Added new arc sector drawing routines (Thanks to steved for the inspiration).

Added demo to match.

2 files changed, 360 insertions, 14 deletions

diff --git a/src/gdisp/gdisp_gdisp.c b/src/gdisp/gdisp_gdisp.c
index 1552cea6..f5675a82 100644
--- a/src/gdisp/gdisp_gdisp.c
+++ b/src/gdisp/gdisp_gdisp.c
@@ -1420,8 +1420,233 @@ void gdispGBlitArea(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, c
 	}
 #endif
 
+#if GDISP_NEED_ARCSECTORS
+	void gdispGDrawArcSectors(GDisplay *g, coord_t x, coord_t y, coord_t radius, uint8_t sectors, color_t color) {
+		coord_t a, b, P;
+
+		MUTEX_ENTER(g);
+
+		// Calculate intermediates
+		a = 1;              // x in many explanations
+		b = radius;         // y in many explanations
+		P = 4 - radius;
+		g->p.color = color;
+
+		// Away we go using Bresenham's circle algorithm
+		// Optimized to prevent double drawing
+		if (sectors & 0x06) { g->p.x = x; g->p.y = y - b; drawpixel_clip(g); }				// Upper upper
+		if (sectors & 0x60) { g->p.x = x; g->p.y = y + b; drawpixel_clip(g); }				// Lower lower
+		if (sectors & 0x81) { g->p.x = x + b; g->p.y = y; drawpixel_clip(g); }				// Right right
+		if (sectors & 0x18) { g->p.x = x - b; g->p.y = y; drawpixel_clip(g); }				// Left left
+
+		do {
+			if (sectors & 0x01) { g->p.x = x + b; g->p.y = y - a; drawpixel_clip(g); }		// Upper right right
+			if (sectors & 0x02) { g->p.x = x + a; g->p.y = y - b; drawpixel_clip(g); }		// Upper upper right
+			if (sectors & 0x04) { g->p.x = x - a; g->p.y = y - b; drawpixel_clip(g); }		// Upper upper left
+			if (sectors & 0x08) { g->p.x = x - b; g->p.y = y - a; drawpixel_clip(g); }		// Upper left  left
+			if (sectors & 0x10) { g->p.x = x - b; g->p.y = y + a; drawpixel_clip(g); }		// Lower left  left
+			if (sectors & 0x20) { g->p.x = x - a; g->p.y = y + b; drawpixel_clip(g); }		// Lower lower left
+			if (sectors & 0x40) { g->p.x = x + a; g->p.y = y + b; drawpixel_clip(g); }		// Lower lower right
+			if (sectors & 0x80) { g->p.x = x + b; g->p.y = y + a; drawpixel_clip(g); }		// Lower right right
+			if (P < 0)
+				P += 3 + 2*a++;
+			else
+				P += 5 + 2*(a++ - b--);
+		} while(a < b);
+
+		if (sectors & 0xC0) { g->p.x = x + a; g->p.y = y + b; drawpixel_clip(g); }			// Lower right
+		if (sectors & 0x03) { g->p.x = x + a; g->p.y = y - b; drawpixel_clip(g); }			// Upper right
+		if (sectors & 0x30) { g->p.x = x - a; g->p.y = y + b; drawpixel_clip(g); }			// Lower left
+		if (sectors & 0x0C) { g->p.x = x - a; g->p.y = y - b; drawpixel_clip(g); }			// Upper left
+
+		autoflush(g);
+		MUTEX_EXIT(g);
+	}
+#endif
+
+#if GDISP_NEED_ARCSECTORS
+	void gdispGFillArcSectors(GDisplay *g, coord_t x, coord_t y, coord_t radius, uint8_t sectors, color_t color) {
+		coord_t a, b, P;
+
+		MUTEX_ENTER(g);
+
+		// Calculate intermediates
+		a = 1;              // x in many explanations
+		b = radius;         // y in many explanations
+		P = 4 - radius;
+		g->p.color = color;
+
+		// Away we go using Bresenham's circle algorithm
+		// Optimized to prevent double drawing
+		if (sectors & 0x06) { g->p.x = x; g->p.y = y - b; drawpixel_clip(g); }					// Upper upper
+		if (sectors & 0x60) { g->p.x = x; g->p.y = y + b; drawpixel_clip(g); }					// Lower lower
+		if (sectors & 0x81) {																	// Center right
+			g->p.y = y; g->p.x = x; g->p.x1 = x + b;
+			if (sectors & 0x18) g->p.x -= b;													// Left right
+			hline_clip(g);
+		} else if (sectors & 0x18) {															// Left center
+			g->p.x = x - b; g->p.x1 = x; g->p.y = y;
+			hline_clip(g);
+		}
+
+		do {
+			// Top half
+			switch(sectors & 0x0F) {
+			case 0x01:
+				g->p.y = y - a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x02:
+				g->p.y = y - b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x03:
