// Listen will tell X to report events corresponding to the event masks
// provided for the given window. If a call to Listen is omitted, you will
// not receive the events you desire.
// Event masks are constants declare in the xgb/xproto package starting with the
// EventMask prefix.
func (w *Window) Listen(evMasks ...int) {
evMask := 0
for _, mask := range evMasks {
evMask |= mask
}
xproto.ChangeWindowAttributes(w.X.Conn(), w.Id, xproto.CwEventMask,
[]uint32{uint32(evMask)})
}
// XSurfaceSet will set the given window's background to this image's pixmap.
// Note that an image can have multiple surfaces, which is why the window
// id still needs to be passed to XPaint. A call to XSurfaceSet simply tells
// X that the window specified should use the pixmap in Image as its
// background image.
// Note that XSurfaceSet cannot be called on a sub-image. (An error will be
// returned if you do.)
// XSurfaceSet will also allocate an X pixmap if one hasn't been created for
// this image yet.
// (Generating a pixmap id can cause an error, so this call could return
// an error.)
func (im *Image) XSurfaceSet(wid xproto.Window) error {
if im.Subimg {
return fmt.Errorf("XSurfaceSet cannot be called on sub-images." +
"Please set the surface using the original parent image.")
}
if im.Pixmap == 0 {
if err := im.CreatePixmap(); err != nil {
return err
}
}
// Tell the surface (window) to use this pixmap.
xproto.ChangeWindowAttributes(im.X.Conn(), wid,
xproto.CwBackPixmap, []uint32{uint32(im.Pixmap)})
return nil
}
// Change issues a ChangeWindowAttributes request with the provided mask
// and value list. Please see Window.Create for an example on how to use
// the mask and value list.
func (w *Window) Change(valueMask int, valueList ...uint32) {
xproto.ChangeWindowAttributes(w.X.Conn(), w.Id,
uint32(valueMask), valueList)
}
func main() {
X, err := xgb.NewConn()
if err != nil {
fmt.Println(err)
return
}
// xproto.Setup retrieves the Setup information from the setup bytes
// gathered during connection.
setup := xproto.Setup(X)
// This is the default screen with all its associated info.
screen := setup.DefaultScreen(X)
// Any time a new resource (i.e., a window, pixmap, graphics context, etc.)
// is created, we need to generate a resource identifier.
// If the resource is a window, then use xproto.NewWindowId. If it's for
// a pixmap, then use xproto.NewPixmapId. And so on...
wid, _ := xproto.NewWindowId(X)
// CreateWindow takes a boatload of parameters.
xproto.CreateWindow(X, screen.RootDepth, wid, screen.Root,
0, 0, 500, 500, 0,
xproto.WindowClassInputOutput, screen.RootVisual, 0, []uint32{})
// This call to ChangeWindowAttributes could be factored out and
// included with the above CreateWindow call, but it is left here for
// instructive purposes. It tells X to send us events when the 'structure'
// of the window is changed (i.e., when it is resized, mapped, unmapped,
// etc.) and when a key press or a key release has been made when the
// window has focus.
// We also set the 'BackPixel' to white so that the window isn't butt ugly.
xproto.ChangeWindowAttributes(X, wid,
xproto.CwBackPixel|xproto.CwEventMask,
[]uint32{ // values must be in the order defined by the protocol
0xffffffff,
xproto.EventMaskStructureNotify |
xproto.EventMaskKeyPress |
xproto.EventMaskKeyRelease})
// MapWindow makes the window we've created appear on the screen.
// We demonstrated the use of a 'checked' request here.
// A checked request is a fancy way of saying, "do error handling
// synchronously." Namely, if there is a problem with the MapWindow request,
// we'll get the error *here*. If we were to do a normal unchecked
// request (like the above CreateWindow and ChangeWindowAttributes
// requests), then we would only see the error arrive in the main event
// loop.
//
// Typically, checked requests are useful when you need to make sure they
// succeed. Since they are synchronous, they incur a round trip cost before
// the program can continue, but this is only going to be noticeable if
// you're issuing tons of requests in succession.
//
// Note that requests without replies are by default unchecked while
// requests *with* replies are checked by default.
err = xproto.MapWindowChecked(X, wid).Check()
if err != nil {
fmt.Printf("Checked Error for mapping window %d: %s\n", wid, err)
} else {
fmt.Printf("Map window %d successful!\n", wid)
}
// This is an example of an invalid MapWindow request and what an error
// looks like.
err = xproto.MapWindowChecked(X, 0).Check()
if err != nil {
fmt.Printf("Checked Error for mapping window 0x1: %s\n", err)
} else { // neva
fmt.Printf("Map window 0x1 successful!\n")
}
// Start the main event loop.
for {
// WaitForEvent either returns an event or an error and never both.
// If both are nil, then something went wrong and the loop should be
// halted.
//
// An error can only be seen here as a response to an unchecked
// request.
ev, xerr := X.WaitForEvent()
if ev == nil && xerr == nil {
fmt.Println("Both event and error are nil. Exiting...")
return
}
if ev != nil {
fmt.Printf("Event: %s\n", ev)
}
if xerr != nil {
fmt.Printf("Error: %s\n", xerr)
}
}
}
