Add a mechanism to insert non-model items into list contexts

Not used by anything yet.

pkg/gui/context/list_context_trait.go

@@ -29,7 +29,8 @@ func (self *ListContextTrait) FocusLine() {
 	self.c.AfterLayout(func() error {
 		oldOrigin, _ := self.GetViewTrait().ViewPortYBounds()
 
-		self.GetViewTrait().FocusPoint(self.list.GetSelectedLineIdx())
+		self.GetViewTrait().FocusPoint(
+			self.ModelIndexToViewIndex(self.list.GetSelectedLineIdx()))
 
 		// If FocusPoint() caused the view to scroll (because the selected line
 		// was out of view before), we need to rerender the view port again.
@@ -84,7 +85,7 @@ func (self *ListContextTrait) HandleFocusLost(opts types.OnFocusLostOpts) error
 // OnFocus assumes that the content of the context has already been rendered to the view. OnRender is the function which actually renders the content to the view
 func (self *ListContextTrait) HandleRender() error {
 	self.list.RefreshSelectedIdx()
-	content := self.renderLines(0, self.list.Len())
+	content := self.renderLines(-1, -1)
 	self.GetViewTrait().SetContent(content)
 	self.c.Render()
 	self.setFooter()

pkg/gui/context/list_renderer.go

@@ -5,26 +5,120 @@ import (
 
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 	"github.com/jesseduffield/lazygit/pkg/utils"
+	"github.com/samber/lo"
+	"golang.org/x/exp/slices"
 )
 
+type NonModelItem struct {
+	// Where in the model this should be inserted
+	Index int
+	// Content to render
+	Content string
+	// The column from which to render the item
+	Column int
+}
+
 type ListRenderer struct {
-	list              types.IList
+	list types.IList
+	// Function to get the display strings for each model item in the given
+	// range. startIdx and endIdx are model indices. For each model item, return
+	// an array of strings, one for each column; the list renderer will take
+	// care of aligning the columns appropriately.
 	getDisplayStrings func(startIdx int, endIdx int) [][]string
 	// Alignment for each column. If nil, the default is left alignment
 	getColumnAlignments func() []utils.Alignment
+	// Function to insert non-model items (e.g. section headers). If nil, no
+	// such items are inserted
+	getNonModelItems func() []*NonModelItem
+
+	// The remaining fields are private and shouldn't be initialized by clients
+	numNonModelItems        int
+	viewIndicesByModelIndex []int
+	modelIndicesByViewIndex []int
 }
 
 func (self *ListRenderer) GetList() types.IList {
 	return self.list
 }
 
+func (self *ListRenderer) ModelIndexToViewIndex(modelIndex int) int {
+	modelIndex = lo.Clamp(modelIndex, 0, self.list.Len())
+	if self.viewIndicesByModelIndex != nil {
+		return self.viewIndicesByModelIndex[modelIndex]
+	}
+
+	return modelIndex
+}
+
+func (self *ListRenderer) ViewIndexToModelIndex(viewIndex int) int {
+	viewIndex = utils.Clamp(viewIndex, 0, self.list.Len()+self.numNonModelItems)
+	if self.modelIndicesByViewIndex != nil {
+		return self.modelIndicesByViewIndex[viewIndex]
+	}
+
+	return viewIndex
+}
+
+// startIdx and endIdx are view indices, not model indices. If you want to
+// render the whole list, pass -1 for both.
 func (self *ListRenderer) renderLines(startIdx int, endIdx int) string {
 	var columnAlignments []utils.Alignment
 	if self.getColumnAlignments != nil {
 		columnAlignments = self.getColumnAlignments()
 	}
-	lines, _ := utils.RenderDisplayStrings(
-		self.getDisplayStrings(startIdx, utils.Min(endIdx, self.list.Len())),
+	nonModelItems := []*NonModelItem{}
+	self.numNonModelItems = 0
+	if self.getNonModelItems != nil {
+		nonModelItems = self.getNonModelItems()
+		self.prepareConversionArrays(nonModelItems)
+	}
+	startModelIdx := 0
+	if startIdx == -1 {
+		startIdx = 0
+	} else {
+		startModelIdx = self.ViewIndexToModelIndex(startIdx)
+	}
+	endModelIdx := self.list.Len()
+	if endIdx == -1 {
+		endIdx = endModelIdx + len(nonModelItems)
+	} else {
+		endModelIdx = self.ViewIndexToModelIndex(endIdx)
+	}
+	lines, columnPositions := utils.RenderDisplayStrings(
+		self.getDisplayStrings(startModelIdx, endModelIdx),
 		columnAlignments)
+	lines = self.insertNonModelItems(nonModelItems, endIdx, startIdx, lines, columnPositions)
 	return strings.Join(lines, "\n")
 }
+
+func (self *ListRenderer) prepareConversionArrays(nonModelItems []*NonModelItem) {
+	self.numNonModelItems = len(nonModelItems)
+	self.viewIndicesByModelIndex = lo.Range(self.list.Len() + 1)
+	self.modelIndicesByViewIndex = lo.Range(self.list.Len() + 1)
+	offset := 0
+	for _, item := range nonModelItems {
+		for i := item.Index; i <= self.list.Len(); i++ {
+			self.viewIndicesByModelIndex[i]++
+		}
+		self.modelIndicesByViewIndex = slices.Insert(
+			self.modelIndicesByViewIndex, item.Index+offset, self.modelIndicesByViewIndex[item.Index+offset])
+		offset++
+	}
+}
+
+func (self *ListRenderer) insertNonModelItems(
+	nonModelItems []*NonModelItem, endIdx int, startIdx int, lines []string, columnPositions []int,
+) []string {
+	offset := 0
+	for _, item := range nonModelItems {
+		if item.Index+offset >= endIdx {
+			break
+		}
+		if item.Index+offset >= startIdx {
+			padding := strings.Repeat(" ", columnPositions[item.Column])
+			lines = slices.Insert(lines, item.Index+offset-startIdx, padding+item.Content)
+		}
+		offset++
+	}
+	return lines
+}

