Speed up SetContent by checking length of combining characters before reflect.DeepEqual

[kivattt]

Adding these length checks before the reflect.DeepEqual speeds up SetContent when not drawing Unicode combining characters

With xset r rate 300 255 (key repeating 255 times per second), I recorded myself scrolling through 2000 files in my file manager project where I'm using tview with and without (left) this change:

tcell_change.mp4

(6x sped up)

I believe the performance difference is a lot less dramatic for most projects, since in this old version of my file manager the screen was always unnecessarily being cleared with Box.DrawForSubclass() in tview

[kivattt]

With the way I'm testing it, I see no difference with your change, but it's certainly easier to read and I'm not that familiar with the problem

[kivattt]

Nevermind, I can see a stuck character on the screen when I use your change, I'll send a video demonstrating it

[gdamore]

My concern is that there may be cases where the lengths are unequal.  Those need to be treated as dirty.

…

On Oct 6, 2024 at 6:10 PM -0700, kivattt ***@***.***>, wrote: Nevermind, I can see a stuck character on the screen when I use your change, I'll send a video demonstrating it — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you commented.Message ID: ***@***.***>

[kivattt]

On second glance, I think you just had the ! in the wrong place, this new commit fixes the stuck character issue I noticed

[kivattt]

Nevermind, my commit changes the behaviour, so I think your change is the more correct one and the "stuck" character I'm seeing is not an issue with tcell

[kivattt]

I use this to bruteforce check if something changed

package main

import (
        "fmt"
        "math/rand"
        "os"
        "reflect"
        "strconv"
)

func oldOne(c cell, mainc rune, combc []rune) bool {
        return (c.width > 0) && (mainc != c.currMain || !reflect.DeepEqual(combc, c.currComb))
}

func newOne(c cell, mainc rune, combc []rune) bool {
        return (c.width > 0) && (mainc != c.currMain || len(combc) != len(c.currComb) || (len(combc) > 0 && !reflect.DeepEqual(combc, c.currComb)))
}

func randRune() rune {
        return rune(rand.Intn(10)) // Low enough so 2 random runes can match
}

func randRuneSlice() []rune {
        var ret []rune
        upper := rand.Intn(5)
        for i := 1; i < upper; i++ {
                ret = append(ret, randRune())
        }
        return ret
}

type cell struct {
        currMain rune
        currComb []rune
        width    int
}

func main() {
        for i := 0; i < 10000000; i++ {
                c := cell{
                        currMain: randRune(),
                        currComb: randRuneSlice(),
                        width:    rand.Intn(5),
                }
                mainc := randRune()
                combc := randRuneSlice()

                if oldOne(c, mainc, combc) != newOne(c, mainc, combc) {
                        fmt.Println("oldOne and newOne differ!")
                        fmt.Println("c.currMain:", c.currMain)
                        fmt.Println("c.currComb:", c.currComb)
                        fmt.Println("c.width:", c.width)
                        fmt.Println("mainc: " + strconv.Itoa(int(mainc)))
                        fmt.Println("combc:", combc)
                        os.Exit(1)
                }
        }

        fmt.Println("oldOne and newOne match!")
}