ui: drag to resize the side panel

docs/telemetry.md

@@ -895,8 +895,8 @@ which is how a binding nobody uses becomes visible.
 The clickable regions of the UI.
 
 `channel`, `composer`, `feed`, `feed_blobs`, `feed_mark_all`, `info`,
-`jump_bottom`, `message`, `nothing`, `reference`, `search`, `sql`, `tab`,
-`thread`, `toast`
+`jump_bottom`, `message`, `nothing`, `pane_divider`, `reference`, `search`,
+`sql`, `tab`, `thread`, `toast`
 
 ### Command palette ids
 

internal/telemetry/catalogue_events.go

@@ -129,7 +129,7 @@ var ActionIDs = []string{
 var MouseTargets = []string{
 	"tab", "channel", "message", "thread", "feed", "search", "reference",
 	"info", "sql", "composer", "jump_bottom", "feed_mark_all", "feed_blobs", "toast",
-	"nothing",
+	"pane_divider", "nothing",
 }
 
 // PaletteIDs are the ">" command-palette entries, by stable id rather than by

internal/ui/model.go

@@ -193,7 +193,14 @@ type Model struct {
 	// box is in flight; the editor owns the selection itself (see editor.Model),
 	// this only routes motion/release back to it. Lives in mouse.go.
 	composerDrag bool
-	wrapIdx      wrapCache
+	// sidePaneW is the right detail pane's width once its divider has been
+	// dragged (0 = half the right area); paneDrag is true while that drag is in
+	// flight; paneDragOff is the pressed column's distance left of the border,
+	// so grabbing either side of it doesn't make it jump. All live in mouse.go.
+	sidePaneW   int
+	paneDrag    bool
+	paneDragOff int
+	wrapIdx     wrapCache
 	// clickCount / lastClick* synthesise double- and triple-clicks: the terminal
 	// only reports individual presses, so handleMouseClick counts presses landing
 	// at (about) the same cell within multiClickInterval. 2 selects a word, 3 a

internal/ui/mouse.go

@@ -41,6 +41,7 @@ const (
 	hitFeedBlobs
 	hitToast
 	hitAttachment
+	hitDivider
 )
 
 // hit is the result of hitTest. idx's meaning depends on zone: a tab index
@@ -214,6 +215,15 @@ func (m Model) handleMouseClick(msg tea.MouseClickMsg) (tea.Model, tea.Cmd) {
 	// things. A no-op otherwise.
 	recordClick(h.zone)
 	switch h.zone {
+	case hitDivider:
+		m.clearTextSel()
+		if count == 2 {
+			// Double-click restores the default half/half split.
+			return m.setSidePaneW(0)
+		}
+		m.paneDrag = true
+		m.paneDragOff = m.width - m.splitRightPane(m.width-channelsWidth) - msg.X
+		return m, nil
 	case hitTab:
 		m.clearTextSel()
 		return m.gotoTab(h.idx)
@@ -394,6 +404,10 @@ func (m Model) handleMouseRelease(msg tea.MouseReleaseMsg) (tea.Model, tea.Cmd)
 	if msg.Button != tea.MouseLeft {
 		return m, nil
 	}
+	if m.paneDrag {
+		m.paneDrag = false
+		return m, nil
+	}
 	if m.composerDrag {
 		// Leave the selection live so backspace/delete removes it and typing
 		// replaces it — the point of selecting in an editable field. No clipboard
@@ -443,6 +457,9 @@ func (m Model) handleMouseMotion(msg tea.MouseMotionMsg) (tea.Model, tea.Cmd) {
 		m.setInfoHover(-1)
 		return m, nil
 	}
+	if m.paneDrag && msg.Button == tea.MouseLeft {
+		return m.setSidePaneW(m.width - msg.X - m.paneDragOff)
+	}
 	if m.composerDrag && msg.Button == tea.MouseLeft {
 		return m.dragComposerSel(msg.X, msg.Y)
 	}
@@ -796,6 +813,9 @@ func (m *Model) hitTest(x, y int) hit {
 	if m.onSQLTab() {
 		return m.hitSQLRow(x, y)
 	}
+	if m.onPaneDivider(x) {
+		return hit{zone: hitDivider}
+	}
 	// Read-only right panes (reference / channel-info) own their full column —
 	// including the rows that sit at the same height as the composer under the
 	// messages pane. Check them before inComposer so a link at the bottom of
@@ -807,7 +827,7 @@ func (m *Model) hitTest(x, y int) hit {
 		if rightW < 10 {
 			rightW = 10
 		}
-		sideW := splitRightPane(rightW)
+		sideW := m.splitRightPane(rightW)
 		if x >= channelsWidth+(rightW-sideW) {
 			if m.refOpen {
 				if h := m.hitRefContent(x, y); h.zone != hitNone {
@@ -848,7 +868,7 @@ func (m *Model) hitTest(x, y int) hit {
 	}
 	msgsW := rightW
 	if m.threadOpen {
-		threadW := splitRightPane(rightW)
+		threadW := m.splitRightPane(rightW)
 		msgsW = rightW - threadW
 		if x >= channelsWidth+msgsW {
 			tx0, top, w, h, yoff := m.threadGeom()
@@ -859,6 +879,43 @@ func (m *Model) hitTest(x, y int) hit {
 	return m.hitViewportPost(x, y, top, mx0, w, h, yoff, focusMessages, m.msgRowStarts, len(m.posts))
 }
 
