Reset everything from a held on-screen button or space

ui.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"math"
 	"time"
 )
 
@@ -9,6 +10,7 @@ var (
 	uiBg     = rgb{0x12, 0x14, 0x18}
 	uiPanel  = rgb{0x1c, 0x20, 0x26}
 	uiRule   = rgb{0x2e, 0x34, 0x3c}
+	uiButton = rgb{0x25, 0x2b, 0x33}
 	uiFg     = rgb{0xe6, 0xe8, 0xea}
 	uiDim    = rgb{0x7a, 0x82, 0x8c}
 	uiCyan   = rgb{0x5c, 0xc8, 0xe0}
@@ -37,14 +39,31 @@ const (
 	colLateEnd   = 46
 	colCRCEnd    = 53
 	colKdropEnd  = 62
+
+	btnW         = 200
+	btnH         = 64
+	holdDuration = time.Second
 )
 
+type rect struct {
+	x, y, w, h int
+}
+
+func (r rect) contains(x, y int) bool {
+	return x >= r.x && x < r.x+r.w && y >= r.y && y < r.y+r.h
+}
+
 type display struct {
 	fb    *framebuffer
 	huge  *textFace
 	grid  *textFace
 	gridB *textFace
 	small *textFace
+
+	resetBtn  rect
+	holdStart time.Time
+	holdFrac  float64
+	fired     bool
 }
 
 func newDisplay() (*display, error) {
@@ -75,9 +94,71 @@ func newDisplay() (*display, error) {
 		return nil, fmt.Errorf("grid faces disagree on cell width: %d vs %d",
 			d.grid.cellW, d.gridB.cellW)
 	}
+	d.resetBtn = rect{
+		x: fb.w - uiMargin - btnW,
+		y: fb.h - uiMargin - btnH,
+		w: btnW,
+		h: btnH,
+	}
 	return d, nil
 }
 
+// Tracks a press and hold on the reset button, returning true once it has been
+// held long enough. Lifting or sliding off cancels, and the press has to be
+// released before it can arm again.
+func (d *display) holdReset(x, y int, down bool, now time.Time) bool {
+	if !down {
+		d.holdStart, d.holdFrac, d.fired = time.Time{}, 0, false
+		return false
+	}
+	if d.fired || !d.resetBtn.contains(x, y) {
+		d.holdStart, d.holdFrac = time.Time{}, 0
+		return false
+	}
+	if d.holdStart.IsZero() {
+		d.holdStart = now
+	}
+	d.holdFrac = now.Sub(d.holdStart).Seconds() / holdDuration.Seconds()
+	if d.holdFrac < 1 {
+		return false
+	}
+	d.holdFrac, d.fired, d.holdStart = 0, true, time.Time{}
+	return true
+}
+
+func (d *display) drawResetButton() {
+	r := d.resetBtn
+	d.fb.rect(r.x, r.y, r.w, r.h, uiButton)
+
+	if d.holdFrac > 0 {
+		w := int(float64(r.w) * math.Min(d.holdFrac, 1))
+		d.fb.rect(r.x, r.y, w, r.h, uiCyan)
+	}
+	for _, e := range []rect{
+		{r.x, r.y, r.w, 2},
+		{r.x, r.y + r.h - 2, r.w, 2},
+		{r.x, r.y, 2, r.h},
+		{r.x + r.w - 2, r.y, 2, r.h},
+	} {
+		d.fb.rect(e.x, e.y, e.w, e.h, uiCyan)
+	}
+
+	label := "RESET"
+	lx := r.x + (r.w-len(label)*d.gridB.cellW)/2
+	ly := r.y + (r.h-d.gridB.cellH)/2
+	// The label straddles the fill, so each glyph takes the colour that reads
+	// against whatever is behind it.
+	split := r.x + int(float64(r.w)*math.Min(d.holdFrac, 1))
+	for i, c := range label {
+		gx := lx + i*d.gridB.cellW
+		col := uiFg
+		if gx+d.gridB.cellW/2 < split {
+			col = uiBg
+		}
+		d.gridB.draw(d.fb, gx, ly, string(c), col)
+	}
+}
+
 func (d *display) close() {
 	d.fb.close()
 }
@@ -164,7 +245,7 @@ func (d *display) render(dirs []*direction, views []view, elapsed time.Duration,
 	lineH := d.grid.cellH + 4
 	sectionH := d.small.cellH + 10 + (1+len(dirs))*lineH
 	gap := 30
-	avail := fb.h - (bandY + bandH) - 16
+	avail := fb.h - (bandY + bandH) - btnH - 2*uiMargin
 	y := bandY + bandH + 8 + (avail-2*sectionH-gap)/2
 
 	y = d.section(y, "RATE")
@@ -204,6 +285,7 @@ func (d *display) render(dirs []*direction, views []view, elapsed time.Duration,
 		y += lineH
 	}
 
+	d.drawResetButton()
 	fb.flush()
 }