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// Example create-window shows how to create a window, map it, resize it,
// and listen to structure and key events (i.e., when the window is resized
// by the window manager, or when key presses/releases are made when the
// window has focus). The events are printed to stdout.
package main
import (
"fmt"
"github.com/jezek/xgb"
"github.com/jezek/xgb/xproto"
)
func main() {
X, err := xgb.NewConn()
if err != nil {
fmt.Println(err)
return
}
defer X.Close()
// 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)
}
// This is how accepting events work:
// The application checks what event we got
// (the event must be registered using either xproto.CreateWindow (see l.35) or
// xproto.ChangeWindowAttributes (see l.50)).
// and reacts to it accordingly. All events are defined in the xproto subpackage.
switch ev.(type) {
case xproto.KeyPressEvent:
// See https://pkg.go.dev/github.com/jezek/xgb/xproto#KeyPressEvent
// for documentation about a key press event.
kpe := ev.(xproto.KeyPressEvent)
fmt.Printf("Key pressed: %d", kpe.Detail)
// The Detail value depends on the keyboard layout,
// for QWERTY, q is #24.
if kpe.Detail == 24 {
return // exit on q
}
case xproto.DestroyNotifyEvent:
// Depending on the user's desktop environment (especially
// window manager), killing a window might close the
// client's X connection (e. g. the default Ubuntu
// desktop environment).
//
// If that's the case for your environment, closing this example's window
// will also close the underlying Go program (because closing the X
// connection gives a nil event and EOF error).
//
// Consider how a single application might have multiple windows
// (e.g. an open popup or dialog, ...)
//
// With other DEs, the X connection will still stay open even after the
// X window is closed. For these DEs (e.g. i3) we have to check whether
// the WM sent us a DestroyNotifyEvent and close our program.
//
// For more information about closing windows while maintaining
// the X connection see
// https://github.com/jezek/xgbutil/blob/master/_examples/graceful-window-close/main.go
return
}
}
}
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