Merge branch 'master' into docking

# Conflicts:
#	backends/imgui_impl_glfw.cpp
#	backends/imgui_impl_glfw.h

backends/imgui_impl_glfw.cpp

@@ -10,6 +10,7 @@
 //  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility (ImGuiBackendFlags_HasMouseCursors). Resizing cursors requires GLFW 3.4+! Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
 //  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+//  [X] Multiple Dear ImGui contexts support.
 // Missing features or Issues:
 //  [ ] Touch events are only correctly identified as Touch on Windows. This create issues with some interactions. GLFW doesn't provide a way to identify touch inputs from mouse inputs, we cannot call io.AddMouseSourceEvent() to identify the source. We provide a Windows-specific workaround.
 //  [ ] Missing ImGuiMouseCursor_Wait and ImGuiMouseCursor_Progress cursors.
@@ -31,6 +32,7 @@
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
 //  2025-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
+//  2025-06-18: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)
 //  2025-06-11: Added ImGui_ImplGlfw_GetContentScaleForWindow(GLFWwindow* window) and ImGui_ImplGlfw_GetContentScaleForMonitor(GLFWmonitor* monitor) helper to facilitate making DPI-aware apps.
 //  2025-05-15: [Docking] Add Platform_GetWindowFramebufferScale() handler, to allow varying Retina display density on multiple monitors.
 //  2025-04-26: [Docking] Disable multi-viewports under Wayland. (#8587)
@@ -168,6 +170,16 @@
 #define GLFW_HAS_GETERROR               (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetError()
 #define GLFW_HAS_GETPLATFORM            (GLFW_VERSION_COMBINED >= 3400) // 3.4+ glfwGetPlatform()
 
+// Map GLFWWindow* to ImGuiContext*. 
+// - Would be simpler if we could use glfwSetWindowUserPointer()/glfwGetWindowUserPointer(), but this is a single and shared resource.
+// - Would be simpler if we could use e.g. std::map<> as well. But we don't.
+// - This is not particularly optimized as we expect size to be small and queries to be rare.
+struct ImGui_ImplGlfw_WindowToContext { GLFWwindow* Window; ImGuiContext* Context; };
+static ImVector<ImGui_ImplGlfw_WindowToContext> g_ContextMap;
+static void ImGui_ImplGlfw_ContextMap_Add(GLFWwindow* window, ImGuiContext* ctx) { g_ContextMap.push_back(ImGui_ImplGlfw_WindowToContext{ window, ctx }); }
+static void ImGui_ImplGlfw_ContextMap_Remove(GLFWwindow* window)                 { for (ImGui_ImplGlfw_WindowToContext& entry : g_ContextMap) if (entry.Window == window) { g_ContextMap.erase_unsorted(&entry); return; } }
+static ImGuiContext* ImGui_ImplGlfw_ContextMap_Get(GLFWwindow* window)           { for (ImGui_ImplGlfw_WindowToContext& entry : g_ContextMap) if (entry.Window == window) return entry.Context; return nullptr; }
+
 // GLFW data
 enum GlfwClientApi
 {
@@ -178,6 +190,7 @@ enum GlfwClientApi
 
 struct ImGui_ImplGlfw_Data
 {
+    ImGuiContext*           Context;
     GLFWwindow*             Window;
     GlfwClientApi           ClientApi;
     double                  Time;
@@ -217,10 +230,18 @@ struct ImGui_ImplGlfw_Data
 //   (passing install_callbacks=false in ImGui_ImplGlfw_InitXXX functions), set the current dear imgui context and then call our callbacks.
 // - Otherwise we may need to store a GLFWWindow* -> ImGuiContext* map and handle this in the backend, adding a little bit of extra complexity to it.
 // FIXME: some shared resources (mouse cursor shape, gamepad) are mishandled when using multi-context.
+namespace ImGui { extern ImGuiIO& GetIO(ImGuiContext*); }
 static ImGui_ImplGlfw_Data* ImGui_ImplGlfw_GetBackendData()
 {
+    // Get data for current context
     return ImGui::GetCurrentContext() ? (ImGui_ImplGlfw_Data*)ImGui::GetIO().BackendPlatformUserData : nullptr;
 }
+static ImGui_ImplGlfw_Data* ImGui_ImplGlfw_GetBackendData(GLFWwindow* window)
+{
+    // Get data for a given GLFW window, regardless of current context (since GLFW events are sent together)
+    ImGuiContext* ctx = ImGui_ImplGlfw_ContextMap_Get(window);
+    return (ImGui_ImplGlfw_Data*)ImGui::GetIO(ctx).BackendPlatformUserData;
+}
 
