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pixels: Add comments

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Hajime Hoshi 2016-07-25 10:32:16 +09:00
parent 939284820c
commit 1ec503e1b5
1 changed files with 13 additions and 4 deletions
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17
internal/pixels/pixels.go
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@ -30,10 +30,15 @@ type drawImageHistoryItem struct {
mode opengl.CompositeMode mode opengl.CompositeMode
} }
// basePixels and baseColor are exclusive. // Pixels represents pixels of an image for restoring when GL context is lost.
//
// Until GL context is available,
// Pixels member states might not match with actual pixels in GPU so
// there is few function to retrieve the current state.
type Pixels struct { type Pixels struct {
image *graphics.Image image *graphics.Image
// basePixels and baseColor are exclusive.
basePixels []uint8 basePixels []uint8
baseColor color.Color baseColor color.Color
drawImageHistory []*drawImageHistoryItem drawImageHistory []*drawImageHistoryItem
@ -77,6 +82,10 @@ func (p *Pixels) AppendDrawImageHistory(image *graphics.Image, vertices []int16,
p.drawImageHistory = append(p.drawImageHistory, item) p.drawImageHistory = append(p.drawImageHistory, item)
} }
// At returns a color value at idx.
//
// Note that this must not be called until context is available.
// This means Pixels members must match with acutal state in GPU.
func (p *Pixels) At(idx int, context *opengl.Context) (color.Color, error) { func (p *Pixels) At(idx int, context *opengl.Context) (color.Color, error) {
if p.basePixels == nil || p.drawImageHistory != nil { if p.basePixels == nil || p.drawImageHistory != nil {
var err error var err error
@ -132,7 +141,7 @@ func (p *Pixels) HasHistory() bool {
return p.drawImageHistory != nil return p.drawImageHistory != nil
} }
// restore restores the pixels using its history. // Restore restores the pixels using its history.
// //
// restore is the only function that the pixel data is not present on GPU when this is called. // restore is the only function that the pixel data is not present on GPU when this is called.
func (p *Pixels) Restore(context *opengl.Context, width, height int, filter opengl.Filter) (*graphics.Image, error) { func (p *Pixels) Restore(context *opengl.Context, width, height int, filter opengl.Filter) (*graphics.Image, error) {