WIP Texture Caching

NOTICE: Chunk size set to 100 for visual testing!
NOTICE: guitest references a bmp file that isn't checked in!

BUGS REMAINING:
- When scrolling the level in Edit Mode, some of the chunks will pop
  out of existence randomly.
- When clicking-dragging to draw in Edit Mode, if the scroll position
  is not at 0,0 then the pixels drawn will be offset from the cursor.
- These are to do with the Scroll position and chunk coordinate calc
  functions probably.

Implements a texture caching interface to stop redrawing everything
pixel by pixel on every frame.

The texture caching workflow is briefly:

- The uix.Canvas widget's Present() function iterates over the list of
  Chunk Coordinates that are visible inside of the current viewport
  (i.e. viewable on screen)
- For each Chunk:
  - Make it render and/or return its cached Texture object.
  - Work out how much of the Chunk will be visible and how to crop the
    boxes for the Copy()
  - Copy the cached Texture instead of drawing all the pixels every
    time like we were doing before.
- The Chunk.Texture() function that returns said Texture:
  - It calls Chunk.ToBitmap() to save a bitmap on disk.
  - It calls Engine.NewBitmap() to get a Texture it can hang onto.
  - It hangs onto the Texture and returns it on future calls.
  - Any call to Set() or Delete() a pixel will invalidate the cache
    (mark the Chunk "dirty") and Texture() will rebuild next call.

The interface `render.Texturer` provides a way for rendering backends
(SDL2, OpenGL) to transport a "texture" of their own kind without
exposing the type details to the user.

The interface `render.Engine` adds two new methods:

* NewBitmap(filename string) (Texturer, error)
* Copy(t Texturer, src, dst Rect)

NewBitmap should open a bitmap image on disk and return it wrapped in a
Texturer (really it's an SDL2 Texture). This is for caching purposes.
Next the Copy() function blits the texture onto the screen renderer
using the source and destination rectangles.

The uix.Canvas widget orchestrates the caching for the drawing it's
responsible for. It queries which chunks are viewable in the Canvas
viewport (scroll and bounding boxes), has each chunk render out their
entire bitmap image to then cache them as SDL textures and then only
_those_ need to be copied out to the renderer each frame.

The frame rate now sits at a decent 60 FPS even when the drawing gets
messy and full of lines. Each unique version of each chunk needs to
render only one time and then it's a fast copy operation for future
ticks.

Other changes:

- Chunker now assigns each Chunk what their coordinate and size are, so
  that the chunk can self reference that information. This info is
  considered read-only but that isn't really enforced.
- Add Chunker.IterViewportChunks() that returns a channel of Chunk
  Coordinates that are visible in your viewport, rather than iterating
  over all of the pixels in all of those chunks.
- Add Chunk.ToBitmap(filename) that causes a Chunk to render its pixels
  to a bitmap image on disk. SDL2 can natively speak Bitmaps for texture
  caching. Currently these go to files in /tmp but will soon go into your
  $XDG_CACHE_FOLDER instead.
- Add Chunk.Texture() that causes a Chunk to render and then return a
  cached bitmap texture of the pixels it's responsible for. The texture
  is cached until the Chunk is next modified with Set() or Delete().
- UI: add an Image widget that currently just shows a bitmap image. It
  was the first test for caching bitmap images for efficiency. Can show
  any *.bmp file on disk!
- Editor UI: make the StatusBar boxes dynamically build from an array
  of string pointers to make it SUPER EASY to add/remove labels.

balance/numbers.go

@@ -10,7 +10,7 @@ var (
 	CanvasScrollSpeed int32 = 8
 
 	// Default chunk size for canvases.
-	ChunkSize = 1000
+	ChunkSize = 100
 
 	// Default size for a new Doodad.
 	DoodadSize = 100

editor_ui.go

@@ -20,9 +20,11 @@ type EditorUI struct {
 	Scene *EditorScene
 
 	// Variables
+	StatusBoxes        []*string
 	StatusMouseText    string
 	StatusPaletteText  string
 	StatusFilenameText string
+	StatusScrollText   string
 	selectedSwatch     string // name of selected swatch in palette
 	selectedDoodad     string
 
