lots of docs and examples

nexgb/examples/create-window/main.go

@@ -0,0 +1,98 @@
+// 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/BurntSushi/xgb"
+)
+
+func main() {
+	X, err := xgb.NewConn()
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	// Any time a new resource (i.e., a window, pixmap, graphics context, etc.)
+	// is created, we need to generate a resource identifier with NewId.
+	wid, _ := X.NewId()
+
+	// CreateWindow takes a boatload of parameters.
+	X.CreateWindow(X.DefaultScreen().RootDepth, wid, X.DefaultScreen().Root,
+		0, 0, 500, 500, 0,
+		xgb.WindowClassInputOutput, X.DefaultScreen().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.
+	X.ChangeWindowAttributes(wid,
+		xgb.CwBackPixel|xgb.CwEventMask,
+		[]uint32{ // values must be in the order defined by the protocol
+			0xffffffff,
+			xgb.EventMaskStructureNotify |
+				xgb.EventMaskKeyPress |
+				xgb.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 = X.MapWindowChecked(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 = X.MapWindowChecked(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)
+		}
+	}
+}