Support triangles

Code provided by @mtsem.

Fixes #329

Author: marcelstoer

README.md

@@ -1,4 +1,4 @@
-[![Build Status](https://travis-ci.org/ThingPulse/esp8266-oled-ssd1306.svg?branch=master)](https://travis-ci.org/ThingPulse/esp8266-oled-ssd1306)
+[![Build Status](https://travis-ci.com/ThingPulse/esp8266-oled-ssd1306.svg?branch=master)](https://travis-ci.com/ThingPulse/esp8266-oled-ssd1306)
 
 # ThingPulse OLED SSD1306 (ESP8266/ESP32/Mbed-OS)
 
@@ -9,7 +9,7 @@ This library drives the OLED display included in the [ThingPulse IoT starter kit
 
 [![ThingPulse ESP8266 WeatherStation Classic Kit](https://github.com/ThingPulse/esp8266-weather-station/blob/master/resources/ThingPulse-ESP8266-Weather-Station.jpeg?raw=true)](https://thingpulse.com/product/esp8266-iot-electronics-starter-kit-weatherstation-planespotter-worldclock/)
 
-You can either download this library as a zip file and unpack it to your Arduino/libraries folder or find it in the Arduino library manager under "ESP8266 and ESP32 Oled Driver for SSD1306 display". For mbed-os a copy of the files are available as an mbed-os library. 
+You can either download this library as a zip file and unpack it to your Arduino/libraries folder or find it in the Arduino library manager under "ESP8266 and ESP32 Oled Driver for SSD1306 display". For mbed-os a copy of the files are available as an mbed-os library.
 
 It is also available as a [PlatformIO library](https://platformio.org/lib/show/2978/ESP8266%20and%20ESP32%20OLED%20driver%20for%20SSD1306%20displays/examples). Just execute the following command:
 ```
@@ -71,7 +71,7 @@ The library supports different protocols to access the OLED display. Currently t
 ### I2C with Wire.h
 
 ```C++
-#include <Wire.h>  
+#include <Wire.h>
 #include "SSD1306Wire.h"
 
 // for 128x64 displays:
@@ -87,7 +87,7 @@ SSD1306Wire display(0x3c, SDA, SCL);  // ADDRESS, SDA, SCL
 
