Keep both ends of a selected range across a re-render

A range or hunk selection covers a stretch of the diff, and restoring only
the cursor left the other end pointing at whatever line the new rendering
happened to put there — with more context lines above, a selected hunk
would grow a tail of context it never covered.

So the other end is remembered by identity too, and put back before the
cursor. If it is a line the re-render dropped, the selection is left as the
single line we landed on: there is no telling which line inherits a
selection's edge, and a wrong guess acts on lines the user never chose.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/gocui/view.go

@@ -637,6 +637,13 @@ func (v *View) CancelRangeSelect() {
 	v.rangeSelectStartY = -1
 }
 
+// HasRangeSelect reports whether a range selection is anchored, as opposed to the
+// view showing a plain cursor. A range whose ends are on the same view line is still
+// one, which SelectedLineRange alone can't tell you.
+func (v *View) HasRangeSelect() bool {
+	return v.rangeSelectStartY != -1
+}
+
 func calculateNewOrigin(selectedLine int, oldOrigin int, lineCount int, viewHeight int) int {
 	if viewHeight >= lineCount {
 		return 0

pkg/gui/controllers/helpers/diff_line_helper.go

@@ -32,53 +32,56 @@ func NewDiffLineHelper(c *HelperCommon) *DiffLineHelper {
 // ok is false when the row's identity can't be recovered, in which case the
 // caller must not act on the line at all.
 func (self *DiffLineHelper) GetDiffLineInfo(view *gocui.View, viewLineIdx int) (types.DiffLineInfo, bool) {
-	// The cursor and clicks land on a view line, which counts wrapped segments;
-	// the contents are indexed by unwrapped buffer line.
-	bufferLineIdx, ok := view.BufferLineForViewLine(viewLineIdx)
+	identities, ok := self.diffLineIdentitiesAt(view, viewLineIdx)
 	if !ok {
 		return types.DiffLineInfo{}, false
 	}
-
-	contents := view.DiffLineContents()
-	if bufferLineIdx >= len(contents) {
-		return types.DiffLineInfo{}, false
-	}
-
-	if renderingStatesDiffLines(contents) {
-		if info, ok := self.diffLineInfoFromRecords(contents[bufferLineIdx].Metadata); ok {
-			return info, true
-		}
-		return types.DiffLineInfo{}, false
-	}
-
-	parsed, ok := parseDiffLineFromBuffer(diffLineTexts(contents), bufferLineIdx)
-	if !ok {
-		return types.DiffLineInfo{}, false
-	}
-
-	return self.diffLineInfo(parsed), true
-}
-
-// diffLineInfoFromRecords recovers a row's identity from the records the diff
-// renderer stated for it. ok is false when the row carries no record we understand.
-//
-// A row can carry more than one record, when the rendering puts two diff lines on it
-// (a side-by-side row shows a deletion and the addition replacing it); the leftmost
-// is the one a reader would call the row's own, so it is the row's identity.
-func (self *DiffLineHelper) diffLineInfoFromRecords(metadata []string) (types.DiffLineInfo, bool) {
-	identities := self.diffLineIdentitiesFromRecords(metadata)
-	if len(identities) == 0 {
-		return types.DiffLineInfo{}, false
-	}
 	return identities[0], true
 }
 
