xgb-keys: minimal example of reading keys

prototypes/xgb-keys.go

@@ -0,0 +1,213 @@
+package main
+
+import (
+	"github.com/BurntSushi/xgb"
+	//"github.com/BurntSushi/xgb/xkb"
+	"github.com/BurntSushi/xgb/xproto"
+	"log"
+)
+
+func main() {
+	X, err := xgb.NewConn()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	/*
+		// Use the extension if available, makes better use of state bits.
+		if err := xkb.Init(X); err == nil {
+			if _, err := xkb.UseExtension(X, 1, 0).Reply(); err != nil {
+				log.Fatalln(err)
+			}
+		}
+	*/
+
+	setup := xproto.Setup(X)
+	screen := setup.DefaultScreen(X)
+
+	visual, depth := screen.RootVisual, screen.RootDepth
+	// TODO: We should check that we find it, though we don't /need/ alpha here,
+	// it's just a minor improvement--affects the backpixel value.
+	for _, i := range screen.AllowedDepths {
+		for _, v := range i.Visuals {
+			// TODO: Could/should check other parameters.
+			if i.Depth == 32 && v.Class == xproto.VisualClassTrueColor {
+				visual, depth = v.VisualId, i.Depth
+				break
+			}
+		}
+	}
+
+	mid, err := xproto.NewColormapId(X)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	_ = xproto.CreateColormap(
+		X, xproto.ColormapAllocNone, mid, screen.Root, visual)
+
+	wid, err := xproto.NewWindowId(X)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// Border pixel and colormap are required when depth differs from parent.
+	_ = xproto.CreateWindow(X, depth, wid, screen.Root,
+		0, 0, 500, 500, 0, xproto.WindowClassInputOutput,
+		visual, xproto.CwBackPixel|xproto.CwBorderPixel|xproto.CwEventMask|
+			xproto.CwColormap, []uint32{0x80808080, 0,
+			xproto.EventMaskStructureNotify | xproto.EventMaskKeyPress |
+				/* KeymapNotify */ xproto.EventMaskKeymapState, uint32(mid)})
+
+	title := []byte("Keys")
+	_ = xproto.ChangeProperty(X, xproto.PropModeReplace, wid, xproto.AtomWmName,
+		xproto.AtomString, 8, uint32(len(title)), title)
+
+	_ = xproto.MapWindow(X, wid)
+
+	mapping, err := xproto.GetKeyboardMapping(X, setup.MinKeycode,
+		byte(setup.MaxKeycode-setup.MinKeycode+1)).Reply()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// The order is "Shift, Lock, Control, Mod1, Mod2, Mod3, Mod4, and Mod5."
+	mm, err := xproto.GetModifierMapping(X).Reply()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// XXX: This seems pointless, the key will just end up switching groups
+	// instead of levels without full XKB handling. Though perhaps it might
+	// at least work as intended when there's only one XKB group.
+	const MODE_SWITCH = 0xff7e
+
+	var modeSwitchMask uint16
+	for mod := 0; mod < 8; mod++ {
+		perMod := int(mm.KeycodesPerModifier)
+		for _, kc := range mm.Keycodes[mod*perMod : (mod+1)*perMod] {
+			if kc == 0 {
+				continue
+			}
+
+			perKc := int(mapping.KeysymsPerKeycode)
+			k := int(kc - setup.MinKeycode)
+			for _, ks := range mapping.Keysyms[k*perKc : (k+1)*perKc] {
+				if ks == MODE_SWITCH {
+					modeSwitchMask |= 1 << uint(mod)
+				}
+			}
+		}
+	}
+
+	for {
+		ev, xerr := X.WaitForEvent()
+		if xerr != nil {
+			log.Printf("Error: %s\n", xerr)
+			return
+		}
+		if ev == nil {
+			return
+		}
+
+		log.Printf("Event: %s\n", ev)
+		switch e := ev.(type) {
+		case xproto.UnmapNotifyEvent:
+			return
+
+		case xproto.KeymapNotifyEvent:
+			// e.Keys is a 32 * 8 large bitmap indicating which keys are
+			// currently pressed down. This is sent "after every EnterNotify
+			// and FocusIn" but it also seems to fire when the keyboard layout
+			// changes. aixterm manual even speaks of that explicitly.
+			//
+			// But since changing the effective group involves no changes to
+			// the compatibility mapping, there's nothing for us to do.
+
+		case xproto.MappingNotifyEvent:
+			// e.FirstKeyCode .. e.Count changes have happened but rereading
+			// everything is the simpler thing to do.
+			mapping, err = xproto.GetKeyboardMapping(X, setup.MinKeycode,
+				byte(setup.MaxKeycode-setup.MinKeycode+1)).Reply()
+			if err != nil {
+				log.Fatalln(err)
+			}
+
+			// TODO: We should also repeat the search for MODE SWITCH.
+
+		case xproto.KeyPressEvent:
+			step := int(mapping.KeysymsPerKeycode)
+			from := int(e.Detail-setup.MinKeycode) * step
+			ks := mapping.Keysyms[from : from+step]
+
+			// Strip trailing NoSymbol entries.
+			for len(ks) > 0 && ks[len(ks)-1] == 0 {
+				ks = ks[:len(ks)-1]
+			}
+
+			// Expand back to at least 4.
+			switch {
+			case len(ks) == 1:
+				ks = append(ks, 0, ks[0], 0)
+			case len(ks) == 2:
+				ks = append(ks, ks[0], ks[1])
+			case len(ks) == 3:
+				ks = append(ks, 0)
+			}
+
+			// Other silly expansion rules, only applied to basic ASCII.
+			if ks[1] == 0 {
+				ks[1] = ks[0]
+				if ks[0] >= 'A' && ks[0] <= 'Z' ||
+					ks[0] >= 'a' && ks[0] <= 'z' {
+					ks[0] = ks[0] | 32
+					ks[1] = ks[0] &^ 32
+				}
+			}
+
+			if ks[3] == 0 {
+				ks[3] = ks[2]
+				if ks[2] >= 'A' && ks[2] <= 'Z' ||
+					ks[2] >= 'a' && ks[2] <= 'z' {
+					ks[2] = ks[2] | 32
+					ks[3] = ks[2] &^ 32
+				}
+			}
+
+			// We only have enough information to switch between two groups.
+			offset := 0
+			if e.State&modeSwitchMask != 0 {
+				offset += 2
+			}
+
+			var result xproto.Keysym
+
+			shift := e.State&xproto.ModMaskShift != 0
+			lock := e.State&xproto.ModMaskLock != 0
+			switch {
+			case !shift && !lock:
+				result = ks[offset+0]
+			case !shift && lock:
+				if ks[offset+0] >= 'a' && ks[offset+0] <= 'z' {
+					result = ks[offset+1]
+				} else {
+					result = ks[offset+0]
+				}
+			case shift && lock:
+				if ks[offset+1] >= 'a' && ks[offset+1] <= 'z' {
+					result = ks[offset+1] &^ 32
+				} else {
+					result = ks[offset+1]
+				}
+			case shift:
+				result = ks[offset+1]
+			}
+
+			if result <= 0xff {
+				log.Printf("%c (Latin-1)\n", rune(result))
+			} else {
+				log.Println(result)
+			}
+		}
+	}
+}