SDL2: Cache Bitmaps in Memory, Not on Disk

* Update the SDL2 engine's texture caching to use an sdl.RWops file
  buffer in memory instead of outputting bitmap images to the
  filesystem.

sdl/sdl.go

@@ -25,6 +25,7 @@ type Renderer struct {
 	renderer *sdl.Renderer
 	running  bool
 	ticks    uint64
+	textures map[string]*Texture // cached textures
 
 	// Optimizations to minimize SDL calls.
 	lastColor render.Color
@@ -33,10 +34,11 @@ type Renderer struct {
 // New creates the SDL renderer.
 func New(title string, width, height int) *Renderer {
 	return &Renderer{
-		events: events.New(),
-		title:  title,
-		width:  int32(width),
-		height: int32(height),
+		events:   events.New(),
+		title:    title,
+		width:    int32(width),
+		height:   int32(height),
+		textures: map[string]*Texture{},
 	}
 }
 

sdl/texture.go

@@ -1,9 +1,9 @@
 package sdl
 
 import (
+	"bytes"
 	"fmt"
 	"image"
-	"os"
 
 	"git.kirsle.net/apps/doodle/lib/render"
 	"github.com/veandco/go-sdl2/sdl"
@@ -30,26 +30,24 @@ type Texture struct {
 
 // NewTexture caches an SDL texture from a bitmap.
 func (r *Renderer) NewTexture(filename string, img image.Image) (render.Texturer, error) {
-	fh, err := os.Create(filename)
+	var (
+		fh = bytes.NewBuffer([]byte{})
+	)
+
+	err := bmp.Encode(fh, img)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("NewTexture: bmp.Encode: %s", err)
 	}
-	defer fh.Close()
-
-	err = bmp.Encode(fh, img)
-	return nil, err
-}
 
-// Size returns the dimensions of the texture.
-func (t *Texture) Size() render.Rect {
-	return render.NewRect(t.width, t.height)
-}
+	// Create an SDL RWOps from the bitmap data in memory.
+	sdlRW, err := sdl.RWFromMem(fh.Bytes())
+	if err != nil {
+		return nil, fmt.Errorf("NewTexture: sdl.RWFromMem: %s", err)
+	}
 
-// NewBitmap initializes a texture from a bitmap image.
-func (r *Renderer) NewBitmap(filename string) (render.Texturer, error) {
-	surface, err := sdl.LoadBMP(filename)
+	surface, err := sdl.LoadBMPRW(sdlRW, true)
 	if err != nil {
-		return nil, fmt.Errorf("NewBitmap: LoadBMP: %s", err)
+		return nil, fmt.Errorf("NewTexture: sdl.LoadBMPRW: %s", err)
 	}
 	defer surface.Free()
 
@@ -57,14 +55,30 @@ func (r *Renderer) NewBitmap(filename string) (render.Texturer, error) {
 	key := sdl.MapRGB(surface.Format, 255, 255, 255)
 	surface.SetColorKey(true, key)
 
-	tex, err := r.renderer.CreateTextureFromSurface(surface)
+	texture, err := r.renderer.CreateTextureFromSurface(surface)
 	if err != nil {
 		return nil, fmt.Errorf("NewBitmap: create texture: %s", err)
 	}
 
-	return &Texture{
+	tex := &Texture{
 		width:  surface.W,
 		height: surface.H,
-		tex:    tex,
-	}, nil
+		tex:    texture,
+	}
+	r.textures[filename] = tex
+
+	return tex, nil
+}
+
+// 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) {
+	if tex, ok := r.textures[filename]; ok {
+		return tex, nil
+	}
+	return nil, fmt.Errorf("NewBitmap(%s): not found in texture cache", filename)
 }