fix: improve width calculation for ratios option (#2347)

* fix: improve width calculation for `ratios` option

* Update `CHANGELOG.md`

* round window ends instead of floor

* grammar

Author: joelim-work

CHANGELOG.md

@@ -32,6 +32,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 - Newline characters are now ignored when drawing the ruler with the `ruler` file configured (#2319).
 - A potential crash when using the `scroll-up`/`scroll-down` commands is now fixed (#2320).
 - Case-insensitive command-line completions no longer cause user input to be displayed in lowercase (#2336).
+- Calculation of window widths for the `ratios` option is now more accurate (#2347).
 
 ## [r40](https://github.com/gokcehan/lf/releases/tag/r40)
 

misc.go

@@ -513,6 +513,39 @@ func readLines(reader io.ByteReader, maxLines int) (lines []string, binary bool,
 	}
 }
 
+// This function calculates the widths of windows as the result of applying the
+// `ratios` option to the screen width. One column is allocated for each divider
+// between windows. The `drawbox` option requires an additional two columns to
+// draw the left and right borders.
+func getWidths(wtot int, ratios []int, drawbox bool) []int {
+	rlen := len(ratios)
+	wtot -= rlen - 1
+	if drawbox {
+		wtot -= 2
+	}
+	wtot = max(wtot, 0)
+
+	rtot := 0
+	for _, r := range ratios {
+		rtot += r
+	}
+
+	divround := func(x, y int) int {
+		return (x + y/2) / y
+	}
+
+	widths := make([]int, rlen)
+	rsum := 0
+	wsum := 0
+	for i, r := range ratios {
+		rsum += r
+		widths[i] = divround(wtot*rsum, rtot) - wsum
+		wsum += widths[i]
+	}
+
+	return widths
+}
+
 // We don't need no generic code
 // We don't need no type control
 // No dark templates in compiler

misc_test.go

@@ -559,3 +559,30 @@ func TestReadLines(t *testing.T) {
 		}
 	}
 }
+
+func TestGetWidths(t *testing.T) {
+	tests := []struct {
+		wtot    int
+		ratios  []int
+		drawbox bool
+		exp     []int
+	}{
+		{0, []int{1}, false, []int{0}},
+		{0, []int{1}, true, []int{0}},
+		{0, []int{1, 3, 2}, false, []int{0, 0, 0}},
+		{0, []int{1, 3, 2}, true, []int{0, 0, 0}},
+		{14, []int{1, 3, 2}, false, []int{2, 6, 4}},
+		{16, []int{1, 3, 2}, true, []int{2, 6, 4}},
+		{23, []int{1, 3, 2, 4}, false, []int{2, 6, 4, 8}}, // windows end at 2.0, 8.0, 12.0, 20.0 respectively
+		{24, []int{1, 3, 2, 4}, false, []int{2, 6, 5, 8}}, // windows end at 2.1, 8.4, 12.6, 21.0 respectively
+		{25, []int{1, 3, 2, 4}, false, []int{2, 7, 4, 9}}, // windows end at 2.2, 8.8, 13.2, 22.0 respectively
+		{26, []int{1, 3, 2, 4}, false, []int{2, 7, 5, 9}}, // windows end at 2.3, 9.2, 13.8, 23.0 respectively
+	}
+
+	for _, test := range tests {
+		widths := getWidths(test.wtot, test.ratios, test.drawbox)
+		if !reflect.DeepEqual(widths, test.exp) {
+			t.Errorf("at input (%v, %v, %v) expected %v but got %v", test.wtot, test.ratios, test.drawbox, test.exp, widths)
+		}
+	}
+}

ui.go

@@ -480,10 +480,6 @@ func (win *win) printDir(ui *ui, dir *dir, context *dirContext, dirStyle *dirSty
 
 		// make space for select marker, and leave another space at the end
 		maxWidth := win.w - lnwidth - 2
-		// make extra space to separate windows if drawbox is not enabled
-		if !gOpts.drawbox {
-			maxWidth--
-		}
 
 		var icon []rune
 		var iconDef iconDef
@@ -598,45 +594,23 @@ func getCustomWidth(dir *dir, beg, end int) int {
 	return maxw
 }
 
-func getWidths(wtot int) []int {
-	rsum := 0
-	for _, r := range gOpts.ratios {
-		rsum += r
-	}
-
-	wlen := len(gOpts.ratios)
-	widths := make([]int, wlen)
-
-	if gOpts.drawbox {
-		wtot -= (wlen + 1)
-	}
-
-	wsum := 0
-	for i := range wlen - 1 {
-		widths[i] = gOpts.ratios[i] * wtot / rsum
-		wsum += widths[i]
-	}
-	widths[wlen-1] = wtot - wsum
-
-	return widths
-}
-
 func getWins(screen tcell.Screen) []*win {
 	wtot, htot := screen.Size()
 
-	widths := getWidths(wtot)
+	h := max(htot-2, 0)
+	x := 0
+	y := 1
+	if gOpts.drawbox {
+		h = max(htot-4, 0)
+		x = 1
+		y = 2
+	}
 
-	wacc := 0
-	wlen := len(widths)
-	wins := make([]*win, 0, wlen)
-	for i := range wlen {
-		if gOpts.drawbox {
-			wacc++
-			wins = append(wins, newWin(widths[i], max(htot-4, 0), wacc, 2))
-		} else {
-			wins = append(wins, newWin(widths[i], max(htot-2, 0), wacc, 1))
-		}
-		wacc += widths[i]
+	widths := getWidths(wtot, gOpts.ratios, gOpts.drawbox)
+	wins := make([]*win, 0, len(widths))
+	for _, w := range widths {
+		wins = append(wins, newWin(w, h, x, y))
+		x += w + 1
 	}
 
 	return wins