+				g->p.y = y - b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x04:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				break;
+			case 0x05:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y - a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x06:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x07:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x08:
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				break;
+			case 0x09:
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0A:
+				g->p.y = y - b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x0B:
+				g->p.y = y - b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0C:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x; hline_clip(g);
+				break;
+			case 0x0D:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x; hline_clip(g);
+				g->p.y = y - a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0E:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x0F:
+				g->p.y = y - b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y - a; g->p.x = x - b; g->p.x1 = x + b; hline_clip(g);
+				break;
+			}
+
+			// Bottom half
+			switch((sectors & 0xF0)>>4) {
+			case 0x01:
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				break;
+			case 0x02:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				break;
+			case 0x03:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x; hline_clip(g);
+				break;
+			case 0x04:
+				g->p.y = y + b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x05:
+				g->p.y = y + b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x06:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x07:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x + a; hline_clip(g);
+				break;
+			case 0x08:
+				g->p.y = y + a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x09:
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0A:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y + a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0B:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x; hline_clip(g);
+				g->p.y = y + a; g->p.x = x + a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0C:
+				g->p.y = y + b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0D:
+				g->p.y = y + b; g->p.x = x; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x - a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0E:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - a; g->p.x1 = x + b; hline_clip(g);
+				break;
+			case 0x0F:
+				g->p.y = y + b; g->p.x = x - a; g->p.x1 = x + a; hline_clip(g);
+				g->p.y = y + a; g->p.x = x - b; g->p.x1 = x + b; hline_clip(g);
+				break;
+			}
+
+			if (P < 0)
+				P += 3 + 2*a++;
+			else
+				P += 5 + 2*(a++ - b--);
+		} while(a < b);
+
+		// Top half
+		if (sectors & 0x02)			{ g->p.y = y - a; g->p.x = x; g->p.x1 = x + a; hline_clip(g); }
+		else if (sectors & 0x01)	{ g->p.y = y - a; g->p.x = x + a; drawpixel_clip(g); }
+		if (sectors & 0x04)			{ g->p.y = y - a; g->p.x = x - a; g->p.x1 = x; hline_clip(g); }
+		else if (sectors & 0x08)	{ g->p.y = y - a; g->p.x = x - a; drawpixel_clip(g); }
+
+		// Bottom half
+		if (sectors & 0x40)			{ g->p.y = y + a; g->p.x = x; g->p.x1 = x + a; hline_clip(g); }
+		else if (sectors & 0x80)	{ g->p.y = y + a; g->p.x = x + a; drawpixel_clip(g); }
+		if (sectors & 0x20)			{ g->p.y = y + a; g->p.x = x - a; g->p.x1 = x; hline_clip(g); }
+		else if (sectors & 0x10)	{ g->p.y = y + a; g->p.x = x - a; drawpixel_clip(g); }
+
+		autoflush(g);
+		MUTEX_EXIT(g);
+	}
+#endif
+
 #if GDISP_NEED_ARC
-	#if !GMISC_NEED_FIXEDTRIG && !GMISC_NEED_FASTTRIG
+	#if (!GMISC_NEED_FIXEDTRIG && !GMISC_NEED_FASTTRIG) || !GFX_USE_GMISC
 		#include <math.h>
 	#endif
 
@@ -2102,27 +2327,34 @@ void gdispGBlitArea(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, c
 		autoflush(g);
 		MUTEX_EXIT(g);
 	}
-
 #endif
 
