feat: render API shim - a game's renpy.Displayable subclasses are drawn and receive events

Games write their own displayables with render(), renpy.Render, blit, fill, canvas() and renpy.redraw.
render.ts keeps a tree of placed pieces (child renders, ordinary displayables, fills and drawing
commands) and turns it into DOM elements that stay put between redraws; pointer events reach event()
as pygame-style objects, and a returned value ends the interaction. Shaders and GPU properties are
accepted and ignored. The converter whitelists the calls and methods and accepts `import pygame`.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

backend/app/converter/compatibility.py

@@ -120,6 +120,10 @@ CALLS |= {"renpy.start_predict", "renpy.stop_predict", "renpy.start_predict_scre
           "renpy.ui.imagebutton", "renpy.return_statement"}
 from app.games.renpy_native import NATIVE_CLASSES, NATIVE_METHODS  # noqa: E402
 CALLS |= set(NATIVE_CLASSES)
+# The render API for games' own displayables (frontend/src/player/render.ts)
+CALLS |= {"renpy.Render", "renpy.render", "renpy.redraw", "renpy.displayable", "renpy.IgnoreEvent",
+          "renpy.display.layout.LiveComposite", "renpy.display.layout.Fixed", "pygame.key.get_mods",
+          "pygame.mouse.get_pressed", "pygame.mouse.get_pos"}
 CALLS |= {"Matrix", "renpy.has_live2d", "renpy.fetch", "renpy.display.draw.kill_textures",
           "renpy.display.render.free_memory", "cache.get_total_size"}
 CALLS |= {"Move", "absolute", "type", "id", "vars", "Flatten", "LiveComposite", "Composite", "defaultdict", "OrderedDict", "deepcopy",
@@ -169,6 +173,8 @@ METHODS = set("append extend insert pop remove index count reverse sort clear co
 
 METHODS |= NATIVE_METHODS
 # Methods of generators made by `renpy.random.Random()` / `random.Random()`
+METHODS |= {"blit", "subpixel_blit", "fill", "canvas", "get_size", "add_shader", "add_uniform", "add_property",
+           "add_focus", "circle", "rect", "line", "lines", "polygon"}
 METHODS |= {"fullmatch", "hexdigest", "randint", "randrange", "random", "choice", "choices", "sample", "shuffle", "uniform"}
 
 

backend/app/converter/pyexpr.py

@@ -25,7 +25,7 @@ UNARY_OPS = {ast.Not: "not", ast.USub: "-", ast.UAdd: "+", ast.Invert: "~"}
 
 # Modules whose import is harmless: the player provides the functions it supports.
 KNOWN_MODULES = {"random", "math", "renpy", "store", "time", "datetime", "re", "copy", "collections",
-                 "itertools", "string", "functools", "operator", "json", "gc", "hashlib", "uuid"}
+                 "itertools", "string", "functools", "operator", "json", "gc", "hashlib", "uuid", "pygame"}
 
 
 class Unsupported(Exception):