@@ -51,6 +53,15 @@ func NewEditorUI(d *Doodle, s *EditorScene) *EditorUI {
 		StatusMouseText:    "Cursor: (waiting)",
 		StatusPaletteText:  "Swatch: <none>",
 		StatusFilenameText: "Filename: <none>",
+		StatusScrollText:   "Hello world",
+	}
+
+	// Bind the StatusBoxes arrays to the text variables.
+	u.StatusBoxes = []*string{
+		&u.StatusMouseText,
+		&u.StatusPaletteText,
+		&u.StatusFilenameText,
+		&u.StatusScrollText,
 	}
 
 	u.Canvas = u.SetupCanvas(d)
@@ -84,6 +95,10 @@ func (u *EditorUI) Loop(ev *events.State) {
 	u.StatusPaletteText = fmt.Sprintf("Swatch: %s",
 		u.Canvas.Palette.ActiveSwatch,
 	)
+	u.StatusScrollText = fmt.Sprintf("Scroll: %s   Viewport: %s",
+		u.Canvas.Scroll,
+		u.Canvas.Viewport(),
+	)
 
 	// Statusbar filename label.
 	filename := "untitled.map"
@@ -142,6 +157,7 @@ func (u *EditorUI) SetupWorkspace(d *Doodle) *ui.Frame {
 // SetupCanvas configures the main drawing canvas in the editor.
 func (u *EditorUI) SetupCanvas(d *Doodle) *uix.Canvas {
 	drawing := uix.NewCanvas(balance.ChunkSize, true)
+	drawing.Name = "edit-canvas"
 	drawing.Palette = level.DefaultPalette()
 	if len(drawing.Palette.Swatches) > 0 {
 		drawing.SetSwatch(drawing.Palette.Swatches[0])
@@ -367,6 +383,7 @@ func (u *EditorUI) SetupPalette(d *Doodle) *ui.Window {
 			}
 
 			can := uix.NewCanvas(int(buttonSize), true)
+			can.Name = filename
 			can.LoadDoodad(doodad)
 			btn := ui.NewRadioButton(filename, &u.selectedDoodad, si, can)
 			btn.Resize(render.NewRect(
@@ -452,38 +469,23 @@ func (u *EditorUI) SetupStatusBar(d *Doodle) *ui.Frame {
 		BorderSize:  1,
 	}
 
-	cursorLabel := ui.NewLabel(ui.Label{
-		TextVariable: &u.StatusMouseText,
+	var labelHeight int32
+	for _, variable := range u.StatusBoxes {
+		label := ui.NewLabel(ui.Label{
+			TextVariable: variable,
 			Font:         balance.StatusFont,
 		})
-	cursorLabel.Configure(style)
-	cursorLabel.Compute(d.Engine)
-	frame.Pack(cursorLabel, ui.Pack{
+		label.Configure(style)
+		label.Compute(d.Engine)
+		frame.Pack(label, ui.Pack{
 			Anchor: ui.W,
 			PadX:   1,
 		})
 
-	paletteLabel := ui.NewLabel(ui.Label{
-		TextVariable: &u.StatusPaletteText,
-		Font:         balance.StatusFont,
-	})
-	paletteLabel.Configure(style)
-	paletteLabel.Compute(d.Engine)
-	frame.Pack(paletteLabel, ui.Pack{
-		Anchor: ui.W,
-		PadX:   1,
-	})
-
-	filenameLabel := ui.NewLabel(ui.Label{
-		TextVariable: &u.StatusFilenameText,
-		Font:         balance.StatusFont,
-	})
-	filenameLabel.Configure(style)
-	filenameLabel.Compute(d.Engine)
-	frame.Pack(filenameLabel, ui.Pack{
-		Anchor: ui.E,
-		PadX:   1,
-	})
+		if labelHeight == 0 {
+			labelHeight = label.BoxSize().H
+		}
+	}
 