-#if GDISP_NEED_ARC
+#if GDISP_NEED_ARC || GDISP_NEED_ARCSECTORS
 	void gdispGDrawRoundedBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, coord_t radius, color_t color) {
 		if (2*radius > cx || 2*radius > cy) {
 			gdispGDrawBox(g, x, y, cx, cy, color);
 			return;
 		}
-		gdispGDrawArc(g, x+radius, y+radius, radius, 90, 180, color);
+
+		#if GDISP_NEED_ARCSECTORS
+			gdispGFillArcSectors(g, x+radius, y+radius, radius, 0x0C, color);
+			gdispGFillArcSectors(g, x+cx-1-radius, y+radius, radius, 0x03, color);
+			gdispGFillArcSectors(g, x+cx-1-radius, y+cy-1-radius, radius, 0xC0, color);
+			gdispGFillArcSectors(g, x+radius, y+cy-1-radius, radius, 0x30, color);
+		#else
+			gdispGDrawArc(g, x+radius, y+radius, radius, 90, 180, color);
+			gdispGDrawArc(g, x+cx-1-radius, y+radius, radius, 0, 90, color);
+			gdispGDrawArc(g, x+cx-1-radius, y+cy-1-radius, radius, 270, 360, color);
+			gdispGDrawArc(g, x+radius, y+cy-1-radius, radius, 180, 270, color);
+		#endif
 		gdispGDrawLine(g, x+radius+1, y, x+cx-2-radius, y, color);
-		gdispGDrawArc(g, x+cx-1-radius, y+radius, radius, 0, 90, color);
 		gdispGDrawLine(g, x+cx-1, y+radius+1, x+cx-1, y+cy-2-radius, color);
-		gdispGDrawArc(g, x+cx-1-radius, y+cy-1-radius, radius, 270, 360, color);
 		gdispGDrawLine(g, x+radius+1, y+cy-1, x+cx-2-radius, y+cy-1, color);
-		gdispGDrawArc(g, x+radius, y+cy-1-radius, radius, 180, 270, color);
 		gdispGDrawLine(g, x, y+radius+1, x, y+cy-2-radius, color);
 	}
 #endif
 
-#if GDISP_NEED_ARC
+#if GDISP_NEED_ARC || GDISP_NEED_ARCSECTORS
 	void gdispGFillRoundedBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, coord_t radius, color_t color) {
 		coord_t radius2;
 
@@ -2131,12 +2363,19 @@ void gdispGBlitArea(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, c
 			gdispGFillArea(g, x, y, cx, cy, color);
 			return;
 		}
-		gdispGFillArc(g, x+radius, y+radius, radius, 90, 180, color);
+		#if GDISP_NEED_ARCSECTORS
+			gdispGFillArcSectors(g, x+radius, y+radius, radius, 0x0C, color);
+			gdispGFillArcSectors(g, x+cx-1-radius, y+radius, radius, 0x03, color);
+			gdispGFillArcSectors(g, x+cx-1-radius, y+cy-1-radius, radius, 0xC0, color);
+			gdispGFillArcSectors(g, x+radius, y+cy-1-radius, radius, 0x30, color);
+		#else
+			gdispGFillArc(g, x+radius, y+radius, radius, 90, 180, color);
+			gdispGFillArc(g, x+cx-1-radius, y+radius, radius, 0, 90, color);
+			gdispGFillArc(g, x+cx-1-radius, y+cy-1-radius, radius, 270, 360, color);
+			gdispGFillArc(g, x+radius, y+cy-1-radius, radius, 180, 270, color);
+		#endif
 		gdispGFillArea(g, x+radius+1, y, cx-radius2, radius, color);
-		gdispGFillArc(g, x+cx-1-radius, y+radius, radius, 0, 90, color);
-		gdispGFillArc(g, x+cx-1-radius, y+cy-1-radius, radius, 270, 360, color);
 		gdispGFillArea(g, x+radius+1, y+cy-radius, cx-radius2, radius, color);
-		gdispGFillArc(g, x+radius, y+cy-1-radius, radius, 180, 270, color);
 		gdispGFillArea(g, x, y+radius, cx, cy-radius2, color);
 	}
 #endif
diff --git a/src/gdisp/sys_defs.h b/src/gdisp/sys_defs.h
index 6ebfe8b5..e5580e90 100644
--- a/src/gdisp/sys_defs.h
+++ b/src/gdisp/sys_defs.h
@@ -430,6 +430,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Start a streaming operation.
 	 * @details Stream data to a window on the display sequentially and very fast.
+	 * @pre		GDISP_NEED_STREAMING must be TRUE in your gfxconf.h
 	 * @note	While streaming is in operation - no other calls to GDISP functions
 	 * 			can be made (with the exception of @p gdispBlendColor() and streaming
 	 * 			functions). If a call is made (eg in a multi-threaded application) the other
@@ -456,6 +457,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Send pixel data to the stream.
 	 * @details Write a pixel to the next position in the streamed area and increment the position
+	 * @pre		GDISP_NEED_STREAMING must be TRUE in your gfxconf.h
 	 * @pre		@p gdispStreamStart() has been called.
 	 * @note	If the gdispStreamStart() has not been called (or failed due to clipping), the
 	 * 			data provided here is simply thrown away.
@@ -471,6 +473,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Finish the current streaming operation.
 	 * @details	Completes the current streaming operation and allows other GDISP calls to operate again.
+	 * @pre		GDISP_NEED_STREAMING must be TRUE in your gfxconf.h
 	 * @pre		@p gdispStreamStart() has been called.
 	 * @note	If the gdispStreamStart() has not been called (or failed due to clipping), this
 	 * 			call is simply ignored.
@@ -488,6 +491,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_CLIP || defined(__DOXYGEN__)
 	/**
 	 * @brief   Clip all drawing to the defined area.
+	 * @pre		GDISP_NEED_CLIP must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The start position
@@ -504,6 +508,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_CIRCLE || defined(__DOXYGEN__)
 	/**
 	 * @brief   Draw a circle.
+	 * @pre		GDISP_NEED_CIRCLE must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The center of the circle
@@ -517,6 +522,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a filled circle.
+	 * @pre		GDISP_NEED_CIRCLE must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The center of the circle
@@ -534,6 +540,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_ELLIPSE || defined(__DOXYGEN__)
 	/**
 	 * @brief   Draw an ellipse.
+	 * @pre		GDISP_NEED_ELLIPSE must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The center of the ellipse
@@ -547,6 +554,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a filled ellipse.
+	 * @pre		GDISP_NEED_ELLIPSE must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The center of the ellipse
@@ -560,10 +568,70 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #endif
 
