SaveTool: add basic skeleton for the M.A.S.S. viewer.

src/SaveTool/SaveTool_MassViewer.cpp

@@ -46,5 +46,42 @@ void SaveTool::drawMassViewer() {
         _uiState = UiState::MainManager;
     }
 
+    ImGui::TextColored(ImColor(255, 255, 0), ICON_FA_EXCLAMATION_TRIANGLE);
+    ImGui::SameLine();
+    ImGui::TextWrapped("WARNING: Colours in this app may look different from in-game colours, due to unavoidable differences in the rendering pipeline.");
+
+    if(ImGui::BeginChild("##MassInfo",
+                         {ImGui::GetContentRegionAvailWidth() * 0.60f, 0.0f},
+                         true, ImGuiWindowFlags_MenuBar))
+    {
+        if(ImGui::BeginMenuBar()) {
+            ImGui::TextUnformatted("M.A.S.S. Information");
+            ImGui::EndMenuBar();
+        }
+
+        if(ImGui::BeginTabBar("##MassTabBar")) {
+            if(ImGui::BeginTabItem("Frame")) {
+                ImGui::EndTabItem();
+            }
+
+            ImGui::EndTabBar();
+        }
+    }
+    ImGui::EndChild();
+
+    ImGui::SameLine();
+
+    if(ImGui::BeginChild("##GlobalStyles", {0.0f, 0.0f},
+                         true, ImGuiWindowFlags_MenuBar))
+    {
+        if(ImGui::BeginMenuBar()) {
+            ImGui::TextUnformatted("Global styles");
+            ImGui::EndMenuBar();
+        }
+
+        ImGui::TextUnformatted("Placeholder");
+    }
+    ImGui::EndChild();
+
     ImGui::End();
 }