= (templ & mask);
        }
    }
}