82 lines
1.8 KiB
Markdown
82 lines
1.8 KiB
Markdown
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# Hello WASM
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This is a port of the "hello-world" example for a WebAssembly target.
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Differences compared to the SDL2 version include:
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* Import render/canvas instead of render/sdl
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* Load the gopher.png via ajax HTTP request, as the syscall to open a file from
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disk is not supported in a WASM environment.
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* A call to the `canvas.AddEventListeners()` function to set up DOM event
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bindings, which enables key and mouse events to be handled in the
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canvas.Engine.
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```diff
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--- ../hello-world/main.go 2019-12-22 15:17:42.186838967 -0800
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+++ main_wasm.go 2019-12-22 16:21:58.449699021 -0800
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@@ -1,13 +1,17 @@
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+// +build js,wasm
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+
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+// This is a version of the 'hello-world' example but build for WebAssembly.
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+
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package main
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import (
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"image/png"
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"log"
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- "os"
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+ "net/http"
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"time"
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"git.kirsle.net/go/render"
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- "git.kirsle.net/go/render/sdl"
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+ "git.kirsle.net/go/render/canvas"
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)
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var (
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@@ -30,7 +34,11 @@
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)
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func main() {
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- mw := sdl.New("Hello World", 800, 600)
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+ mw, _ := canvas.New("canvas")
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setup(mw)
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for {
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@@ -61,17 +69,22 @@
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}
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}
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-func setup(e render.Engine) {
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+func setup(e *canvas.Engine) {
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if err := e.Setup(); err != nil {
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panic(err)
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}
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- // Load gopher sprite.
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- fh, err := os.Open("gopher.png")
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+ // Bind DOM event handlers.
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+ e.AddEventListeners()
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+
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+ // Load gopher sprite via ajax request.
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+ resp, err := http.Get("gopher.png")
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if err != nil {
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log.Fatalf("read gopher.png: %s", err)
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}
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+ defer resp.Body.Close()
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- img, _ := png.Decode(fh)
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+ img, _ := png.Decode(resp.Body)
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gopher, _ = e.StoreTexture("gopher.png", img)
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texSize = gopher.Size()
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```
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## Credits
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Gopher image was created by Takuya Ueda (https://twitter.com/tenntenn)
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from https://github.com/golang-samples/gopher-vector
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This example comes with the DejaVu Sans font. License information
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at https://dejavu-fonts.github.io/License.html
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