termdash/widgets/donut/circle.go

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// Copyright 2019 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
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package donut
// circle.go assists in calculation of points and angles on a circle.
import (
"image"
"github.com/mum4k/termdash/internal/canvas/braille"
"github.com/mum4k/termdash/internal/numbers"
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)
// startEndAngles given progress indicators and the desired start angle and
// direction, returns the starting and the ending angle of the partial circle
// that represents this progress.
func startEndAngles(current, total, startAngle, direction int) (start, end int) {
const fullCircle = 360
if total == 0 {
return startAngle, startAngle
}
mult := float64(current) / float64(total)
angleSize := numbers.Round(float64(360) * mult)
if angleSize == fullCircle {
return 0, fullCircle
}
end = startAngle + int(numbers.Round(float64(direction)*angleSize))
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if end < 0 {
end += fullCircle
if startAngle == 0 {
startAngle = fullCircle
}
return end, startAngle
}
if end < startAngle {
return end, startAngle
}
if end > fullCircle {
end = end % fullCircle
}
return startAngle, end
}
// midAndRadius given an area of a braille canvas, determines the mid point in
// pixels and radius to draw the largest circle that fits.
// The circle's mid point is always positioned on the {0,1} pixel in the chosen
// cell so that any text inside of it can be visually centered.
func midAndRadius(ar image.Rectangle) (image.Point, int) {
mid := image.Point{ar.Dx() / 2, ar.Dy() / 2}
if mid.X%2 != 0 {
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mid.X--
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}
switch mid.Y % 4 {
case 0:
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mid.Y++
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case 1:
case 2:
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mid.Y--
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case 3:
mid.Y -= 2
}
// Calculate radius based on the smaller axis.
var radius int
if ar.Dx() < ar.Dy() {
if mid.X < ar.Dx()/2 {
radius = mid.X
} else {
radius = ar.Dx() - mid.X - 1
}
} else {
if mid.Y < ar.Dy()/2 {
radius = mid.Y
} else {
radius = ar.Dy() - mid.Y - 1
}
}
return mid, radius
}
// availableCells given a radius returns the number of cells that are available
// within the circle and the coordinates of the first cell.
// These coordinates are for a normal (non-braille) canvas.
// That is the cells that do not contain any of the circle points. This is
// important since normal characters and braille characters cannot share the
// same cell.
func availableCells(mid image.Point, radius int) (int, image.Point) {
if radius < 3 {
return 0, image.Point{0, 0}
}
// Pixels available for the text only.
// Subtract one for the circle itself.
pixels := radius*2 - 1
startPixel := image.Point{mid.X - pixels/2, mid.Y}
startCell := image.Point{
startPixel.X / braille.ColMult,
mid.Y / braille.RowMult,
}
return pixels / braille.ColMult, startCell
}