Load font variable data on demand

tools/cmd/list_fonts/main.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"sync"
 
 	"kitty/tools/cli"
 	"kitty/tools/tty"
@@ -36,6 +37,20 @@ func to_kitty(v any) error {
 	return nil
 }
 
+var query_kitty_lock sync.Mutex
+
+func query_kitty(action string, cmd map[string]any, result any) error {
+	query_kitty_lock.Lock()
+	defer query_kitty_lock.Unlock()
+	if action != "" {
+		cmd["action"] = action
+		if err := to_kitty(cmd); err != nil {
+			return err
+		}
+	}
+	return json_decode(result)
+}
+
 func main() (rc int, err error) {
 	json_decoder = json.NewDecoder(os.Stdin)
 	lp, err := loop.New()

tools/cmd/list_fonts/types.go

@@ -2,6 +2,7 @@ package list_fonts
 
 import (
 	"fmt"
+	"sync"
 )
 
 var _ = fmt.Print
@@ -42,6 +43,15 @@ type MultiAxisStyle struct {
 	Values []AxisValue `json:"values"`
 }
 
+type ListedFont struct {
+	Family          string         `json:"family"`
+	Fullname        string         `json:"full_name"`
+	Postscript_name string         `json:"postscript_name"`
+	Is_monospace    bool           `json:"is_monospace"`
+	Is_variable     bool           `json:"is_variable"`
+	Descriptor      map[string]any `json:"descriptor"`
+}
+
 type VariableData struct {
 	Axes                              []VariableAxis   `json:"axes"`
 	Named_styles                      []NamedStyle     `json:"named_styles"`
@@ -51,12 +61,68 @@ type VariableData struct {
 	Multi_axis_styles                 []MultiAxisStyle `json:"multi_axis_styles"`
 }
 
-type ListedFont struct {
-	Family          string         `json:"family"`
-	Fullname        string         `json:"full_name"`
-	Postscript_name string         `json:"postscript_name"`
-	Is_monospace    bool           `json:"is_monospace"`
-	Is_variable     bool           `json:"is_variable"`
-	Variable_data   VariableData   `json:"variable_data"`
-	Descriptor      map[string]any `json:"descriptor"`
+var variable_data_cache map[string]VariableData
+var variable_data_cache_mutex sync.Mutex
+
+func (f ListedFont) cache_key() string {
+	key := f.Postscript_name
+	if key == "" {
+		key = "path:" + f.Descriptor["path"].(string)
+	} else {
+		key = "psname:" + key
+	}
+	return key
+}
+
+func ensure_variable_data_for_fonts(fonts ...ListedFont) error {
+	descriptors := make([]map[string]any, 0, len(fonts))
+	keys := make([]string, 0, len(fonts))
+	variable_data_cache_mutex.Lock()
+	for _, f := range fonts {
+		key := f.cache_key()
+		if _, found := variable_data_cache[key]; !found {
+			descriptors = append(descriptors, f.Descriptor)
+			keys = append(keys, key)
+		}
+	}
+	variable_data_cache_mutex.Unlock()
+	var data []VariableData
+	if err := query_kitty("read_variable_data", map[string]any{"descriptors": descriptors}, &data); err != nil {
+		return err
+	}
+	variable_data_cache_mutex.Lock()
+	for i, key := range keys {
+		variable_data_cache[key] = data[i]
+	}
+	variable_data_cache_mutex.Unlock()
+	return nil
+}
+
+func initialize_variable_data_cache() {
+	variable_data_cache = make(map[string]VariableData)
+}
+
+func _cached_vd(key string) (ans VariableData, found bool) {
+	variable_data_cache_mutex.Lock()
+	defer variable_data_cache_mutex.Unlock()
+	ans, found = variable_data_cache[key]
+	return
+}
+
+func variable_data_for(f ListedFont) VariableData {
+	key := f.cache_key()
+	ans, found := _cached_vd(key)
+	if found {
+		return ans
+	}
+	if err := ensure_variable_data_for_fonts(f); err != nil {
+		panic(err)
+	}
+	ans, found = _cached_vd(key)
+	return ans
+}
+
+func has_variable_data_for_font(font ListedFont) bool {
+	_, found := _cached_vd(font.cache_key())
+	return found
 }

tools/cmd/list_fonts/ui.go

@@ -31,8 +31,9 @@ type handler struct {
 	err_in_worker_thread error
 
 	// Listing
-	rl          *readline.Readline
-	family_list FamilyList
+	rl                          *readline.Readline
+	family_list                 FamilyList
+	variable_data_requested_for *utils.Set[string]
 }
 
 func (h *handler) set_worker_error(err error) {
@@ -77,6 +78,22 @@ func (h *handler) draw_family_summary(start_x int, sz loop.ScreenSize) (err erro
 		h.lp.SprintStyled("fg=green bold", center_string(family, int(sz.WidthCells)-start_x)),
 		"",
 	}
+	fonts := h.fonts[family]
+	if len(fonts) == 0 {
+		return fmt.Errorf("The family: %s has no fonts", family)
+	}
+	if has_variable_data_for_font(fonts[0]) {
+	} else {
+		lines = append(lines, "Reading font data, please wait…")
+		key := fonts[0].cache_key()
+		if !h.variable_data_requested_for.Has(key) {
+			h.variable_data_requested_for.Add(key)
+			go func() {
+				h.set_worker_error(ensure_variable_data_for_fonts(fonts...))
+				h.lp.WakeupMainThread()
+			}()
+		}
+	}
 
 	for i, line := range lines {
 		if i >= int(sz.HeightCells)-1 {
@@ -115,7 +132,7 @@ func (h *handler) draw_listing_screen() (err error) {
 		h.lp.Println(SEPARATOR)
 	}
 	if h.family_list.Len() > 0 {
-		if err = h.draw_family_summary(mw+2, sz); err != nil {
+		if err = h.draw_family_summary(mw+3, sz); err != nil {
 			return err
 		}
 	}
@@ -207,9 +224,11 @@ func (h *handler) handle_listing_text(text string, from_key_event bool, in_brack
 func (h *handler) initialize() {
 	h.lp.SetCursorVisible(false)
 	h.rl = readline.New(h.lp, readline.RlInit{DontMarkPrompts: true, Prompt: "Family: "})
+	h.variable_data_requested_for = utils.NewSet[string](256)
 	h.draw_screen()
+	initialize_variable_data_cache()
 	go func() {
-		h.set_worker_error(json_decode(&h.fonts))
+		h.set_worker_error(query_kitty("", nil, &h.fonts))
 		h.lp.WakeupMainThread()
 	}()
 }
@@ -243,6 +262,8 @@ func (h *handler) on_wakeup() (err error) {
 		h.state = LISTING_FAMILIES
 		h.family_list.UpdateFamilies(utils.StableSortWithKey(maps.Keys(h.fonts), strings.ToLower))
 		return h.draw_screen()
+	case LISTING_FAMILIES:
+		return h.draw_screen()
 	}
 	return
 }