feat: new layout, diff on RHS screen

README.md

@@ -124,7 +124,7 @@ sits below them. The mouse is enabled: **click** a pane to focus it, or a row in
 splits (unavailable when zoomed, scanning, on error, or with an overlay open). The Status table
 lists dirty files with **Worktree** and **Staged** columns (same left-to-right
 order as the Diff pane). The Diff pane runs `git diff` with basic colorization;
-use **←** / **→** in Status or Diff to switch between **Worktree** and **Staged** views.
+use **Space** in Status or Diff to toggle between **Worktree** and **Staged** views.
 With a file row selected, **a** runs `git add` and **r** runs `git reset` (unstage) on
 that path (from the Status or Diff pane), then the current repo is refreshed. **C**
 asks for confirmation, then runs `git checkout HEAD -- <path>` to restore that path to
@@ -145,12 +145,12 @@ compresses each remote into a short status (`ok`, `missing`, `differs`, or
 | Key                   | Action                                                                                                                                                                               |
 | --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
 | *Mouse*               | Click to focus a pane; in Repositories or Status (when focused), select a row. Drag a border to resize splits (unavailable when zoomed, scanning, on error, or with an overlay open) |
-| `Tab` / `Shift+Tab`   | Next / previous pane; when zoomed, cycle which pane is fullscreen                                                                                                                    |
+| `Tab` / `Shift+Tab`   | Next / previous pane: Repositories, Status, Branches, Log (not Diff; click to focus); when zoomed, cycle fullscreen                                                                  |
 | `Enter`               | Zoom the focused pane; `Enter` again restores the split layout                                                                                                                       |
 | `Esc`                 | Exit zoom, or clear the Status file selection                                                                                                                                        |
 | `↑` / `↓`             | Move repo selection, or scroll Status / Diff / Log                                                                                                                                   |
 | `Shift+↑` / `Shift+↓` | Same, in steps of 10 lines                                                                                                                                                           |
-| `←` / `→`             | In Status or Diff: Worktree vs Staged diff                                                                                                                                           |
+| `Space`               | In Status or Diff: toggle Worktree vs Staged diff                                                                                                                                    |
 | `a` / `r`             | With a status file row selected (Status or Diff): `git add` / `git reset` that path                                                                                                  |
 | `C`                   | With a status file row selected (Status or Diff): confirm, then `git checkout HEAD --` that path (restore to last commit)                                                            |
 | `s`                   | Scan or rescan                                                                                                                                                                       |

demo.tape

@@ -102,7 +102,7 @@ Sleep 200ms
 Tab
 Sleep 200ms
 
-# tab to diff
+# tab to log (Diff is not in the Tab cycle; click the Diff pane to focus it)
 Tab
 Sleep 200ms
 

