Step 88: drag-and-drop open

PROGRESS.md

@@ -185,6 +185,7 @@ All 38 steps implemented and passing. Each step has a corresponding test (`step1
 - [x] Step 85: **IMPLEMENTED** — Filesystem tree with .gitignore filtering, recursive Explorer rendering (1/1 tests pass)
 - [x] Step 86: **IMPLEMENTED** — Multi-tab editing with BufferManager and per-buffer editor state (3/3 tests pass)
 - [x] Step 87: **IMPLEMENTED** — Welcome screen wired with recent files persistence and quick actions (2/2 tests pass)
+- [x] Step 88: **IMPLEMENTED** — Drag-and-drop file/folder open via SDL_DROPFILE (2/2 tests pass)
 
 ---
 
@@ -251,6 +252,7 @@ vcpkg's imgui 1.91.9 removed the `sdl2-binding` feature (only `sdl3-binding` exi
 **Step 85:** Compile and pass (1/1)
 **Step 86:** Compile and pass (3/3)
 **Step 87:** Compile and pass (2/2)
+**Step 88:** Compile and pass (2/2)
 
 ---
 
@@ -346,3 +348,4 @@ Sprint 4 in progress. Step 76 (LayoutManager) done. Next: Step 77 (custom code e
 | 2026-02-09 | Codex | Step 85: Filesystem tree with .gitignore filtering and Explorer rendering. 1/1 tests pass. |
 | 2026-02-09 | Codex | Step 86: Multi-tab editing wired via BufferManager with per-buffer state. 3/3 tests pass. |
 | 2026-02-09 | Codex | Step 87: Welcome screen wired with recent files persistence and quick actions. 2/2 tests pass. |
+| 2026-02-09 | Codex | Step 88: Drag-and-drop open for files and folders. 2/2 tests pass. |

editor/CMakeLists.txt

@@ -496,6 +496,9 @@ target_include_directories(step86_test PRIVATE src)
 add_executable(step87_test tests/step87_test.cpp)
 target_include_directories(step87_test PRIVATE src)
 
+add_executable(step88_test tests/step88_test.cpp)
+target_include_directories(step88_test PRIVATE src)
+
 find_package(SDL2 CONFIG REQUIRED)
 find_package(OpenGL REQUIRED)
 find_package(glad CONFIG REQUIRED)

editor/src/DragDropHandler.h

@@ -0,0 +1,24 @@
+#pragma once
+// Step 88: Drag-and-drop handler
+
+#include <string>
+#include <functional>
+#include <filesystem>
+
+class DragDropHandler {
+public:
+    using FileCallback = std::function<void(const std::string&)>;
+    using FolderCallback = std::function<void(const std::string&)>;
+
+    static void handleDrop(const std::string& path,
+                           const FileCallback& onFile,
+                           const FolderCallback& onFolder) {
+        if (path.empty()) return;
+        std::filesystem::path p(path);
+        if (std::filesystem::is_directory(p)) {
+            if (onFolder) onFolder(path);
+        } else {
+            if (onFile) onFile(path);
+        }
+    }
+};

editor/src/main.cpp

@@ -22,6 +22,7 @@
 #include "FileDialog.h"
 #include "FileTree.h"
 #include "WelcomeScreen.h"
+#include "DragDropHandler.h"
 #include "ast/Generator.h"
 
 #include <cstdio>
@@ -624,6 +625,18 @@ int main(int, char**) {
                 event.window.event == SDL_WINDOWEVENT_CLOSE &&
                 event.window.windowID == SDL_GetWindowID(window))
                 done = true;
+            if (event.type == SDL_DROPFILE) {
+                char* droppedFile = event.drop.file;
+                if (droppedFile) {
+                    DragDropHandler::handleDrop(droppedFile,
+                        [&](const std::string& p) { state.doOpen(p); },
+                        [&](const std::string& p) {
+                            state.workspaceRoot = p;
+                            state.fileTreeDirty = true;
+                        });
+                    SDL_free(droppedFile);
+                }
+            }
 
             // Handle keyboard shortcuts via KeybindingManager
             if (event.type == SDL_KEYDOWN && !io.WantTextInput) {

editor/tests/step88_test.cpp

@@ -0,0 +1,49 @@
+// Step 88 TDD Test: Drag-and-drop handler
+//
+// Tests:
+// 1. File drop invokes file callback
+// 2. Folder drop invokes folder callback
+
+#include <cassert>
+#include <iostream>
+#include <filesystem>
+#include <fstream>
+#include "DragDropHandler.h"
+
+int main() {
+    int passed = 0;
+    int failed = 0;
+
+    std::filesystem::path root = std::filesystem::current_path() / "tmp_step88";
+    std::filesystem::create_directories(root / "dir");
+    std::filesystem::path file = root / "file.txt";
+    std::ofstream f(file.string());
+    f << "x";
+    f.close();
+
+    bool fileCalled = false;
+    bool folderCalled = false;
+
+    DragDropHandler::handleDrop(file.string(),
+        [&](const std::string& p){ fileCalled = (p == file.string()); },
+        [&](const std::string& p){ folderCalled = (p == (root / "dir").string()); }
+    );
+    assert(fileCalled);
+    std::cout << "Test 1 PASS: File drop" << std::endl;
+    ++passed;
+
+    fileCalled = false;
+    folderCalled = false;
+    DragDropHandler::handleDrop((root / "dir").string(),
+        [&](const std::string& p){ fileCalled = (p == file.string()); },
+        [&](const std::string& p){ folderCalled = (p == (root / "dir").string()); }
+    );
+    assert(folderCalled);
+    std::cout << "Test 2 PASS: Folder drop" << std::endl;
+    ++passed;
+
+    std::filesystem::remove_all(root);
+
+    std::cout << "\n=== Step 88 Results: " << passed << " passed, " << failed << " failed ===" << std::endl;
+    return failed > 0 ? 1 : 0;
+}