Create image manager and related stuff

application.go

@@ -11,6 +11,7 @@ type Application struct {
 	backend Backend
 	config Config
 	callbackManager CallbackManager
+	imageManager ImageManager
 }
 
 // Run initializes the application, starts it, and then returns a channel that
@@ -114,3 +115,21 @@ func (application *Application) Config () (config *Config) {
 	config = &application.config
 	return
 }
+
+// AddImage adds a new image buffer and returns a pointer to it.
+func (application *Application) NewImage () (im *ColorImage) {
+	cellWidth, cellHeight := application.backend.CellMetrics()
+	im = &ColorImage {
+		cellWidth:  cellWidth,
+		cellHeight: cellHeight,
+	}
+	application.imageManager.Add(im)
+	return
+}
+
+// Remove removes the specified image buffer, if the application has it. If the
+// image was found and removed, removed will be true.
+func (application *Application) RemoveImage (im *ColorImage) (removed bool) {
+	removed = application.imageManager.Remove(im)
+	return
+}

backend.go

@@ -8,11 +8,13 @@ type Backend interface {
 	SetTitle (title string) (err error)
 	SetIcon  (icons []image.Image) (err error)
 	Draw     ()
+	CellMetrics () (width, height int)
 }
 
 type BackendFactory func (
-	application *Application,
+	application     *Application,
 	callbackManager *CallbackManager,
+	imageManager    *ImageManager,
 ) (
 	backend Backend,
 	err error,
@@ -27,7 +29,10 @@ func RegisterBackend (factory BackendFactory) {
 func instantiateBackend (application *Application) (backend Backend, err error) {
 	// find a suitable backend
 	for _, factory := range factories {
-		backend, err = factory(application, &application.callbackManager)
+		backend, err = factory (
+			application,
+			&application.callbackManager,
+			&application.imageManager)
 		if err == nil && backend != nil { return }
 	}
 

backends/x/factory.go

@@ -19,8 +19,9 @@ import "github.com/flopp/go-findfont"
 
 // factory instantiates an X backend.
 func factory (
-	application *stone.Application,
+	application     *stone.Application,
 	callbackManager *stone.CallbackManager,
+	imageManager    *stone.ImageManager,
 ) (
 	output stone.Backend,
 	err error,
@@ -29,6 +30,7 @@ func factory (
 		application:     application,
 		config:          application.Config(),
 		callbackManager: callbackManager,
+		imageManager:    imageManager,
 	}
 
 	// load font

backends/x/x.go

@@ -17,6 +17,7 @@ type Backend struct {
 	application     *stone.Application
 	config          *stone.Config
 	callbackManager *stone.CallbackManager
+	imageManager    *stone.ImageManager
 	connection      *xgbutil.XUtil
 	window          *xwindow.Window
 	canvas          *xgraphics.Image
@@ -88,6 +89,12 @@ func (backend *Backend) SetIcon (icons []image.Image) (err error) {
 	return
 }
 
+func (backend *Backend) CellMetrics () (width, height int) {
+	width  = backend.metrics.cellWidth
+	height = backend.metrics.cellHeight
+	return
+}
+
 // calculateWindowSize calculates window bounds based on the internal buffer
 // size.
 func (backend *Backend) calculateWindowSize () (x, y int) {

image.go

@@ -1,8 +1,65 @@
 package stone
 
+import "sync"
 import "image"
 import "image/color"
 
+type ImageManager struct {
+	lock sync.RWMutex
+	images []*ColorImage
+}
+
+func (manager *ImageManager) For (callback func (im *ColorImage)) {
+	manager.lock.RLock()
+	defer manager.lock.RUnlock()
+
+	for _, im := range manager.images {
+		callback(im)
+	}
+}
+
+func (manager *ImageManager) Add (im *ColorImage) {
+	manager.lock.Lock()
+	defer manager.lock.Unlock()
+	
+	manager.images = append(manager.images, im)
+}
+
+func (manager *ImageManager) Size () (size int) {
+	manager.lock.RLock()
+	defer manager.lock.RUnlock()
+	
+	size = len(manager.images)
+	return
+}
+
+func (manager *ImageManager) At (index int) (im *ColorImage) {
+	manager.lock.RLock()
+	defer manager.lock.RUnlock()
+	
+	if index < 0 || index > len(manager.images) { return }
+	im = manager.images[index]
+	return
+}
+
+func (manager *ImageManager) Remove (im *ColorImage) (removed bool) {
+	manager.lock.Lock()
+	defer manager.lock.Unlock()
+
+	index := 0
+	for manager.images[index] != im && index < len(manager.images) {
+		index ++
+	}
+
+	if index >= len(manager.images) { return }
+	
+	manager.images = append (
+		manager.images[:index],
+		manager.images[index + 1:]...)
+	removed = true
+	return
+}
+
 type ColorImage struct {
 	x,           y            int
 	width,       height       int