pkg/gui/context/list_renderer_test.go

@@ -1,6 +1,7 @@
 package context
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
@@ -10,11 +11,12 @@ import (
 
 func TestListRenderer_renderLines(t *testing.T) {
 	scenarios := []struct {
-		name           string
-		modelStrings   []string
-		startIdx       int
-		endIdx         int
-		expectedOutput string
+		name            string
+		modelStrings    []string
+		nonModelIndices []int
+		startIdx        int
+		endIdx          int
+		expectedOutput  string
 	}{
 		{
 			name:         "Render whole list",
@@ -52,16 +54,79 @@ func TestListRenderer_renderLines(t *testing.T) {
 			expectedOutput: `
 				c`,
 		},
+		{
+			name:            "Whole list with section headers",
+			modelStrings:    []string{"a", "b", "c"},
+			nonModelIndices: []int{1, 3},
+			startIdx:        0,
+			endIdx:          5,
+			expectedOutput: `
+				a
+				--- 1 (0) ---
+				b
+				c
+				--- 3 (1) ---`,
+		},
+		{
+			name:            "Multiple consecutive headers",
+			modelStrings:    []string{"a", "b", "c"},
+			nonModelIndices: []int{0, 0, 2, 2, 2},
+			startIdx:        0,
+			endIdx:          8,
+			expectedOutput: `
+				--- 0 (0) ---
+				--- 0 (1) ---
+				a
+				b
+				--- 2 (2) ---
+				--- 2 (3) ---
+				--- 2 (4) ---
+				c`,
+		},
+		{
+			name:            "Partial list with headers, beginning",
+			modelStrings:    []string{"a", "b", "c"},
+			nonModelIndices: []int{1, 3},
+			startIdx:        0,
+			endIdx:          3,
+			expectedOutput: `
+				a
+				--- 1 (0) ---
+				b`,
+		},
+		{
+			name:            "Partial list with headers, end (beyond end index)",
+			modelStrings:    []string{"a", "b", "c"},
+			nonModelIndices: []int{1, 3},
+			startIdx:        2,
+			endIdx:          7,
+			expectedOutput: `
+				b
+				c
+				--- 3 (1) ---`,
+		},
 	}
 	for _, s := range scenarios {
 		t.Run(s.name, func(t *testing.T) {
 			viewModel := NewListViewModel[string](func() []string { return s.modelStrings })
+			var getNonModelItems func() []*NonModelItem
+			if s.nonModelIndices != nil {
+				getNonModelItems = func() []*NonModelItem {
+					return lo.Map(s.nonModelIndices, func(modelIndex int, nonModelIndex int) *NonModelItem {
+						return &NonModelItem{
+							Index:   modelIndex,
+							Content: fmt.Sprintf("--- %d (%d) ---", modelIndex, nonModelIndex),
+						}
+					})
+				}
+			}
 			self := &ListRenderer{
 				list: viewModel,
 				getDisplayStrings: func(startIdx int, endIdx int) [][]string {
 					return lo.Map(s.modelStrings[startIdx:endIdx],
 						func(s string, _ int) []string { return []string{s} })
 				},
+				getNonModelItems: getNonModelItems,
 			}
 
