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.

lib/render/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
@@ -37,6 +38,7 @@ func New(title string, width, height int) *Renderer {
 		title:    title,
 		width:    int32(width),
 		height:   int32(height),
+		textures: map[string]*Texture{},
 	}
 }
 

lib/render/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"
@@ -30,14 +30,44 @@ 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)
-	if err != nil {
-		return nil, err
-	}
-	defer fh.Close()
+	var (
+		fh = bytes.NewBuffer([]byte{})
+	)
 
-	err = bmp.Encode(fh, img)
-	return nil, err
+	err := bmp.Encode(fh, img)
+	if err != nil {
+		return nil, fmt.Errorf("NewTexture: bmp.Encode: %s", err)
+	}
+
+	// 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)
+	}
+
+	surface, err := sdl.LoadBMPRW(sdlRW, true)
+	if err != nil {
+		return nil, fmt.Errorf("NewTexture: sdl.LoadBMPRW: %s", err)
+	}
+	defer surface.Free()
+
+	// TODO: chroma key color hardcoded to white here
+	key := sdl.MapRGB(surface.Format, 255, 255, 255)
+	surface.SetColorKey(true, key)
+
+	texture, err := r.renderer.CreateTextureFromSurface(surface)
+	if err != nil {
+		return nil, fmt.Errorf("NewBitmap: create texture: %s", err)
+	}
+
+	tex := &Texture{
+		width:  surface.W,
+		height: surface.H,
+		tex:    texture,
+	}
+	r.textures[filename] = tex
+
+	return tex, nil
 }
 
 // Size returns the dimensions of the texture.
@@ -47,24 +77,8 @@ func (t *Texture) Size() render.Rect {
 
 // NewBitmap initializes a texture from a bitmap image.
 func (r *Renderer) NewBitmap(filename string) (render.Texturer, error) {
-	surface, err := sdl.LoadBMP(filename)
-	if err != nil {
-		return nil, fmt.Errorf("NewBitmap: LoadBMP: %s", err)
+	if tex, ok := r.textures[filename]; ok {
+		return tex, nil
 	}
-	defer surface.Free()
-
-	// TODO: chroma key color hardcoded to white here
-	key := sdl.MapRGB(surface.Format, 255, 255, 255)
-	surface.SetColorKey(true, key)
-
-	tex, err := r.renderer.CreateTextureFromSurface(surface)
-	if err != nil {
-		return nil, fmt.Errorf("NewBitmap: create texture: %s", err)
-	}
-
-	return &Texture{
-		width:  surface.W,
-		height: surface.H,
-		tex:    tex,
-	}, nil
+	return nil, fmt.Errorf("NewBitmap(%s): not found in texture cache", filename)
 }

pkg/wallpaper/texture.go

@@ -4,13 +4,11 @@ package wallpaper
 
 import (
 	"errors"
-	"fmt"
 	"image"
-	"os"
 
 	"git.kirsle.net/apps/doodle/lib/render"
+	"git.kirsle.net/apps/doodle/pkg/shmem"
 	"git.kirsle.net/apps/doodle/pkg/userdir"
-	"golang.org/x/image/bmp"
 )
 
 // CornerTexture returns the Texture.
@@ -57,28 +55,9 @@ func (wp *Wallpaper) RepeatTexture(e render.Engine) (render.Texturer, error) {
 	return wp.tex.repeat, nil
 }
 
+// texture creates or returns a cached texture for a wallpaper.
 func texture(e render.Engine, img *image.RGBA, name string) (render.Texturer, error) {
 	filename := userdir.CacheFilename("wallpaper", name+".bmp")
-	if _, err := os.Stat(filename); os.IsNotExist(err) {
-		fh, err := os.Create(filename)
-		if err != nil {
-			return nil, fmt.Errorf("texture(%s): %s", name, err.Error())
-		}
-
-		err = bmp.Encode(fh, img)
-		if err != nil {
-			return nil, fmt.Errorf("texture(%s): bmp.Encode: %s", name, err.Error())
-		}
-
-		err = fh.Close()
-		if err != nil {
-			return nil, fmt.Errorf("texture(%s): fh.Close: %s", name, err.Error())
-		}
-	}
-
-	texture, err := e.NewBitmap(filename)
-	if err != nil {
-		return nil, fmt.Errorf("CornerTexture: NewBitmap(%s): %s", filename, err.Error())
-	}
-	return texture, nil
+	texture, err := shmem.CurrentRenderEngine.NewTexture(filename, img)
+	return texture, err
 }