 // Forward Declarations
 static void ImGui_ImplGlfw_UpdateMonitors();
@@ -361,42 +382,40 @@ ImGuiKey ImGui_ImplGlfw_KeyToImGuiKey(int keycode, int scancode)
 
 // X11 does not include current pressed/released modifier key in 'mods' flags submitted by GLFW
 // See https://github.com/ocornut/imgui/issues/6034 and https://github.com/glfw/glfw/issues/1630
-static void ImGui_ImplGlfw_UpdateKeyModifiers(GLFWwindow* window)
+static void ImGui_ImplGlfw_UpdateKeyModifiers(ImGuiIO& io, GLFWwindow* window)
 {
-    ImGuiIO& io = ImGui::GetIO();
     io.AddKeyEvent(ImGuiMod_Ctrl,  (glfwGetKey(window, GLFW_KEY_LEFT_CONTROL) == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_CONTROL) == GLFW_PRESS));
     io.AddKeyEvent(ImGuiMod_Shift, (glfwGetKey(window, GLFW_KEY_LEFT_SHIFT)   == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_SHIFT)   == GLFW_PRESS));
     io.AddKeyEvent(ImGuiMod_Alt,   (glfwGetKey(window, GLFW_KEY_LEFT_ALT)     == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_ALT)     == GLFW_PRESS));
     io.AddKeyEvent(ImGuiMod_Super, (glfwGetKey(window, GLFW_KEY_LEFT_SUPER)   == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_SUPER)   == GLFW_PRESS));
 }
 
-static bool ImGui_ImplGlfw_ShouldChainCallback(GLFWwindow* window)
+static bool ImGui_ImplGlfw_ShouldChainCallback(ImGui_ImplGlfw_Data* bd, GLFWwindow* window)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
     return bd->CallbacksChainForAllWindows ? true : (window == bd->Window);
 }
 
 void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow* window, int button, int action, int mods)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackMousebutton != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+
+    if (bd->PrevUserCallbackMousebutton != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackMousebutton(window, button, action, mods);
 
     // Workaround for Linux: ignore mouse up events which are following an focus loss following a viewport creation
     if (bd->MouseIgnoreButtonUp && action == GLFW_RELEASE)
         return;
 
-    ImGui_ImplGlfw_UpdateKeyModifiers(window);
-
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
+    ImGui_ImplGlfw_UpdateKeyModifiers(io, window);
     if (button >= 0 && button < ImGuiMouseButton_COUNT)
         io.AddMouseButtonEvent(button, action == GLFW_PRESS);
 }
 
 void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackScroll != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+    if (bd->PrevUserCallbackScroll != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackScroll(window, xoffset, yoffset);
 
 #ifdef EMSCRIPTEN_USE_EMBEDDED_GLFW3
@@ -404,7 +423,7 @@ void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yo
     return;
 #endif
 
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
     io.AddMouseWheelEvent((float)xoffset, (float)yoffset);
 }
 
@@ -444,21 +463,21 @@ static int ImGui_ImplGlfw_TranslateUntranslatedKey(int key, int scancode)
 
 void ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int keycode, int scancode, int action, int mods)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackKey != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+    if (bd->PrevUserCallbackKey != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackKey(window, keycode, scancode, action, mods);
 
     if (action != GLFW_PRESS && action != GLFW_RELEASE)
         return;
 
