90 lines
2.2 KiB
Go
90 lines
2.2 KiB
Go
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package internal
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import "fyne.io/fyne/v2"
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// ClipStack keeps track of the areas that should be clipped when drawing a canvas.
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// If no clips are present then adding one will be added as-is.
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// Subsequent items pushed will be completely within the previous clip.
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type ClipStack struct {
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clips []*ClipItem
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}
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// Pop removes the current top clip and returns it.
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func (c *ClipStack) Pop() *ClipItem {
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if len(c.clips) == 0 {
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return nil
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}
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top := len(c.clips) - 1
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ret := c.clips[top]
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c.clips[top] = nil // release memory reference
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c.clips = c.clips[:top]
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return ret
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}
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// Length returns the number of items in this clip stack. 0 means no clip.
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func (c *ClipStack) Length() int {
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return len(c.clips)
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}
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// Push a new clip onto this stack at position and size specified.
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// The returned clip item is the result of calculating the intersection of the requested clip and it's parent.
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func (c *ClipStack) Push(p fyne.Position, s fyne.Size) *ClipItem {
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outer := c.Top()
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inner := outer.Intersect(p, s)
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c.clips = append(c.clips, inner)
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return inner
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}
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// Top returns the current clip item - it will always be within the bounds of any parent clips.
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func (c *ClipStack) Top() *ClipItem {
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if len(c.clips) == 0 {
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return nil
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}
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return c.clips[len(c.clips)-1]
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}
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// ClipItem represents a single clip in a clip stack, denoted by a size and position.
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type ClipItem struct {
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pos fyne.Position
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size fyne.Size
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}
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// Rect returns the position and size parameters of the clip.
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func (i *ClipItem) Rect() (fyne.Position, fyne.Size) {
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return i.pos, i.size
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}
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// Intersect returns a new clip item that is the intersection of the requested parameters and this clip.
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func (i *ClipItem) Intersect(p fyne.Position, s fyne.Size) *ClipItem {
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ret := &ClipItem{p, s}
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if i == nil {
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return ret
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}
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if ret.pos.X < i.pos.X {
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ret.pos.X = i.pos.X
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ret.size.Width -= i.pos.X - p.X
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}
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if ret.pos.Y < i.pos.Y {
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ret.pos.Y = i.pos.Y
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ret.size.Height -= i.pos.Y - p.Y
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}
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if p.X+s.Width > i.pos.X+i.size.Width {
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ret.size.Width = (i.pos.X + i.size.Width) - ret.pos.X
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}
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if p.Y+s.Height > i.pos.Y+i.size.Height {
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ret.size.Height = (i.pos.Y + i.size.Height) - ret.pos.Y
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}
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if ret.size.Width < 0 || ret.size.Height < 0 {
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ret.size = fyne.NewSize(0, 0)
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return ret
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}
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return ret
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}
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