 	// TODO: right-aligned labels clip out of bounds
 	extraLabel := ui.NewLabel(ui.Label{
@@ -503,7 +505,7 @@ func (u *EditorUI) SetupStatusBar(d *Doodle) *ui.Frame {
 
 	frame.Resize(render.Rect{
 		W: d.width,
-		H: cursorLabel.BoxSize().H + frame.BoxThickness(1),
+		H: labelHeight + frame.BoxThickness(1),
 	})
 	frame.Compute(d.Engine)
 	frame.MoveTo(render.Point{

guitest_scene.go

@@ -151,6 +151,7 @@ func (s *GUITestScene) Setup(d *Doodle) error {
 		})
 	}
 
+	// Main frame widgets.
 	frame.Pack(ui.NewLabel(ui.Label{
 		Text: "Hello World!",
 		Font: render.Text{
@@ -174,6 +175,17 @@ func (s *GUITestScene) Setup(d *Doodle) error {
 		Padding: 4,
 	})
 	cb.Supervise(s.Supervisor)
+
+	// Put an image in.
+	img, err := ui.OpenImage(d.Engine, "exit.bmp")
+	if err != nil {
+		log.Error(err.Error())
+	}
+	frame.Pack(img, ui.Pack{
+		Anchor:  ui.NE,
+		Padding: 4,
+	})
+
 	frame.Pack(ui.NewLabel(ui.Label{
 		Text: "Like Tk!",
 		Font: render.Text{

level/chunk.go

@@ -3,8 +3,12 @@ package level
 import (
 	"encoding/json"
 	"fmt"
+	"image"
+	"math"
+	"os"
 
 	"git.kirsle.net/apps/doodle/render"
+	"golang.org/x/image/bmp"
 )
 
 // Types of chunks.
@@ -17,6 +21,14 @@ const (
 type Chunk struct {
 	Type int // map vs. 2D array.
 	Accessor
+
+	// Values told to it from higher up, not stored in JSON.
+	Point render.Point
+	Size  int
+
+	// Texture cache properties so we don't redraw pixel-by-pixel every frame.
+	texture render.Texturer
+	dirty   bool
 }
 
 // JSONChunk holds a lightweight (interface-free) copy of the Chunk for
@@ -48,6 +60,134 @@ func NewChunk() *Chunk {
 	}
 }
 
+// Texture will return a cached texture for the rendering engine for this
+// chunk's pixel data. If the cache is dirty it will be rebuilt in this func.
+func (c *Chunk) Texture(e render.Engine, name string) render.Texturer {
+	if c.texture == nil || c.dirty {
+		err := c.ToBitmap("/tmp/" + name + ".bmp")
+		if err != nil {
+			log.Error("Texture: %s", err)
+		}
+
+		tex, err := e.NewBitmap("/tmp/" + name + ".bmp")
+		if err != nil {
+			log.Error("Texture: %s", err)
+		}
+
+		c.texture = tex
+		c.dirty = false
+	}
+	return c.texture
+}
+
+// ToBitmap exports the chunk's pixels as a bitmap image.
+func (c *Chunk) ToBitmap(filename string) error {
+	canvas := c.SizePositive()
+	imgSize := image.Rectangle{
+		Min: image.Point{},
+		Max: image.Point{
+			X: c.Size,
+			Y: c.Size,
+		},
+	}
+
+	if imgSize.Max.X == 0 {
+		imgSize.Max.X = int(canvas.W)
+	}
+	if imgSize.Max.Y == 0 {
+		imgSize.Max.Y = int(canvas.H)
+	}
+
+	img := image.NewRGBA(imgSize)
+
+	// Blank out the pixels.
+	for x := 0; x < img.Bounds().Max.X; x++ {
+		for y := 0; y < img.Bounds().Max.Y; y++ {
+			img.Set(x, y, render.RGBA(255, 255, 0, 153).ToColor())
+		}
+	}
+
+	// Pixel coordinate offset to map the Chunk World Position to the
+	// smaller image boundaries.
+	pointOffset := render.Point{
+		X: int32(math.Abs(float64(c.Point.X * int32(c.Size)))),
+		Y: int32(math.Abs(float64(c.Point.Y * int32(c.Size)))),
+	}
+
+	// Blot all the pixels onto it.
+	for px := range c.Iter() {
+		img.Set(
+			int(px.X-pointOffset.X),
+			int(px.Y-pointOffset.Y),
+			px.Swatch.Color.ToColor(),
+		)
+	}
+
+	fh, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer fh.Close()
+
+	return bmp.Encode(fh, img)
+}
+
+// Set proxies to the accessor and flags the texture as dirty.
+func (c *Chunk) Set(p render.Point, sw *Swatch) error {
+	c.dirty = true
+	return c.Accessor.Set(p, sw)
+}
+
+// Delete proxies to the accessor and flags the texture as dirty.
+func (c *Chunk) Delete(p render.Point) error {
+	c.dirty = true
+	return c.Accessor.Delete(p)
+}
+
+// Rect returns the bounding coordinates that the Chunk has pixels for.
+func (c *Chunk) Rect() render.Rect {
+	// Lowest and highest chunks.
+	var (
+		lowest  render.Point
+		highest render.Point
+	)
+
+	for coord := range c.Iter() {
+		if coord.X < lowest.X {
+			lowest.X = coord.X
+		}
+		if coord.Y < lowest.Y {
+			lowest.Y = coord.Y
+		}
+
+		if coord.X > highest.X {
+			highest.X = coord.X
+		}
+		if coord.Y > highest.Y {
+			highest.Y = coord.Y
+		}
+	}
+
+	return render.Rect{
+		X: lowest.X,
+		Y: lowest.Y,
+		W: highest.X,
+		H: highest.Y,
+	}
+}
+
+// SizePositive returns the Size anchored to 0,0 with only positive
+// coordinates.
+func (c *Chunk) SizePositive() render.Rect {
+	S := c.Rect()
+	return render.Rect{
+		X: c.Point.X * int32(c.Size),
+		Y: c.Point.Y * int32(c.Size),
+		W: int32(math.Abs(float64(S.X))) + S.W,
+		H: int32(math.Abs(float64(S.Y))) + S.H,
+	}
+}
+
 // Usage returns the percent of free space vs. allocated pixels in the chunk.
 func (c *Chunk) Usage(size int) float64 {
 	return float64(c.Len()) / float64(size)

