restorable

Documentation

Overview

Package restorable offers an Image struct that stores image commands and restores its pixel data from the commands when context lost happens.

When a function like DrawImage or Fill is called, an Image tries to record the information for restoring.

* Context lost

Contest lost is a process that information on GPU memory are removed by OS to make more room on GPU memory. This can happen e.g. when GPU memory usage is high, or just switching applications might cause context lost on mobiles. As Ebiten's image data is on GPU memory, the game can't continue when context lost happens without restoring image information. The package restorable is the package to record information for such restoring.

* DrawImage

DrawImage function tries to record an item of 'draw image history' in the target image. If a target image is stale or volatile, no item is created. If an item of the history is created, it can be said that the target image depends on the source image. In other words, If A.DrawImage(B, ...) is called, it can be said that the image A depends on the image B.

* Fill, ReplacePixels and Dispose

These functions are also drawing functions and the target image stores the pixel data instead of draw image history items. There is no dependency here.

* Making images stale

After any of the drawing functions is called, the target image can't be depended on by any other images. For example, if an image A depends on an image B, and B is changed by a Fill call after that, the image A can't depend on the image B any more. In this case, as the image B can no longer be used to restore the image A, the image A becomes 'stale'. As all the stale images are resolved before context lost happens, draw image history items are kept as they are (even if an image C depends on the stale image A, it is still fine).

* Stale image

A stale image is an image that can't be restored from the recorded information. All stale images must be resolved by reading pixels from GPU before the frame ends. If a source image of DrawImage is a stale image, the target always becomes stale.

* Volatile image

A volatile image is a special image that is always cleared when a frame starts. For instance, the game screen passed via the update function is a volatile image. A volatile image doesn't have to record the drawing history. If a source image of DrawImage is a volatile image, the target always becomes stale.

Index

• func DumpImages(dir string) error
• func EnableRestoringForTesting()
• func InitializeGraphicsDriverState() error
• func ResolveStaleImages() error
• func RestoreIfNeeded() error
• type Image
  • func NewImage(width, height int, volatile bool) *Image
  • func NewScreenFramebufferImage(width, height int) *Image
  • func (i *Image) At(x, y int) (byte, byte, byte, byte, error)
  • func (i *Image) BasePixelsForTesting() *Pixels
  • func (i *Image) ClearPixels(x, y, width, height int)
  • func (i *Image) Dispose()
  • func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16, colorm *affine.ColorM, ...)
  • func (i *Image) Dump(path string, blackbg bool) error
  • func (i *Image) Extend(width, height int) *Image
  • func (i *Image) Fill(clr color.RGBA)
  • func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int)
• type Pixels
  • func (p *Pixels) AddOrReplace(pix []byte, x, y, width, height int)
  • func (p *Pixels) Apply(img *graphicscommand.Image)
  • func (p *Pixels) At(i, j int) (byte, byte, byte, byte)
  • func (p *Pixels) Remove(x, y, width, height int)

Functions

func DumpImages

func DumpImages(dir string) error

DumpImages dumps all the current images to the specified directory.

This is for testing usage.

func EnableRestoringForTesting

func EnableRestoringForTesting()

EnableRestoringForTesting forces to enable restoring for testing.

func InitializeGraphicsDriverState

func InitializeGraphicsDriverState() error

InitializeGraphicsDriverState initializes the graphics driver state.

func ResolveStaleImages

func ResolveStaleImages() error

ResolveStaleImages flushes the queued draw commands and resolves all stale images.

ResolveStaleImages is intended to be called at the end of a frame.

func RestoreIfNeeded

func RestoreIfNeeded() error

RestoreIfNeeded restores the images.

Restoring means to make all *graphicscommand.Image objects have their textures and framebuffers.

Types

type Image

type Image struct {
	// contains filtered or unexported fields
}

Image represents an image that can be restored when GL context is lost.

func NewImage

func NewImage(width, height int, volatile bool) *Image

NewImage creates an empty image with the given size.

volatile indicates whether the image is volatile. Regular non-volatile images need to record drawing history or read its pixels from GPU if necessary so that all the images can be restored automatically from the context lost. However, such recording the drawing history or reading pixels from GPU are expensive operations. Volatile images can skip such oprations, but the image content is cleared every frame instead.

The returned image is cleared.

Note that Dispose is not called automatically.

func NewScreenFramebufferImage

func NewScreenFramebufferImage(width, height int) *Image

NewScreenFramebufferImage creates a special image that framebuffer is one for the screen.

The returned image is cleared.

Note that Dispose is not called automatically.

func (*Image) At

func (i *Image) At(x, y int) (byte, byte, byte, byte, error)

At returns a color value at (x, y).

Note that this must not be called until context is available.

func (*Image) BasePixelsForTesting

func (i *Image) BasePixelsForTesting() *Pixels

BasePixelsForTesting returns the image's basePixels for testing.

func (*Image) ClearPixels

func (i *Image) ClearPixels(x, y, width, height int)

ClearPixels clears the specified region by ReplacePixels.

func (*Image) Dispose

func (i *Image) Dispose()

Dispose disposes the image.

After disposing, calling the function of the image causes unexpected results.

func (*Image) DrawTriangles

func (i *Image) DrawTriangles(img *Image, vertices []float32, indices []uint16, colorm *affine.ColorM, mode driver.CompositeMode, filter driver.Filter, address driver.Address)

DrawTriangles draws triangles with the given image.

The vertex floats are:

0:  Destination X in pixels
1:  Destination Y in pixels
2:  Source X in pixels (not texels!)
3:  Source Y in pixels
4:  Bounds of the source min X in pixels
5:  Bounds of the source min Y in pixels
6:  Bounds of the source max X in pixels
7:  Bounds of the source max Y in pixels
8:  Color R [0.0-1.0]
9:  Color G
10: Color B
11: Color Y

func (*Image) Dump

func (i *Image) Dump(path string, blackbg bool) error

func (*Image) Extend

func (i *Image) Extend(width, height int) *Image

Extend extends the image by the given size. Extend creates a new image with the given size and copies the pixels of the given source image. Extend disposes itself after its call.

If the given size (width and height) is smaller than the source image, ExtendImage panics.

The image must be ReplacePixels-only image. Extend panics when Fill or DrawTriangles are applied on the image.

Extend panics when the image is stale.

func (*Image) Fill

func (i *Image) Fill(clr color.RGBA)

Fill fills the specified part of the image with a solid color.

func (*Image) ReplacePixels

func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int)

ReplacePixels replaces the image pixels with the given pixels slice.

ReplacePixels for a part is forbidden if the image is rendered with DrawTriangles or Fill.

type Pixels

type Pixels struct {
	// contains filtered or unexported fields
}

func (*Pixels) AddOrReplace

func (p *Pixels) AddOrReplace(pix []byte, x, y, width, height int)

func (*Pixels) Apply

func (p *Pixels) Apply(img *graphicscommand.Image)

Apply applies the Pixels state to the given image especially for restoring.

func (*Pixels) At

func (p *Pixels) At(i, j int) (byte, byte, byte, byte)

func (*Pixels) Remove

func (p *Pixels) Remove(x, y, width, height int)