99 lines
3.3 KiB
Go
99 lines
3.3 KiB
Go
// Example create-window shows how to create a window, map it, resize it,
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// and listen to structure and key events (i.e., when the window is resized
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// by the window manager, or when key presses/releases are made when the
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// window has focus). The events are printed to stdout.
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package main
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import (
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"fmt"
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"github.com/BurntSushi/xgb"
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)
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func main() {
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X, err := xgb.NewConn()
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if err != nil {
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fmt.Println(err)
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return
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}
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// Any time a new resource (i.e., a window, pixmap, graphics context, etc.)
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// is created, we need to generate a resource identifier with NewId.
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wid, _ := X.NewId()
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// CreateWindow takes a boatload of parameters.
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X.CreateWindow(X.DefaultScreen().RootDepth, wid, X.DefaultScreen().Root,
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0, 0, 500, 500, 0,
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xgb.WindowClassInputOutput, X.DefaultScreen().RootVisual,
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0, []uint32{})
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// This call to ChangeWindowAttributes could be factored out and
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// included with the above CreateWindow call, but it is left here for
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// instructive purposes. It tells X to send us events when the 'structure'
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// of the window is changed (i.e., when it is resized, mapped, unmapped,
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// etc.) and when a key press or a key release has been made when the
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// window has focus.
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// We also set the 'BackPixel' to white so that the window isn't butt ugly.
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X.ChangeWindowAttributes(wid,
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xgb.CwBackPixel|xgb.CwEventMask,
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[]uint32{ // values must be in the order defined by the protocol
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0xffffffff,
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xgb.EventMaskStructureNotify |
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xgb.EventMaskKeyPress |
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xgb.EventMaskKeyRelease})
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// MapWindow makes the window we've created appear on the screen.
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// We demonstrated the use of a 'checked' request here.
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// A checked request is a fancy way of saying, "do error handling
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// synchronously." Namely, if there is a problem with the MapWindow request,
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// we'll get the error *here*. If we were to do a normal unchecked
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// request (like the above CreateWindow and ChangeWindowAttributes
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// requests), then we would only see the error arrive in the main event
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// loop.
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//
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// Typically, checked requests are useful when you need to make sure they
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// succeed. Since they are synchronous, they incur a round trip cost before
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// the program can continue, but this is only going to be noticeable if
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// you're issuing tons of requests in succession.
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//
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// Note that requests without replies are by default unchecked while
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// requests *with* replies are checked by default.
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err = X.MapWindowChecked(wid).Check()
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if err != nil {
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fmt.Printf("Checked Error for mapping window %d: %s\n", wid, err)
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} else {
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fmt.Printf("Map window %d successful!\n", wid)
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}
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// This is an example of an invalid MapWindow request and what an error
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// looks like.
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err = X.MapWindowChecked(0).Check()
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if err != nil {
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fmt.Printf("Checked Error for mapping window 0x1: %s\n", err)
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} else { // neva
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fmt.Printf("Map window 0x1 successful!\n")
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}
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// Start the main event loop.
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for {
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// WaitForEvent either returns an event or an error and never both.
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// If both are nil, then something went wrong and the loop should be
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// halted.
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//
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// An error can only be seen here as a response to an unchecked
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// request.
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ev, xerr := X.WaitForEvent()
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if ev == nil && xerr == nil {
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fmt.Println("Both event and error are nil. Exiting...")
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return
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}
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if ev != nil {
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fmt.Printf("Event: %s\n", ev)
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}
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if xerr != nil {
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fmt.Printf("Error: %s\n", xerr)
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}
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}
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}
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