Step 107a: add text mode toggle

PROGRESS.md

@@ -207,8 +207,9 @@ All 38 steps implemented and passing. Each step has a corresponding test (`step1
 - [x] Step 104: **IMPLEMENTED** — Cross-language projection button with read-only projected tabs and annotation summary (2/2 tests pass)
 - [x] Step 105: **IMPLEMENTED** — Optimization controls panel with constraint-aware buttons and summaries (2/2 tests pass)
 - [x] Step 106: **IMPLEMENTED** — Transform history panel with undo controls and provenance coloring (1/1 tests pass)
-- [ ] Step 107a–107c: **PLANNED** — Text-Editor Mode toggle, UI behavior by mode, and per-buffer persistence (not started)
 - [x] Step 107: **IMPLEMENTED** — Before/after diff view with preview and accept/reject (1/1 tests pass)
+- [x] Step 107a: **IMPLEMENTED** — Text-Editor Mode toggle and per-buffer mode tracking (2/2 tests pass)
+- [ ] Step 107b–107c: **PLANNED** — Mode-specific UI behavior and per-buffer persistence (not started)
 
 ---
 
@@ -296,6 +297,7 @@ vcpkg's imgui 1.91.9 removed the `sdl2-binding` feature (only `sdl3-binding` exi
 **Step 105:** Compile and pass (2/2)
 **Step 106:** Compile and pass (1/1)
 **Step 107:** Compile and pass (1/1)
+**Step 107a:** Compile and pass (2/2)
 
 ---
 
@@ -413,3 +415,4 @@ Sprint 4 in progress. Step 76 (LayoutManager) done. Next: Step 77 (custom code e
 | 2026-02-09 | Codex | Step 106: Transform history panel with undo controls and provenance coloring. 1/1 tests pass. |
 | 2026-02-09 | Codex | Planned Step 107a–107c: add Text-Editor Mode toggle, mode-specific UI behavior, and per-buffer persistence. |
 | 2026-02-09 | Codex | Step 107: Before/after diff view with preview and accept/reject. 1/1 tests pass. |
+| 2026-02-09 | Codex | Step 107a: Text-Editor Mode toggle and per-buffer mode tracking. 2/2 tests pass. |

editor/CMakeLists.txt

@@ -578,6 +578,10 @@ add_executable(step107_test tests/step107_test.cpp)
 target_include_directories(step107_test PRIVATE src)
 target_link_libraries(step107_test PRIVATE nlohmann_json::nlohmann_json)
 
+add_executable(step107a_test tests/step107a_test.cpp)
+target_include_directories(step107a_test PRIVATE src)
+target_link_libraries(step107a_test PRIVATE nlohmann_json::nlohmann_json)
+
 find_package(SDL2 CONFIG REQUIRED)
 find_package(OpenGL REQUIRED)
 find_package(glad CONFIG REQUIRED)

editor/src/BufferManager.h

@@ -11,20 +11,27 @@
 
 class BufferManager {
 public:
+    enum class BufferMode {
+        Structured,
+        Text
+    };
+
     struct BufferInfo {
         std::string path;
         std::string content;
         std::string language;
         bool modified = false;
+        BufferMode mode = BufferMode::Structured;
     };
 
     BufferManager() = default;
 
     // Open a file into a buffer (makes it active)
     bool openBuffer(const std::string& path, const std::string& content,
-                    const std::string& language) {
+                    const std::string& language,
+                    BufferMode mode = BufferMode::Structured) {
         if (hasBuffer(path)) return false;  // already open
-        BufferInfo info{path, content, language, false};
+        BufferInfo info{path, content, language, false, mode};
         buffers_[path] = info;
         activeBuffer_ = path;
         return true;
@@ -70,6 +77,19 @@ public:
         }
     }
 
