TextEdit & Highlighting: performance improvements & changes to architecture

I ran pprof to find what was causing stuttering, and found it to be the
getTabCountInLineAtCol function in TextEdit, because it was iterating
many bytes of the buffer, for each rune rendered. Replaced it with a more
optimal system. Also changed the architecture of the highlighting system
to use a single RegexpRange structure for all regular expressions. This
allows for optimizations and multiline matches in the future.

main.go

@@ -2,15 +2,24 @@ package main
 
 import (
 	"errors"
+	"flag"
 	"fmt"
+	"log"
 	"io/fs"
 	"io/ioutil"
 	"os"
+	"runtime"
+	"runtime/pprof"
 
 	"github.com/fivemoreminix/qedit/ui"
 	"github.com/gdamore/tcell/v2"
 )
 
+var (
+	cpuprofile = flag.String("cpuprofile", "", "write cpu profile to `file`")
+	memprofile = flag.String("memprofile", "", "write memory profile to `file`")
+)
+
 var theme = ui.Theme{
 	"StatusBar": tcell.Style{}.Foreground(tcell.ColorBlack).Background(tcell.ColorSilver),
 }
@@ -32,6 +41,19 @@ func changeFocus(to ui.Component) {
 }
 
 func main() {
+	flag.Parse()
+	if *cpuprofile != "" {
+		f, err := os.Create(*cpuprofile)
+		if err != nil {
+			log.Fatal("Could not create CPU profile: ", err)
+		}
+		defer f.Close()
+		if err := pprof.StartCPUProfile(f); err != nil {
+			log.Fatal("Could not start CPU profile: ", err)
+		}
+		defer pprof.StopCPUProfile()
+	}
+
 	s, e := tcell.NewScreen()
 	if e != nil {
 		fmt.Fprintf(os.Stderr, "%v\n", e)
@@ -43,6 +65,7 @@ func main() {
 	}
 	defer s.Fini() // Useful for handling panics
 
+	var closing bool
 	sizex, sizey := s.Size()
 
 	tabContainer = ui.NewTabContainer(&theme)
@@ -57,6 +80,11 @@ func main() {
 	// Open files from command-line arguments
 	if len(os.Args) > 1 {
 		for i := 1; i < len(os.Args); i++ {
+			if os.Args[i] == "-cpuprofile" || os.Args[i] == "-memprofile" {
+				i++
+				continue
+			}
+
 			_, err := os.Stat(os.Args[i])
 
 			var dirty bool
@@ -167,8 +195,7 @@ func main() {
 		if tabContainer.GetTabCount() > 0 {
 			tabContainer.RemoveTab(tabContainer.GetSelectedTabIdx())
 		} else { // No tabs open; close the editor
-			s.Fini()
-			os.Exit(0)
+			closing = true
 		}
 	}}})
 
@@ -254,7 +281,7 @@ func main() {
 
 	changeFocus(tabContainer) // TabContainer is focused by default
 
-	for {
+	for !closing {
 		s.Clear()
 
 		// Draw background (grey and black checkerboard)
@@ -332,4 +359,16 @@ func main() {
 			focusedComponent.HandleEvent(ev)
 		}
 	}
+
+	if *memprofile != "" {
+		f, err := os.Create(*memprofile)
+		if err != nil {
+			log.Fatal("Could not create memory profile: ", err)
+		}
+		defer f.Close()
+		runtime.GC() // Get updated statistics
+		if err := pprof.WriteHeapProfile(f); err != nil {
+			log.Fatal("Could not write memory profile: ", err)
+		}
+	}
 }