--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Xcode-iPhoneOS/Demos/src/touch.c	Sat Sep 19 07:32:36 2009 +0000
@@ -0,0 +1,125 @@
+/*
+ *	touch.c
+ *	written by Holmes Futrell
+ *	use however you want
+ */
+
+#include "SDL.h"
+#include "math.h"
+#include "common.h"
+
+#define BRUSH_SIZE 32           /* width and height of the brush */
+#define PIXELS_PER_ITERATION 5  /* number of pixels between brush blots when forming a line */
+
+static SDL_TextureID brushID = 0;       /* texture for the brush */
+
+/*
+	draws a line from (startx, starty) to (startx + dx, starty + dy)
+	this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart
+*/
+void
+drawLine(float startx, float starty, float dx, float dy)
+{
+
+    float distance = sqrt(dx * dx + dy * dy);   /* length of line segment (pythagoras) */
+    int iterations = distance / PIXELS_PER_ITERATION + 1;       /* number of brush sprites to draw for the line */
+    float dx_prime = dx / iterations;   /* x-shift per iteration */
+    float dy_prime = dy / iterations;   /* y-shift per iteration */
+    SDL_Rect dstRect;           /* rect to draw brush sprite into */
+
+    dstRect.w = BRUSH_SIZE;
+    dstRect.h = BRUSH_SIZE;
+
+    /* setup x and y for the location of the first sprite */
+    float x = startx - BRUSH_SIZE / 2.0f;
+    float y = starty - BRUSH_SIZE / 2.0f;
+
+    int i;
+    /* draw a series of blots to form the line */
+    for (i = 0; i < iterations; i++) {
+        dstRect.x = x;
+        dstRect.y = y;
+        /* shift x and y for next sprite location */
+        x += dx_prime;
+        y += dy_prime;
+        /* draw brush blot */
+        SDL_RenderCopy(brushID, NULL, &dstRect);
+    }
+}
+
+/*
+	loads the brush texture
+*/
+void
+initializeTexture()
+{
+    SDL_Surface *bmp_surface;
+    bmp_surface = SDL_LoadBMP("stroke.bmp");
+    if (bmp_surface == NULL) {
+        fatalError("could not load stroke.bmp");
+    }
+    brushID =
+        SDL_CreateTextureFromSurface(SDL_PIXELFORMAT_ABGR8888, bmp_surface);
+    SDL_FreeSurface(bmp_surface);
+    if (brushID == 0) {
+        fatalError("could not create brush texture");
+    }
+    /* additive blending -- laying strokes on top of eachother makes them brighter */
+    SDL_SetTextureBlendMode(brushID, SDL_BLENDMODE_ADD);
+    /* set brush color (red) */
+    SDL_SetTextureColorMod(brushID, 255, 100, 100);
+}
+
+int
+main(int argc, char *argv[])
+{
+
+    int x, y, dx, dy;           /* mouse location          */
+    Uint8 state;                /* mouse (touch) state */
+    SDL_Event event;
+    SDL_WindowID windowID;      /* main window */
+    int done;                   /* does user want to quit? */
+
+    /* initialize SDL */
+    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+        fatalError("Could not initialize SDL");
+    }
+
+    /* create main window and renderer */
+    windowID = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,
+                                SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN |
+                                SDL_WINDOW_BORDERLESS);
+    SDL_CreateRenderer(windowID, 0, 0);
+
+    /*load brush texture */
+    initializeTexture();
+
+    /* fill canvass initially with all black */
+    SDL_SetRenderDrawColor(0, 0, 0, 255);
+    SDL_RenderFill(NULL);
+    SDL_RenderPresent();
+
+    done = 0;
+    while (!done && SDL_WaitEvent(&event)) {
+        switch (event.type) {
+        case SDL_QUIT:
+            done = 1;
+            break;
+        case SDL_MOUSEMOTION:
+            SDL_SelectMouse(event.motion.which);        /* select 'mouse' (touch) that moved */
+            state = SDL_GetMouseState(&x, &y);  /* get its location */
+            SDL_GetRelativeMouseState(&dx, &dy);        /* find how much the mouse moved */
+            if (state & SDL_BUTTON_LMASK) {     /* is the mouse (touch) down? */
+                drawLine(x - dx, y - dy, dx, dy);       /* draw line segment */
+                SDL_RenderPresent();
+            }
+            break;
+        }
+    }
+
+    /* cleanup */
+    SDL_DestroyTexture(brushID);
+    SDL_Quit();
+
+    return 0;
+}