Added new finder primitive

demos/finder/README.md

@@ -0,0 +1,9 @@
+![Screenshot](screenshot.png)
+
+The finder primitive is inspired by [go-fuzzyfinder](https://github.com/ktr0731/go-fuzzyfinder) but is more 
+configurable in terms of appearance.
+
+In contrast to `go-fuzzyfinder`, this implementation does not use a fuzzy search algorithm. It will just 
+search for and highlight the first substring that matches the entered text.
+
+If you want to perform a more elaborate search, you can also provide a custom matcher function (see example `customatcher`).

demos/finder/customatcher/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"github.com/rivo/tview"
+	"regexp"
+)
+
+func main() {
+
+	app := tview.NewApplication()
+
+	items := []string{
+		"foo",
+		"bar",
+		"foo bar foo",
+		"baz",
+		"baz two",
+		"lorem ipsum",
+	}
+
+	// Don't use the default matcher (which will just return the first substring indices and uses a fixed score of 0).
+	// This custom implementation uses a regex expression and returns all matching substring indices.
+	// Moreover, it uses the number of matches for each item as score value (the default matcher assumes score 0 for
+	// every item). Thus, items with more matches will be sorted before items with fewer matches (e.g. when searching
+	// for "foo", item "foo bar foo" will be sorted before "foo".
+	matcher := func(item string, filter string) ([][2]int, int, bool) {
+
+		re := regexp.MustCompile(filter)
+
+		matchedIndices := re.FindAllStringSubmatchIndex(item, -1)
+		if matchCount := len(matchedIndices); matchCount > 0 {
+			matches := make([][2]int, matchCount)
+			for i := range matchedIndices {
+				matches[i] = [2]int{matchedIndices[i][0], matchedIndices[i][1]}
+			}
+			return matches, len(matchedIndices), true
+		}
+
+		// no match
+		return [][2]int{}, 0, false
+	}
+
+	finder := tview.NewFinder().
+		SetItems(len(items), func(index int) string {
+			return items[index]
+		}).
+		SetDoneFunc(func(index int) {
+			app.Stop()
+		}).
+		SetMatcherFunc(matcher)
+
+	if err := app.SetRoot(finder, true).Run(); err != nil {
+		panic(err)
+	}
+}

demos/finder/main.go

@@ -0,0 +1,64 @@
+// Demo code for the finder primitive.
+package main
+
+import (
+	"fmt"
+	"github.com/rivo/tview"
+)
+
+type Item struct {
+	Title string
+}
+
+func (i *Item) preview() string {
+	return fmt.Sprintf("\033[1;33;4;44mTitle: %s\033[0m", i.Title)
+}
+
+func main() {
+
+	app := tview.NewApplication()
+
+	items := []*Item{
+		{Title: "foo"},
+		{Title: "bar"},
+		{Title: "foo foo"},
+		{Title: "baz one - this is a very long item which should overflow horizontally at some point"},
+		{Title: "baz two"},
+		{Title: "lorem ipsum"},
+	}
+
+	selectedView := tview.NewTextView()
+	selectedView.SetBorder(true)
+	selectedView.SetTitle("Selected item")
+	selectedView.SetDynamicColors(true)
+
+	finder := tview.NewFinder().
+		SetItems(len(items), func(index int) string {
+			return items[index].Title
+		}).
+		SetDoneFunc(func(index int) {
+			app.Stop()
+			fmt.Printf("Selected index: %d", index)
+		}).
+		SetChangedFunc(func(index int) {
+			if index >= 0 {
+				selectedView.SetText("")
+				writer := tview.ANSIWriter(selectedView)
+				_, _ = writer.Write([]byte(items[index].preview()))
+			} else {
+				selectedView.SetText("")
+			}
+		})
+
+	finder.
+		SetBorder(true).
+		SetTitle("Pick an item")
+
+	flex := tview.NewFlex().SetDirection(tview.FlexColumn).
+		AddItem(finder, 0, 1, true).
+		AddItem(selectedView, 0, 1, false)
+
+	if err := app.SetRoot(flex, true).Run(); err != nil {
+		panic(err)
+	}
+}