Update drawArc, add new example

TFT_eSPI.cpp

@@ -3895,7 +3895,7 @@ void TFT_eSPI::drawSmoothArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_
 {
   inTransaction = true;
 
-  if (endAngle != startAngle)
+  if (endAngle != startAngle && (startAngle != 0 || endAngle != 360))
   {
     float sx = -sinf(startAngle * deg2rad);
     float sy = +cosf(startAngle * deg2rad);
@@ -3927,17 +3927,9 @@ void TFT_eSPI::drawSmoothArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_
       drawWedgeLine(asx, asy, aex, aey, 0.3, 0.3, fg_color, bg_color);
     }
 
-    if (endAngle > startAngle)
-    {
-      // Draw arc in single sweep
-      drawArc(x, y, r, ir, startAngle, endAngle, fg_color, bg_color);
-    }
-    else
-    {
-      // Arc sweeps through 6 o'clock so draw in two parts
-      drawArc(x, y, r, ir, startAngle, 360, fg_color, bg_color);
-      drawArc(x, y, r, ir, 0, endAngle, fg_color, bg_color);
-    }
+    // Draw arc
+    drawArc(x, y, r, ir, startAngle, endAngle, fg_color, bg_color);
+
   }
   else // Draw full 360
   {
@@ -3949,7 +3941,7 @@ void TFT_eSPI::drawSmoothArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_
 }
 
 /***************************************************************************************
-** Function name:           sqrt_fraction
+** Function name:           sqrt_fraction (private function)
 ** Description:             Smooth graphics support function for alpha derivation
 ***************************************************************************************/
 // Compute the fixed point square root of an integer and
@@ -3983,7 +3975,7 @@ inline uint8_t TFT_eSPI::sqrt_fraction(uint32_t num) {
 ***************************************************************************************/
 // Centre at x,y
 // r = arc outer radius, ir = arc inner radius. Inclusive, so arc thickness = r-ir+1
-// Angles MUST be in range 0-360, end angle MUST be greater than start angle
+// Angles MUST be in range 0-360
 // Arc foreground fg_color anti-aliased with background colour along sides
 // smooth is optional, default is true, smooth=false means no antialiasing
 // Note: Arc ends are not anti-aliased (use drawSmoothArc instead for that)
@@ -3992,10 +3984,15 @@ void TFT_eSPI::drawArc(int32_t x, int32_t y, int32_t r, int32_t ir,
                        uint32_t fg_color, uint32_t bg_color,
                        bool smooth)
 {
-  if (_vpOoB) return;
+  if (endAngle < startAngle) {
+    // Arc sweeps through 6 o'clock so draw in two parts
+    drawArc(x, y, r, ir, startAngle, 360, fg_color, bg_color, smooth);
+    startAngle = 0;
+  }
+
+  if (_vpOoB || startAngle == endAngle) return;
   if (r < ir) transpose(r, ir);  // Required that r > ir
   if (r <= 0 || ir < 0) return;  // Invalid r, ir can be zero (circle sector)
-  if (endAngle < startAngle) transpose(startAngle, endAngle);
   if (startAngle < 0) startAngle = 0;
   if (endAngle > 360) endAngle = 360;
 
@@ -4020,8 +4017,8 @@ void TFT_eSPI::drawArc(int32_t x, int32_t y, int32_t r, int32_t ir,
   //    ---¦---    Arc quadrant index
   //     0 | 3
   // Fixed point U16.16 slope table for arc start/end in each quadrant
-  uint32_t startSlope[4] = {0,  0, 0xFFFFFFFF, 0};
-  uint32_t   endSlope[4] = {0, 0xFFFFFFFF,  0, 0};
+  uint32_t startSlope[4] = {0, 0, 0xFFFFFFFF, 0};
+  uint32_t   endSlope[4] = {0, 0xFFFFFFFF, 0, 0};
 
   // Ensure maximum U16.16 slope of arc ends is ~ 0x8000 0000
   constexpr float minDivisor = 1.0f/0x8000;

TFT_eSPI.h

@@ -530,9 +530,9 @@ class TFT_eSPI : public Print { friend class TFT_eSprite; // Sprite class has ac
            // The start angle may be larger than the end angle. Arcs are always drawn clockwise from the start angle.
   void     drawSmoothArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_t startAngle, int32_t endAngle, uint32_t fg_color, uint32_t bg_color, bool roundEnds = false);
 
-           // As per "drawSmoothArc" except endAngle should be greater than startAngle (angles will be swapped otherwise)
+           // As per "drawSmoothArc" except the ends of the arc are NOT anti-aliased, this facilitates dynamic arc length changes with
+           // arc segments and ensures clean segment joints. 
            // The sides of the arc are anti-aliased by default. If smoothArc is false sides will NOT be anti-aliased
-           // The ends of the arc are NOT anti-aliased, this facilitates dynamic arc length changes with arc segments and ensures clean segment joints
   void     drawArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_t startAngle, int32_t endAngle, uint32_t fg_color, uint32_t bg_color, bool smoothArc = true);
 