+// diffLineIdentitiesAt recovers every diff line the row at the given (wrapped) view
+// line shows, left to right. It is GetDiffLineInfo's form for a reader that can't
+// settle for the line the row leads with: an end of a selection covers its whole
+// row, so where a rendering puts a modification's two halves side by side it covers
+// both of them. ok is false when the row's identity can't be recovered at all.
+func (self *DiffLineHelper) diffLineIdentitiesAt(
+	view *gocui.View, viewLineIdx int,
+) ([]types.DiffLineInfo, bool) {
+	// The cursor and clicks land on a view line, which counts wrapped segments;
+	// the contents are indexed by unwrapped buffer line.
+	bufferLineIdx, ok := view.BufferLineForViewLine(viewLineIdx)
+	if !ok {
+		return nil, false
+	}
+
+	contents := view.DiffLineContents()
+	if bufferLineIdx >= len(contents) {
+		return nil, false
+	}
+
+	if renderingStatesDiffLines(contents) {
+		if identities := self.diffLineIdentitiesFromRecords(contents[bufferLineIdx].Metadata); len(identities) > 0 {
+			return identities, true
+		}
+		return nil, false
+	}
+
+	parsed, ok := parseDiffLineFromBuffer(diffLineTexts(contents), bufferLineIdx)
+	if !ok {
+		return nil, false
+	}
+
+	return []types.DiffLineInfo{self.diffLineInfo(parsed)}, true
+}
+
 // diffLineIdentitiesFromRecords recovers the identity of every diff line the row's
-// records state, left to right. Which of them a reader is after depends on the
-// reader: the one the row leads with is the row's own identity (see
-// diffLineInfoFromRecords), while a reader looking for a particular line has to
-// consider them all, since which of a modification's two halves leads a row is up to
-// the rendering.
+// records state, left to right. A row can carry more than one record, when the
+// rendering puts two diff lines on it (a side-by-side row shows a deletion and the
+// addition replacing it). Which of them a reader is after depends on the reader: the
+// one the row leads with is the row's own identity (see GetDiffLineInfo and
+// resolveDiffLines), while a reader looking for a particular line has to consider
+// them all, since which of a modification's two halves leads a row is up to the
+// rendering.
 func (self *DiffLineHelper) diffLineIdentitiesFromRecords(metadata []string) []types.DiffLineInfo {
 	return self.diffLineInfos(parseDiffLineRecords(metadata))
 }

pkg/gui/controllers/helpers/diff_line_restore.go

@@ -26,19 +26,22 @@ type diffLineAnchor struct {
 // window where both are being rendered again, since either of them may hold the diff
 // being read; a pane that isn't showing is left alone.
 //
-// The line to keep is the selected one, and the middle visible line when there is no
-// selection or it has been scrolled out of sight — what the user is looking at, rather
-// than the view's top edge or a selection they have long since left behind. It may not
-// survive the re-render: a context line goes when the context size shrinks, and a
-// whole hunk or file goes when whitespace stops counting. So the lines around it come
-// along as fallbacks and the view lands on the nearest one that is still there, put
-// back on the screen row it was on. With none of them left — and with a renderer that
-// says nothing about its rows there is nothing to look for in the first place — the
-// view keeps the scroll offset it had, which is still nearer to what was being read
-// than the top of the diff.
+// The line to keep is the end of the selection that is on screen, and the middle
+// visible line when there is no selection or the whole of it has been scrolled out of
+// sight — what the user is looking at, rather than the view's top edge or a selection
+// they have long since left behind. It may not survive the re-render: a context line
+// goes when the context size shrinks, and a whole hunk or file goes when whitespace
+// stops counting. So the lines around it come along as fallbacks and the view lands on
+// the nearest one that is still there, put back on the screen row it was on. With none
+// of them left — and with a renderer that says nothing about its rows there is nothing
+// to look for in the first place — the view keeps the scroll offset it had, which is
+// still nearer to what was being read than the top of the diff.
 //
 // An off-screen selection is still put back on the diff line it was on, wherever the
 // new rendering has that; it is only the view that stays where it is.
+//
+// A range or hunk selection has a second end, which is remembered the same way, so
+// that it still covers the same lines of the diff afterwards.
 func (self *DiffLineHelper) PreserveDiffPositionOnRerender(view *gocui.View) {
 	// A view that isn't the one its window is currently showing — the merge-conflicts
 	// view takes the main window over — isn't the one about to be re-rendered, so a
@@ -57,17 +60,20 @@ func (self *DiffLineHelper) PreserveDiffPositionOnRerender(view *gocui.View) {
 	}
 