 /* Arc Functions */
+#if GDISP_NEED_ARCSECTORS || defined(__DOXYGEN__)
+	/**
+	 * @brief	Draw a selection of 45 degree arcs of a circle
+	 * @pre		GDISP_NEED_ARCSECTORS must be TRUE in your gfxconf.h
+	 *
+	 * @param[in] g 		The display to use
+	 * @param[in] x,y		The center of the circle
+	 * @param[in] radius	The radius of the circle
+	 * @param[in] sectors	Bits determine which sectors are drawn.
+	 * 						Bits go anti-clockwise from the 0 degree mark (y = 0, x is positive), as follows:
+	 *  						bit 0 - upper right right		  -----
+	 *  						bit 1 - upper upper right		 /2   1\
+	 *  						bit 2 - upper upper left		/3     0\
+	 *  						bit 3 - upper left  left		\4     7/
+	 *  						bit 4 - lower left  left		 \5   6/
+	 *  						bit 5 - lower lower left		  -----
+	 *  						bit 6 - lower lower right
+	 *  						bit 7 - lower left  left
+	 * @param[in] color		The color to use
+	 *
+	 * @note	This is a more limited versions of the general arc drawing routine. It
+	 * 			doesn't require trig libraries or tables or floating point and is smaller in code size.
+	 * 			There is probably little point in including both this and the general
+	 * 			arc routine as the general arc routine can do everything this can do.
+	 *
+	 * @api
+	 */
+	void gdispGDrawArcSectors(GDisplay *g, coord_t x, coord_t y, coord_t radius, uint8_t sectors, color_t color);
+	#define gdispDrawArcSectors(x,y,r,s,c)						gdispGDrawArcSectors(GDISP,x,y,r,s,c)
+
+	/**
+	 * @brief	Fill a selection of 45 degree arcs of a circle
+	 * @pre		GDISP_NEED_ARCSECTORS must be TRUE in your gfxconf.h
+	 *
+	 * @param[in] g 		The display to use
+	 * @param[in] x,y		The center of the circle
+	 * @param[in] radius	The radius of the circle
+	 * @param[in] sectors	Bits determine which sectors are drawn.
+	 * 						Bits go anti-clockwise from the 0 degree mark (y = 0, x is positive), as follows:
+	 *  						bit 0 - upper right right		  -----
+	 *  						bit 1 - upper upper right		 /2   1\
+	 *  						bit 2 - upper upper left		/3     0\
+	 *  						bit 3 - upper left  left		\4     7/
+	 *  						bit 4 - lower left  left		 \5   6/
+	 *  						bit 5 - lower lower left		  -----
+	 *  						bit 6 - lower lower right
+	 *  						bit 7 - lower left  left
+	 * @param[in] color		The color to use
+	 *
+	 * @note	This is a more limited versions of the general arc filling routine. It
+	 * 			doesn't require trig libraries or tables or floating point and is smaller in code size.
+	 * 			There is probably little point in including both this and the general
+	 * 			arc routine as the general arc routine can do everything this can do.
+	 *
+	 * @api
+	 */
+	void gdispGFillArcSectors(GDisplay *g, coord_t x, coord_t y, coord_t radius, uint8_t sectors, color_t color);
+	#define gdispFillArcSectors(x,y,r,s,c)						gdispGFillArcSectors(GDISP,x,y,r,s,c)
+#endif
 
