repository·master·Indexed 27 days ago
https://github.com/zserge/lorcaA lightweight Go library for building HTML5 desktop applications by leveraging an existing Chrome or Chromium installation (version 70+) via the Chrome DevTools Protocol. It enables seamless communication between Go and JavaScript, allowing developers to bind Go functions to the UI and execute JavaScript from Go without bundling a browser.
To run the basic 'counter' example included in the repository, navigate to the example directory and execute the following commands:
cd examples/counter
go get
go run ./Lorca provides a simple API to create windows, bind Go functions to JavaScript, and evaluate JavaScript code from Go.
Key capabilities:
lorca.New(url, title, width, height): Creates a new window.ui.Bind(name, function): Exposes a Go function to the JavaScript environment. In JS, this function is represented as a Promise and can handle long-running or blocking Go code.ui.Eval(js_code): Executes arbitrary JavaScript in the browser window and returns a value object that can be cast to types like .Int() or .Float().ui.Done(): A channel that closes when the browser window is closed.ui, _ := lorca.New("", "", 480, 320)
defer ui.Close()
// Bind Go function to be available in JS.
// In JS it's represented with a Promise.
ui.Bind("add", func(a, b int) int { return a + b })
// Call JS function from Go.
n := ui.Eval(`Math.random()`).Float()
fmt.Println(n)
// Call JS that calls the bound Go function
m := ui.Eval(`add(2, 3)`).Int()
fmt.Println(m)
// Wait for the browser window to be closed
<-ui.Done()If you require more granular control over the browser window, consider using the webview library.
Load to navigate the current UI window to a specific URL.Use New to create a new HTML5 UI instance. You can specify a starting URL, a user profile directory, and window dimensions.
url is empty, a blank page is displayed.dir is empty, a temporary directory is created and automatically removed when ui.Close() is called.customArgs (e.g., --headless for testing).pdf method to print the current page to a PDF buffer. The dimensions are specified in pixels and converted to inches (using a 96 DPI assumption) for the Chrome DevTools Protocol.Eval to execute arbitrary JavaScript code within the UI context. It returns a Value object which can be used to inspect the result of the execution.Lorca provides a mechanism to display a question dialog box to the user on non-Windows platforms. This function uses system-native tools: zenity on Linux and osascript (AppleScript) on macOS.
Note: This implementation is specifically for non-Windows environments (//+build !windows).
The dialog presents a question with 'Yes' and 'No' buttons. It returns true if the user selects 'Yes' and false otherwise.
The PDF function converts a given URL (which can be a local file) into a PDF byte slice. You can provide a script to be evaluated in the browser before the PDF is generated, allowing you to modify page content or wait for rendering to complete.
For standard A4 page dimensions at 96dpi, use the PageA4Width and PageA4Height constants.
Use LocateChrome() to find the path to a Chrome or Chromium executable on the system. It returns the path as a string, or an empty string if no installation is found.
Lorca follows this search priority:
LORCACHROME environment variable (if the file exists).LocateChrome() returns an empty string, you can call PromptDownload() to show a message box asking the user if they want to download and install Chrome. If the user agrees, it opens the official Chrome download page (https://www.google.com/chrome/) using the system's default web opener (xdg-open on Linux, open on macOS, or start on Windows).