+// onPaneDivider reports whether column x is on the border between the messages
+// pane and an open side pane — the side pane's left border or the messages
+// pane's last column beside it — the handle a drag resizes the split with.
+func (m *Model) onPaneDivider(x int) bool {
+	if !m.threadOpen && !m.refOpen && !m.infoOpen {
+		return false
+	}
+	rightW := m.width - channelsWidth
+	if rightW < 10 {
+		rightW = 10
+	}
+	border := m.width - m.splitRightPane(rightW)
+	return x == border || x == border-1
+}
+
+// setSidePaneW sets the side pane's width (0 = default half split), clamped the
+// way splitRightPane clamps it. Like a terminal resize drag, it re-lays-out every
+// frame and defers the content re-render to a settle tick.
+func (m Model) setSidePaneW(w int) (tea.Model, tea.Cmd) {
+	prev := m.sidePaneW
+	m.sidePaneW = w
+	if w > 0 {
+		rightW := m.width - channelsWidth
+		if rightW < 10 {
+			rightW = 10
+		}
+		m.sidePaneW = m.splitRightPane(rightW)
+	}
+	if m.sidePaneW == prev {
+		return m, nil
+	}
+	m.layoutPanes()
+	m.resizeInput()
+	m.resizeGen++
+	return m, resizeSettleCmd(m.resizeGen)
+}
+
 // hitChannel maps a screen row in the sidebar column to a visible-channel
 // index, reproducing renderChannelsPane's scroll window so the row the user
 // sees is the one selected.
@@ -1344,7 +1401,7 @@ func (m *Model) composerGeom() (x0, top, width, height, yoff int) {
 		if rightW < 10 {
 			rightW = 10
 		}
-		msgsW := rightW - splitRightPane(rightW)
+		msgsW := rightW - m.splitRightPane(rightW)
 		x0 = channelsWidth + msgsW + 1
 	} else {
 		x0 = channelsWidth + 1
@@ -1589,7 +1646,7 @@ func (m *Model) threadGeom() (x0, top, width, height, yoff int) {
 	if rightW < 10 {
 		rightW = 10
 	}
-	msgsW := rightW - splitRightPane(rightW)
+	msgsW := rightW - m.splitRightPane(rightW)
 	return channelsWidth + msgsW + 1, tabsHeight + 1, m.threadView.Width(), m.threadView.Height(), m.threadView.YOffset()
 }
 
@@ -1600,7 +1657,7 @@ func (m *Model) refGeom() (x0, top, width, height, yoff int) {
 	if rightW < 10 {
 		rightW = 10
 	}
-	msgsW := rightW - splitRightPane(rightW)
+	msgsW := rightW - m.splitRightPane(rightW)
 	return channelsWidth + msgsW + 1, tabsHeight + 1, m.refView.Width(), m.refView.Height(), m.refView.YOffset()
 }
 
@@ -1612,7 +1669,7 @@ func (m *Model) infoGeom() (x0, top, width, height, yoff int) {
 	if rightW < 10 {
 		rightW = 10
 	}
-	msgsW := rightW - splitRightPane(rightW)
+	msgsW := rightW - m.splitRightPane(rightW)
 	return channelsWidth + msgsW + 1, tabsHeight + 1, m.infoView.Width(), m.infoView.Height(), m.infoView.YOffset()
 }
 