 #if GDISP_NEED_ARC || defined(__DOXYGEN__)
 	/*
 	 * @brief	Draw an arc.
+	 * @pre		GDISP_NEED_ARC must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x0,y0		The center point
@@ -572,6 +640,15 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	 * @param[in] end		The end angle (0 to 360)
 	 * @param[in] color		The color of the arc
 	 *
+	 * @note		If you are just doing 45 degree angles consider using @p gdispDrawArcSectors() instead.
+	 * @note		This routine requires trig support. It can either come from your C runtime library
+	 * 				cos() and sin() which requires floating point support (and is slow), or you can define GFX_USE_GMISC
+	 * 				and either GMISC_NEED_FIXEDTRIG or GMISC_NEED_FASTTRIG.
+	 * 				GMISC_NEED_FASTTRIG uses table based floating point trig operations.
+	 * 				GMISC_NEED_FIXEDTRIG uses fixed point integer trig operations.
+	 * 				Note accuracy on both the table based options are more than adequate for the one degree
+	 * 				resolution provided by these arc routines. Both are much faster than your C runtime library.
+	 *
 	 * @api
 	 */
 	void gdispGDrawArc(GDisplay *g, coord_t x, coord_t y, coord_t radius, coord_t startangle, coord_t endangle, color_t color);
@@ -579,7 +656,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/*
 	 * @brief	Draw a filled arc.
-	 * @note				Not very efficient currently - does lots of overdrawing
+	 * @pre		GDISP_NEED_ARC must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x0,y0		The center point
@@ -588,6 +665,15 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	 * @param[in] end		The end angle (0 to 360)
 	 * @param[in] color		The color of the arc
 	 *
+	 * @note		If you are just doing 45 degree angles consider using @p gdispFillArcSectors() instead.
+	 * @note		This routine requires trig support. It can either come from your C runtime library
+	 * 				cos() and sin() which requires floating point support (and is slow), or you can define GFX_USE_GMISC
+	 * 				and either GMISC_NEED_FIXEDTRIG or GMISC_NEED_FASTTRIG.
+	 * 				GMISC_NEED_FASTTRIG uses table based floating point trig operations.
+	 * 				GMISC_NEED_FIXEDTRIG uses fixed point integer trig operations.
+	 * 				Note accuracy on both the table based options are more than adequate for the one degree
+	 * 				resolution provided by these arc routines. Both are much faster than your C runtime library.
+	 *
 	 * @api
 	 */
 	void gdispGFillArc(GDisplay *g, coord_t x, coord_t y, coord_t radius, coord_t startangle, coord_t endangle, color_t color);
@@ -600,6 +686,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Get the color of a pixel.
 	 * @return  The color of the pixel.
+	 * @pre		GDISP_NEED_PIXELREAD must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The position of the pixel
@@ -636,6 +723,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_CONTROL || defined(__DOXYGEN__)
 	/**
 	 * @brief   Control hardware specific parts of the display. eg powermodes, backlight etc
+	 * @pre		GDISP_NEED_CONTROL must be TRUE in your gfxconf.h
 	 * @note    Depending on the hardware implementation this function may not
 	 *          support some codes. They will be ignored.
 	 *
@@ -654,6 +742,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_QUERY || defined(__DOXYGEN__)
 	/**
 	 * @brief   Query a property of the display.
+	 * @pre		GDISP_NEED_QUERY must be TRUE in your gfxconf.h
 	 * @note    The result must be typecast to the correct type.
 	 * @note    An unsupported query will return (void *)-1.
 	 *
@@ -669,6 +758,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_CONVEX_POLYGON || defined(__DOXYGEN__)
 	/**
 	 * @brief   Draw an enclosed polygon (convex, non-convex or complex).
+	 * @pre		GDISP_NEED_CONVEX_POLYGON must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] tx, ty	Transform all points in pntarray by tx, ty
@@ -684,6 +774,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Fill a convex polygon
 	 * @details Doesn't handle non-convex or complex polygons.
+	 * @pre		GDISP_NEED_CONVEX_POLYGON must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] tx, ty	Transform all points in pntarray by tx, ty
@@ -708,6 +799,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	 * @brief   Draw a line with a specified thickness
 	 * @details The line thickness is specified in pixels. The line ends can
 	 *          be selected to be either flat or round.