 	showSelection := view.Highlight
-	selectionOnScreen := showSelection && view.IsLineVisible(view.SelectedLineIdx())
 	anchorViewLine := view.MiddleVisibleLineIdx()
-	if selectionOnScreen {
-		anchorViewLine = view.SelectedLineIdx()
-	}
-	// A selection that has been scrolled away from is put back by its own lines rather
+	farEnd, hasFarEnd := types.DiffLineInfo{}, false
+	// A cursor that has been scrolled away from is put back by its own lines rather
 	// than by the anchor's, so that it comes out on the same line of the diff without
 	// the view having to go there.
-	var selectionCandidates []diffLineAnchor
-	if showSelection && !selectionOnScreen {
-		selectionCandidates = self.nearbyDiffLines(view, view.SelectedLineIdx())
+	var cursorCandidates []diffLineAnchor
+	if showSelection {
+		farEnd, hasFarEnd = self.selectionFarEndIdentity(view)
+		if end, ok := visibleSelectionEnd(view); ok {
+			anchorViewLine = end
+		}
+		if anchorViewLine != view.SelectedLineIdx() {
+			cursorCandidates = self.nearbyDiffLines(view, view.SelectedLineIdx())
+		}
 	}
 
 	self.restoreDiffLinePositionOnRerender(view, self.nearbyDiffLines(view, anchorViewLine),
@@ -77,16 +83,63 @@ func (self *DiffLineHelper) PreserveDiffPositionOnRerender(view *gocui.View) {
 			row := lo.Clamp(anchor.row, 0, max(0, view.InnerHeight()-1))
 			view.SetOrigin(0, max(0, viewLine-row))
 			if showSelection {
-				// A range's other end is a view line, which the new rendering has made
-				// mean something else, so the selection collapses to the line we landed
-				// on. The origin is already where it should be, so moving the cursor
-				// there mustn't scroll.
+				// Put the far end back before the cursor, so that the selection covers
+				// the same lines again; a selection whose far end didn't survive the
+				// re-render is left as the single line we landed on. The origin is
+				// already where it should be, so moving the cursor mustn't scroll.
 				view.CancelRangeSelect()
-				view.FocusPoint(0, self.selectionLine(view, selectionCandidates, viewLine), false)
+				cursorViewLine := self.selectionLine(view, cursorCandidates, viewLine)
+				if hasFarEnd {
+					if farEndViewLine, ok := self.findDiffLine(view, farEnd); ok {
+						cursorViewLine, farEndViewLine = coverWholeLines(view, cursorViewLine, farEndViewLine)
+						view.SetRangeSelectStart(farEndViewLine)
+					}
+				}
+				view.FocusPoint(0, cursorViewLine, false)
 			}
 		})
 }
 
+// coverWholeLines moves the two ends of a restored selection out to the edges of the
+// diff lines they are on, so that the selection covers those lines whole. Both ends
+// arrive on the first view line of their diff line, which is where looking one up by
+// identity lands, and the view draws a line it wraps as several — of which a
+// selection of that line means all.
+func coverWholeLines(view *gocui.View, cursorViewLine int, farEndViewLine int) (int, int) {
+	if cursorViewLine <= farEndViewLine {
+		return cursorViewLine, lastViewLineOfSameDiffLine(view, farEndViewLine)
+	}
+	return lastViewLineOfSameDiffLine(view, cursorViewLine), farEndViewLine
+}
+
+// lastViewLineOfSameDiffLine returns the last view line showing the same line of the
+// diff as the given one, which is that line itself unless the view wrapped it.
+func lastViewLineOfSameDiffLine(view *gocui.View, viewLine int) int {
+	bufferLine, ok := view.BufferLineForViewLine(viewLine)
+	if !ok {
+		return viewLine
+	}
+	if last, ok := view.LastViewLineForBufferLine(bufferLine); ok {
+		return last
+	}
+	return viewLine
+}
+
+// visibleSelectionEnd returns the end of the selection to keep in place across a
+// re-render: the selected line when it is on screen, and the range's other end when
+// that is and the selected line isn't — a range can be long enough for the user to be
+// looking at one end of it with the other far away. ok is false when the whole
+// selection is off screen, and there is nothing of it to keep in place.
+func visibleSelectionEnd(view *gocui.View) (int, bool) {
+	if view.IsLineVisible(view.SelectedLineIdx()) {
+		return view.SelectedLineIdx(), true
+	}
+	if farEnd, _, ok := selectionFarEndViewLine(view); ok && view.IsLineVisible(farEnd) {
+		return farEnd, true
+	}
+	return 0, false
+}
+
 // selectionLine returns the line to put the cursor on once a re-render is on screen:
 // the line the position anchor landed on, which is the selected one whenever it was
 // on screen, and otherwise the nearest surviving line to where the selection was —
@@ -108,6 +161,60 @@ func (self *DiffLineHelper) selectionLine(
 	return anchorViewLine
 }
 