 for a SH1106:
 ```C++
-#include <Wire.h>  
+#include <Wire.h>
 #include "SH1106Wire.h"
 
 SH1106Wire display(0x3c, SDA, SCL);  // ADDRESS, SDA, SCL
@@ -205,6 +205,12 @@ void drawCircle(int16_t x, int16_t y, int16_t radius);
 // Fill circle
 void fillCircle(int16_t x, int16_t y, int16_t radius);
 
+// Draw an empty triangle i.e. only the outline
+void drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2);
+
+// Draw a solid triangle i.e. filled
+void fillTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2);
+
 // Draw a line horizontally
 void drawHorizontalLine(int16_t x, int16_t y, int16_t length);
 

src/OLEDDisplay.cpp

@@ -99,7 +99,7 @@ bool OLEDDisplay::allocateBuffer() {
 bool OLEDDisplay::init() {
 
   BufferOffset = getBufferOffset();
-  
+
   if(!allocateBuffer()) {
     return false;
   }
@@ -304,6 +304,90 @@ void OLEDDisplay::fillCircle(int16_t x0, int16_t y0, int16_t radius) {
 
 }
 
+void OLEDDisplay::drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1,
+                               int16_t x2, int16_t y2) {
+  drawLine(x0, y0, x1, y1);
+  drawLine(x1, y1, x2, y2);
+  drawLine(x2, y2, x0, y0);
+}
+
+void OLEDDisplay::fillTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1,
+                               int16_t x2, int16_t y2) {
+  int16_t a, b, y, last;
+
+  if (y0 > y1) {
+    _swap_int16_t(y0, y1);
+    _swap_int16_t(x0, x1);
+  }
+  if (y1 > y2) {
+    _swap_int16_t(y2, y1);
+    _swap_int16_t(x2, x1);
+  }
+  if (y0 > y1) {
+    _swap_int16_t(y0, y1);
+    _swap_int16_t(x0, x1);
+  }
+
+  if (y0 == y2) {
+    a = b = x0;
+    if (x1 < a) {
+      a = x1;
+    } else if (x1 > b) {
+      b = x1;
+    }
+    if (x2 < a) {
+      a = x2;
+    } else if (x2 > b) {
+      b = x2;
+    }
+    drawHorizontalLine(a, y0, b - a + 1);
+    return;
+  }
+
+  int16_t
+    dx01 = x1 - x0,
+    dy01 = y1 - y0,
+    dx02 = x2 - x0,
+    dy02 = y2 - y0,
+    dx12 = x2 - x1,
+    dy12 = y2 - y1;
+  int32_t
+    sa   = 0,
+    sb   = 0;
+
+  if (y1 == y2) {
+    last = y1; // Include y1 scanline
+  } else {
+    last = y1 - 1; // Skip it
+  }
+
+  for (y = y0; y <= last; y++) {
+    a = x0 + sa / dy01;
+    b = x0 + sb / dy02;
+    sa += dx01;
+    sb += dx02;
+
+    if (a > b) {
+      _swap_int16_t(a, b);
+    }
+    drawHorizontalLine(a, y, b - a + 1);
+  }
+
+  sa = dx12 * (y - y1);
+  sb = dx02 * (y - y0);
+  for (; y <= y2; y++) {
+    a = x1 + sa / dy12;
+    b = x0 + sb / dy02;
+    sa += dx12;
+    sb += dx02;
+
+    if (a > b) {
+      _swap_int16_t(a, b);
+    }
+    drawHorizontalLine(a, y, b - a + 1);
+  }
+}
+
 void OLEDDisplay::drawHorizontalLine(int16_t x, int16_t y, int16_t length) {
   if (y < 0 || y >= this->height()) { return; }
 
@@ -884,7 +968,7 @@ void OLEDDisplay::sendInitCommands(void) {
   sendCommand(SETDISPLAYOFFSET);
   sendCommand(0x00);
   if(geometry == GEOMETRY_64_32)
-    sendCommand(0x00);  
+    sendCommand(0x00);
   else
     sendCommand(SETSTARTLINE);
   sendCommand(CHARGEPUMP);

src/OLEDDisplay.h

@@ -215,6 +215,12 @@ class OLEDDisplay : public Stream {
     // Fill circle
     void fillCircle(int16_t x, int16_t y, int16_t radius);
 
+    // Draw an empty triangle i.e. only the outline
+    void drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2);
+
+    // Draw a solid triangle i.e. filled
+    void fillTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2);
+
     // Draw a line horizontally
     void drawHorizontalLine(int16_t x, int16_t y, int16_t length);
 
@@ -320,7 +326,7 @@ class OLEDDisplay : public Stream {
     // Implement needed function to be compatible with Print class
     size_t write(uint8_t c);
     size_t write(const char* s);
-	
+
     // Implement needed function to be compatible with Stream class
 #ifdef __MBED__
 	int _putc(int c);
@@ -361,7 +367,7 @@ class OLEDDisplay : public Stream {
 	// the header size of the buffer used, e.g. for the SPI command header
   int BufferOffset;
 	virtual int getBufferOffset(void) = 0;
-	
+
     // Send a command to the display (low level function)
     virtual void sendCommand(uint8_t com) {(void)com;};
 
@@ -377,7 +383,7 @@ class OLEDDisplay : public Stream {
     void inline drawInternal(int16_t xMove, int16_t yMove, int16_t width, int16_t height, const uint8_t *data, uint16_t offset, uint16_t bytesInData) __attribute__((always_inline));
 
     void drawStringInternal(int16_t xMove, int16_t yMove, char* text, uint16_t textLength, uint16_t textWidth);
-	
+
 	FontTableLookupFunction fontTableLookupFunction;
 };