-    ImGui_ImplGlfw_UpdateKeyModifiers(window);
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
+    ImGui_ImplGlfw_UpdateKeyModifiers(io, window);
 
     if (keycode >= 0 && keycode < IM_ARRAYSIZE(bd->KeyOwnerWindows))
         bd->KeyOwnerWindows[keycode] = (action == GLFW_PRESS) ? window : nullptr;
 
     keycode = ImGui_ImplGlfw_TranslateUntranslatedKey(keycode, scancode);
 
-    ImGuiIO& io = ImGui::GetIO();
     ImGuiKey imgui_key = ImGui_ImplGlfw_KeyToImGuiKey(keycode, scancode);
     io.AddKeyEvent(imgui_key, (action == GLFW_PRESS));
     io.SetKeyEventNativeData(imgui_key, keycode, scancode); // To support legacy indexing (<1.87 user code)
@@ -466,25 +485,25 @@ void ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int keycode, int scancode, i
 
 void ImGui_ImplGlfw_WindowFocusCallback(GLFWwindow* window, int focused)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackWindowFocus != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+    if (bd->PrevUserCallbackWindowFocus != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackWindowFocus(window, focused);
 
     // Workaround for Linux: when losing focus with MouseIgnoreButtonUpWaitForFocusLoss set, we will temporarily ignore subsequent Mouse Up events
     bd->MouseIgnoreButtonUp = (bd->MouseIgnoreButtonUpWaitForFocusLoss && focused == 0);
     bd->MouseIgnoreButtonUpWaitForFocusLoss = false;
 
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
     io.AddFocusEvent(focused != 0);
 }
 
 void ImGui_ImplGlfw_CursorPosCallback(GLFWwindow* window, double x, double y)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackCursorPos != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+    if (bd->PrevUserCallbackCursorPos != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackCursorPos(window, x, y);
 
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
     if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
     {
         int window_x, window_y;
@@ -500,11 +519,11 @@ void ImGui_ImplGlfw_CursorPosCallback(GLFWwindow* window, double x, double y)
 // so we back it up and restore on Leave/Enter (see https://github.com/ocornut/imgui/issues/4984)
 void ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackCursorEnter != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+    if (bd->PrevUserCallbackCursorEnter != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackCursorEnter(window, entered);
 
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
     if (entered)
     {
         bd->MouseWindow = window;
@@ -520,11 +539,11 @@ void ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered)
 
 void ImGui_ImplGlfw_CharCallback(GLFWwindow* window, unsigned int c)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
-    if (bd->PrevUserCallbackChar != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
+    if (bd->PrevUserCallbackChar != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
         bd->PrevUserCallbackChar(window, c);
 
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
     io.AddInputCharacter(c);
 }
 
@@ -534,17 +553,18 @@ void ImGui_ImplGlfw_MonitorCallback(GLFWmonitor*, int)
 }
 
 #ifdef EMSCRIPTEN_USE_EMBEDDED_GLFW3
-static EM_BOOL ImGui_ImplEmscripten_WheelCallback(int, const EmscriptenWheelEvent* ev, void*)
+static EM_BOOL ImGui_ImplEmscripten_WheelCallback(int, const EmscriptenWheelEvent* ev, void* user_data)
 {
     // Mimic Emscripten_HandleWheel() in SDL.
     // Corresponding equivalent in GLFW JS emulation layer has incorrect quantizing preventing small values. See #6096
+    ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data*)user_data;
     float multiplier = 0.0f;
     if (ev->deltaMode == DOM_DELTA_PIXEL)       { multiplier = 1.0f / 100.0f; } // 100 pixels make up a step.
     else if (ev->deltaMode == DOM_DELTA_LINE)   { multiplier = 1.0f / 3.0f; }   // 3 lines make up a step.
     else if (ev->deltaMode == DOM_DELTA_PAGE)   { multiplier = 80.0f; }         // A page makes up 80 steps.
     float wheel_x = ev->deltaX * -multiplier;
     float wheel_y = ev->deltaY * -multiplier;
-    ImGuiIO& io = ImGui::GetIO();
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
     io.AddMouseWheelEvent(wheel_x, wheel_y);
     //IMGUI_DEBUG_LOG("[Emsc] mode %d dx: %.2f, dy: %.2f, dz: %.2f --> feed %.2f %.2f\n", (int)ev->deltaMode, ev->deltaX, ev->deltaY, ev->deltaZ, wheel_x, wheel_y);
     return EM_TRUE;
@@ -557,7 +577,7 @@ static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wPara
 
 void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
     IM_ASSERT(bd->InstalledCallbacks == false && "Callbacks already installed!");
     IM_ASSERT(bd->Window == window);
 