+// selectionFarEndIdentity returns the identity of the end of a range or hunk
+// selection the cursor isn't on, so that a re-render can put it back. ok is false for
+// a selection that is only a cursor, where restoring that is the whole job, and for
+// an end that resolves to no diff line.
+//
+// An end covers the whole of its row, so where the row shows more than one diff line
+// — a rendering that puts a modification's two halves side by side, or a word diff
+// that puts both on the one line it changed — the end takes the outermost of them:
+// the last for the range's lower end and the first for its upper one. Otherwise a
+// rendering that splits them apart again would get back only the half the row led
+// with, and half a change selected where a whole one was.
+func (self *DiffLineHelper) selectionFarEndIdentity(view *gocui.View) (types.DiffLineInfo, bool) {
+	farEnd, isLowerEnd, ok := selectionFarEndViewLine(view)
+	if !ok {
+		return types.DiffLineInfo{}, false
+	}
+	identities, ok := self.diffLineIdentitiesAt(view, farEnd)
+	if !ok {
+		return types.DiffLineInfo{}, false
+	}
+	if isLowerEnd {
+		return identities[len(identities)-1], true
+	}
+	return identities[0], true
+}
+
+// selectionFarEndViewLine returns the view line of the end of a range or hunk
+// selection the cursor isn't on, and whether that is the lower of the two ends. ok
+// is false when there is no range at all, only a cursor.
+//
+// A range whose two ends are on the same view line still has one, and is not the
+// same thing as a cursor sitting there: it covers everything that row shows, which
+// may be two lines of the diff at once.
+func selectionFarEndViewLine(view *gocui.View) (int, bool, bool) {
+	if !view.HasRangeSelect() {
+		return 0, false, false
+	}
+	first, last := view.SelectedLineRange()
+	if view.SelectedLineIdx() == first {
+		return last, true, true
+	}
+	return first, false, true
+}
+
+// findDiffLine returns the view line showing the given diff line in what view is
+// displaying now, for placing a remembered line once the re-render is on screen.
+func (self *DiffLineHelper) findDiffLine(view *gocui.View, identity types.DiffLineInfo) (int, bool) {
+	bufferLine, ok := self.patchLineRows(view.DiffLineContents())[patchLineOf(identity)]
+	if !ok {
+		return 0, false
+	}
+	return view.ViewLineForBufferLine(bufferLine)
+}
+
 // restoreDiffLinePositionOnRerender arranges for view's next re-render to land on the
 // first of the given candidate lines the new rendering still has, calling place with
 // that candidate and the view line it ended up on. The candidates are in priority

pkg/integration/components/view_driver.go

@@ -300,6 +300,21 @@ func (self *ViewDriver) SelectedLines(matchers ...*TextMatcher) *ViewDriver {
 	return self
 }
 
+// SelectedViewLineRange asserts which view lines the selection covers. View lines
+// count the wrapped segments a line is drawn as, so this can say whether a selection
+// covers a wrapped line to its end; SelectedLines, which reports the lines of the
+// content, cannot.
+func (self *ViewDriver) SelectedViewLineRange(first int, last int) *ViewDriver {
+	self.t.assertWithRetries(func() (bool, string) {
+		actualFirst, actualLast := self.getSelectedRange()
+		return actualFirst == first && actualLast == last,
+			fmt.Sprintf("%s: Expected view lines %d-%d to be selected, but %d-%d were.",
+				self.context, first, last, actualFirst, actualLast)
+	})
+
+	return self
+}
+
 func (self *ViewDriver) validateMatchersPassed(matchers []*TextMatcher) {
 	if len(matchers) < 1 {
 		self.t.fail("'Lines' methods require at least one matcher to be passed as an argument. If you are trying to assert that there are no lines, use .IsEmpty()")

