THE DRAGON HAS BEEN SLAIN

Numlock is fully supported, as well as shift lock. Of course, I
cannot properly test shift lock or caps lock because I have neither
of those things, but I assume they work as well as num lock does.

backends/x/unicode.go

@@ -1,5 +1,7 @@
 package x
 
+// TODO: rename this file? lol
+
 // import "fmt"
 import "unicode"
 import "github.com/jezek/xgb/xproto"
@@ -117,13 +119,11 @@ func (backend *Backend) keycodeToButton (
 	button    stone.Button,
 	numberPad bool,
 ) {
-	// FIXME: also set shift to true if the lock modifier is on and the lock
-	// modifier is interpreted as shiftLock
-	shift    := state & xproto.ModMaskShift > 0
-
-	// FIXME: only set this to true if the lock modifier is on and the lock
-	// modifier is interpreted as capsLock
-	capsLock := state & xproto.ModMaskLock  > 0
+	shift :=
+		state & xproto.ModMaskShift             > 0 ||
+		state & backend.modifierMasks.shiftLock > 0
+	capsLock := state & backend.modifierMasks.capsLock  > 0
+	numLock  := state & backend.modifierMasks.numLock   > 0
 
 	symbol1 := keybind.KeysymGet(backend.connection, keycode, 0)
 	symbol2 := keybind.KeysymGet(backend.connection, keycode, 1)
@@ -132,7 +132,19 @@ func (backend *Backend) keycodeToButton (
 
 	cased := false
 
-	// third paragraph
+	// PARAGRAPH 3
+	//
+	// A list of KeySyms is associated with each KeyCode. The list is
+	// intended to convey the set of symbols on the corresponding key. If
+	// the list (ignoring trailing NoSymbol entries) is a single KeySym
+	// ``K'', then the list is treated as if it were the list ``K NoSymbol
+	// K NoSymbol''. If the list (ignoring trailing NoSymbol entries) is a
+	// pair of KeySyms ``K1 K2'', then the list is treated as if it were the
+	// list ``K1 K2 K1 K2''. If the list (ignoring trailing NoSymbol
+	// entries) is a triple of KeySyms ``K1 K2 K3'', then the list is
+	// treated as if it were the list ``K1 K2 K3 NoSymbol''. When an
+	// explicit ``void'' element is desired in the list, the value
+	// VoidSymbol can be used.
 	switch {
 	case symbol2 == 0 && symbol3 == 0 && symbol4 == 0:
 		symbol3 = symbol1
@@ -151,7 +163,18 @@ func (backend *Backend) keycodeToButton (
 	// FIXME: we ignore mode switch stuff
 	_ = symbol4Rune
 
-	// fourth paragraph
+	// PARAGRAPH 4
+	//
+	// The first four elements of the list are split into two groups of
+	// KeySyms. Group 1 contains the first and second KeySyms; Group 2
+	// contains the third and fourth KeySyms. Within each group, if the
+	// second element of the group is NoSymbol , then the group should be
+	// treated as if the second element were the same as the first element,
+	// except when the first element is an alphabetic KeySym ``K'' for which
+	// both lowercase and uppercase forms are defined. In that case, the
+	// group should be treated as if the first element were the lowercase
+	// form of ``K'' and the second element were the uppercase form of
+	// ``K.''
 	if symbol2 == 0 {
 		upper := unicode.IsUpper(symbol1Rune)
 		lower := unicode.IsLower(symbol1Rune)
@@ -180,30 +203,60 @@ func (backend *Backend) keycodeToButton (
 	var selectedKeysym xproto.Keysym
 	var selectedRune   rune
 	
-	// big ol list in the middle
+	_, symbol2IsNumPad := keypadCodeTable[symbol2]
+
+	// "PARAGRAPH" 5
+	//
+	// Within a group, the choice of KeySym is determined by applying the
+	// first rule that is satisfied from the following list:
 	switch {
-	// FIXME: take into account numlock
+	case numLock && symbol2IsNumPad:
+		// The numlock modifier is on and the second KeySym is a keypad
+		// KeySym. In this case, if the Shift modifier is on, or if the
+		// Lock modifier is on and is interpreted as ShiftLock, then the
+		// first KeySym is used, otherwise the second KeySym is used.
+		if shift {
+			selectedKeysym = symbol1
+			selectedRune   = symbol1Rune
+		} else {
+			selectedKeysym = symbol2
+			selectedRune   = symbol2Rune
+		}
+
 	case !shift && !capsLock:
+		// The Shift and Lock modifiers are both off. In this case, the
+		// first KeySym is used.
 		selectedKeysym = symbol1
 		selectedRune   = symbol1Rune
-		
+
 	case !shift && capsLock:
+		// The Shift modifier is off, and the Lock modifier is on and is
+		// interpreted as CapsLock. In this case, the first KeySym is
+		// used, but if that KeySym is lowercase alphabetic, then the
+		// corresponding uppercase KeySym is used instead.
 		if cased && unicode.IsLower(symbol1Rune) {
 			selectedRune = symbol2Rune
 		} else {
 			selectedKeysym = symbol1
 			selectedRune   = symbol1Rune
 		}
-		
+
 	case shift && capsLock:
+		// The Shift modifier is on, and the Lock modifier is on and is
+		// interpreted as CapsLock. In this case, the second KeySym is
+		// used, but if that KeySym is lowercase alphabetic, then the
+		// corresponding uppercase KeySym is used instead.
 		if cased && unicode.IsLower(symbol2Rune) {
 			selectedRune = unicode.ToUpper(symbol2Rune)
 		} else {
 			selectedKeysym = symbol2
 			selectedRune   = symbol2Rune
 		}
-		
+
 	case shift:
+		// The Shift modifier is on, or the Lock modifier is on and is
+		// interpreted as ShiftLock, or both. In this case, the second
+		// KeySym is used.
 		selectedKeysym = symbol2
 		selectedRune   = symbol2Rune
 	}