100 lines
2.4 KiB
Go
100 lines
2.4 KiB
Go
package pixel
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// Drawer glues all the fundamental interfaces (Target, Triangles, Picture) into a coherent and the
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// only intended usage pattern.
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//
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// Drawer makes it possible to draw any combination of Triangles and Picture onto any Target
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// efficiently.
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//
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// To create a Drawer, just assign it's Triangles and Picture fields:
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//
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// d := pixel.Drawer{Triangles: t, Picture: p}
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//
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// If Triangles is nil, nothing will be drawn. If Picture is nil, Triangles will be drawn without a
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// Picture.
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//
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// Whenever you change the Triangles, call Dirty to notify Drawer that Triangles changed. You don't
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// need to notify Drawer about a change of the Picture.
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//
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// Note, that Drawer caches the results of MakePicture from Targets it's drawn to for each Picture
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// it's set to. What it means is that using a Drawer with an unbounded number of Pictures leads to a
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// memory leak, since Drawer caches them and never forgets. In such a situation, create a new Drawer
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// for each Picture.
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type Drawer struct {
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Triangles Triangles
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Picture Picture
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tris map[Target]TargetTriangles
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clean map[Target]bool
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pics map[targetPicturePair]TargetPicture
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dirty bool
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inited bool
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}
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type targetPicturePair struct {
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Target Target
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Picture Picture
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}
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func (d *Drawer) lazyInit() {
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if !d.inited {
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d.tris = make(map[Target]TargetTriangles)
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d.clean = make(map[Target]bool)
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d.pics = make(map[targetPicturePair]TargetPicture)
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d.inited = true
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}
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}
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// Dirty marks the Triangles of this Drawer as changed. If not called, changes will not be visible
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// when drawing.
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func (d *Drawer) Dirty() {
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d.lazyInit()
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d.dirty = true
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}
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// Draw efficiently draws Triangles with Picture onto the provided Target.
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//
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// If Triangles is nil, nothing will be drawn. If Picture is nil, Triangles will be drawn without a
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// Picture.
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func (d *Drawer) Draw(t Target) {
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d.lazyInit()
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if d.dirty {
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for t := range d.clean {
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d.clean[t] = false
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}
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d.dirty = false
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}
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if d.Triangles == nil {
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return
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}
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tri := d.tris[t]
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if tri == nil {
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tri = t.MakeTriangles(d.Triangles)
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d.tris[t] = tri
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d.clean[t] = true
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}
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if !d.clean[t] {
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tri.SetLen(d.Triangles.Len())
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tri.Update(d.Triangles)
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d.clean[t] = true
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}
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if d.Picture == nil {
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tri.Draw()
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return
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}
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pic := d.pics[targetPicturePair{t, d.Picture}]
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if pic == nil {
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pic = t.MakePicture(d.Picture)
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d.pics[targetPicturePair{t, d.Picture}] = pic
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}
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pic.Draw(tri)
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}
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