ImGui: avoid non-reentrant call to VideoPresentScreen().

The debugger (which calls VideoPresentScreen) is execute in immediate mode from VideoPresentScreen. Is this a design problem? Signed-off-by: Andrea Odetti <mariofutire@gmail.com>
jvernet · Jan 11, 2022 · c70377f · c70377f
1 parent 2abca0c
commit c70377f
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Showing 2 changed files with 21 additions and 12 deletions.
diff --git a/source/frontends/sdl/imgui/sdlimguiframe.cpp b/source/frontends/sdl/imgui/sdlimguiframe.cpp
@@ -36,6 +36,7 @@ namespace sa2
 
   SDLImGuiFrame::SDLImGuiFrame(const common2::EmulatorOptions & options)
     : SDLFrame(options)
+    , myPresenting(false)
   {
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SA2_CONTEXT_FLAGS);
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SA2_CONTEXT_PROFILE_MASK);
@@ -187,18 +188,25 @@ namespace sa2
 
   void SDLImGuiFrame::VideoPresentScreen()
   {
-    ImGui_ImplOpenGL3_NewFrame();
-    ImGui_ImplSDL2_NewFrame(myWindow.get());
-    ImGui::NewFrame();
-
-    // "this" is a bit circular
-    mySettings.show(this);
-    DrawAppleVideo();
-
-    ImGui::Render();
-    ClearBackground();
-    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
-    SDL_GL_SwapWindow(myWindow.get());
+    // this is NOT REENTRANT
+    // the debugger (executed via mySettings.show(this)) might call it recursively
+    if (!myPresenting)
+    {
+      myPresenting = true;
+      ImGui_ImplOpenGL3_NewFrame();
+      ImGui_ImplSDL2_NewFrame();
+      ImGui::NewFrame();
+
+      // "this" is a bit circular
+      mySettings.show(this);
+      DrawAppleVideo();
+
+      ImGui::Render();
+      ClearBackground();
+      ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+      SDL_GL_SwapWindow(myWindow.get());
+      myPresenting = false;
+    }
   }
 
   void SDLImGuiFrame::ProcessSingleEvent(const SDL_Event & event, bool & quit)

diff --git a/source/frontends/sdl/imgui/sdlimguiframe.h b/source/frontends/sdl/imgui/sdlimguiframe.h
@@ -41,6 +41,7 @@ namespace sa2
     size_t myBorderlessHeight;
 
     int myDeadTopZone; // for mouse position
+    bool myPresenting; // VideoPresentScreen() is NOT REENTRANT
 
     SDL_GLContext myGLContext;
     ImTextureID myTexture;