 			expectedOutput := strings.Join(lo.Map(
@@ -72,3 +137,120 @@ func TestListRenderer_renderLines(t *testing.T) {
 		})
 	}
 }
+
+func TestListRenderer_ModelIndexToViewIndex_and_back(t *testing.T) {
+	scenarios := []struct {
+		name            string
+		numModelItems   int
+		nonModelIndices []int
+
+		modelIndices        []int
+		expectedViewIndices []int
+
+		viewIndices          []int
+		expectedModelIndices []int
+	}{
+		{
+			name:            "no headers (no getNonModelItems provided)",
+			numModelItems:   3,
+			nonModelIndices: nil, // no get
+
+			modelIndices:        []int{-1, 0, 1, 2, 3, 4},
+			expectedViewIndices: []int{0, 0, 1, 2, 3, 3},
+
+			viewIndices:          []int{-1, 0, 1, 2, 3, 4},
+			expectedModelIndices: []int{0, 0, 1, 2, 3, 3},
+		},
+		{
+			name:            "no headers (getNonModelItems returns zero items)",
+			numModelItems:   3,
+			nonModelIndices: []int{},
+
+			modelIndices:        []int{-1, 0, 1, 2, 3, 4},
+			expectedViewIndices: []int{0, 0, 1, 2, 3, 3},
+
+			viewIndices:          []int{-1, 0, 1, 2, 3, 4},
+			expectedModelIndices: []int{0, 0, 1, 2, 3, 3},
+		},
+		{
+			name:            "basic",
+			numModelItems:   3,
+			nonModelIndices: []int{1, 2},
+
+			/*
+				0: model 0
+				1: --- header 0 ---
+				2: model 1
+				3: --- header 1 ---
+				4: model 2
+			*/
+
+			modelIndices:        []int{-1, 0, 1, 2, 3, 4},
+			expectedViewIndices: []int{0, 0, 2, 4, 5, 5},
+
+			viewIndices:          []int{-1, 0, 1, 2, 3, 4, 5, 6},
+			expectedModelIndices: []int{0, 0, 1, 1, 2, 2, 3, 3},
+		},
+		{
+			name:            "consecutive section headers",
+			numModelItems:   3,
+			nonModelIndices: []int{0, 0, 2, 2, 2, 3, 3},
+
+			/*
+				0: --- header 0 ---
+				1: --- header 1 ---
+				2: model 0
+				3: model 1
+				4: --- header 2 ---
+				5: --- header 3 ---
+				6: --- header 4 ---
+				7: model 2
+				8: --- header 5 ---
+				9: --- header 6 ---
+			*/
+			modelIndices:        []int{-1, 0, 1, 2, 3, 4},
+			expectedViewIndices: []int{2, 2, 3, 7, 10, 10},
+
+			viewIndices:          []int{-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11},
+			expectedModelIndices: []int{0, 0, 0, 0, 1, 2, 2, 2, 2, 3, 3, 3, 3},
+		},
+	}
+
+	for _, s := range scenarios {
+		t.Run(s.name, func(t *testing.T) {
+			// Expect lists of equal length for each test:
+			assert.Equal(t, len(s.modelIndices), len(s.expectedViewIndices))
+			assert.Equal(t, len(s.viewIndices), len(s.expectedModelIndices))
+
+			modelInts := lo.Range(s.numModelItems)
+			viewModel := NewListViewModel[int](func() []int { return modelInts })
+			var getNonModelItems func() []*NonModelItem
+			if s.nonModelIndices != nil {
+				getNonModelItems = func() []*NonModelItem {
+					return lo.Map(s.nonModelIndices, func(modelIndex int, _ int) *NonModelItem {
+						return &NonModelItem{Index: modelIndex, Content: ""}
+					})
+				}
+			}
+			self := &ListRenderer{
+				list: viewModel,
+				getDisplayStrings: func(startIdx int, endIdx int) [][]string {
+					return lo.Map(modelInts[startIdx:endIdx],
+						func(i int, _ int) []string { return []string{fmt.Sprint(i)} })
+				},
+				getNonModelItems: getNonModelItems,
+			}
+
+			// Need to render first so that it knows the non-model items
+			self.renderLines(-1, -1)
+
+			for i := 0; i < len(s.modelIndices); i++ {
+				assert.Equal(t, s.expectedViewIndices[i], self.ModelIndexToViewIndex(s.modelIndices[i]))
+			}
+
+			for i := 0; i < len(s.viewIndices); i++ {
+				assert.Equal(t, s.expectedModelIndices[i], self.ViewIndexToModelIndex(s.viewIndices[i]))
+			}
+		})
+	}
+}