lua: Add params to app.useTool() to change the cel where we'll draw

src/app/script/app_object.cpp

@@ -197,14 +197,43 @@ int App_useTool(lua_State* L)
     return luaL_error(L, "app.useTool() must be called with a table as its first argument");
 
   auto ctx = App::instance()->context();
-  Doc* doc = ctx->activeDocument();
-  if (!doc)
+  Site site = ctx->activeSite();
+
+  // Draw in a specific cel, layer, or frame
+  int type = lua_getfield(L, 1, "layer");
+  if (type != LUA_TNIL) {
+    if (auto layer = get_docobj<Layer>(L, -1)) {
+      site.document(static_cast<Doc*>(layer->sprite()->document()));
+      site.sprite(layer->sprite());
+      site.layer(layer);
+    }
+  }
+  lua_pop(L, 1);
+
+  type = lua_getfield(L, 1, "frame");
+  if (type != LUA_TNIL) {
+    site.frame(get_frame_number_from_arg(L, -1));
+  }
+  lua_pop(L, 1);
+
+  type = lua_getfield(L, 1, "cel");
+  if (type != LUA_TNIL) {
+    if (auto cel = get_docobj<Cel>(L, -1)) {
+      site.document(static_cast<Doc*>(cel->sprite()->document()));
+      site.sprite(cel->sprite());
+      site.layer(cel->layer());
+      site.frame(cel->frame());
+    }
+  }
+  lua_pop(L, 1);
+
+  if (!site.document())
     return luaL_error(L, "there is no active document to draw with the tool");
 
   // Select tool by name
   tools::Tool* tool = App::instance()->activeToolManager()->activeTool();
   tools::Ink* ink = tool->getInk(0);
-  int type = lua_getfield(L, 1, "tool");
+  type = lua_getfield(L, 1, "tool");
   if (auto toolArg = get_tool_from_arg(L, -1)) {
     tool = toolArg;
     ink = tool->getInk(0);
@@ -222,7 +251,10 @@ int App_useTool(lua_State* L)
   type = lua_getfield(L, 1, "points");
   if (type == LUA_TTABLE) {
     std::unique_ptr<tools::ToolLoop> loop(
-      create_tool_loop_for_script(ctx, tool, ink, color));
+      create_tool_loop_for_script(ctx, site, tool, ink, color));
+    if (!loop)
+      return luaL_error(L, "cannot draw in the active site");
+
     tools::ToolLoopManager manager(loop.get());
     tools::Pointer lastPointer;
     bool first = true;

src/app/ui/editor/tool_loop_impl.cpp

@@ -686,21 +686,20 @@ tools::ToolLoop* create_tool_loop(
 
 tools::ToolLoop* create_tool_loop_for_script(
   Context* context,
+  const Site& site,
   tools::Tool* tool,
   tools::Ink* ink,
   const app::Color& color)
 {
   ASSERT(tool);
   ASSERT(ink);
-
-  Site site = context->activeSite();
   if (!site.layer())
     return nullptr;
 
   try {
-    tools::ToolLoop::Button toolLoopButton = tools::ToolLoop::Left;
+    const tools::ToolLoop::Button toolLoopButton = tools::ToolLoop::Left;
     tools::Controller* controller = tool->getController(toolLoopButton);
-    BrushRef brush;
+    BrushRef brush(nullptr);
 #ifdef ENABLE_UI
     if (App::instance()->contextBar())
       brush = App::instance()->contextBar()->activeBrush(tool, ink);
@@ -710,8 +709,7 @@ tools::ToolLoop* create_tool_loop_for_script(
 
     return new ToolLoopImpl(
       nullptr, site, context,
-      tool, ink, controller,
-      brush,
+      tool, ink, controller, brush,
       toolLoopButton, color, color, false);
   }
   catch (const std::exception& ex) {

src/app/ui/editor/tool_loop_impl.h

@@ -21,6 +21,7 @@ namespace app {
   class Color;
   class Context;
   class Editor;
+  class Site;
 
   namespace tools {
     class Ink;
@@ -36,6 +37,7 @@ namespace app {
 
   tools::ToolLoop* create_tool_loop_for_script(
     Context* context,
+    const Site& site,
     tools::Tool* tool,
     tools::Ink* ink,
     const app::Color& color);