Viewports: added opaque void* PlatformIconData storage in viewport and ImGuiWindowClass to allow passing icon information to a custom backend or hook. (#2715)

docs/CHANGELOG.txt

@@ -66,6 +66,12 @@ Other Changes:
   - Metal: avoid redundant vertex buffer bind in SetupRenderState, which leads
     to validation issue. (#9343) [@Hunam6]
 
+Docking+Viewports Branch:
+
+- Viewports:
+  - Added opaque `void* PlatformIconData` storage in viewport and ImGuiWindowClass
+    to allow passing icon information to a custom backend or hook. (#2715)
+
 
 -----------------------------------------------------------------------
  VERSION 1.92.7 (Released 2026-04-02)

imgui.cpp

@@ -17377,6 +17377,8 @@ void ImGui::WindowSyncOwnedViewport(ImGuiWindow* window, ImGuiWindow* parent_win
 
     window->Viewport->Flags = viewport_flags;
 
+    window->Viewport->PlatformIconData = window->WindowClass.PlatformIconData;
+
     // Update parent viewport ID
     // (the !IsFallbackWindow test mimic the one done in WindowSelectViewport())
     if (window->WindowClass.ParentViewportId != (ImGuiID)-1)

imgui.h

@@ -2809,6 +2809,7 @@ struct ImGuiWindowClass
     ImGuiDockNodeFlags  DockNodeFlagsOverrideSet;   // [EXPERIMENTAL] Dock node flags to set when a window of this class is hosted by a dock node (it doesn't have to be selected!)
     bool                DockingAlwaysTabBar;        // Set to true to enforce single floating windows of this class always having their own docking node (equivalent of setting the global io.ConfigDockingAlwaysTabBar)
     bool                DockingAllowUnclassed;      // Set to true to allow windows of this class to be docked/merged with an unclassed window. // FIXME-DOCK: Move to DockNodeFlags override?
+    void*               PlatformIconData;           // [EXPERIMENTAL] Pass opaque data for Platform backend to handle.
 
     ImGuiWindowClass() { memset((void*)this, 0, sizeof(*this)); ParentViewportId = (ImGuiID)-1; DockingAllowUnclassed = true; }
 };
@@ -4121,6 +4122,7 @@ struct ImGuiViewport
     // The library never uses those fields, they are merely storage to facilitate backend implementation.
     void*               RendererUserData;       // void* to hold custom data structure for the renderer (e.g. swap chain, framebuffers etc.). generally set by your Renderer_CreateWindow function.
     void*               PlatformUserData;       // void* to hold custom data structure for the OS / platform (e.g. windowing info, render context). generally set by your Platform_CreateWindow function.
+    void*               PlatformIconData;       // void* to hold custom data structure for the OS / platform to specify an icon. Currently unused for exposed to allow experiments.
     void*               PlatformHandle;         // void* to hold higher-level, platform window handle (e.g. HWND for Win32 backend, Uint32 WindowID for SDL, GLFWWindow* for GLFW), for FindViewportByPlatformHandle().
     void*               PlatformHandleRaw;      // void* to hold lower-level, platform-native window handle (always HWND on Win32 platform, unused for other platforms).
     bool                PlatformWindowCreated;  // Platform window has been created (Platform_CreateWindow() has been called). This is false during the first frame where a viewport is being created.