Add a console command to dump a snapshot

src/tangara/app_console/app_console.cpp

@@ -683,6 +683,26 @@ void RegisterLua() {
   esp_console_cmd_register(&cmd_luarun);
 }
 
+int CmdSnapshot(int argc, char** argv) {
+  if (argc != 2) {
+    std::cout << "snapshot expects 1 argument" << std::endl;
+    return 1;
+  }
+
+  events::Ui().Dispatch(ui::Screenshot{.filename = argv[1]});
+  return 0;
+}
+
+void RegisterSnapshot() {
+  esp_console_cmd_t cmd_snapshot{
+      .command = "snapshot",
+      .help = "Saves a screenshot of the display to a file",
+      .hint = "filename",
+      .func = &CmdSnapshot,
+      .argtable = NULL};
+  esp_console_cmd_register(&cmd_snapshot);
+}
+
 auto AppConsole::PrerunCallback() -> void {
   Console::PrerunCallback();
   esp_log_level_set("*", ESP_LOG_NONE);
@@ -713,6 +733,7 @@ auto AppConsole::RegisterExtraComponents() -> void {
 
   RegisterHapticEffect();
   RegisterLua();
+  RegisterSnapshot();
 }
 
 }  // namespace console

src/tangara/ui/ui_events.hpp

@@ -30,6 +30,10 @@ struct OnLuaError : tinyfsm::Event {
 
 struct DumpLuaStack : tinyfsm::Event {};
 
+struct Screenshot : tinyfsm::Event {
+  std::string filename;
+};
+
 namespace internal {
 
 struct InitDisplay : tinyfsm::Event {

src/tangara/ui/ui_fsm.cpp

@@ -13,6 +13,7 @@
 #include <variant>
 
 #include "FreeRTOSConfig.h"
+#include "draw/lv_draw_buf.h"
 #include "drivers/bluetooth.hpp"
 #include "lvgl.h"
 
@@ -26,6 +27,9 @@
 #include "freertos/projdefs.h"
 #include "lua.hpp"
 #include "luavgl.h"
+#include "misc/lv_color.h"
+#include "misc/lv_utils.h"
+#include "others/snapshot/lv_snapshot.h"
 #include "tick/lv_tick.h"
 #include "tinyfsm.hpp"
 
@@ -363,6 +367,28 @@ int UiState::PopScreen() {
   return sScreens.size();
 }
 
+void UiState::react(const Screenshot& ev) {
+  if (!sCurrentScreen) {
+    return;
+  }
+  ESP_LOGI(kTag, "taking snapshot");
+  lv_draw_buf_t* buf =
+      lv_snapshot_take(sCurrentScreen->root(), LV_COLOR_FORMAT_RGB888);
+  if (!buf) {
+    ESP_LOGW(kTag, "snapshot failed");
+    return;
+  }
+  ESP_LOGI(kTag, "writing to file");
+  std::string fullpath = "//sdcard/" + ev.filename;
+  auto res = lv_draw_buf_save_to_file(buf, fullpath.c_str());
+  lv_draw_buf_destroy(buf);
+  if (res == LV_RESULT_OK) {
+    ESP_LOGI(kTag, "write okay!");
+  } else {
+    ESP_LOGE(kTag, "write failed!");
+  }
+}
+
 void UiState::react(const system_fsm::KeyLockChanged& ev) {
   sDisplay->SetDisplayOn(!ev.locking);
   sInput->lock(ev.locking);

src/tangara/ui/ui_fsm.hpp

@@ -53,6 +53,7 @@ class UiState : public tinyfsm::Fsm<UiState> {
   /* Fallback event handler. Does nothing. */
   void react(const tinyfsm::Event& ev) {}
 
+  void react(const Screenshot&);
   virtual void react(const OnLuaError&) {}
   virtual void react(const DumpLuaStack&) {}
   virtual void react(const internal::BackPressed&) {}