From 2503fba46f285c8459b65695def9a5ad2ed06957 Mon Sep 17 00:00:00 2001
From: vilmibm <vilmibm@github.com>
Date: Wed, 14 Jun 2023 15:13:58 -0700
Subject: [PATCH] implement viewport

---
 main.go | 85 +++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 74 insertions(+), 11 deletions(-)

diff --git a/main.go b/main.go
index 46c054d..1cfe492 100644
--- a/main.go
+++ b/main.go
@@ -21,10 +21,11 @@ const (
 )
 
 type UI struct {
-	Mode   mode
-	App    *tview.Application
-	Fields []field
-	Nodes  []node
+	Mode     mode
+	App      *tview.Application
+	Fields   []field
+	Nodes    []*node
+	Viewport *viewport
 
 	// UI things
 	Pages     *tview.Pages
@@ -54,6 +55,18 @@ func (ui *UI) handleInput(event *tcell.EventKey) *tcell.EventKey {
 		case ':':
 			ui.setMode(modeEx)
 			return nil
+		case 'h':
+			ui.Viewport.X--
+			return nil
+		case 'j':
+			ui.Viewport.Y++
+			return nil
+		case 'k':
+			ui.Viewport.Y--
+			return nil
+		case 'l':
+			ui.Viewport.X++
+			return nil
 		}
 	case modeEx:
 	case modeFocus:
@@ -81,6 +94,31 @@ func (ui *UI) handleExInput(key tcell.Key) {
 	fmt.Fprintf(ui.ExOutput, "did not understand '%s', sorry", text)
 }
 
+/*
+
+three coordinate systems:
+
+- the infinite coordinate plane where nodes live. it is centered at 0,0 but nodes can be placed anywhere.
+- the viewport representing what part of the infinite plane the user is looking at. the viewport has an origin in the infinite plane and a width and height
+- the screen onto which characters are drawn. always rooted at 0,0; always has a width and a height that matches the width and height of the viewport
+
+the viewport is the most pressing question. nodes exist in an XY plane and the field view is a viewport onto that plane.
+
+nodes have a "real" X,Y coordinate pair and a width and a height. the viewport has a width, a height, and point A,B from which it originates.
+
+Moving the viewport means changing A,B. To see what should be shown on the screen, compare a node's X,Y to A,B. If X+width > A and Y+height > B && X+width < A+width and Y+maxheight < B+maxheight then it should be shown. For each node, it also has coordinates H,J in the screen based on the viewport position.
+
+But how to reconcile this with tview? can i add all of the nodes to the scene tree then update their H,J as the viewport changes and hope tview just does the right thing? I think I should start there.
+
+*/
+
+type viewport struct {
+	X int
+	Y int
+	W int
+	H int
+}
+
 type field struct {
 	Name     string
 	Selected bool
@@ -91,13 +129,15 @@ type node struct {
 	Edges []*node
 	X     int
 	Y     int
+	widg  *tview.TextView
+	// "screen" x and y are stored on corresponding tview widget as well as width/height
 }
 
 type Edge struct {
+	nodes []*node
 }
 
 func (e Edge) Draw(screen tcell.Screen) {
-
 	screen.SetContent(0, 0, tview.BoxDrawingsLightDiagonalUpperLeftToLowerRight, []rune{}, tcell.StyleDefault)
 	screen.SetContent(1, 1, tview.BoxDrawingsLightDiagonalUpperLeftToLowerRight, []rune{}, tcell.StyleDefault)
 	screen.SetContent(2, 2, tview.BoxDrawingsLightDiagonalUpperLeftToLowerRight, []rune{}, tcell.StyleDefault)
@@ -139,7 +179,8 @@ func NewUI() *UI {
 		Mode:      modeNormal,
 		App:       app,
 		Fields:    []field{{"scratch", true}, {"test", false}},
-		Nodes:     []node{},
+		Nodes:     []*node{},
+		Viewport:  &viewport{},
 		Pages:     tview.NewPages(),
 		TopFlex:   tview.NewFlex(),
 		Field:     tview.NewPages(),
@@ -169,14 +210,23 @@ func NewUI() *UI {
 
 	ui.FieldBar.SetDirection(tview.FlexColumn)
 
-	ui.Nodes = append(ui.Nodes, node{
+	ui.Nodes = append(ui.Nodes, &node{
 		Text: "foobar\nbaz\nquux",
 	})
-	ui.Nodes = append(ui.Nodes, node{
+	ui.Nodes = append(ui.Nodes, &node{
+		Text: "the wild box",
+	})
+	ui.Nodes = append(ui.Nodes, &node{
+		Text: "cool stories bros",
+	})
+	ui.Nodes = append(ui.Nodes, &node{
+		Text: "why not",
+	})
+	ui.Nodes = append(ui.Nodes, &node{
 		Text: "hello\nthere\nhow",
 	})
 
-	x := 0
+	x := 60
 	y := 0
 
 	rand.Seed(time.Now().Unix())
@@ -186,14 +236,27 @@ func NewUI() *UI {
 		b.SetText(n.Text)
 		b.SetBorder(true)
 		b.SetRect(x, y, 10, 5)
-		x += 20
+		n.X = x
+		n.Y = y
+		x -= 20
 		ui.Field.AddPage(fmt.Sprintf("%d", rand.Intn(10000)), b, false, true)
+		n.widg = b
 	}
 	ui.Field.AddPage("edge", Edge{}, false, true)
 
 	app.SetBeforeDrawFunc(func(_ tcell.Screen) bool {
+		// Viewport
+		_, _, w, h := ui.Field.GetRect()
+		ui.Viewport.W = w
+		ui.Viewport.H = h
+
 		// Handle nodes
-		// TODO
+		for _, n := range ui.Nodes {
+			_, _, w, h := n.widg.GetRect()
+			x := n.X - ui.Viewport.X
+			y := n.Y - ui.Viewport.Y
+			n.widg.SetRect(x, y, w, h)
+		}
 
 		// Handle field bar
 		ui.FieldBar.Clear()