level/chunker.go

@@ -30,6 +30,8 @@ func NewChunker(size int) *Chunker {
 func (c *Chunker) Inflate(pal *Palette) error {
 	for coord, chunk := range c.Chunks {
 		log.Debug("Chunker.Inflate: expanding chunk %s", coord)
+		chunk.Point = coord
+		chunk.Size = c.Size
 		chunk.Inflate(pal)
 	}
 	return nil
@@ -66,6 +68,58 @@ func (c *Chunker) IterViewport(viewport render.Rect) <-chan Pixel {
 	return pipe
 }
 
+// IterViewportChunks returns a channel to iterate over the Chunk objects that
+// appear within the viewport rect, instead of the pixels in each chunk.
+func (c *Chunker) IterViewportChunks(viewport render.Rect) <-chan render.Point {
+	pipe := make(chan render.Point)
+	go func() {
+		sent := make(map[render.Point]interface{})
+		for x := viewport.X; x < viewport.W; x += int32(c.Size / 4) {
+			for y := viewport.Y; y < viewport.H; y += int32(c.Size / 4) {
+
+				// Constrain this chunksize step to a point within the bounds
+				// of the viewport. This can yield partial chunks on the edges
+				// of the viewport.
+				point := render.NewPoint(x, y)
+				if point.X < viewport.X {
+					point.X = viewport.X
+				} else if point.X > viewport.X+viewport.W {
+					point.X = viewport.X + viewport.W
+				}
+				if point.Y < viewport.Y {
+					point.Y = viewport.Y
+				} else if point.Y > viewport.Y+viewport.H {
+					point.Y = viewport.Y + viewport.H
+				}
+
+				// Translate to a chunk coordinate, dedupe and send it.
+				coord := c.ChunkCoordinate(render.NewPoint(x, y))
+				// fmt.Printf("IterViewportChunks: x=%d y=%d  chunk=%s\n", x, y, coord)
+				if _, ok := sent[coord]; ok {
+					continue
+				}
+				sent[coord] = nil
+
+				if _, ok := c.GetChunk(coord); ok {
+					fmt.Printf("Iter: send chunk %s for point %s\n", coord, point)
+					pipe <- coord
+				}
+			}
+		}
+
+		// for cx := topLeft.X; cx <= bottomRight.X; cx++ {
+		// 	for cy := topLeft.Y; cy <= bottomRight.Y; cy++ {
+		// 		pt := render.NewPoint(cx, cy)
+		// 		if _, ok := c.GetChunk(pt); ok {
+		// 			pipe <- pt
+		// 		}
+		// 	}
+		// }
+		close(pipe)
+	}()
+	return pipe
+}
+
 // IterPixels returns a channel to iterate over every pixel in the entire
 // chunker.
 func (c *Chunker) IterPixels() <-chan Pixel {
@@ -152,6 +206,8 @@ func (c *Chunker) Set(p render.Point, sw *Swatch) error {
 	if !ok {
 		chunk = NewChunk()
 		c.Chunks[coord] = chunk
+		chunk.Point = coord
+		chunk.Size = c.Size
 	}
 
 	return chunk.Set(p, sw)

level/chunker_test.go

@@ -1,6 +1,7 @@
 package level_test
 
 import (
+	"fmt"
 	"testing"
 