internal/ui/mouse_test.go

@@ -837,3 +837,46 @@ func TestInfoDragThenReleaseCopiesSelection(t *testing.T) {
 		t.Fatalf("selectedText=%q want %q", got, needle)
 	}
 }
+
+// TestDragPaneDivider: dragging the border between the messages pane and an
+// open side pane resizes the side pane; a double-click restores the half split.
+func TestDragPaneDivider(t *testing.T) {
+	m := mouseModel(nil)
+	m.infoOpen = true
+	rightW := m.width - channelsWidth
+	x := m.width - m.splitRightPane(rightW)
+	for _, dx := range []int{x - 1, x} {
+		if h := m.hitTest(dx, tabsHeight+2); h.zone != hitDivider {
+			t.Fatalf("hitTest(%d) = %v, want hitDivider", dx, h.zone)
+		}
+	}
+	next, _ := m.Update(click(tea.MouseLeft, x, tabsHeight+2))
+	next, _ = next.(Model).Update(motion(tea.MouseLeft, x-5, tabsHeight+2))
+	next, _ = next.(Model).Update(release(tea.MouseLeft, x-5, tabsHeight+2))
+	m = next.(Model)
+	if m.paneDrag {
+		t.Error("paneDrag still set after release")
+	}
+	if got, want := m.splitRightPane(rightW), m.width-(x-5); got != want {
+		t.Errorf("side pane width = %d, want %d", got, want)
+	}
+
+	// Dragging past the edge clamps to the minimum pane width.
+	next, _ = m.Update(click(tea.MouseLeft, x-5, tabsHeight+2))
+	next, _ = next.(Model).Update(motion(tea.MouseLeft, m.width-1, tabsHeight+2))
+	m = next.(Model)
+	if got := m.splitRightPane(rightW); got != threadPaneMinWidth {
+		t.Errorf("clamped width = %d, want %d", got, threadPaneMinWidth)
+	}
+	next, _ = m.Update(release(tea.MouseLeft, m.width-1, tabsHeight+2))
+	m = next.(Model)
+
+	x = m.width - threadPaneMinWidth
+	next, _ = m.Update(click(tea.MouseLeft, x, tabsHeight+2))
+	next, _ = next.(Model).Update(release(tea.MouseLeft, x, tabsHeight+2))
+	next, _ = next.(Model).Update(click(tea.MouseLeft, x, tabsHeight+2))
+	m = next.(Model)
+	if m.sidePaneW != 0 {
+		t.Errorf("double-click left sidePaneW = %d, want 0", m.sidePaneW)
+	}
+}

internal/ui/telemetrykeys.go

@@ -193,6 +193,8 @@ func (z hitZone) telemetryTarget() string {
 		return "feed_blobs"
 	case hitToast:
 		return "toast"
+	case hitDivider:
+		return "pane_divider"
 	}
 	return "nothing"
 }

internal/ui/view.go

@@ -170,13 +170,13 @@ func (m *Model) layoutPanes() {
 	// The thread sidebar, reference panel and channel-info panel share the single
 	// right slot — at most one is ever open — so each splits rightW the same way.
 	if m.threadOpen {
-		threadW = splitRightPane(rightW)
+		threadW = m.splitRightPane(rightW)
 		msgsW = rightW - threadW
 	} else if m.refOpen {
-		refW = splitRightPane(rightW)
+		refW = m.splitRightPane(rightW)
 		msgsW = rightW - refW
 	} else if m.infoOpen {
-		infoW = splitRightPane(rightW)
+		infoW = m.splitRightPane(rightW)
 		msgsW = rightW - infoW
 	}
 	// The scrollbar overlays the right border column (rendered by
@@ -292,11 +292,15 @@ func (m *Model) renderAllPanes() {
 
 const threadPaneMinWidth = 24
 
-// splitRightPane returns the width of the right detail pane (thread or Jira)
-// when the right area is rightW wide: half, clamped so neither the detail pane
-// nor the messages pane drops below threadPaneMinWidth.
-func splitRightPane(rightW int) int {
-	w := rightW / 2
+// splitRightPane returns the width of the right detail pane (thread, reference
+// or channel-info) when the right area is rightW wide: the width the divider
+// was dragged to, else half, clamped so neither the detail pane nor the
+// messages pane drops below threadPaneMinWidth.
+func (m *Model) splitRightPane(rightW int) int {
+	w := m.sidePaneW
+	if w <= 0 {
+		w = rightW / 2
+	}
 	if w < threadPaneMinWidth {
 		w = threadPaneMinWidth
 	}
@@ -315,14 +319,7 @@ func (m *Model) resizeInput() {
 		if rightW < 10 {
 			rightW = 10
 		}
-		threadW := rightW / 2
-		if threadW < threadPaneMinWidth {
-			threadW = threadPaneMinWidth
-		}
-		if threadW > rightW-threadPaneMinWidth {
-			threadW = rightW - threadPaneMinWidth
-		}
-		w := threadW - 2
+		w := m.splitRightPane(rightW) - 2
 		if w < 10 {
 			w = 10
 		}
@@ -336,7 +333,7 @@ func (m *Model) resizeInput() {
 		if rightW < 10 {
 			rightW = 10
 		}
-		w := rightW - splitRightPane(rightW) - 2
+		w := rightW - m.splitRightPane(rightW) - 2
 		if w < 10 {
 			w = 10
 		}
@@ -1761,13 +1758,13 @@ func (m *Model) renderViewContent() string {
 		refW := 0
 		infoW := 0
 		if m.threadOpen {
-			threadW = splitRightPane(rightW)
+			threadW = m.splitRightPane(rightW)
 			msgsW = rightW - threadW
 		} else if m.refOpen {
-			refW = splitRightPane(rightW)
+			refW = m.splitRightPane(rightW)
 			msgsW = rightW - refW
 		} else if m.infoOpen {
-			infoW = splitRightPane(rightW)
+			infoW = m.splitRightPane(rightW)
 			msgsW = rightW - infoW
 		}
 		messagesPane := m.renderMessagesPane(bodyH, msgsW)