+	 * @pre		GDISP_NEED_CONVEX_POLYGON must be TRUE in your gfxconf.h
 	 * @note	Uses gdispGFillConvexPoly() internally to perform the drawing.
 	 *
 	 * @param[in] g			The display to use
@@ -728,6 +820,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 #if GDISP_NEED_TEXT || defined(__DOXYGEN__)
 	/**
 	 * @brief   Draw a text character.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The position for the text
@@ -742,6 +835,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a text character with a filled background.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The position for the text
@@ -757,6 +851,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a text string.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The position for the text
@@ -771,6 +866,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a text string.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The position for the text
@@ -786,6 +882,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a text string vertically centered within the specified box.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The position for the text (need to define top-right or base-line - check code)
@@ -802,6 +899,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a text string vertically centered within the specified box. The box background is filled with the specified background color.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 * @note    The entire box is filled
 	 *
 	 * @param[in] g 		The display to use
@@ -821,6 +919,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Get a metric of a font.
 	 * @return  The metric requested in pixels.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] font    The font to test
 	 * @param[in] metric  The metric to measure
@@ -832,6 +931,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Get the pixel width of a character.
 	 * @return  The width of the character in pixels. Does not include any between character padding.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] c       The character to draw
 	 * @param[in] font    The font to use
@@ -843,6 +943,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief   Get the pixel width of a string.
 	 * @return  The width of the string in pixels.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] str     The string to measure
 	 * @param[in] font    The font to use
@@ -855,6 +956,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	 * @brief	Find a font and return it.
 	 * @details	The supplied name is matched against the font name. A '*' will replace 0 or more characters.
 	 * @return	Returns a font or NULL if no matching font could be found.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] name		The font name to find.
 	 *
@@ -866,6 +968,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief	Release a font after use.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] font		The font to release.
 	 *
@@ -877,6 +980,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	 * @brief	Make a scaled copy of an existing font.
 	 * @details	Allocates memory for new font metadata using gfxAlloc, remember to close font after use!
 	 * @return	A new font or NULL if out of memory.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] font	The base font to use.
 	 * @param[in] scale_x	The scale factor in horizontal direction.
@@ -887,6 +991,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 	/**
 	 * @brief	Get the name of the specified font.
 	 * @returns	The name of the font.
+	 * @pre		GDISP_NEED_TEXT must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] font		The font to get the name for.
 	 *
@@ -897,9 +1002,10 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 /* Extra Arc Functions */
 
-#if GDISP_NEED_ARC || defined(__DOXYGEN__)
+#if GDISP_NEED_ARC || GDISP_NEED_ARCSECTORS || defined(__DOXYGEN__)
 	/**
 	 * @brief   Draw a rectangular box with rounded corners
+	 * @pre		GDISP_NEED_ARC or GDISP_NEED_ARCSECTORS must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The start position
@@ -914,6 +1020,7 @@ void gdispGDrawBox(GDisplay *g, coord_t x, coord_t y, coord_t cx, coord_t cy, co
 
 	/**
 	 * @brief   Draw a filled rectangular box with rounded corners
+	 * @pre		GDISP_NEED_ARC or GDISP_NEED_ARCSECTORS must be TRUE in your gfxconf.h
 	 *
 	 * @param[in] g 		The display to use
 	 * @param[in] x,y		The start position