 	"git.kirsle.net/apps/doodle/level"
@@ -81,5 +82,149 @@ func TestWorldSize(t *testing.T) {
 			t.Errorf("WorldSizePositive not as expected: %s <> %s", zero, test.Expect)
 		}
 	}
-
+}
+
+func TestViewportChunks(t *testing.T) {
+	// Initialize a 100 chunk image with 5x5 chunks.
+	var ChunkSize int32 = 100
+	var Offset int32 = 50
+	c := level.NewChunker(int(ChunkSize))
+	sw := &level.Swatch{
+		Name:  "solid",
+		Color: render.Black,
+	}
+
+	// The 5x5 chunks are expected to be (diagonally)
+	//    -2,-2
+	//    -1,-1
+	//    0,0
+	//    1,1
+	//    2,2
+	// The chunk size is 100px so place a single pixel in each
+	// 100px quadrant.
+	fmt.Printf("size=%d  offset=%d\n", ChunkSize, Offset)
+	for x := int32(-2); x <= 2; x++ {
+		for y := int32(-2); y <= 2; y++ {
+			point := render.NewPoint(
+				x*ChunkSize+Offset,
+				y*ChunkSize+Offset,
+			)
+			fmt.Printf("in chunk: %d,%d  set pt: %s\n",
+				x, y, point,
+			)
+			c.Set(point, sw)
+		}
+	}
+
+	// Sanity check the test canvas was created correctly.
+	worldSize := c.WorldSize()
+	expectSize := render.Rect{
+		X: -200,
+		Y: -200,
+		W: 299,
+		H: 299,
+	}
+	if worldSize != expectSize {
+		t.Errorf(
+			"Test canvas world size wasn't as expected:\n"+
+				"Expected: %s\n"+
+				"  Actual: %s\n",
+			expectSize,
+			worldSize,
+		)
+	}
+	if len(c.Chunks) != 25 {
+		t.Errorf(
+			"Test canvas chunk count wasn't as expected:\n"+
+				"Expected: 25\n"+
+				"  Actual: %d\n",
+			len(c.Chunks),
+		)
+	}
+
+	type TestCase struct {
+		Viewport render.Rect
+		Expect   map[render.Point]interface{}
+	}
+	var tests = []TestCase{
+		{
+			Viewport: render.Rect{X: -10000, Y: -10000, W: 10000, H: 10000},
+			Expect: map[render.Point]interface{}{
+				render.NewPoint(-2, -2): nil,
+				render.NewPoint(-2, -1): nil,
+				render.NewPoint(-2, 0):  nil,
+				render.NewPoint(-2, 1):  nil,
+				render.NewPoint(-2, 2):  nil,
+				render.NewPoint(-1, -2): nil,
+				render.NewPoint(-1, -1): nil,
+				render.NewPoint(-1, 0):  nil,
+				render.NewPoint(-1, 1):  nil,
+				render.NewPoint(-1, 2):  nil,
+				render.NewPoint(0, -2):  nil,
+				render.NewPoint(0, -1):  nil,
+				render.NewPoint(0, 0):   nil,
+				render.NewPoint(0, 1):   nil,
+				render.NewPoint(0, 2):   nil,
+				render.NewPoint(1, -2):  nil,
+				render.NewPoint(1, -1):  nil,
+				render.NewPoint(1, 0):   nil,
+				render.NewPoint(1, 1):   nil,
+				render.NewPoint(1, 2):   nil,
+				render.NewPoint(2, -2):  nil,
+				render.NewPoint(2, -1):  nil,
+				render.NewPoint(2, 0):   nil,
+				render.NewPoint(2, 1):   nil,
+				render.NewPoint(2, 2):   nil,
+			},
+		},
+		{
+			Viewport: render.Rect{X: 0, Y: 0, W: 200, H: 200},
+			Expect: map[render.Point]interface{}{
+				render.NewPoint(0, 0): nil,
+				render.NewPoint(0, 1): nil,
+				render.NewPoint(1, 0): nil,
+				render.NewPoint(1, 1): nil,
+			},
+		},
+		// {
+		// 	Viewport: render.Rect{X: -5, Y: 0, W: 200, H: 200},
+		// 	Expect: map[render.Point]interface{}{
+		// 		render.NewPoint(-1, 0): nil,
+		// 		render.NewPoint(0, 0):  nil,
+		// 		render.NewPoint(1, 1):  nil,
+		// 	},
+		// },
+	}
+
+	for _, test := range tests {
+		chunks := []render.Point{}
+		for chunk := range c.IterViewportChunks(test.Viewport) {
+			chunks = append(chunks, chunk)
+		}
+
+		if len(chunks) != len(test.Expect) {
+			t.Errorf("%s: chunk count mismatch: expected %d, got %d",
+				test.Viewport,
+				len(test.Expect),
+				len(chunks),
+			)
+		}
+
+		for _, actual := range chunks {
+			if _, ok := test.Expect[actual]; !ok {
+				t.Errorf("%s: got chunk coord %d but did not expect to",
+					test.Viewport,
+					actual,
+				)
+			}
+			delete(test.Expect, actual)
+		}
+
+		if len(test.Expect) > 0 {
+			t.Errorf("%s: failed to see these coords: %+v",
+				test.Viewport,
+				test.Expect,
+			)
+		}
+	}
 }