@@ -574,7 +594,7 @@ void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
 
 void ImGui_ImplGlfw_RestoreCallbacks(GLFWwindow* window)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
     IM_ASSERT(bd->InstalledCallbacks == true && "Callbacks not installed!");
     IM_ASSERT(bd->Window == window);
 
@@ -644,8 +664,10 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
     io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport; // We can call io.AddMouseViewportEvent() with correct data (optional)
 #endif
 
+    bd->Context = ImGui::GetCurrentContext();
     bd->Window = window;
     bd->Time = 0.0;
+    ImGui_ImplGlfw_ContextMap_Add(window, bd->Context);
 
     ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
 #if GLFW_VERSION_COMBINED < 3300
@@ -710,7 +732,9 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
 
     // Windows: register a WndProc hook so we can intercept some messages.
 #ifdef _WIN32
-    bd->PrevWndProc = (WNDPROC)::GetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC);
+    HWND hwnd = (HWND)main_viewport->PlatformHandleRaw;
+    ::SetPropA(hwnd, "IMGUI_BACKEND_DATA", bd);
+    bd->PrevWndProc = (WNDPROC)::GetWindowLongPtrW(hwnd, GWLP_WNDPROC);
     IM_ASSERT(bd->PrevWndProc != nullptr);
     ::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)ImGui_ImplGlfw_WndProc);
 #endif
@@ -721,7 +745,7 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
 #if EMSCRIPTEN_USE_PORT_CONTRIB_GLFW3 >= 34020240817
     if (emscripten::glfw3::IsRuntimePlatformApple())
     {
-        ImGui::GetIO().ConfigMacOSXBehaviors = true;
+        io.ConfigMacOSXBehaviors = true;
 
         // Due to how the browser (poorly) handles the Meta Key, this line essentially disables repeats when used.
         // This means that Meta + V only registers a single key-press, even if the keys are held.
@@ -772,6 +796,7 @@ void ImGui_ImplGlfw_Shutdown()
     // Windows: restore our WndProc hook
 #ifdef _WIN32
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
+    ::SetPropA((HWND)main_viewport->PlatformHandleRaw, "IMGUI_BACKEND_DATA", nullptr);
     ::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)bd->PrevWndProc);
     bd->PrevWndProc = nullptr;
 #endif
@@ -779,6 +804,7 @@ void ImGui_ImplGlfw_Shutdown()
     io.BackendPlatformName = nullptr;
     io.BackendPlatformUserData = nullptr;
     io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_PlatformHasViewports | ImGuiBackendFlags_HasMouseHoveredViewport);
+    ImGui_ImplGlfw_ContextMap_Remove(bd->Window);
     IM_DELETE(bd);
 }
 
