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Class (inherits from RectControl)

Renders HTML and provides basic navigation features.

CancelLoad Error Open
Close JavaScriptRequest SecurityChanged
DocumentBegin KeyDown StatusChanged
DocumentComplete KeyUp TitleChanged
DocumentProgressChanged NewWindow

Active fa-lock-32.png LockBottom Scope fa-lock-32.png
AllowAutoDeactivate LockLeft TabIndex
AllowTabStop LockRight Tooltip
CanGoBack fa-lock-32.png LockTop Top
CanGoForward fa-lock-32.png MouseCursor Transparent
Enabled MouseX fa-lock-32.png TrueWindow fa-lock-32.png
Handle fa-lock-32.png MouseY fa-lock-32.png UseSandbox
Height Name fa-lock-32.png UserAgent
Index fa-lock-32.png PanelIndex Visible
IsAvailable fa-lock-32.png Parent Width
Left Renderer fa-lock-32.png Window fa-lock-32.png

AcceptFileDrop ExecuteJavaScript Print
AcceptPictureDrop ExecuteJavaScriptSync Refresh
AcceptRawDataDrop GoBack SetFocus
AcceptTextDrop GoForward ZoomTextIn
Cancel Invalidate ZoomTextOut
Close LoadPage
DrawInto LoadURL


On macOS, the HTMLViewer supports getting and setting a custom user agent string and increasing or decreasing the font size.

Exchanging Data With JavaScript

A JavaScript executed via ExecuteJavaScript or ExecuteJavaScriptSync can call executeInXojo() or executeInXojoSync() to pass data back to the HTMLViewer via the JavaScriptRequest event. Both can be passed any number of parameters though the first parameter must be a string. For all subsequent parameters, only strings and numbers are supported. The executeInXojo() method is asynchronous and thus will not receive a value returned by the JavaScriptRequest event. The executeInXojoSync() method is synchronous and thus should be called as a function as it will receive the value returned by the JavaScriptRequest event.

On Windows you need to use the WebKit rendering engine for executeInXojo() or executeInXojoSync() to work.

App Transport Security

Starting with MacOS 10.11 and Xojo 2018r4, your apps have to use secure "https" connections or you will get this error: "The resource could not be loaded because the App Transport Security policy requires the use of a secure connection". You can work around this by providing a plist with your app to indicate what non-secure URLs you are using. For more information:

Webkit on Windows

You can use WebKit on Windows by setting the Renderer property to WebKit (1). Using WebKit on Windows adds the entire Chromium Embedded Framework 3 (CEF3) engine to your app, increasing its size by about 100MB.

To make plugins available to WebKit on Windows, create a folder called WebKitPlugins within your Libs folder in your application folder and place the plugins you need there.

When using WebKit on Windows, HTMLViewer.Handle returns a pointer to the cef_browser_t struct.

Windows IE Version

On Windows, the Native Renderer is probably using an older version of the Internet Explorer renderer. This may result in web pages that do not display or work as you expect. You can tell Windows to use a newer version of the IE rendering engine with a Registry setting. This is how you can change it using Xojo:

#If TargetWindows
// This code handles both 64 and 32-bit builds
Var reg As New RegistryItem("HKEY_CURRENT_USER\SOFTWARE\Microsoft")
reg = reg.AddFolder("Internet Explorer")
reg = reg.AddFolder("Main")
reg = reg.AddFolder("FeatureControl")

// Source MS documentation:
reg.Value(App.ExecutableFile.Name) = CType(11000 , Int32)

Another issue to keep in mind is if Internet Explorer 11 has the option "Display intranet sites in Compatibility View" selected in the "Compatibility View Settings" pane, then IE will most likely still render using IE7. If you control the source to the content you want to display, you can include this in the <head> section of the HTML document:

<meta http-equiv="X-UA-Compatible" content="IE=11">

And also use HTML5 DOCTYPE at the start of the document:

<!DOCTYPE html>

Windows Performance

On Windows, the Native Renderer might not use the GPU by default, which may result in slower rendering speeds depending on what you are displaying. You can enable it via the Registry:

Var reg As New RegistryItem("HKEY_CURRENT_USER\SOFTWARE\Microsoft")
reg = reg.AddFolder("Internet Explorer")
reg = reg.AddFolder("Main")
reg = reg.AddFolder("FeatureControl")
reg = reg.AddFolder("FEATURE_GPU_RENDERING")
reg.Value(App.ExecutableFile.Name) = 1

Linux Support

If it is available, the Linux HTMLViewer uses WebKit (libwebkitgtk version 3).

Refer to the Resources:System_Requirements#64-bit Configuration for Running 32-bit_Apps section for commands that you can use to install libwebkitgtk v3 on various Linux distributions.

On Linux, HTMLViewer.Handle returns the GtkScrolledWindow that hosts the WebKitWebView control (please refer to the WebKitGTK site for information on how to use this system control).

Sample Code

To implement a simple web browser, create a window with a large HTML Viewer control. Set its LockLeft, LockTop, LockRight, and LockBottom properties so that it resizes as the user resizes the window. Use a TextField as the URL entry area and a PushButton as the browser's Go button. That is, the user clicks Go to display the URL entered into the TextField.

In this example, the HTMLViewer is named “HTML”. The following code is in the Action event of the PushButton:


You can use a ProgressBar to indicate that the web page is loading. In the HTMLViewer's DocumentBegin event, initialize and show the ProgressBar with the code:

ProgressBar1.Value = 0
ProgressBar1.Visible = True

In the DocumentProgressChanged event, increment the value of the ProgressBar. This event handler is passed the value of PercentageComplete (0 to 100).

If percentageComplete = -1 Then // if it cannot be determined
ProgressBar1.Maximum = 0 // display indeterminate progress
ProgressBar1.Maximum = 100
End if

ProgressBar1.Value = percentageComplete

In the DocumentComplete event handler, hide the ProgressBar with the line:

ProgressBar1.Visible = False

When the title of the web page has been received, you can display it in the window's Title bar using the HTMLViewer's TitleChanged event. It is passed the new title in the String parameter newTitle. Update the window title with the line:

Title = newTitle

Use a second TextField to display the status of the load process. In the HTMLViewer's StatusChanged event handler, set the value of this TextField. This event handler is passed the current status in the String parameter, NewStatus. Display this string with the following line in the StatusChanged event:

TextField1.Value3 = NewStatus

If a new browser window is supposed to open, you need to insert some code to handle this event. For example, the user clicks a link that is supposed to display the new page in another window. Use the NewWindow event handler to create the window. The following code assumes that the browser is contained in a window called MainWindow.

Var w As New MainWindow
Title = "New Window" //Title property of new window
Return w.HTML

See Also

HTTPSocket and URLConnection classes