16 /* |
16 /* |
17 draws a line from (startx, starty) to (startx + dx, starty + dy) |
17 draws a line from (startx, starty) to (startx + dx, starty + dy) |
18 this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart |
18 this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart |
19 */ |
19 */ |
20 void |
20 void |
21 drawLine(float startx, float starty, float dx, float dy) |
21 drawLine(SDL_Renderer *renderer, float startx, float starty, float dx, float dy) |
22 { |
22 { |
23 |
23 |
24 float distance = sqrt(dx * dx + dy * dy); /* length of line segment (pythagoras) */ |
24 float distance = sqrt(dx * dx + dy * dy); /* length of line segment (pythagoras) */ |
25 int iterations = distance / PIXELS_PER_ITERATION + 1; /* number of brush sprites to draw for the line */ |
25 int iterations = distance / PIXELS_PER_ITERATION + 1; /* number of brush sprites to draw for the line */ |
26 float dx_prime = dx / iterations; /* x-shift per iteration */ |
26 float dx_prime = dx / iterations; /* x-shift per iteration */ |
41 dstRect.y = y; |
41 dstRect.y = y; |
42 /* shift x and y for next sprite location */ |
42 /* shift x and y for next sprite location */ |
43 x += dx_prime; |
43 x += dx_prime; |
44 y += dy_prime; |
44 y += dy_prime; |
45 /* draw brush blot */ |
45 /* draw brush blot */ |
46 SDL_RenderCopy(brush, NULL, &dstRect); |
46 SDL_RenderCopy(renderer, brush, NULL, &dstRect); |
47 } |
47 } |
48 } |
48 } |
49 |
49 |
50 /* |
50 /* |
51 loads the brush texture |
51 loads the brush texture |
52 */ |
52 */ |
53 void |
53 void |
54 initializeTexture() |
54 initializeTexture(SDL_Renderer *renderer) |
55 { |
55 { |
56 SDL_Surface *bmp_surface; |
56 SDL_Surface *bmp_surface; |
57 bmp_surface = SDL_LoadBMP("stroke.bmp"); |
57 bmp_surface = SDL_LoadBMP("stroke.bmp"); |
58 if (bmp_surface == NULL) { |
58 if (bmp_surface == NULL) { |
59 fatalError("could not load stroke.bmp"); |
59 fatalError("could not load stroke.bmp"); |
60 } |
60 } |
61 brush = |
61 brush = |
62 SDL_CreateTextureFromSurface(SDL_PIXELFORMAT_ABGR8888, bmp_surface); |
62 SDL_CreateTextureFromSurface(renderer, bmp_surface); |
63 SDL_FreeSurface(bmp_surface); |
63 SDL_FreeSurface(bmp_surface); |
64 if (brush == 0) { |
64 if (brush == 0) { |
65 fatalError("could not create brush texture"); |
65 fatalError("could not create brush texture"); |
66 } |
66 } |
67 /* additive blending -- laying strokes on top of eachother makes them brighter */ |
67 /* additive blending -- laying strokes on top of eachother makes them brighter */ |
76 |
76 |
77 int x, y, dx, dy; /* mouse location */ |
77 int x, y, dx, dy; /* mouse location */ |
78 Uint8 state; /* mouse (touch) state */ |
78 Uint8 state; /* mouse (touch) state */ |
79 SDL_Event event; |
79 SDL_Event event; |
80 SDL_Window *window; /* main window */ |
80 SDL_Window *window; /* main window */ |
|
81 SDL_Renderer *renderer; |
81 int done; /* does user want to quit? */ |
82 int done; /* does user want to quit? */ |
82 |
83 |
83 /* initialize SDL */ |
84 /* initialize SDL */ |
84 if (SDL_Init(SDL_INIT_VIDEO) < 0) { |
85 if (SDL_Init(SDL_INIT_VIDEO) < 0) { |
85 fatalError("Could not initialize SDL"); |
86 fatalError("Could not initialize SDL"); |
87 |
88 |
88 /* create main window and renderer */ |
89 /* create main window and renderer */ |
89 window = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, |
90 window = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, |
90 SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | |
91 SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | |
91 SDL_WINDOW_BORDERLESS); |
92 SDL_WINDOW_BORDERLESS); |
92 SDL_CreateRenderer(window, 0, 0); |
93 renderer = SDL_CreateRenderer(window, 0, 0); |
93 |
94 |
94 /*load brush texture */ |
95 /*load brush texture */ |
95 initializeTexture(); |
96 initializeTexture(renderer); |
96 |
97 |
97 /* fill canvass initially with all black */ |
98 /* fill canvass initially with all black */ |
98 SDL_SetRenderDrawColor(0, 0, 0, 255); |
99 SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); |
99 SDL_RenderFill(NULL); |
100 SDL_RenderClear(); |
100 SDL_RenderPresent(); |
101 SDL_RenderPresent(renderer); |
101 |
102 |
102 done = 0; |
103 done = 0; |
103 while (!done && SDL_WaitEvent(&event)) { |
104 while (!done && SDL_WaitEvent(&event)) { |
104 switch (event.type) { |
105 switch (event.type) { |
105 case SDL_QUIT: |
106 case SDL_QUIT: |
107 break; |
108 break; |
108 case SDL_MOUSEMOTION: |
109 case SDL_MOUSEMOTION: |
109 state = SDL_GetMouseState(&x, &y); /* get its location */ |
110 state = SDL_GetMouseState(&x, &y); /* get its location */ |
110 SDL_GetRelativeMouseState(&dx, &dy); /* find how much the mouse moved */ |
111 SDL_GetRelativeMouseState(&dx, &dy); /* find how much the mouse moved */ |
111 if (state & SDL_BUTTON_LMASK) { /* is the mouse (touch) down? */ |
112 if (state & SDL_BUTTON_LMASK) { /* is the mouse (touch) down? */ |
112 drawLine(x - dx, y - dy, dx, dy); /* draw line segment */ |
113 drawLine(renderer, x - dx, y - dy, dx, dy); /* draw line segment */ |
113 SDL_RenderPresent(); |
114 SDL_RenderPresent(renderer); |
114 } |
115 } |
115 break; |
116 break; |
116 } |
117 } |
117 } |
118 } |
118 |
119 |