feat: Implement screenshot capture functionality in ImGuiTestHarnessService

src/app/core/service/imgui_test_harness_service.cc

@@ -2,9 +2,12 @@
 
 #ifdef YAZE_WITH_GRPC
 
+#include <SDL.h>
+
 #include <algorithm>
 #include <chrono>
 #include <deque>
+#include <fstream>
 #include <iostream>
 #include <limits>
 #include <thread>
@@ -1184,15 +1187,82 @@ absl::Status ImGuiTestHarnessServiceImpl::Assert(const AssertRequest* request,
   return finalize(absl::OkStatus());
 }
 
+// Helper struct matching imgui_impl_sdlrenderer2.cpp backend data
+struct ImGui_ImplSDLRenderer2_Data {
+  SDL_Renderer* Renderer;
+};
+
 absl::Status ImGuiTestHarnessServiceImpl::Screenshot(
     const ScreenshotRequest* request, ScreenshotResponse* response) {
-  // TODO: Implement actual screenshot capture
-
-  response->set_success(false);
-  response->set_message("Screenshot not yet implemented");
-  response->set_file_path("");
-  response->set_file_size_bytes(0);
-
+  // Get the SDL renderer from ImGui backend
+  ImGuiIO& io = ImGui::GetIO();
+  auto* backend_data = static_cast<ImGui_ImplSDLRenderer2_Data*>(io.BackendRendererUserData);
+  
+  if (!backend_data || !backend_data->Renderer) {
+    response->set_success(false);
+    response->set_message("SDL renderer not available");
+    return absl::FailedPreconditionError("No SDL renderer available");
+  }
+  
+  SDL_Renderer* renderer = backend_data->Renderer;
+  
+  // Get renderer output size
+  int width, height;
+  if (SDL_GetRendererOutputSize(renderer, &width, &height) != 0) {
+    response->set_success(false);
+    response->set_message(absl::StrFormat("Failed to get renderer size: %s", SDL_GetError()));
+    return absl::InternalError("Failed to get renderer output size");
+  }
+  
+  // Create surface to hold screenshot
+  SDL_Surface* surface = SDL_CreateRGBSurface(0, width, height, 32,
+                                              0x00FF0000, 0x0000FF00,
+                                              0x000000FF, 0xFF000000);
+  if (!surface) {
+    response->set_success(false);
+    response->set_message(absl::StrFormat("Failed to create surface: %s", SDL_GetError()));
+    return absl::InternalError("Failed to create SDL surface");
+  }
+  
+  // Read pixels from renderer
+  if (SDL_RenderReadPixels(renderer, nullptr, SDL_PIXELFORMAT_ARGB8888,
+                          surface->pixels, surface->pitch) != 0) {
+    SDL_FreeSurface(surface);
+    response->set_success(false);
+    response->set_message(absl::StrFormat("Failed to read pixels: %s", SDL_GetError()));
+    return absl::InternalError("Failed to read renderer pixels");
+  }
+  
+  // Determine output path
+  std::string output_path = request->output_path();
+  if (output_path.empty()) {
+    // Default: /tmp/yaze_screenshot_<timestamp>.bmp
+    output_path = absl::StrFormat("/tmp/yaze_screenshot_%lld.bmp",
+                                  absl::ToUnixMillis(absl::Now()));
+  }
+  
+  // Save to BMP file (SDL built-in, no external deps needed)
+  if (SDL_SaveBMP(surface, output_path.c_str()) != 0) {
+    SDL_FreeSurface(surface);
+    response->set_success(false);
+    response->set_message(absl::StrFormat("Failed to save BMP: %s", SDL_GetError()));
+    return absl::InternalError("Failed to save screenshot");
+  }
+  
+  // Get file size
+  std::ifstream file(output_path, std::ios::binary | std::ios::ate);
+  int64_t file_size = file.tellg();
+  file.close();
+  
+  // Clean up and return success
+  SDL_FreeSurface(surface);
+  
+  response->set_success(true);
+  response->set_message(absl::StrFormat("Screenshot saved to %s (%dx%d)",
+                                        output_path, width, height));
+  response->set_file_path(output_path);
+  response->set_file_size_bytes(file_size);
+  
   return absl::OkStatus();
 }