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widget: make Fit.scale a pure function

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Most importantly, return dimensions and transformation instead of adding
operations. Makes the function easier to test, and supports scoped
transform and clip stacks.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
This commit is contained in:
Elias Naur
2021-10-02 10:36:45 +02:00
parent cccb8d2c2b
commit cd5a78f3d8
3 changed files with 23 additions and 54 deletions
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widget/fit.go
+12 -23
View File
@@ -7,8 +7,6 @@ import (
"gioui.org/f32"
"gioui.org/layout"
"gioui.org/op"
"gioui.org/op/clip"
)
// Fit scales a widget to fit and clip to the constraints.
@@ -32,25 +30,21 @@ const (
Fill
)
// scale adds clip and scale operations to fit dims to the constraints.
// It positions the widget to the appropriate position.
// It returns dimensions modified accordingly.
func (fit Fit) scale(gtx layout.Context, pos layout.Direction, dims layout.Dimensions) layout.Dimensions {
// scale computes the new dimensions and transformation required to fit dims to cs, given the position.
func (fit Fit) scale(cs layout.Constraints, pos layout.Direction, dims layout.Dimensions) (layout.Dimensions, f32.Affine2D) {
widgetSize := dims.Size
if fit == Unscaled || dims.Size.X == 0 || dims.Size.Y == 0 {
dims.Size = gtx.Constraints.Constrain(dims.Size)
clip.Rect{Max: dims.Size}.Add(gtx.Ops)
dims.Size = cs.Constrain(dims.Size)
offset := pos.Position(widgetSize, dims.Size)
op.Offset(layout.FPt(offset)).Add(gtx.Ops)
dims.Baseline += offset.Y
return dims
return dims, f32.Affine2D{}.Offset(layout.FPt(offset))
}
scale := f32.Point{
X: float32(gtx.Constraints.Max.X) / float32(dims.Size.X),
Y: float32(gtx.Constraints.Max.Y) / float32(dims.Size.Y),
X: float32(cs.Max.X) / float32(dims.Size.X),
Y: float32(cs.Max.Y) / float32(dims.Size.Y),
}
switch fit {
@@ -75,13 +69,11 @@ func (fit Fit) scale(gtx layout.Context, pos layout.Direction, dims layout.Dimen
// The widget would need to be scaled up, no change needed.
if scale.X >= 1 {
dims.Size = gtx.Constraints.Constrain(dims.Size)
clip.Rect{Max: dims.Size}.Add(gtx.Ops)
dims.Size = cs.Constrain(dims.Size)
offset := pos.Position(widgetSize, dims.Size)
op.Offset(layout.FPt(offset)).Add(gtx.Ops)
dims.Baseline += offset.Y
return dims
return dims, f32.Affine2D{}.Offset(layout.FPt(offset))
}
case Fill:
}
@@ -89,18 +81,15 @@ func (fit Fit) scale(gtx layout.Context, pos layout.Direction, dims layout.Dimen
var scaledSize image.Point
scaledSize.X = int(float32(widgetSize.X) * scale.X)
scaledSize.Y = int(float32(widgetSize.Y) * scale.Y)
dims.Size = gtx.Constraints.Constrain(scaledSize)
dims.Size = cs.Constrain(scaledSize)
dims.Baseline = int(float32(dims.Baseline) * scale.Y)
clip.Rect{Max: dims.Size}.Add(gtx.Ops)
offset := pos.Position(scaledSize, dims.Size)
op.Affine(f32.Affine2D{}.
trans := f32.Affine2D{}.
Scale(f32.Point{}, scale).
Offset(layout.FPt(offset)),
).Add(gtx.Ops)
Offset(layout.FPt(offset))
dims.Baseline += offset.Y
return dims
return dims, trans
}