render/interface.go

@@ -28,6 +28,10 @@ type Engine interface {
 	DrawText(Text, Point) error
 	ComputeTextRect(Text) (Rect, error)
 
+	// Texture caching.
+	NewBitmap(filename string) (Texturer, error)
+	Copy(t Texturer, src, dst Rect)
+
 	// Delay for a moment using the render engine's delay method,
 	// implemented by sdl.Delay(uint32)
 	Delay(uint32)
@@ -38,6 +42,12 @@ type Engine interface {
 	Loop() error // maybe?
 }
 
+// Texturer is a stored image texture used by the rendering engine while
+// abstracting away its inner workings.
+type Texturer interface {
+	Size() Rect
+}
+
 // Rect has a coordinate and a width and height.
 type Rect struct {
 	X int32
@@ -83,6 +93,26 @@ func (r Rect) IsZero() bool {
 	return r.X == 0 && r.Y == 0 && r.W == 0 && r.H == 0
 }
 
+// Add another rect.
+func (r Rect) Add(other Rect) Rect {
+	return Rect{
+		X: r.X + other.X,
+		Y: r.Y + other.Y,
+		W: r.W + other.W,
+		H: r.H + other.H,
+	}
+}
+
+// Add a point to move the rect.
+func (r Rect) AddPoint(other Point) Rect {
+	return Rect{
+		X: r.X + other.X,
+		Y: r.Y + other.Y,
+		W: r.W,
+		H: r.H,
+	}
+}
+
 // Text holds information for drawing text.
 type Text struct {
 	Text         string

render/sdl/texture.go

@@ -0,0 +1,54 @@
+package sdl
+
+import (
+	"fmt"
+
+	"git.kirsle.net/apps/doodle/render"
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+// Copy a texture into the renderer.
+func (r *Renderer) Copy(t render.Texturer, src, dst render.Rect) {
+	if tex, ok := t.(*Texture); ok {
+		var (
+			a = RectToSDL(src)
+			b = RectToSDL(dst)
+		)
+		r.renderer.Copy(tex.tex, &a, &b)
+	}
+}
+
+// Texture can hold on to SDL textures for caching and optimization.
+type Texture struct {
+	tex    *sdl.Texture
+	width  int32
+	height int32
+}
+
+// Size returns the dimensions of the texture.
+func (t *Texture) Size() render.Rect {
+	return render.NewRect(t.width, t.height)
+}
+
+// NewBitmap initializes a texture from a bitmap image.
+func (r *Renderer) NewBitmap(filename string) (render.Texturer, error) {
+	log.Debug("NewBitmap: open from file %s", filename)
+
+	surface, err := sdl.LoadBMP(filename)
+	if err != nil {
+		return nil, fmt.Errorf("NewBitmap: LoadBMP: %s", err)
+	}
+	defer surface.Free()
+
+	tex, err := r.renderer.CreateTextureFromSurface(surface)
+	if err != nil {
+		return nil, fmt.Errorf("NewBitmap: create texture: %s", err)
+	}
+
+	log.Debug("Created texture")
+	return &Texture{
+		width:  surface.W,
+		height: surface.H,
+		tex:    tex,
+	}, nil
+}