            // Draw an anti-aliased filled circle at x, y with radius r

examples/Smooth Graphics/Colour_Wheel/Colour_Wheel.ino

+// Arc drawing example - draw a colour wheel
+
+#include <TFT_eSPI.h>       // Include the graphics library
+TFT_eSPI tft = TFT_eSPI();  // Create object "tft"
+
+uint16_t colors[12];
+
+// -------------------------------------------------------------------------
+// Setup
+// -------------------------------------------------------------------------
+void setup(void) {
+  Serial.begin(115200);
+  tft.init();
+  tft.fillScreen(TFT_BLACK);
+
+  // Create the outer ring colours
+  for (uint8_t c = 0; c < 2; c++) {
+    colors[c + 10] = tft.alphaBlend(128 + c * 127, TFT_RED,     TFT_MAGENTA);
+    colors[c +  8] = tft.alphaBlend(128 + c * 127, TFT_MAGENTA, TFT_BLUE);
+    colors[c +  6] = tft.alphaBlend(128 + c * 127, TFT_BLUE,    TFT_GREEN);
+    colors[c +  4] = tft.alphaBlend(128 + c * 127, TFT_GREEN,   TFT_YELLOW);
+    colors[c +  2] = tft.alphaBlend(128 + c * 127, TFT_YELLOW,  TFT_ORANGE);
+    colors[c +  0] = tft.alphaBlend(128 + c * 127, TFT_ORANGE,  TFT_RED);
+  }
+}
+
+// -------------------------------------------------------------------------
+// Main loop
+// -------------------------------------------------------------------------
+void loop() {
+  uint16_t rDelta = (tft.width() - 1) / 10;
+  uint16_t x = tft.width() / 2;
+  uint16_t y = tft.height() / 2;
+  bool smooth = true;
+
+  // Draw rings as a series of arcs, increasingly blend colour with white towards middle
+  for (uint16_t i = 5; i > 0; i--) {
+    for (uint16_t angle = 0; angle <= 330; angle += 30) {
+      uint16_t radius = i * rDelta;
+      uint16_t wheelColor = tft.alphaBlend((i * 255.0)/5.0, colors[angle / 30], TFT_WHITE);
+      tft.drawArc(x, y, radius, radius - rDelta, angle, angle + 30, wheelColor, TFT_BLACK, smooth);
+    }
+    smooth = false;  // Only outer ring is smooth
+  }
+
+  while (1) delay(100);
+}

examples/Smooth Graphics/Draw_Arc/Draw_Arc.ino

@@ -7,8 +7,6 @@
 // The sides of the arc can optionally be smooth or not. Smooth arcs have
 // a much better appearance, especially at small sizes.
 
-// Start angle for drawArc must be smaller than end angle
-
 #include <TFT_eSPI.h>       // Include the graphics library
 TFT_eSPI tft = TFT_eSPI();  // Create object "tft"
 
@@ -42,7 +40,7 @@ void loop()
 
   // 0 degrees is at 6 o'clock position
   // Arcs are drawn clockwise from start_angle to end_angle
-  // Start angle for drawArc must be smaller than end angle (function will swap them otherwise)
+  // Start angle can be greater than end angle, the arc will then be drawn through 0 degrees
   uint16_t start_angle = random(361); // Start angle must be in range 0 to 360
   uint16_t end_angle   = random(361); // End angle must be in range 0 to 360
 
@@ -50,35 +48,6 @@ void loop()
 
   tft.drawArc(x, y, radius, inner_radius, start_angle, end_angle, fg_color, bg_color, smooth);
 
-  //tft.drawArc(x, y, radius, inner_radius, start_angle, end_angle, fg_color, bg_color); // always smooth sides if parameter is missing
-
-  // The following function allows arcs to be drawn through the 6 o'clock position by drawing in 2 segments if
-  // the start angle is greater than the end angle
-  //drawAnyArc(x, y, radius, inner_radius, start_angle, end_angle, fg_color, bg_color, smooth); // smooth sides if parameter is missing
-
   count++;
   if (count < 30) delay(500); // After 15s draw as fast as possible!
 }
-
-
-// The following function allows arcs to be drawn through the 0 degree position by drawing in 2 segments
-
-// Function prototype with default smooth setting
-void drawAnyArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_t startAngle, int32_t endAngle,
-                uint32_t fg_color, uint32_t bg_color,  bool smooth = true);
-
-void drawAnyArc(int32_t x, int32_t y, int32_t r, int32_t ir, int32_t startAngle, int32_t endAngle,
-                uint32_t fg_color, uint32_t bg_color,  bool smooth)
-{
-  if (endAngle > startAngle)
-  {
-    // Draw arc in single sweep
-    tft.drawArc(x, y, r, ir, startAngle, endAngle, fg_color, bg_color);
-  }
-  else
-  {
-    // Arc sweeps through 6 o'clock so draw in two parts
-    tft.drawArc(x, y, r, ir, startAngle, 360, fg_color, bg_color);
-    tft.drawArc(x, y, r, ir, 0, endAngle, fg_color, bg_color);
-  }
-}