From 002d4e40af34fbe5b8eb6c00061b3384308a7ac9 Mon Sep 17 00:00:00 2001
From: Johan Walles <johan.walles@gmail.com>
Date: Sun, 30 May 2021 11:36:07 +0200
Subject: [PATCH] Modify input lines rendering API

Make the rendering function return both the lines and the clipped
first-line-number value.
---
 m/pager.go       | 10 +++-------
 m/screenLines.go | 17 +++++++++--------
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/m/pager.go b/m/pager.go
index fc8e48e..7daf839 100644
--- a/m/pager.go
+++ b/m/pager.go
@@ -164,14 +164,10 @@ func (p *Pager) _Redraw(spinner string) {
 		wrapLongLines:   p.WrapLongLines,
 	}
 
-	// If we're asking for past-the-end lines, the Reader will clip for us,
-	// and we should adapt to that. Otherwise if you scroll 100 lines past
-	// the end, you'll then have to scroll 100 lines up again before the
-	// display starts scrolling visibly.
-	p.firstLineOneBased = screenLines.firstLineOneBased()
-
 	var screenLineNumber int
-	for lineNumber, row := range screenLines.getScreenLines(p.searchPattern) {
+	var renderedScreenLines [][]twin.Cell
+	renderedScreenLines, p.firstLineOneBased = screenLines.renderScreenLines(p.searchPattern)
+	for lineNumber, row := range renderedScreenLines {
 		screenLineNumber = lineNumber
 		for column, cell := range row {
 			p.screen.SetCell(column, screenLineNumber, cell)
diff --git a/m/screenLines.go b/m/screenLines.go
index 6bac186..8cb1c74 100644
--- a/m/screenLines.go
+++ b/m/screenLines.go
@@ -19,7 +19,11 @@ type ScreenLines struct {
 	wrapLongLines   bool
 }
 
-func (sl *ScreenLines) getScreenLines(searchPattern *regexp.Regexp) [][]twin.Cell {
+// Render screen lines into an array of lines consisting of Cells.
+//
+// The second return value is the same as firstInputLineOneBased, but clipped if
+// needed so that the end of the input is visible.
+func (sl *ScreenLines) renderScreenLines(searchPattern *regexp.Regexp) ([][]twin.Cell, int) {
 	// Count the length of the last line number
 	//
 	// Offsets figured out through trial-and-error...
@@ -39,7 +43,7 @@ func (sl *ScreenLines) getScreenLines(searchPattern *regexp.Regexp) [][]twin.Cel
 	returnLines := make([][]twin.Cell, 0, sl.height)
 	screenFull := false
 	for lineIndex, line := range sl.inputLines.lines {
-		lineNumber := sl.firstLineOneBased() + lineIndex
+		lineNumber := sl.inputLines.firstLineOneBased + lineIndex
 
 		highlighted := line.HighlightedTokens(searchPattern)
 		var wrapped [][]twin.Cell
@@ -71,7 +75,9 @@ func (sl *ScreenLines) getScreenLines(searchPattern *regexp.Regexp) [][]twin.Cel
 		}
 	}
 
-	return returnLines
+	// FIXME: We can't just use firstInputLineOneBased, in the presence of
+	// wrapped lines that number can be too low.
+	return returnLines, sl.firstInputLineOneBased
 }
 
 func (sl *ScreenLines) createScreenLine(lineNumberToShow *int, numberPrefixLength int, contents []twin.Cell) []twin.Cell {
@@ -145,8 +151,3 @@ func createLineNumberPrefix(fileLineNumber *int, numberPrefixLength int) []twin.
 
 	return lineNumberPrefix
 }
-
-func (sl *ScreenLines) firstLineOneBased() int {
-	// FIXME: This is wrong when wrapping is enabled
-	return sl.inputLines.firstLineOneBased
-}