track buffers which must be preserved for imgui render (#319)

* track buffers which must be preserved for imgui render

* fix comment typo

include/polyscope/render/engine.h

@@ -445,9 +445,9 @@ class Engine {
   virtual void shutdown() {};
   virtual void checkError(bool fatal = false) = 0;
   void buildEngineGui();
-  
+
   // 'headless' means there is no physical display to actually render to, e.g. when running on a remote server
-  virtual bool isHeadless() { return false; } 
+  virtual bool isHeadless() { return false; }
 
   virtual void clearDisplay();
   virtual void bindDisplay();
@@ -519,6 +519,10 @@ class Engine {
 
   void setImGuiStyle();
   ImFontAtlas* getImGuiGlobalFontAtlas();
+
+  // Display an ImGui window showing a texture
+  // WARNING: you must ensure that the texture buffer pointer stays valid until after the ImGui frame is rendered, which
+  // is not until the end of a main loop iteration.
   virtual void showTextureInImGuiWindow(std::string windowName, TextureBuffer* buffer);
 
 
@@ -630,6 +634,11 @@ class Engine {
   ImFont* monoFont = nullptr;
   FrameBuffer* currRenderFramebuffer = nullptr;
 
+  // Manage some resources that we need to preserve because ImGui will use them to render at the end of the frame
+  // This matters if we delete something mid-frame but have already passed a pointer to a texture for imgui to render,
+  // which happens at the end of the frame.
+  void preserveResourceUntilImguiFrameCompletes(std::shared_ptr<TextureBuffer> texture);
+
 protected:
   // TODO Manage a cache of compiled shaders?
 
@@ -664,6 +673,10 @@ class Engine {
   std::vector<std::string> defaultRules_sceneObject{"GLSL_VERSION", "GLOBAL_FRAGMENT_FILTER"};
   std::vector<std::string> defaultRules_pick{"GLSL_VERSION", "GLOBAL_FRAGMENT_FILTER", "SHADE_COLOR", "LIGHT_PASSTHRU"};
   std::vector<std::string> defaultRules_process{"GLSL_VERSION"};
+
+  // Lists of points to support preserving resources until the end of an ImGUI frame (see note above)
+  void clearResourcesPreservedForImguiFrame();
+  std::vector<std::shared_ptr<TextureBuffer>> resourcesPreservedForImGuiFrame;
 };
 
 

src/color_image_quantity.cpp

@@ -111,6 +111,7 @@ void ColorImageQuantity::showInImGuiWindow() {
   } else if (imageOrigin == ImageOrigin::UpperLeft) {
     ImGui::Image(colors.getRenderTextureBuffer()->getNativeHandle(), ImVec2(w, h));
   }
+  render::engine->preserveResourceUntilImguiFrameCompletes(colors.getRenderTextureBuffer());
 
   ImGui::End();
 }

src/histogram.cpp

@@ -202,6 +202,7 @@ void Histogram::buildUI(float width) {
 
   // Render image
   ImGui::Image(texture->getNativeHandle(), ImVec2(w, h), ImVec2(0, 1), ImVec2(1, 0));
+  render::engine->preserveResourceUntilImguiFrameCompletes(texture);
 
   // Helpful info for drawing annotations below
   ImU32 annoColor = ImGui::ColorConvertFloat4ToU32(ImVec4(254 / 255., 221 / 255., 66 / 255., 1.0));

src/render/engine.cpp

@@ -1183,5 +1183,11 @@ void Engine::showTextureInImGuiWindow(std::string windowName, TextureBuffer* buf
 
 ImFontAtlas* Engine::getImGuiGlobalFontAtlas() { return globalFontAtlas; }
 
+void Engine::preserveResourceUntilImguiFrameCompletes(std::shared_ptr<TextureBuffer> texture) {
+  resourcesPreservedForImGuiFrame.push_back(texture);
+}
+
+void Engine::clearResourcesPreservedForImguiFrame() { resourcesPreservedForImGuiFrame.clear(); }
+
 } // namespace render
 } // namespace polyscope

src/render/mock_opengl/mock_gl_engine.cpp

@@ -1659,7 +1659,10 @@ void MockGLEngine::ImGuiNewFrame() {
   ImGui::NewFrame();
 }
 
-void MockGLEngine::ImGuiRender() { ImGui::Render(); }
+void MockGLEngine::ImGuiRender() {
+  ImGui::Render();
+  clearResourcesPreservedForImguiFrame();
+}
 
 void MockGLEngine::setDepthMode(DepthMode newMode) {}
 

src/render/opengl/gl_engine_egl.cpp

@@ -396,7 +396,10 @@ void GLEngineEGL::ImGuiNewFrame() {
   ImGui::NewFrame();
 }
 
-void GLEngineEGL::ImGuiRender() { ImGui::Render(); }
+void GLEngineEGL::ImGuiRender() {
+  ImGui::Render();
+  clearResourcesPreservedForImguiFrame();
+}
 
 
 void GLEngineEGL::swapDisplayBuffers() {

src/render/opengl/gl_engine_glfw.cpp

@@ -140,6 +140,7 @@ void GLEngineGLFW::ImGuiNewFrame() {
 void GLEngineGLFW::ImGuiRender() {
   ImGui::Render();
   ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+  clearResourcesPreservedForImguiFrame();
 }
 
 

src/scalar_image_quantity.cpp

@@ -115,6 +115,7 @@ void ScalarImageQuantity::showInImGuiWindow() {
   // here we always use the same ImVec2 UV coords below, because the texture order is always openGL convention after the
   // intermediate render pass
   ImGui::Image(textureIntermediateRendered->getNativeHandle(), ImVec2(w, h), ImVec2(0, 1), ImVec2(1, 0));
+  render::engine->preserveResourceUntilImguiFrameCompletes(textureIntermediateRendered);
 
 
   ImGui::End();