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API Reference

Table of Contents

JavaScript API

To communicate from JavaScript to C++, use the method window.external.invoke:

// JavaScript
window.exteral.invoke('hello world!');
// C++
void callback(WebView &w, wv::String &arg) {
  // arg = "hello world!"
}

This method can only accept strings, so objects must be serialized in some way:

// JavaScript
window.external.invoke(JSON.stringify({ foo: 'bar' }));

C++ API

Note: On Windows, all strings are std::wstring. On MacOS and Linux, they are std::string.

If you need to support Windows, make sure to use Win32 WinMain entry point:

#ifdef WIN32
int __stdcall WinMain(HINSTANCE, HINSTANCE, LPSTR, int) {
#else
int main() {
#endif
  // ...
}

Constructor

WebView(int width, int height, bool resizable, bool debug, string title,
        string url = DEFAULT_URL)

The default url (DEFAULT_URL) will render a blank page with a single root div:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  </head>
  <body>
    <div id="app"></div>
    <script type="text/javascript"></script>
  </body>
</html>

init

int init();

Initializes the webview window.

Returns

0 if successful, otherwise -1.

Example

#include "webview.h"

int main() {
  wv::WebView w{800, 600, true, true, "My WebView"};

  // Initialize the webview
  if (w.init() == -1) {
    return 1;
  }

  // Do stuff with the webview

  return 0;
}

setCallback

void setCallback(std::function<void(WebView &, std::string &)> callback);

Attaches a function that will run when receiving messages from JavaScript.

Params

  • callback: A callback function

Example

#include "webview.h"

void callback(WebView &w, std::string &arg) {
  if (arg == "color") {
    w.css("body { background-color: red; }");
  }
}

// ...

w.setCallback(callback);

setTitle

void setTitle(string title);

Sets the title of the webview window.

Params

  • title: The new title of the webview

setFullscreen

void setFullscreen(bool fs);

Sets the webview window to fullscreen or windowed mode.

Params

  • fs: True if setting to fullscreen, false if windowed

setFullscreenFromJS

void setFullscreenFromJS(bool allow);

Sets whether JavaScript can directly switch between fullscreen and windowed mode. By default, JavaScript cannot change the window using requestFullscreen() and exitFullscreen(). Any fullscreen element will take up the size of the window itself rather than the screen.

Note: on Mac (WEBVIEW_MAC), this method will only apply when called before init. After init, this will be a no-op. For fine-grained control, consider polyfilling the fullscreen API with a call to C++ and manually call setFullscreen. For example,

Element.prototype.requestFullscreen = () => window.external.invoke('full');
Document.prototype.exitFullscreen = () => window.external.invoke('exit');
WEBVIEW_MAIN {
  bool allow = false;
  wv::WebView w{};

  if (w.init() == -1) return 1;
  w.setCallback([](wv::WebView& w, wv::String& arg) {
    if (allow) {
      if (arg == "full") w.setFullscreen(true);
      else if (arg == "exit") w.setFullscreen(false);
    }
  });

  while (w.run() == 0);

  return 0;
}

setBgColor

Sets the background color of the webview. If the webpage has a background color, it will take precedence over this color.

void setBgColor(uint8_t r, uint8_t g, uint8_t b, uint8_t a)

Params

  • r: Red component of the color (0 to 255)
  • g: Green component of the color (0 to 255)
  • b: Blue component of the color (0 to 255)
  • a: Alpha component of the color (0 to 255)

run

bool run();

Runs one iteration of the main loop. This method is blocking if no events are pending.

Returns

True if the webview window will be closed, otherwise false.

Example

#include "webview.h"

int main() {
  wv::WebView w{800, 600, true, true, "My WebView"};

  if (w.init() == -1) {
    return 1;
  }

  // Keep running until the window will close
  while (w.run() == 0);

  return 0;
}

navigate

void navigate(string uri);

Navigates the webview to the specified URI.

Params

  • uri: URI to the webpage

preEval

void preEval(string js);

Injects the JavaScript string into the webpage before it loads.

Note: in some cases, the JavaScript will be run before the DOM loads. If you need access to the DOM, make sure to wait for it to load:

window.onload = () => {
  const el = document.getElementById('id');
};

// or

window.addEventListener('DOMContentLoaded', () => {
  // or the 'load' event
  const el = document.getElementById('id');
});

eval

void eval(string js);

Executes the JavaScript string in the current webpage.

Params

  • js: JavaScript string to execute

Example

#include "webview.h"

void callback(wv::WebView &w, std::string &arg) {
  if (arg == "eval") {
    w.eval("alert('boo!')");
  }
}

int main() {
  wv::WebView w{800, 600, true, true, "My WebView"};

  if (w.init() == -1) {
    return 1;
  }

  w.setCallback(callback);

  while (w.run() == 0);

  return 0;
}

The alert will display when this is executed in the webpage:

window.external.invoke('eval');

css

void css(string css);

Applies the CSS string to the current webpage.

Params

  • css: CSS string to apply

Example

This method works similar to WebView::eval.

#include "webview.h"

void callback(wv::WebView &w, std::string &arg) {
  if (arg == "style") {
    w.css("p { color: red; }");
  }
}

int main() {
  wv::WebView w{800, 600, true, true, "My WebView"};

  if (w.init() == -1) {
    return 1;
  }

  w.setCallback(callback);

  while (w.run() == 0);

  return 0;
}

All p tags will be colored red when this is executed in the webpage:

window.external.invoke('style');

exit

void exit();

Closes the webview window. This will cause the next invocation of WebView::run to return true.