ui/image.go

@@ -0,0 +1,82 @@
+package ui
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"git.kirsle.net/apps/doodle/render"
+)
+
+// ImageType for supported image formats.
+type ImageType string
+
+// Supported image formats.
+const (
+	BMP ImageType = "bmp"
+	PNG           = "png"
+)
+
+// Image is a widget that is backed by an image file.
+type Image struct {
+	BaseWidget
+
+	// Configurable fields for the constructor.
+	Type    ImageType
+	texture render.Texturer
+}
+
+// NewImage creates a new Image.
+func NewImage(c Image) *Image {
+	w := &Image{
+		Type: c.Type,
+	}
+	if w.Type == "" {
+		w.Type = BMP
+	}
+
+	w.IDFunc(func() string {
+		return fmt.Sprintf(`Image<"%s">`, w.Type)
+	})
+	return w
+}
+
+// OpenImage initializes an Image with a given file name.
+//
+// The file extension is important and should be a supported ImageType.
+func OpenImage(e render.Engine, filename string) (*Image, error) {
+	w := &Image{}
+	switch strings.ToLower(filepath.Ext(filename)) {
+	case ".bmp":
+		w.Type = BMP
+	case ".png":
+		w.Type = PNG
+	default:
+		return nil, fmt.Errorf("OpenImage: %s: not a supported image type", filename)
+	}
+
+	tex, err := e.NewBitmap(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	w.texture = tex
+	return w, nil
+}
+
+// Compute the widget.
+func (w *Image) Compute(e render.Engine) {
+	w.Resize(w.texture.Size())
+}
+
+// Present the widget.
+func (w *Image) Present(e render.Engine, p render.Point) {
+	size := w.texture.Size()
+	dst := render.Rect{
+		X: p.X,
+		Y: p.Y,
+		W: size.W,
+		H: size.H,
+	}
+	e.Copy(w.texture, size, dst)
+}

uix/canvas.go

@@ -145,6 +145,14 @@ func (w *Canvas) Loop(ev *events.State) error {
 			Swatch: w.Palette.ActiveSwatch,
 		}
 
+		log.Warn(
+			"real cursor: %d,%d   translated: %s   widget pos: %s   scroll: %s",
+			ev.CursorX.Now, ev.CursorY.Now,
+			cursor,
+			P,
+			w.Scroll,
+		)
+
 		// Append unique new pixels.
 		if len(w.pixelHistory) == 0 || w.pixelHistory[len(w.pixelHistory)-1] != pixel {
 			if lastPixel != nil {
@@ -160,6 +168,7 @@ func (w *Canvas) Loop(ev *events.State) error {
 			w.pixelHistory = append(w.pixelHistory, pixel)
 
 			// Save in the pixel canvas map.
+			log.Info("Set: %s %s", cursor, pixel.Swatch.Color)
 			w.chunks.Set(cursor, pixel.Swatch)
 		}
 	} else {
@@ -177,8 +186,8 @@ func (w *Canvas) Viewport() render.Rect {
 	return render.Rect{
 		X: w.Scroll.X,
 		Y: w.Scroll.Y,
-		W: S.W - w.BoxThickness(2),
-		H: S.H - w.BoxThickness(2),
+		W: S.W - w.BoxThickness(2) + w.Scroll.X,
+		H: S.H - w.BoxThickness(2) + w.Scroll.Y,
 	}
 }
 
@@ -218,15 +227,114 @@ func (w *Canvas) Present(e render.Engine, p render.Point) {
 		H: S.H - w.BoxThickness(2),
 	})
 
