From c5ceb31e730b31f003b3b61c1172670e6e549994 Mon Sep 17 00:00:00 2001
From: inmarket <andrewh@inmarket.com.au>
Date: Wed, 25 Sep 2013 17:15:50 +1000
Subject: [PATCH] Update to streaming demo program to only update the needed
 area (results in much faster display on slow devices) Also now demonstrates
 streaming to a non-full screen area.

---
 demos/modules/gdisp/gdisp_streaming/gfxconf.h |  2 +-
 demos/modules/gdisp/gdisp_streaming/main.c    | 61 ++++++++++++-------
 2 files changed, 41 insertions(+), 22 deletions(-)

diff --git a/demos/modules/gdisp/gdisp_streaming/gfxconf.h b/demos/modules/gdisp/gdisp_streaming/gfxconf.h
index 0b5701ba..72bb0618 100644
--- a/demos/modules/gdisp/gdisp_streaming/gfxconf.h
+++ b/demos/modules/gdisp/gdisp_streaming/gfxconf.h
@@ -27,7 +27,7 @@
 #define GDISP_NEED_ARC			FALSE
 #define GDISP_NEED_SCROLL		FALSE
 #define GDISP_NEED_PIXELREAD	FALSE
-#define GDISP_NEED_CONTROL		TRUE
+#define GDISP_NEED_CONTROL		FALSE
 #define GDISP_NEED_MULTITHREAD  FALSE
 #define GDISP_NEED_STREAMING	TRUE
 
diff --git a/demos/modules/gdisp/gdisp_streaming/main.c b/demos/modules/gdisp/gdisp_streaming/main.c
index cc5eb8b3..41b900c3 100644
--- a/demos/modules/gdisp/gdisp_streaming/main.c
+++ b/demos/modules/gdisp/gdisp_streaming/main.c
@@ -40,35 +40,44 @@
 #define WALLCOLOR	HTML2COLOR(0x303030)
 #define BACKCOLOR	HTML2COLOR(0xC0C0C0)
 #define FLOORCOLOR	HTML2COLOR(0x606060)
-#define SHADOW		(255-255*0.2)
+#define SHADOWALPHA		(255-255*0.2)
 
 int main(void) {
-	coord_t		width, height, x, y, i, l, m, n, floor;
+	coord_t		width, height, x, y, radius, ballx, bally, dx, floor;
+	coord_t		minx, miny, maxx, maxy;
+	coord_t		ballcx, ballcy;
 	color_t		colour;
-	float		ii, spin, o, spinspeed, h, f, g;
+	float		ii, spin, dy, spinspeed, h, f, g;
 
 	gfxInit();
-	gdispSetOrientation(GDISP_ROTATE_90);
+	#if GDISP_NEED_CONTROL
+		gdispSetOrientation(GDISP_ROTATE_90);
+	#endif
 
 	width = gdispGetWidth();
 	height = gdispGetHeight();
 
-	i=height/5+height%2+1;
-	ii = 1.0/i;
-	floor=height/5-1;
-	spin=0.0;
-	l=width/2;
-	m=height/4;
-	n=.01*width;
-	o=0.0;
-	spinspeed=0.1;
+	radius=height/5+height%2+1;	// The ball radius
+	ii = 1.0/radius;			// radius as easy math
+	floor=height/5-1;			// floor position
+	spin=0.0;					// current spin angle on the ball
+	spinspeed=0.1;				// current spin speed of the ball
+	ballx=width/2;				// ball x position (relative to the ball center)
+	bally=height/4;				// ball y position (relative to the ball center)
+	dx=.01*width;				// motion in the x axis
+	dy=0.0;						// motion in the y axis
+	ballcx = 12*radius/5;		// ball x diameter including the shadow
+	ballcy = 21*radius/10;		// ball y diameter including the shadow
+
+
+	minx = miny = 0; maxx = width; maxy = height;		// The clipping window for this frame.
 
 	while(1) {
 		// Draw one frame
-		gdispStreamStart(0, 0, width, height);
-		for (y=0; h = (m-y)*ii, y<height; y++) {
-			for (x=0; x < width; x++) {
-				g=(l-x)*ii;
+		gdispStreamStart(minx, miny, maxx-minx, maxy-miny);
+		for (y=miny; h = (bally-y)*ii, y<maxy; y++) {
+			for (x=minx; x < maxx; x++) {
+				g=(ballx-x)*ii;
 				f=-.3*g+.954*h;
 				if (g*g < 1-h*h) {
 					/* The inside of the ball */
@@ -90,17 +99,27 @@ int main(void) {
 
 					// The ball shadow is darker
 					if (g*(g+.4)+h*(h+.1) < 1)
-						colour = gdispBlendColor(colour, Black, SHADOW);
+						colour = gdispBlendColor(colour, Black, SHADOWALPHA);
 				}
 				gdispStreamColor(colour);	/* pixel to the LCD */
 			}
 		}
 		gdispStreamStop();
 
+		// Calculate the new frame size (note this is a drawing optimisation only)
+		minx = ballx - radius; miny = bally - radius;
+		maxx = minx + ballcx; maxy = miny + ballcy;
+		if (dx > 0) maxx += dx; else minx += dx;
+		if (dy > 0) maxy += dy; else miny += dy;
+		if (minx < 0) minx = 0;
+		if (maxx > width) maxx = width;
+		if (miny < 0) miny = 0;
+		if (maxy > height) maxy = height;
+
 		// Motion
 		spin += spinspeed;
-		m += o;
-		o = m > height-1.75*floor ? -.04*height : o+.002*height;
-		n = (l+=n)<i || l>width-i ? spinspeed=-spinspeed,-n : n;
+		ballx += dx; bally += dy;
+		dx = ballx < radius || ballx > width-radius ? spinspeed=-spinspeed,-dx : dx;
+		dy = bally > height-1.75*floor ? -.04*height : dy+.002*height;
 	}
 }