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annotate XCodeiPhoneOS/Demos/src/touch.c @ 2386:c5cbbba41c65 gsoc2008_iphone

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Touch input demo (multitouch)
author Holmes Futrell <hfutrell@umail.ucsb.edu>
date Fri, 18 Jul 2008 20:52:32 +0000
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1 /*
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2 * touch.c
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3 * written by Holmes Futrell
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4 * use however you want
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5 */
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6
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7 #include "SDL.h"
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8 #include "math.h"
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9 #include "common.h"
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10
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11 #define BRUSH_SIZE 32 /* width and height of the brush */
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12 #define PIXELS_PER_ITERATION 5 /* number of pixels between brush blots when forming a line */
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13
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14 static SDL_TextureID brushID=0; /* texture for the brush */
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15
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16 /*
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17 draws a line from (startx, starty) to (startx + dx, starty + dy)
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18 this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart
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19 */
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20 void drawLine(float startx, float starty, float dx, float dy) {
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21
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22 float distance = sqrt(dx*dx+dy*dy); /* length of line segment (pythagoras) */
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23 int iterations = distance / PIXELS_PER_ITERATION + 1; /* number of brush sprites to draw for the line */
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24 float dx_prime = dx / iterations; /* x-shift per iteration */
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25 float dy_prime = dy / iterations; /* y-shift per iteration */
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26 SDL_Rect dstRect; /* rect to draw brush sprite into */
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27
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28 dstRect.w = BRUSH_SIZE;
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29 dstRect.h = BRUSH_SIZE;
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30
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31 /* setup x and y for the location of the first sprite */
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32 float x = startx - BRUSH_SIZE / 2.0f;
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33 float y = starty - BRUSH_SIZE / 2.0f;
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34
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35 int i;
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36 /* draw a series of blots to form the line */
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37 for (i=0; i<iterations; i++) {
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38 dstRect.x = x;
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39 dstRect.y = y;
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40 /* shift x and y for next sprite location */
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41 x += dx_prime;
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42 y += dy_prime;
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43 /* draw brush blot */
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44 SDL_RenderCopy(brushID, NULL, &dstRect);
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45 }
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46 }
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47
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48 /*
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49 loads the brush texture
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50 */
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51 void initializeTexture() {
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52 SDL_Surface *bmp_surface;
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53 bmp_surface = SDL_LoadBMP("stroke.bmp");
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54 if (bmp_surface == NULL) {
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55 fatalError("could not load stroke.bmp");
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56 }
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57 brushID = SDL_CreateTextureFromSurface(SDL_PIXELFORMAT_ABGR8888, bmp_surface);
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58 SDL_FreeSurface(bmp_surface);
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59 if (brushID == 0) {
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60 fatalError("could not create brush texture");
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61 }
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62 /* additive blending -- laying strokes on top of eachother makes them brighter */
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63 SDL_SetTextureBlendMode(brushID, SDL_TEXTUREBLENDMODE_ADD);
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64 /* set brush color (red) */
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65 SDL_SetTextureColorMod(brushID, 255, 100, 100);
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66 }
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67
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68 int main(int argc, char *argv[]) {
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69
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70 int x, y, dx, dy; /* mouse location */
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71 Uint8 state; /* mouse (touch) state */
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72 SDL_Event event;
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73 SDL_WindowID windowID; /* main window */
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74 int done; /* does user want to quit? */
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75
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76 /* initialize SDL */
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77 if (SDL_Init(SDL_INIT_VIDEO) < 0) {
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78 fatalError("Could not initialize SDL");
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79 }
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80
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81 /* create main window and renderer */
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82 windowID = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,\
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83 SDL_WINDOW_OPENGL|SDL_WINDOW_SHOWN|SDL_WINDOW_BORDERLESS);
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84 SDL_CreateRenderer(windowID, 0, 0);
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85
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86 /*load brush texture */
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87 initializeTexture();
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88
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89 /* fill canvass initially with all black */
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90 SDL_RenderFill(0, 0, 0, 255, NULL);
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91 SDL_RenderPresent();
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92
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93 done = 0;
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94 while (!done && SDL_WaitEvent(&event)) {
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95 switch (event.type) {
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96 case SDL_QUIT:
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97 done = 1;
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98 break;
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99 case SDL_MOUSEMOTION:
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100 SDL_SelectMouse(event.motion.which); /* select 'mouse' (touch) that moved */
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101 state = SDL_GetMouseState(&x, &y); /* get its location */
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102 SDL_GetRelativeMouseState(&dx, &dy); /* find how much the mouse moved */
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103 if (state & SDL_BUTTON_LMASK) { /* is the mouse (touch) down? */
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104 drawLine(x - dx, y - dy, dx, dy); /* draw line segment */
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105 SDL_RenderPresent();
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106 }
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107 break;
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108 }
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109 }
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110
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111 /* cleanup */
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112 SDL_DestroyTexture(brushID);
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113 SDL_Quit();
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114
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115 return 0;
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116 }