+    void setBufferMode(const std::string& path, BufferMode mode) {
+        auto it = buffers_.find(path);
+        if (it != buffers_.end()) {
+            it->second.mode = mode;
+        }
+    }
+
+    BufferMode getBufferMode(const std::string& path) const {
+        auto it = buffers_.find(path);
+        if (it != buffers_.end()) return it->second.mode;
+        return BufferMode::Structured;
+    }
+
     // Get list of all open buffer paths
     std::vector<std::string> getOpenBuffers() const {
         std::vector<std::string> result;

editor/src/main.cpp

@@ -17,6 +17,7 @@
 #include "TextASTSync.h"
 #include "SyntaxHighlighter.h"
 #include "KeybindingManager.h"
+#include "BufferManager.h"
 #include "CodeEditorWidget.h"
 #include "EditorMode.h"
 #include "FileDialog.h"
@@ -70,6 +71,7 @@ struct BufferState {
     std::string       generatedLanguage = "python";
     std::string       path        = "(untitled)";
     bool              readOnly    = false;
+    BufferManager::BufferMode mode = BufferManager::BufferMode::Structured;
     bool              modified    = false;
     int               cursorLine  = 1;
     int               cursorCol   = 1;
@@ -251,7 +253,8 @@ struct EditorState {
         state->generatedHighlightsDirty = true;
         state->modified = false;
         state->lspVersion = 1;
-        buffers.openBuffer(path, content, language);
+        buffers.openBuffer(path, content, language, BufferManager::BufferMode::Structured);
+        state->mode = BufferManager::BufferMode::Structured;
         activeBuffer = state.get();
         bufferStates[path] = std::move(state);
         if (path.rfind("(untitled", 0) != 0) watcher.watch(path);
@@ -1328,6 +1331,15 @@ int main(int, char**) {
                 ImGui::MenuItem("Show Minimap", nullptr, &state.showMinimap);
                 ImGui::MenuItem("Show Annotations", nullptr, &state.showAnnotations);
                 ImGui::MenuItem("LSP Servers...", nullptr, &state.showLspSettings);
+                if (state.active()) {
+                    bool textMode = state.active()->mode == BufferManager::BufferMode::Text;
+                    if (ImGui::MenuItem("Text-Editor Mode", nullptr, textMode)) {
+                        state.active()->mode = textMode ?
+                            BufferManager::BufferMode::Structured :
+                            BufferManager::BufferMode::Text;
+                        state.buffers.setBufferMode(state.active()->path, state.active()->mode);
+                    }
+                }
                 if (ImGui::BeginMenu("Layout")) {
                     if (ImGui::MenuItem("VSCode", nullptr, state.layoutPreset == LayoutPreset::VSCode))
                         state.layoutPreset = LayoutPreset::VSCode;
@@ -2575,6 +2587,16 @@ int main(int, char**) {
                 ImGui::Text("-");
             ImGui::SameLine(0, 30);
 
+            // Mode
+            if (state.active()) {
+                const char* modeLabel =
+                    state.active()->mode == BufferManager::BufferMode::Text ? "Text" : "Structured";
+                ImGui::Text("Mode: %s", modeLabel);
+            } else {
+                ImGui::Text("Mode: -");
+            }
+            ImGui::SameLine(0, 30);
+
             // Keybinding profile
             ImGui::Text("Keys: %s", KeybindingManager::profileName(state.keys.getProfile()));
             ImGui::SameLine(0, 30);

editor/tests/step107a_test.cpp

@@ -0,0 +1,28 @@
+// Step 107a TDD Test: Text editor mode toggle persistence in BufferManager
+//
+// Tests:
+// 1. Default mode is Structured
+// 2. setBufferMode updates mode
+
+#include <cassert>
+#include <iostream>
+#include "BufferManager.h"
+
+int main() {
+    int passed = 0;
+    int failed = 0;
+
+    BufferManager bm;
+    bm.openBuffer("file1", "", "python");
+    assert(bm.getBufferMode("file1") == BufferManager::BufferMode::Structured);
+    std::cout << "Test 1 PASS: default mode structured" << std::endl;
+    ++passed;
+
+    bm.setBufferMode("file1", BufferManager::BufferMode::Text);
+    assert(bm.getBufferMode("file1") == BufferManager::BufferMode::Text);
+    std::cout << "Test 2 PASS: mode updated" << std::endl;
+    ++passed;
+
+    std::cout << "\n=== Step 107a Results: " << passed << " passed, " << failed << " failed ===" << std::endl;
+    return failed > 0 ? 1 : 0;
+}