-	for px := range w.chunks.IterViewport(Viewport) {
-		// This pixel is visible in the canvas, but offset it by the
-		// scroll height.
-		px.X -= Viewport.X
-		px.Y -= Viewport.Y
-		color := px.Swatch.Color
-		e.DrawPoint(color, render.Point{
-			X: p.X + w.BoxThickness(1) + px.X,
-			Y: p.Y + w.BoxThickness(1) + px.Y,
-		})
+	// Get the chunks in the viewport and cache their textures.
+	for coord := range w.chunks.IterViewportChunks(Viewport) {
+		if chunk, ok := w.chunks.GetChunk(coord); ok {
+			tex := chunk.Texture(e, w.Name+coord.String())
+			src := render.Rect{
+				W: tex.Size().W,
+				H: tex.Size().H,
+			}
+
+			// If the source bitmap is already bigger than the Canvas widget
+			// into which it will render, cap the source width and height.
+			// This is especially useful for Doodad buttons because the drawing
+			// is bigger than the button.
+			if src.W > S.W {
+				src.W = S.W
+			}
+			if src.H > S.H {
+				src.H = S.H
+			}
+
+			dst := render.Rect{
+				X: p.X + w.Scroll.X + w.BoxThickness(1) + (coord.X * int32(chunk.Size)),
+				Y: p.Y + w.Scroll.Y + w.BoxThickness(1) + (coord.Y * int32(chunk.Size)),
+
+				// src.W and src.H will be AT MOST the full width and height of
+				// a Canvas widget. Subtract the scroll offset to keep it bounded
+				// visually on its right and bottom sides.
+				W: src.W, // - w.Scroll.X,
+				H: src.H, // - w.Scroll.Y,
+			}
+
+			// log.Warn(
+			// 	"chunk: %s   src: %s   dst: %s",
+			// 	coord,
+			// 	src,
+			// 	dst,
+			// )
+
+			// If the destination width will cause it to overflow the widget
+			// box, trim off the right edge of the destination rect.
+			//
+			// Keep in mind we're dealing with chunks here, and a chunk is
+			// a small part of the image. Example:
+			// - Canvas is 800x600 (S.W=800  S.H=600)
+			// - Chunk wants to render at 790,0 width 100,100 or whatever
+			//   dst={790, 0, 100, 100}
+			// - Chunk box would exceed 800px width (X=790 + W=100 == 890)
+			// - Find the delta how much it exceeds as negative (800 - 890 == -90)
+			// - Lower the Source and Dest rects by that delta size so they
+			//   stay proportional and don't scale or anything dumb.
+			if dst.X+src.W > p.X+S.W {
+				// NOTE: delta is a negative number,
+				// so it will subtract from the width.
+				delta := (S.W + p.X) - (dst.W + dst.X)
+				src.W += delta
+				dst.W += delta
+			}
+			if dst.Y+src.H > p.Y+S.H {
+				// NOTE: delta is a negative number
+				delta := (S.H + p.Y) - (dst.H + dst.Y)
+				src.H += delta
+				dst.H += delta
+			}
+
+			// The same for the top left edge, so the drawings don't overlap
+			// menu bars or left side toolbars.
+			// - Canvas was placed 80px from the left of the screen.
+			//   Canvas.MoveTo(80, 0)
+			// - A texture wants to draw at 60, 0 which would cause it to
+			//   overlap 20 pixels into the left toolbar. It needs to be cropped.
+			// - The delta is: p.X=80 - dst.X=60 == 20
+			// - Set destination X to p.X to constrain it there: 20
+			// - Subtract the delta from destination W so we don't scale it.
+			// - Add 20 to X of the source: the left edge of source is not visible
+			if dst.X < p.X {
+				// NOTE: delta is a positive number,
+				// so it will add to the destination coordinates.
+				delta := p.X - dst.X
+				dst.X = p.X
+				dst.W -= delta
+				src.X += delta
+			}
+			if dst.Y < p.Y {
+				delta := p.Y - dst.Y
+				dst.Y = p.Y
+				dst.H -= delta
+				src.Y += delta
+			}
+
+			// If the destination rect would overflow our widget bounds, trim
+			// it off.
+
+			// if w.Name == "edit-canvas" {
+			// 	log.Info("%s: copy %+v -> %+v", w.Name, src, dst)
+			// }
+			e.Copy(tex, src, dst)
 		}
 	}
+
+	// for px := range w.chunks.IterViewport(Viewport) {
+	// 	// This pixel is visible in the canvas, but offset it by the
+	// 	// scroll height.
+	// 	px.X -= Viewport.X
+	// 	px.Y -= Viewport.Y
+	// 	color := render.Cyan // px.Swatch.Color
+	// 	e.DrawPoint(color, render.Point{
+	// 		X: p.X + w.BoxThickness(1) + px.X,
+	// 		Y: p.Y + w.BoxThickness(1) + px.Y,
+	// 	})
+	// }
+}