pkg/integration/tests/main_view/keep_a_wrapped_line_covered_across_a_rerender.go

@@ -0,0 +1,60 @@
+package main_view
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var KeepAWrappedLineCoveredAcrossARerender = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "A selection over a line too long for the view still covers all of it after a re-render",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	Width:        80,
+	Height:       20,
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().Gui.UseHunkModeInStagingView = true
+	},
+	SetupRepo: func(shell *Shell) {
+		long := strings.Repeat("word ", 40)
+		lines := make([]string, 20)
+		for i := range lines {
+			lines[i] = fmt.Sprintf("line%02d", i+1)
+		}
+		before := strings.Join(lines[:10], "\n") + "\n"
+		after := strings.Join(lines[10:], "\n") + "\n"
+
+		shell.CreateFileAndAdd("file1", before+long+"\n"+after)
+		shell.Commit("one")
+
+		shell.UpdateFile("file1", before+"CHANGED "+long+"\n"+after)
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Press(keys.Universal.FocusMainView)
+
+		// The changed line is far too long for the view, so each half of the change
+		// is drawn as several view lines, and hunk mode selects all of them.
+		t.Views().Main().
+			IsFocused().
+			SelectedLines(
+				Contains("-word word"),
+				Contains("+CHANGED word"),
+			).
+			SelectedViewLineRange(8, 16).
+			// The same two lines of the diff, wrapped the same way, are still covered
+			// to their ends once the diff has been rendered again.
+			Press(keys.Universal.IncreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 4"))
+			}).
+			SelectedLines(
+				Contains("-word word"),
+				Contains("+CHANGED word"),
+			).
+			SelectedViewLineRange(9, 17)
+	},
+})

pkg/integration/tests/main_view/keep_both_halves_of_a_change_selected.go

@@ -0,0 +1,68 @@
+package main_view
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var KeepBothHalvesOfAChangeSelected = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "A change selected on the one row a renderer draws it as is selected on both rows of a renderer that splits it",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().Gui.UseHunkModeInStagingView = true
+		cfg.GetUserConfig().Git.DiffRenderers = []config.DiffRendererConfig{
+			// Git's own diff, which has a row for each half of a change. It announces
+			// the metadata protocol, so lazygit acts on its output rather than
+			// replacing it; it states no records of its own, so the rows are located
+			// by parsing the text, which still looks like a diff.
+			{Name: "unified", Command: `printf '\033]1717;1\007'; cat`},
+			// A renderer that puts the two halves of a change beside each other on one
+			// row. Only the records it states can say where those halves are; parsing
+			// the text could not. It ignores its input and prints this one.
+			{Name: "columns", Command: `printf '\033]1717;1\007'; ` +
+				`printf '\033]1717;1;f;;;file1\007file1\n'; ` +
+				`printf '\033]1717;1;h;1;;file1\007@@\n'; ` +
+				`printf '\033]1717;1;c;1;;file1\007one    one\n'; ` +
+				`printf '\033]1717;1;d;2;2;file1\007two    \033]1717;1;a;2;;file1\007TWO\n'; ` +
+				`printf '\033]1717;1;c;3;;file1\007three  three\n'; ` +
+				`cat >/dev/null`},
+		}
+	},
+	SetupRepo: func(shell *Shell) {
+		shell.CreateFileAndAdd("file1", "one\ntwo\nthree\n")
+		shell.Commit("one")
+
+		shell.UpdateFile("file1", "one\nTWO\nthree\n")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Press(keys.Universal.FocusMainView)
+
+		t.Views().Main().
+			IsFocused().
+			SelectedLines(
+				Contains("-two"),
+				Contains("+TWO"),
+			).
+			// The change is one row here, and selecting it selects that row: both
+			// halves are on it.
+			Press(keys.Universal.CycleDiffRenderers).
+			Tap(func() {
+				t.ExpectToast(Equals("Diff renderer: columns (2 of 2)"))
+			}).
+			SelectedLines(
+				Contains("two    TWO"),
+			).
+			// Split apart again, the same change is the same two lines it was.
+			Press(keys.Universal.CycleDiffRenderers).
+			Tap(func() {
+				t.ExpectToast(Equals("Diff renderer: unified (1 of 2)"))
+			}).
+			SelectedLines(
+				Contains("-two"),
+				Contains("+TWO"),
+			)
+	},
+})

