1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/*
* This example creates an SDL window and renderer, and then draws a scene
* to it every frame, while sliding around a clipping rectangle.
*
* This code is public domain. Feel free to use it for any purpose!
*/
#define SDL_MAIN_USE_CALLBACKS 1 /* use the callbacks instead of main() */
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480
#define CLIPRECT_SIZE 250
#define CLIPRECT_SPEED 200 /* pixels per second */
/* We will use this renderer to draw into this window every frame. */
static SDL_Window *window = NULL;
static SDL_Renderer *renderer = NULL;
static SDL_Texture *texture = NULL;
static SDL_FPoint cliprect_position;
static SDL_FPoint cliprect_direction;
static Uint64 last_time = 0;
/* A lot of this program is examples/renderer/02-primitives, so we have a good
visual that we can slide a clip rect around. The actual new magic in here
is the SDL_SetRenderClipRect() function. */
/* This function runs once at startup. */
SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
{
SDL_Surface *surface = NULL;
char *bmp_path = NULL;
SDL_SetAppMetadata("Example Renderer Clipping Rectangle", "1.0", "com.example.renderer-cliprect");
if (!SDL_Init(SDL_INIT_VIDEO)) {
SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
if (!SDL_CreateWindowAndRenderer("examples/renderer/cliprect", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
cliprect_direction.x = cliprect_direction.y = 1.0f;
last_time = SDL_GetTicks();
/* Textures are pixel data that we upload to the video hardware for fast drawing. Lots of 2D
engines refer to these as "sprites." We'll do a static texture (upload once, draw many
times) with data from a bitmap file. */
/* SDL_Surface is pixel data the CPU can access. SDL_Texture is pixel data the GPU can access.
Load a .bmp into a surface, move it to a texture from there. */
SDL_asprintf(&bmp_path, "%ssample.bmp", SDL_GetBasePath()); /* allocate a string of the full file path */
surface = SDL_LoadBMP(bmp_path);
if (!surface) {
SDL_Log("Couldn't load bitmap: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
SDL_free(bmp_path); /* done with this, the file is loaded. */
texture = SDL_CreateTextureFromSurface(renderer, surface);
if (!texture) {
SDL_Log("Couldn't create static texture: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
SDL_DestroySurface(surface); /* done with this, the texture has a copy of the pixels now. */
return SDL_APP_CONTINUE; /* carry on with the program! */
}
/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
{
if (event->type == SDL_EVENT_QUIT) {
return SDL_APP_SUCCESS; /* end the program, reporting success to the OS. */
}
return SDL_APP_CONTINUE; /* carry on with the program! */
}
/* This function runs once per frame, and is the heart of the program. */
SDL_AppResult SDL_AppIterate(void *appstate)
{
const SDL_Rect cliprect = { (int) SDL_roundf(cliprect_position.x), (int) SDL_roundf(cliprect_position.y), CLIPRECT_SIZE, CLIPRECT_SIZE };
const Uint64 now = SDL_GetTicks();
const float elapsed = ((float) (now - last_time)) / 1000.0f; /* seconds since last iteration */
const float distance = elapsed * CLIPRECT_SPEED;
/* Set a new clipping rectangle position */
cliprect_position.x += distance * cliprect_direction.x;
if (cliprect_position.x < 0.0f) {
cliprect_position.x = 0.0f;
cliprect_direction.x = 1.0f;
} else if (cliprect_position.x >= (WINDOW_WIDTH - CLIPRECT_SIZE)) {
cliprect_position.x = (WINDOW_WIDTH - CLIPRECT_SIZE) - 1;
cliprect_direction.x = -1.0f;
}
cliprect_position.y += distance * cliprect_direction.y;
if (cliprect_position.y < 0.0f) {
cliprect_position.y = 0.0f;
cliprect_direction.y = 1.0f;
} else if (cliprect_position.y >= (WINDOW_HEIGHT - CLIPRECT_SIZE)) {
cliprect_position.y = (WINDOW_HEIGHT - CLIPRECT_SIZE) - 1;
cliprect_direction.y = -1.0f;
}
SDL_SetRenderClipRect(renderer, &cliprect);
last_time = now;
/* okay, now draw! */
/* Note that SDL_RenderClear is _not_ affected by the clipping rectangle! */
SDL_SetRenderDrawColor(renderer, 33, 33, 33, SDL_ALPHA_OPAQUE); /* grey, full alpha */
SDL_RenderClear(renderer); /* start with a blank canvas. */
/* stretch the texture across the entire window. Only the piece in the
clipping rectangle will actually render, though! */
SDL_RenderTexture(renderer, texture, NULL, NULL);
SDL_RenderPresent(renderer); /* put it all on the screen! */
return SDL_APP_CONTINUE; /* carry on with the program! */
}
/* This function runs once at shutdown. */
void SDL_AppQuit(void *appstate, SDL_AppResult result)
{
SDL_DestroyTexture(texture);
/* SDL will clean up the window/renderer for us. */
}
|
