add modified colors section to palette editor

src/app/editor/graphics/palette_editor.cc

@@ -107,6 +107,8 @@ absl::Status PaletteEditor::Update() {
     TableHeadersRow();
     TableNextRow();
     TableNextColumn();
+    DrawModifiedColors();
+
     DrawCustomPalette();
     Separator();
     gui::SnesColorEdit4("Current Color Picker", &current_color_,
@@ -300,10 +302,33 @@ absl::Status PaletteEditor::DrawPaletteGroup(int category, bool right_side) {
   return absl::OkStatus();
 }
 
+void PaletteEditor::DrawModifiedColors() {
+  if (BeginChild("ModifiedColors", ImVec2(0, 100), true,
+                 ImGuiWindowFlags_HorizontalScrollbar)) {
+    for (int i = 0; i < history_.size(); i++) {
+      PushID(i);
+      gui::SnesColorEdit4("Original ", &history_.GetOriginalColor(i),
+                          ImGuiColorEditFlags_NoInputs);
+      SameLine(0.0f, GetStyle().ItemSpacing.y);
+      gui::SnesColorEdit4("Modified ", &history_.GetModifiedColor(i),
+                          ImGuiColorEditFlags_NoInputs);
+      PopID();
+    }
+  }
+  EndChild();
+}
+
 absl::Status PaletteEditor::HandleColorPopup(gfx::SnesPalette& palette, int i,
                                              int j, int n) {
   auto col = gfx::ToFloatArray(palette[n]);
-  gui::SnesColorEdit4("Edit Color", &palette[n], kColorPopupFlags);
+  auto original_color = palette[n];
+  if (gui::SnesColorEdit4("Edit Color", &palette[n], kColorPopupFlags)) {
+    history_.RecordChange(/*group_name=*/std::string(kPaletteGroupNames[i]),
+                          /*palette_index=*/j, /*color_index=*/n,
+                          original_color, palette[n]);
+    palette[n].set_modified(true);
+  }
+
   if (Button("Copy as..", ImVec2(-1, 0))) OpenPopup("Copy");
   if (BeginPopup("Copy")) {
     int cr = F32_TO_INT8_SAT(col[0]);

src/app/editor/graphics/palette_editor.h

@@ -46,9 +46,9 @@ class PaletteEditorHistory {
   }
 
   // Restore the original color
-  gfx::SnesColor GetOriginalColor(const std::string& groupName,
+  gfx::SnesColor RestoreOriginalColor(const std::string& groupName,
-                                  size_t paletteIndex,
+                                      size_t paletteIndex,
-                                  size_t colorIndex) const {
+                                      size_t colorIndex) const {
     for (const auto& change : recentChanges) {
       if (change.group_name == groupName &&
           change.palette_index == paletteIndex &&
@@ -61,6 +61,15 @@ class PaletteEditorHistory {
     return gfx::SnesColor();
   }
 
+  auto size() const { return recentChanges.size(); }
+
+  gfx::SnesColor& GetModifiedColor(size_t index) {
+    return recentChanges[index].new_color;
+  }
+  gfx::SnesColor& GetOriginalColor(size_t index) {
+    return recentChanges[index].original_color;
+  }
+
  private:
   std::deque<PaletteChange> recentChanges;
   static const size_t maxHistorySize = 50;  // or any other number you deem fit
@@ -96,6 +105,8 @@ class PaletteEditor : public SharedRom, public Editor {
 
   void DrawCustomPalette();
 
+  void DrawModifiedColors();
+
  private:
   absl::Status HandleColorPopup(gfx::SnesPalette& palette, int i, int j, int n);
   absl::Status InitializeSavedPalette(const gfx::SnesPalette& palette) {