├── LICENSE
├── Makefile
├── README.md
└── main.c


/LICENSE:
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 1 | MIT License
 2 | 
 3 | Copyright (c) 2020 programmeruser2
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 


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/Makefile:
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1 | SRC = main.c
2 | 
3 | .PHONY: all
4 | all: main.wasm
5 | 
6 | main.wasm: 
7 | 	clang --target=wasm32 -nostdlib -Wl,--no-entry -Wl,--export-all -Wl,--allow-undefined -o $@ $(SRC)
8 | 


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/README.md:
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 1 | # wasm-canvas
 2 | [![Run on repl.it](https://repl.it/badge/github/programmeruser2/wasm-canvas)](https://repl.it/github/programmeruser2/wasm-canvas)
 3 | 
 4 | A simple example of calling JavaScript functions from C to draw on the canvas.
 5 | 
 6 | https://programmeruser2.github.io/wasm-canvas
 7 | 
 8 | ## Imports Object
 9 | ```
10 | const canvas = //... HTMLElement representing a canvas
11 | const ctx = //... Canvas2DRenderingContext
12 | const imports = {
13 |   env: {
14 |     getCanvasWidth: function() { return canvas.width; },
15 |     getCanvasHeight: function() { return canvas.height; },
16 |     jsSetInterval: function(callback, interval) {
17 |       setInterval(function() {
18 |         instance.exports.runCallback(callback);
19 |       },interval);
20 |     },
21 |     jsFillRect: function(x,y,w,h) {
22 |       ctx.fillRect(x,y,w,h);
23 |     },
24 |     jsClearRect: function(x,y,w,h) {
25 |       ctx.clearRect(x,y,w,h);
26 |     }
27 |   }
28 | };
29 | ```
30 | 


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/main.c:
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 1 | //imports
 2 | extern void jsSetInterval(void (*callback)(void), float interval);
 3 | extern void jsFillRect(int x, int y, int w, int h);
 4 | extern void jsClearRect(int x, int y, int w, int h);
 5 | extern int getCanvasWidth(void);
 6 | extern int getCanvasHeight(void);
 7 | 
 8 | typedef struct {
 9 |   float x;
10 |   float y;
11 |   float width;
12 |   float height;
13 |   int direction;
14 | } Sprite;
15 | Sprite* sprite;
16 | 
17 | void runCallback(void (*callback)()) {
18 |   return callback();
19 | }
20 | 
21 | void mainloop(void) {
22 |   jsClearRect(0,0,getCanvasWidth(), getCanvasHeight());
23 |   if(sprite->x + sprite->width == getCanvasWidth()) {
24 |     sprite->direction = -1;
25 |   } else if(sprite->x == 0) {
26 |     sprite->direction = 1;
27 |   }
28 |   sprite->x += 50 * sprite->direction;
29 |   jsFillRect(sprite->x, sprite->y, sprite->width, sprite->height);
30 | }
31 | 
32 | int main(void) { 
33 |   sprite->x = 0;
34 |   sprite->y = 0;
35 |   sprite->width = 50;
36 |   sprite->height = 50;
37 |   sprite->direction = 1;
38 |   jsSetInterval(mainloop, 16.67);
39 |   return 0;
40 | }
41 | 


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