pkg/integration/tests/main_view/keep_position_by_the_visible_end_of_a_selection.go

@@ -0,0 +1,102 @@
+package main_view
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var KeepPositionByTheVisibleEndOfASelection = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "A re-render keeps the place by the end of a selected hunk that is on screen when its other end isn't",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	Width:        120,
+	Height:       30,
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().Gui.UseHunkModeInStagingView = true
+		// One line per scroll, so that the test can put the top of the view exactly
+		// where it wants it.
+		cfg.GetUserConfig().Gui.ScrollHeight = 1
+	},
+	SetupRepo: func(shell *Shell) {
+		lines := make([]string, 60)
+		for i := range lines {
+			lines[i] = fmt.Sprintf("line%02d", i+1)
+		}
+		shell.CreateFileAndAdd("file1", strings.Join(lines, "\n")+"\n")
+		shell.Commit("one")
+
+		// A first change tall enough to be scrolled halfway out of the view, and more
+		// of them below it, so that a context-size change moves the lines further down
+		// the diff by more than it moves the first change.
+		for _, i := range []int{10, 11, 12, 13, 14, 15, 30, 45} {
+			lines[i-1] = strings.ToUpper(lines[i-1])
+		}
+		shell.UpdateFile("file1", strings.Join(lines, "\n")+"\n")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Press(keys.Universal.FocusMainView)
+
+		t.Views().Main().
+			IsFocused().
+			SelectedLines(
+				Contains("-line10"),
+				Contains("-line11"),
+				Contains("-line12"),
+				Contains("-line13"),
+				Contains("-line14"),
+				Contains("-line15"),
+				Contains("+LINE10"),
+				Contains("+LINE11"),
+				Contains("+LINE12"),
+				Contains("+LINE13"),
+				Contains("+LINE14"),
+				Contains("+LINE15"),
+			).
+			SelectedLineIdx(8).
+			// Scroll past the start of the selected block, leaving its last lines on
+			// screen and the cursor above the top of the view.
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			Press(keys.Universal.ScrollDownMain).
+			OriginY(14).
+			Press(keys.Universal.IncreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 4"))
+			}).
+			// The block's last line was the fifth row of the screen, and one context
+			// line more above the block puts it a line further down the diff: the view
+			// follows it, rather than the middle visible line, which the hunks below
+			// have pushed further still.
+			OriginY(15).
+			SelectedLines(
+				Contains("-line10"),
+				Contains("-line11"),
+				Contains("-line12"),
+				Contains("-line13"),
+				Contains("-line14"),
+				Contains("-line15"),
+				Contains("+LINE10"),
+				Contains("+LINE11"),
+				Contains("+LINE12"),
+				Contains("+LINE13"),
+				Contains("+LINE14"),
+				Contains("+LINE15"),
+			)
+	},
+})

pkg/integration/tests/main_view/keep_selected_range_when_changing_context_size.go

