mitigate the broken-ness of screenshots with UI

Author: nmwsharp

include/polyscope/internal.h

@@ -23,6 +23,9 @@ namespace internal {
 // Get a unique identifier
 uint64_t getNextUniqueID();
 
+// How many layers deep in the polyscope context stack are we
+extern int contextStackSize;
+
 // track various fire-once warnings
 extern bool& pointCloudEfficiencyWarningReported;
 

src/internal.cpp

@@ -11,6 +11,8 @@ uint64_t uniqueID = 42;
 
 uint64_t getNextUniqueID() { return uniqueID++; }
 
+int contextStackSize = 0;
+
 bool& pointCloudEfficiencyWarningReported = state::globalContext.pointCloudEfficiencyWarningReported;
 FloatingQuantityStructure*& globalFloatingQuantityStructure = state::globalContext.globalFloatingQuantityStructure;
 

src/polyscope.cpp

@@ -244,6 +244,7 @@ void init(std::string backend) {
   // Create an initial context based context. Note that calling show() never actually uses this context, because it
   // pushes a new one each time. But using frameTick() may use this context.
   contextStack.push_back(ContextEntry{ImGui::GetCurrentContext(), ImPlot::GetCurrentContext(), nullptr, true});
+  internal::contextStackSize++;
 
   view::invalidateView();
 
@@ -293,6 +294,7 @@ void pushContext(std::function<void()> callbackFunction, bool drawDefaultUI) {
   ImGuizmo::PushContext();
 
   contextStack.push_back(ContextEntry{newContext, newPlotContext, callbackFunction, drawDefaultUI});
+  internal::contextStackSize++;
 
   if (contextStack.size() > 50) {
     // Catch bugs with nested show()
@@ -340,6 +342,7 @@ void popContext() {
     return;
   }
   contextStack.pop_back();
+  internal::contextStackSize--;
 }
 
 ImGuiContext* getCurrentContext() { return contextStack.empty() ? nullptr : contextStack.back().context; }
@@ -743,7 +746,7 @@ void buildPolyscopeGui() {
   if (ImGui::BeginPopup("ScreenshotOptionsPopup")) {
 
     ImGui::Checkbox("with transparency", &options::screenshotTransparency);
-    ImGui::Checkbox("with UI", &options::screenshotWithImGuiUI);
+    // ImGui::Checkbox("with UI", &options::screenshotWithImGuiUI); // temporarily disabled while broken
 
     if (ImGui::BeginMenu("file format")) {
       if (ImGui::MenuItem(".png", NULL, options::screenshotExtension == ".png")) options::screenshotExtension = ".png";
@@ -1201,6 +1204,7 @@ void shutdown(bool allowMidFrameShutdown) {
   render::engine->shutdown();
   delete render::engine;
   contextStack.clear();
+  internal::contextStackSize = 0;
   render::engine = nullptr;
   state::backend = "";
   state::initialized = false;

src/screenshot.cpp

@@ -41,6 +41,11 @@ bool hasExtension(std::string str, std::string ext) {
 std::vector<unsigned char> getRenderInBuffer(const ScreenshotOptions& options = {}) {
   checkInitialized();
 
+  if (options.includeUI && internal::contextStackSize > 1) {
+    error("Screenshot with includeUI=true is not supported within show(). See docs for details and workarounds.");
+    return std::vector<unsigned char>();
+  }
+
   render::engine->useAltDisplayBuffer = true;
   if (options.transparentBackground) render::engine->lightCopy = true; // copy directly in to buffer without blending
 
@@ -67,6 +72,7 @@ std::vector<unsigned char> getRenderInBuffer(const ScreenshotOptions& options =
   ImGuiIO* newIO;
   if (options.includeUI) {
 
+    // NOTE: error check above ensure internal::contextStackSize == 1 (cannot be called during show())
 
     // Create a new context and push it on to the stack
     oldIO = &ImGui::GetIO(); // used to GLFW + OpenGL data to the new IO object