Backends: clear bits set in io.BackendFlags on backend Shutdown(). Clear BackendPlatformName. (#6334, #6335)

Amended with fix for missing clear for ImGuiBackendFlags_HasGamepad.

backends/imgui_impl_allegro5.cpp

@@ -462,8 +462,9 @@ void ImGui_ImplAllegro5_Shutdown()
     if (bd->ClipboardTextData)
         al_free(bd->ClipboardTextData);
 
-    io.BackendPlatformUserData = nullptr;
     io.BackendPlatformName = io.BackendRendererName = nullptr;
+    io.BackendPlatformUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_HasMouseCursors;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_android.cpp

@@ -269,6 +269,8 @@ bool ImGui_ImplAndroid_Init(ANativeWindow* window)
 
 void ImGui_ImplAndroid_Shutdown()
 {
+    ImGuiIO& io = ImGui::GetIO();
+    io.BackendPlatformName = nullptr;
 }
 
 void ImGui_ImplAndroid_NewFrame()

backends/imgui_impl_dx10.cpp

@@ -567,6 +567,7 @@ void ImGui_ImplDX10_Shutdown()
     if (bd->pd3dDevice) { bd->pd3dDevice->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_dx11.cpp

@@ -583,6 +583,7 @@ void ImGui_ImplDX11_Shutdown()
     if (bd->pd3dDeviceContext)    { bd->pd3dDeviceContext->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_dx12.cpp

@@ -739,6 +739,7 @@ void ImGui_ImplDX12_Shutdown()
     delete[] bd->pFrameResources;
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_dx9.cpp

@@ -304,6 +304,7 @@ void ImGui_ImplDX9_Shutdown()
     if (bd->pd3dDevice) { bd->pd3dDevice->Release(); }
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_glfw.cpp

@@ -643,6 +643,7 @@ void ImGui_ImplGlfw_Shutdown()
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
     IM_DELETE(bd);
 }
 

backends/imgui_impl_glut.cpp

@@ -191,6 +191,8 @@ void ImGui_ImplGLUT_InstallFuncs()
 
 void ImGui_ImplGLUT_Shutdown()
 {
+    ImGuiIO& io = ImGui::GetIO();
+    io.BackendPlatformName = nullptr;
 }
 
 void ImGui_ImplGLUT_NewFrame()

backends/imgui_impl_metal.mm

@@ -135,6 +135,12 @@ bool ImGui_ImplMetal_Init(id<MTLDevice> device)
 
 void ImGui_ImplMetal_Shutdown()
 {
+    ImGui_ImplMetal_Data* bd = ImGui_ImplMetal_GetBackendData();
+    IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
+    ImGuiIO& io = ImGui::GetIO();
+    io.BackendRendererName = nullptr;
+    io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     ImGui_ImplMetal_DestroyDeviceObjects();
     ImGui_ImplMetal_DestroyBackendData();
 }

backends/imgui_impl_opengl3.cpp

@@ -355,6 +355,7 @@ void    ImGui_ImplOpenGL3_Shutdown()
     ImGui_ImplOpenGL3_DestroyDeviceObjects();
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_osx.mm

@@ -476,12 +476,19 @@ bool ImGui_ImplOSX_Init(NSView* view)
 void ImGui_ImplOSX_Shutdown()
 {
     ImGui_ImplOSX_Data* bd = ImGui_ImplOSX_GetBackendData();
+    IM_ASSERT(bd != nullptr && "No platform backend to shutdown, or already shutdown?");
+    ImGuiIO& io = ImGui::GetIO();
+
     bd->Observer = nullptr;
     if (bd->Monitor != nullptr)
     {
         [NSEvent removeMonitor:bd->Monitor];
         bd->Monitor = nullptr;
     }
+
+    io.BackendPlatformName = nullptr;
+    io.BackendPlatformUserData = nullptr;
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasGamepad);
     ImGui_ImplOSX_DestroyBackendData();
 }
 

backends/imgui_impl_sdl2.cpp

@@ -491,6 +491,7 @@ void ImGui_ImplSDL2_Shutdown()
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
     IM_DELETE(bd);
 }
 

backends/imgui_impl_sdl3.cpp

@@ -425,6 +425,7 @@ void ImGui_ImplSDL3_Shutdown()
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
     IM_DELETE(bd);
 }
 

backends/imgui_impl_sdlrenderer.cpp

@@ -86,6 +86,7 @@ void ImGui_ImplSDLRenderer_Shutdown()
 
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_vulkan.cpp

@@ -1000,6 +1000,7 @@ void ImGui_ImplVulkan_Shutdown()
     ImGui_ImplVulkan_DestroyDeviceObjects();
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_wgpu.cpp

@@ -751,6 +751,7 @@ void ImGui_ImplWGPU_Shutdown()
 
     io.BackendRendererName = nullptr;
     io.BackendRendererUserData = nullptr;
+    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;
     IM_DELETE(bd);
 }
 

backends/imgui_impl_win32.cpp

@@ -178,6 +178,7 @@ void    ImGui_ImplWin32_Shutdown()
 
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
+    io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
     IM_DELETE(bd);
 }
 

docs/CHANGELOG.txt

@@ -42,6 +42,9 @@ Breaking changes:
 
 Other changes:
 
+- Backends: Clear bits sets io.BackendFlags on backend Shutdown(). (#6334, #6335] [@GereonV]
+  Potentially this would facilitate switching runtime backend mid-session.
+
 
 
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