99 lines
2.3 KiB
Go
99 lines
2.3 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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targets map[Target]*drawerTarget
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allTargets []*drawerTarget
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inited bool
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}
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type drawerTarget struct {
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tris TargetTriangles
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pics map[Picture]TargetPicture
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clean bool
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}
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func (d *Drawer) lazyInit() {
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if !d.inited {
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d.targets = make(map[Target]*drawerTarget)
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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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for _, t := range d.allTargets {
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t.clean = false
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}
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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.Triangles == nil {
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return
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}
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dt := d.targets[t]
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if dt == nil {
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dt = &drawerTarget{
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pics: make(map[Picture]TargetPicture),
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}
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d.targets[t] = dt
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d.allTargets = append(d.allTargets, dt)
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}
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if dt.tris == nil {
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dt.tris = t.MakeTriangles(d.Triangles)
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dt.clean = true
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}
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if !dt.clean {
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dt.tris.SetLen(d.Triangles.Len())
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dt.tris.Update(d.Triangles)
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dt.clean = true
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}
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if d.Picture == nil {
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dt.tris.Draw()
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return
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}
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pic := dt.pics[d.Picture]
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if pic == nil {
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pic = t.MakePicture(d.Picture)
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dt.pics[d.Picture] = pic
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}
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pic.Draw(dt.tris)
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}
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