@@ -0,0 +1,123 @@
+package main_view
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var KeepSelectedRangeWhenChangingContextSize = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "A range selection still covers the same lines of the diff after the context size changes",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	Width:        120,
+	Height:       30,
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().Gui.UseHunkModeInStagingView = false
+	},
+	SetupRepo: func(shell *Shell) {
+		lines := make([]string, 40)
+		for i := range lines {
+			lines[i] = fmt.Sprintf("line%02d", i+1)
+		}
+		shell.CreateFileAndAdd("file1", strings.Join(lines, "\n")+"\n")
+		shell.Commit("one")
+
+		for _, i := range []int{5, 15, 25, 35} {
+			lines[i-1] = strings.ToUpper(lines[i-1])
+		}
+		shell.UpdateFile("file1", strings.Join(lines, "\n")+"\n")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Press(keys.Universal.FocusMainView)
+
+		// A range from a change down into the context below it, so that the cursor is
+		// on the last line of the selection and the other end is three lines above.
+		t.Views().Main().
+			IsFocused().
+			Press(keys.Main.NextHunk).
+			Press(keys.Main.NextHunk).
+			Press(keys.Universal.ToggleRangeSelect).
+			Press(keys.Universal.NextItem).
+			Press(keys.Universal.NextItem).
+			Press(keys.Universal.NextItem).
+			SelectedLines(
+				Contains("-line25"),
+				Contains("+LINE25"),
+				Contains(" line26"),
+				Contains(" line27"),
+			).
+			// Both ends are still lines of the diff with more context around the
+			// change, so the selection still covers the same four.
+			Press(keys.Universal.IncreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 4"))
+			}).
+			SelectedLines(
+				Contains("-line25"),
+				Contains("+LINE25"),
+				Contains(" line26"),
+				Contains(" line27"),
+			).
+			// With a single line of context, the line the cursor was on is no longer in
+			// the diff. The end that survived stays put and the cursor lands on the
+			// nearest line that is left, so the selection shrinks with the diff.
+			Press(keys.Universal.DecreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 3"))
+			}).
+			Press(keys.Universal.DecreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 2"))
+			}).
+			Press(keys.Universal.DecreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 1"))
+			}).
+			SelectedLines(
+				Contains("-line25"),
+				Contains("+LINE25"),
+				Contains(" line26"),
+			).
+			// The other way round: a range extended upwards, so that it is the far end
+			// that the shrinking context takes away. There is no guessing which line
+			// inherits it, so what is left is the line the cursor is on.
+			PressEscape().
+			Press(keys.Universal.IncreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 2"))
+			}).
+			Press(keys.Universal.IncreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 3"))
+			}).
+			SelectedLines(
+				Contains(" line26"),
+			).
+			Press(keys.Universal.NextItem).
+			Press(keys.Universal.RangeSelectUp).
+			Press(keys.Universal.RangeSelectUp).
+			Press(keys.Universal.RangeSelectUp).
+			SelectedLines(
+				Contains("-line25"),
+				Contains("+LINE25"),
+				Contains(" line26"),
+				Contains(" line27"),
+			).
+			Press(keys.Universal.DecreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 2"))
+			}).
+			Press(keys.Universal.DecreaseContextInDiffView).
+			Tap(func() {
+				t.ExpectToast(Equals("Changed diff context size to 1"))
+			}).
+			SelectedLines(
+				Contains("-line25"),
+			)
+	},
+})

pkg/integration/tests/test_list.go

@@ -371,6 +371,9 @@ var tests = []*components.IntegrationTest{
 	main_view.EscapeDismissesSelection,
 	main_view.FileNavigationScrollsToTheTop,
 	main_view.HideSelectionWhenChangesVanish,
+	main_view.KeepAWrappedLineCoveredAcrossARerender,
+	main_view.KeepBothHalvesOfAChangeSelected,
+	main_view.KeepPositionByTheVisibleEndOfASelection,
 	main_view.KeepPositionInBothPanesWhenChangingContextSize,
 	main_view.KeepPositionInBothPanesWhenIgnoringWhitespace,
 	main_view.KeepPositionInBothPanesWhenSwitchingDiffRenderers,
@@ -380,6 +383,7 @@ var tests = []*components.IntegrationTest{
 	main_view.KeepPositionWhenSwitchingDiffRenderers,
 	main_view.KeepPositionWhenTheSelectionIsOffScreen,
 	main_view.KeepScrollWhenTheDiffCantBeRead,
+	main_view.KeepSelectedRangeWhenChangingContextSize,
 	main_view.KeepSelectionVisibleWhenDiffShrinks,
 	main_view.NavigateByHunkAndFile,
 	main_view.NoSelectionOverABinaryDiff,