ui/layout_geometry.go

@@ -0,0 +1,95 @@
+package ui
+
+// paneLayout holds inner body heights for the main stack (one pane may be
+// non-zero in zoom mode; all zero means layout could not be computed).
+type paneLayout struct {
+	repo, status, branch, diff, logBody int
+}
+
+func (p paneLayout) isZero() bool {
+	return p.repo == 0 && p.status == 0 && p.branch == 0 && p.diff == 0 && p.logBody == 0
+}
+
+// innerVerticalBudget is total inner body lines available below the outer chrome
+// (status bar, titles, etc.).
+func innerVerticalBudget(termHeight int) int {
+	return termHeight - layoutFrameStackOuterRows
+}
+
+// panelOuter converts an inner body height into full framed panel height.
+func panelOuter(body int) int {
+	return body + 2 // top border (with title) + body + bottom border
+}
+
+// diffBodyFromStackedStatusBranch returns diff inner body height so the Diff pane
+// outer height matches Status and Branches stacked (each pane contributes top+bottom borders).
+func diffBodyFromStackedStatusBranch(statusBody, branchBody int) int {
+	return statusBody + branchBody + 2
+}
+
+// tightenRepoAndLogForMiddleSpare shrinks log then repo until the middle row has at
+// least layoutMinSpareForSplit lines, or returns ok=false.
+func tightenRepoAndLogForMiddleSpare(effH, repoBody, logBody int) (repo, log int, available int, ok bool) {
+	repo, log = repoBody, logBody
+	available = effH - layoutFrameStackOuterRows - repo - log
+	for available < layoutMinSpareForSplit && log > layoutMinBodyLines {
+		log--
+		available = effH - layoutFrameStackOuterRows - repo - log
+	}
+	for available < layoutMinSpareForSplit && repo > layoutMinBodyLines {
+		repo--
+		available = effH - layoutFrameStackOuterRows - repo - log
+	}
+	if available < layoutMinSpareForSplit {
+		return 0, 0, 0, false
+	}
+	return repo, log, available, true
+}
+
+// splitStatusBranchEvenly divides available inner lines between status and branch tables.
+func splitStatusBranchEvenly(available int) (statusBody, branchBody int) {
+	statusBody = available / 2
+	branchBody = available - statusBody
+	return statusBody, branchBody
+}
+
+// nonZoomStackBodiesValid checks minimum inner heights and that status+branch fill
+// the middle vertical budget (diff height is derived from the stack).
+func nonZoomStackBodiesValid(repo, status, branch, diff, logBody, available int) bool {
+	if status < layoutMinBodyLines || branch < layoutMinBodyLines || diff < layoutMinBodyLines ||
+		logBody < layoutMinBodyLines || repo < layoutMinBodyLines ||
+		status+branch != available {
+		return false
+	}
+	return true
+}
+
+// customVerticalLayoutOK validates user-resized vertical splits against the same
+// invariants as layoutBodies.
+func customVerticalLayoutOK(status, branch, diff, available int) bool {
+	if available < layoutMinSpareForSplit || diff < layoutMinBodyLines ||
+		status+branch != available ||
+		panelOuter(status)+panelOuter(branch) != panelOuter(diff) {
+		return false
+	}
+	return true
+}
+
+// clampDiffColumnOuterWidth maps a mouse X (left column outer width) to a valid
+// Diff column outer width for the middle row.
+func clampDiffColumnOuterWidth(termWidth, leftOuter int) (rightOuter int, ok bool) {
+	if termWidth < layoutMinTermWidth {
+		return 0, false
+	}
+	rightOuter = termWidth - leftOuter
+	if rightOuter < layoutMinStatusBranchesColumn {
+		rightOuter = layoutMinStatusBranchesColumn
+	}
+	if rightOuter > termWidth-layoutMinStatusBranchesColumn {
+		rightOuter = termWidth - layoutMinStatusBranchesColumn
+	}
+	if rightOuter < layoutMinStatusBranchesColumn || rightOuter > termWidth-layoutMinStatusBranchesColumn {
+		return 0, false
+	}
+	return rightOuter, true
+}

ui/layout_limits.go

@@ -18,10 +18,14 @@ const (
 	layoutMinTermWidth  = 20
 	layoutMinTermHeight = 22
 
-	// layoutMinStatusBranchesColumn is a minimum for either status or branches column
-	// when splits are computed or user-resized.
+	// layoutMinStatusBranchesColumn is a minimum width for either middle-row column
+	// (status+branches stack vs diff) when splits are computed or user-resized.
 	layoutMinStatusBranchesColumn = 10
 
+	// layoutDefaultMiddleDiffColumnPct is the default share of terminal width for the
+	// framed Diff column in the middle row (remainder goes to Status+Branches).
+	layoutDefaultMiddleDiffColumnPct = 70
+
 	// layoutMinInnerContentWidth is a floor for content inside borders or viewports
 	// (also used as a placeholder size before syncViewports runs).
 	layoutMinInnerContentWidth = 8

ui/model.go

@@ -131,13 +131,14 @@ type model struct {
 	zoomTarget pane // which pane is fullscreen when zoomed
 
 	// layoutUseCustomVertical is true after the user resizes a horizontal seam;
-	// layoutRepoBody, layoutStatusBody, and layoutLogBody are inner body heights.
+	// layoutRepoBody, layoutStatusBody, layoutBranchBody, and layoutLogBody are inner body heights.
 	layoutUseCustomVertical bool
 	layoutRepoBody          int
 	layoutStatusBody        int
+	layoutBranchBody        int
 	layoutLogBody           int
 
