48 lines
1.3 KiB
Go
48 lines
1.3 KiB
Go
package layout
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import (
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"github.com/egoist/mygo/ui"
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"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
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)
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type ViewportOptions struct {
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// W×H is the virtual screen in dots; zero means 160×144.
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W, H int
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}
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// Viewport fills its parent and draws children at W×H dots.
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func Viewport(c *ui.Context, o ViewportOptions, children func()) *ui.Element {
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k := pixel.K(c)
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vw, vh := orDef("Viewport W", o.W, 160), orDef("Viewport H", o.H, 144)
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base := int(k.Dot())
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outer := ui.Box(c).Fill()
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was := outer.Bounds()
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d := fit(vw, vh, was.W, was.H, base)
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// Offsets stay whole outer dots, so both grids line up.
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x := (int(was.W)/base - vw*d/base) / 2 * base
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y := (int(was.H)/base - vh*d/base) / 2 * base
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return outer.Draw(func(p *ui.Painter, r ui.Rect) {
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if r.W != was.W || r.H != was.H {
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c.Invalidate()
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}
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g := k.Canvas(p, r)
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g.Rect(0, 0, g.W, g.H, pixel.Back)
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}).Children(func() {
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s := pixel.Current(c)
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s.Dot = d
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pixel.Scope(c, s, func() {
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ui.Box(c).Absolute().Left(float32(max(0, x))).Top(float32(max(0, y))).Size(float32(vw*d), float32(vh*d)).Clip().Children(children)
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})
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})
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}
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// fit picks the largest fitting multiple of base, ≤ 4.
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func fit(w, h int, roomW, roomH float32, base int) int {
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d := base
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for d+base <= 4 && float32(w*(d+base)) <= roomW && float32(h*(d+base)) <= roomH {
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d += base
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}
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return d
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}
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