tui: add uiCache

Clean up/fix how we calculate the height of the content viewport

pkg/tui/tui.go

@@ -39,6 +39,14 @@ const (
 	selectedMessage
 )
 
+type uiCache struct {
+	header  string
+	content string
+	error   string
+	input   string
+	footer  string
+}
+
 type model struct {
 	width  int
 	height int
@@ -69,6 +77,8 @@ type model struct {
 	content viewport.Model
 	input   textarea.Model
 	spinner spinner.Model
+
+	cache *uiCache
 }
 
 type message struct {
@@ -181,7 +191,6 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.width = msg.Width
 		m.height = msg.Height
 		m.content.Width = msg.Width
-		m.content.Height = msg.Height - m.getFixedComponentHeight()
 		m.input.SetWidth(msg.Width - 1)
 		m.updateContent()
 	case msgConversationLoaded:
@@ -284,9 +293,26 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		}
 	}
 
+	if m.width > 0 {
+		m.cache.header = m.headerView()
+		m.cache.footer = m.footerView()
+		m.cache.error = m.errorView()
+		m.cache.input = m.inputView()
+		fixedHeight := height(m.cache.header) + height(m.cache.error) + height(m.cache.input) + height(m.cache.footer)
+		m.content.Height = m.height - fixedHeight
+		m.cache.content = m.contentView()
+	}
+
 	return m, tea.Batch(cmds...)
 }
 
+func height(str string) int {
+	if str == "" {
+		return 0
+	}
+	return strings.Count(str, "\n") + 1
+}
+
 func (m model) View() string {
 	if m.width == 0 {
 		// this is the case upon initial startup, but it's also a safe bet that
@@ -296,14 +322,13 @@ func (m model) View() string {
 	}
 
 	sections := make([]string, 0, 6)
-	sections = append(sections, m.headerView())
-	sections = append(sections, m.contentView())
-	error := m.errorView()
-	if error != "" {
-		sections = append(sections, error)
+	sections = append(sections, m.cache.header)
+	sections = append(sections, m.cache.content)
+	if m.cache.error != "" {
+		sections = append(sections, m.cache.error)
 	}
-	sections = append(sections, m.inputView())
-	sections = append(sections, m.footerView())
+	sections = append(sections, m.cache.input)
+	sections = append(sections, m.cache.footer)
 
 	return lipgloss.JoinVertical(
 		lipgloss.Left,
@@ -311,20 +336,6 @@ func (m model) View() string {
 	)
 }
 
-// returns the total height of "fixed" components, which are those which don't
-// change height dependent on window size.
-func (m *model) getFixedComponentHeight() int {
-	h := 0
-	h += m.input.Height()
-	h += lipgloss.Height(m.headerView())
-	h += lipgloss.Height(m.footerView())
-	errorView := m.errorView()
-	if errorView != "" {
-		h += lipgloss.Height(errorView)
-	}
-	return h
-}
-
 func (m *model) headerView() string {
 	titleStyle := lipgloss.NewStyle().
 		PaddingLeft(1).
@@ -420,6 +431,8 @@ func initialModel(ctx *lmcli.Context, convShortname string) model {
 
 		wrap:            true,
 		selectedMessage: -1,
+
+		cache: &uiCache{},
 	}
 
 	m.content = viewport.New(0, 0)