From 982a68e5a21f3b2dff494132b34639084fd3e9ac Mon Sep 17 00:00:00 2001
From: seebs <seebs@seebs.net>
Date: Sun, 24 May 2020 13:20:21 -0500
Subject: [PATCH] inpututil: use slices for maps where keys are small
 contiguous integers (#1169)

Durations for key presses and gamepad button presses were being stored
in map[int]int, where the key values were always small integers, and
furthermore, were always contiguous and contained the whole set. It's
much faster and cheaper to do those with slices.

We could probably do this with mouse buttons, but I was wary of that
code because I don't see any handling for more-than-three-button
mice. Similar logic could perhaps apply to touch events, but there
it might make more sense to use a dynamic allocation of some kind.

It might be more efficient to just swap the two slices back and
forth, computing the new values from the previous values and
then swapping the slice arrays themselves, but that seemed like
a more intrusive change.
---
 inpututil/inpututil.go | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/inpututil/inpututil.go b/inpututil/inpututil.go
index df8a6a063..83df34b61 100644
--- a/inpututil/inpututil.go
+++ b/inpututil/inpututil.go
@@ -24,8 +24,8 @@ import (
 )
 
 type inputState struct {
-	keyDurations     map[ebiten.Key]int
-	prevKeyDurations map[ebiten.Key]int
+	keyDurations     []int
+	prevKeyDurations []int
 
 	mouseButtonDurations     map[ebiten.MouseButton]int
 	prevMouseButtonDurations map[ebiten.MouseButton]int
@@ -33,8 +33,8 @@ type inputState struct {
 	gamepadIDs     map[int]struct{}
 	prevGamepadIDs map[int]struct{}
 
-	gamepadButtonDurations     map[int]map[ebiten.GamepadButton]int
-	prevGamepadButtonDurations map[int]map[ebiten.GamepadButton]int
+	gamepadButtonDurations     map[int][]int
+	prevGamepadButtonDurations map[int][]int
 
 	touchDurations     map[int]int
 	prevTouchDurations map[int]int
@@ -43,8 +43,8 @@ type inputState struct {
 }
 
 var theInputState = &inputState{
-	keyDurations:     map[ebiten.Key]int{},
-	prevKeyDurations: map[ebiten.Key]int{},
+	keyDurations:     make([]int, ebiten.KeyMax+1),
+	prevKeyDurations: make([]int, ebiten.KeyMax+1),
 
 	mouseButtonDurations:     map[ebiten.MouseButton]int{},
 	prevMouseButtonDurations: map[ebiten.MouseButton]int{},
@@ -52,8 +52,8 @@ var theInputState = &inputState{
 	gamepadIDs:     map[int]struct{}{},
 	prevGamepadIDs: map[int]struct{}{},
 
-	gamepadButtonDurations:     map[int]map[ebiten.GamepadButton]int{},
-	prevGamepadButtonDurations: map[int]map[ebiten.GamepadButton]int{},
+	gamepadButtonDurations:     map[int][]int{},
+	prevGamepadButtonDurations: map[int][]int{},
 
 	touchDurations:     map[int]int{},
 	prevTouchDurations: map[int]int{},
@@ -71,8 +71,8 @@ func (i *inputState) update() {
 	defer i.m.Unlock()
 
 	// Keyboard
+	copy(i.prevKeyDurations[:], i.keyDurations[:])
 	for k := ebiten.Key(0); k <= ebiten.KeyMax; k++ {
-		i.prevKeyDurations[k] = i.keyDurations[k]
 		if ebiten.IsKeyPressed(k) {
 			i.keyDurations[k]++
 		} else {
@@ -103,19 +103,16 @@ func (i *inputState) update() {
 	}
 
 	// Copy the gamepad button durations.
-	i.prevGamepadButtonDurations = map[int]map[ebiten.GamepadButton]int{}
+	i.prevGamepadButtonDurations = map[int][]int{}
 	for id, ds := range i.gamepadButtonDurations {
-		i.prevGamepadButtonDurations[id] = map[ebiten.GamepadButton]int{}
-		for b, d := range ds {
-			i.prevGamepadButtonDurations[id][b] = d
-		}
+		i.prevGamepadButtonDurations[id] = append([]int{}, ds...)
 	}
 
 	i.gamepadIDs = map[int]struct{}{}
 	for _, id := range ebiten.GamepadIDs() {
 		i.gamepadIDs[id] = struct{}{}
 		if _, ok := i.gamepadButtonDurations[id]; !ok {
-			i.gamepadButtonDurations[id] = map[ebiten.GamepadButton]int{}
+			i.gamepadButtonDurations[id] = make([]int, ebiten.GamepadButtonMax+1)
 		}
 		n := ebiten.GamepadButtonNum(id)
 		for b := ebiten.GamepadButton(0); b < ebiten.GamepadButton(n); b++ {