-	// layoutBranchesOuter is the framed Branches column width in cells (0 = automatic).
+	// layoutBranchesOuter is the framed Diff (right) column outer width in the middle row (0 = default pct).
 	layoutBranchesOuter int
 
 	resizeDrag resizeSplit

ui/mouse_line_select.go

@@ -47,8 +47,8 @@ func (m *model) repoPaneOuterHeight() (outerH int, ok bool) {
 	if m.height < layoutMinTermHeight || m.width < layoutMinTermWidth {
 		return 0, false
 	}
-	repoBody, statusBody, diffBody, logBody := m.layoutBodies()
-	if repoBody == 0 && statusBody == 0 && diffBody == 0 && logBody == 0 {
+	lay := m.layoutBodies()
+	if lay.isZero() {
 		return 0, false
 	}
 	if m.zoomed {
@@ -57,7 +57,7 @@ func (m *model) repoPaneOuterHeight() (outerH int, ok bool) {
 		}
 		return m.height, true
 	}
-	return panelOuter(repoBody), true
+	return panelOuter(lay.repo), true
 }
 
 // statusPaneFrame returns the top Y of the status pane, its outer height, and
@@ -66,8 +66,8 @@ func (m *model) statusPaneFrame() (topY, outerH, outerW int, ok bool) {
 	if m.height < layoutMinTermHeight || m.width < layoutMinTermWidth {
 		return 0, 0, 0, false
 	}
-	repoBody, statusBody, diffBody, logBody := m.layoutBodies()
-	if repoBody == 0 && statusBody == 0 && diffBody == 0 && logBody == 0 {
+	lay := m.layoutBodies()
+	if lay.isZero() {
 		return 0, 0, 0, false
 	}
 	if m.zoomed {
@@ -76,10 +76,10 @@ func (m *model) statusPaneFrame() (topY, outerH, outerW int, ok bool) {
 		}
 		return 0, m.height, m.width, true
 	}
-	repoOuter := panelOuter(repoBody)
-	statusOuter := panelOuter(statusBody)
-	statusW, _ := m.statusBranchesOuterWidths(m.width)
-	return repoOuter, statusOuter, statusW, true
+	repoOuter := panelOuter(lay.repo)
+	statusOuter := panelOuter(lay.status)
+	leftW, _ := m.middleRowColumnOuterWidths(m.width)
+	return repoOuter, statusOuter, leftW, true
 }
 
 // handleMousePaneLineSelect handles left-click row selection when the repo or

ui/mouse_line_select_test.go

@@ -16,8 +16,8 @@ func TestMouseRepoLineSelect(t *testing.T) {
 	m.cursor = 0
 	m.focus = paneRepo
 
-	rb, _, _, _ := m.layoutBodies()
-	repoOuter := panelOuter(rb)
+	lay := m.layoutBodies()
+	repoOuter := panelOuter(lay.repo)
 	if repoOuter < 4 {
 		t.Fatalf("repoOuter=%d too small for test", repoOuter)
 	}
@@ -57,8 +57,8 @@ func TestMouseStatusLineSelect(t *testing.T) {
 	m.focus = paneStatus
 	m.syncViewports()
 
-	rb, _, _, _ := m.layoutBodies()
-	statusTop := panelOuter(rb)
+	lay := m.layoutBodies()
+	statusTop := panelOuter(lay.repo)
 	// First data row: inner starts at statusTop+1, then header, then row 0.
 	y := statusTop + 1 + statusTableHeaderLines(m.statusTable)
 	msg := tea.MouseMsg{
@@ -98,8 +98,8 @@ func TestMouseStatusHeaderClickConsumed(t *testing.T) {
 	m.focus = paneStatus
 	m.syncViewports()
 
-	rb, _, _, _ := m.layoutBodies()
-	statusTop := panelOuter(rb)
+	lay := m.layoutBodies()
+	statusTop := panelOuter(lay.repo)
 	y := statusTop + 1 // first inner line = table header
 	prev := m.statusTable.Cursor()
 	msg := tea.MouseMsg{X: 2, Y: y, Button: tea.MouseButtonLeft, Action: tea.MouseActionPress}