experimental WIP

this commit experiments with node and edge rendering.

For these I'm trying a Page element with a list of Node and Edge
primitives.

Node primitives are textviews.

Edges are a new, custom primitive.

the edge only draws a line from 0,0 to 5,5 right now but shows that I'm
able to implement a Draw that just writes arbitrary characters to the
screen.

I need to do several things, some of which suggest that i'm abusing the
Pages primitive in terrible ways:

- Add and remove nodes as needed. Pages has no Clear() or Reset(). I
  will have to manually keep track of the page -> node relationship
- Give nodes and edges page names that are unique. I won't really be
  using these and I must avoid collisions.
- Relate edges to nodes somehow so they can be drawn properly
- Ensure that all edges are drawn before all nodes

and a lot more

A tremendous amount of work is ahead but I at least have some basic
stuff proven to be workable.

main.go

@@ -2,7 +2,9 @@ package main
 
 import (
 	"fmt"
+	"math/rand"
 	"os"
+	"time"
 
 	"github.com/gdamore/tcell/v2"
 	"github.com/rivo/tview"
@@ -22,11 +24,12 @@ type UI struct {
 	Mode   mode
 	App    *tview.Application
 	Fields []field
+	Nodes  []node
 
 	// UI things
 	Pages     *tview.Pages
 	TopFlex   *tview.Flex
-	Field     *tview.Box
+	Field     *tview.Pages
 	FieldBar  *tview.Flex
 	BottomBar *tview.Pages
 	ExInput   *tview.InputField
@@ -83,15 +86,57 @@ type field struct {
 	Selected bool
 }
 
+type node struct {
+	Text  string
+	Edges []*node
+	X     int
+	Y     int
+}
+
+type Edge struct {
+}
+
+func (e Edge) Draw(screen tcell.Screen) {
+	screen.SetContent(0, 0, '!', []rune{}, tcell.StyleDefault)
+}
+
+func (e Edge) GetRect() (int, int, int, int) {
+	return 0, 0, 0, 0
+}
+
+func (e Edge) SetRect(x, y, width, height int) {
+}
+
+func (e Edge) InputHandler() func(_ *tcell.EventKey, _ func(p tview.Primitive)) {
+	return func(event *tcell.EventKey, setFocus func(p tview.Primitive)) {}
+}
+
+func (e Edge) HasFocus() bool {
+	return false
+}
+
+func (e Edge) Focus(delegate func(p tview.Primitive)) {
+}
+
+func (e Edge) Blur() {
+}
+
+func (e Edge) MouseHandler() func(action tview.MouseAction, event *tcell.EventMouse, setFocus func(p tview.Primitive)) (consumed bool, capture tview.Primitive) {
+	return func(action tview.MouseAction, event *tcell.EventMouse, setFocus func(p tview.Primitive)) (consumed bool, capture tview.Primitive) {
+		return false, nil
+	}
+}
+
 func NewUI() *UI {
 	app := tview.NewApplication()
 	ui := UI{
 		Mode:      modeNormal,
 		App:       app,
 		Fields:    []field{{"scratch", true}, {"test", false}},
+		Nodes:     []node{},
 		Pages:     tview.NewPages(),
 		TopFlex:   tview.NewFlex(),
-		Field:     tview.NewBox(),
+		Field:     tview.NewPages(),
 		FieldBar:  tview.NewFlex(),
 		BottomBar: tview.NewPages(),
 		ExInput:   tview.NewInputField(),
@@ -118,7 +163,33 @@ func NewUI() *UI {
 
 	ui.FieldBar.SetDirection(tview.FlexColumn)
 
+	ui.Nodes = append(ui.Nodes, node{
+		Text: "foobar\nbaz\nquux",
+	})
+	ui.Nodes = append(ui.Nodes, node{
+		Text: "hello\nthere\nhow",
+	})
+
+	x := 0
+	y := 0
+
+	rand.Seed(time.Now().Unix())
+
+	for _, n := range ui.Nodes {
+		b := tview.NewTextView()
+		b.SetText(n.Text)
+		b.SetBorder(true)
+		b.SetRect(x, y, 10, 5)
+		x += 20
+		ui.Field.AddPage(fmt.Sprintf("%d", rand.Intn(10000)), b, false, true)
+	}
+
+	ui.Field.AddPage("edge", Edge{}, false, true)
+
 	app.SetBeforeDrawFunc(func(_ tcell.Screen) bool {
+		// Handle nodes
+		// TODO
+
 		// Handle field bar
 		ui.FieldBar.Clear()