@@ -1083,7 +1109,7 @@ void ImGui_ImplGlfw_InstallEmscriptenCallbacks(GLFWwindow*, const char* canvas_s
     // Register Emscripten Wheel callback to workaround issue in Emscripten GLFW Emulation (#6096)
     // We intentionally do not check 'if (install_callbacks)' here, as some users may set it to false and call GLFW callback themselves.
     // FIXME: May break chaining in case user registered their own Emscripten callback?
-    emscripten_set_wheel_callback(bd->CanvasSelector, nullptr, false, ImGui_ImplEmscripten_WheelCallback);
+    emscripten_set_wheel_callback(bd->CanvasSelector, bd, false, ImGui_ImplEmscripten_WheelCallback);
 }
 #elif defined(EMSCRIPTEN_USE_PORT_CONTRIB_GLFW3)
 // When using --use-port=contrib.glfw3 for the GLFW implementation, you can override the behavior of this call
@@ -1467,7 +1493,9 @@ static ImGuiMouseSource GetMouseSourceFromMessageExtraInfo()
 }
 static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
 {
-    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data*)::GetPropA(hWnd, "IMGUI_BACKEND_DATA");
+    ImGuiIO& io = ImGui::GetIO(bd->Context);
+
     WNDPROC prev_wndproc = bd->PrevWndProc;
     ImGuiViewport* viewport = (ImGuiViewport*)::GetPropA(hWnd, "IMGUI_VIEWPORT");
     if (viewport != NULL)
@@ -1483,7 +1511,7 @@ static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wPara
     case WM_RBUTTONDOWN: case WM_RBUTTONDBLCLK: case WM_RBUTTONUP:
     case WM_MBUTTONDOWN: case WM_MBUTTONDBLCLK: case WM_MBUTTONUP:
     case WM_XBUTTONDOWN: case WM_XBUTTONDBLCLK: case WM_XBUTTONUP:
-        ImGui::GetIO().AddMouseSourceEvent(GetMouseSourceFromMessageExtraInfo());
+        io.AddMouseSourceEvent(GetMouseSourceFromMessageExtraInfo());
         break;
 
         // We have submitted https://github.com/glfw/glfw/pull/1568 to allow GLFW to support "transparent inputs".

backends/imgui_impl_glfw.h

@@ -10,6 +10,7 @@
 //  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [X] Platform: Mouse cursor shape and visibility (ImGuiBackendFlags_HasMouseCursors). Resizing cursors requires GLFW 3.4+! Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
 //  [X] Platform: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
+//  [X] Multiple Dear ImGui contexts support.
 // Missing features or Issues:
 //  [ ] Touch events are only correctly identified as Touch on Windows. This create issues with some interactions. GLFW doesn't provide a way to identify touch inputs from mouse inputs, we cannot call io.AddMouseSourceEvent() to identify the source. We provide a Windows-specific workaround.
 //  [ ] Missing ImGuiMouseCursor_Wait and ImGuiMouseCursor_Progress cursors.

docs/CHANGELOG.txt

@@ -410,6 +410,7 @@ Other changes:
   - Backends: GLFW: added ImGui_ImplGlfw_GetContentScaleForMonitor(), ImGui_ImplGlfw_GetContentScaleForWindow()
     helpers. They are wrappers to glfwGetMonitorContentScale()/glfwGetWindowContentScale(), with compile-time
     GLFW version checks + returning 1.0f on Apple platform.
+  - Backends: GLFW: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)
   - Backends: SDL2: added ImGui_ImplSDL2_GetDpiScaleForDisplay() and ImGui_ImplSDL2_GetContentScaleForWindow()
     helpers. They are wrappers to SDL_GetDisplayDPI(), with compile-time SDL version checks + returning 1.0f
     on Apple platforms. SDL3 already does this by default.

docs/TODO.txt

@@ -324,7 +324,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - nav/windowing: Resizing window will currently fail with certain types of resizing constraints/callback applied
  - focus: preserve ActiveId/focus stack state, e.g. when opening a menu and close it, previously selected InputText() focus gets restored (#622)
 
- - viewport: make it possible to have no main/hosting viewport
+ - viewport: make it possible to have no main/hosting viewport (see #8268)
  - viewport: We set ImGuiViewportFlags_NoFocusOnAppearing in a way that is required for GLFW/SDL binding, but could be handled better without
    on a custom e.g. Win32 bindings. It prevents newly dragged-out viewports from taking the focus, which makes ALT+F4 more ambiguous.
  - viewport: not focusing newly undocked viewport means clicking back on previous one doesn't bring OS window to front.
@@ -333,6 +333,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - viewport: store per-viewport/monitor DPI in .ini file so an application reload or main window changing DPI on reload can be properly patched for.
  - viewport: implicit/fallback Debug window can hog a zombie viewport (harmless, noisy?) > could at least clear out the reference on a per session basis?
  - viewport: need to clarify how to use GetMousePos() from a user point of view.
+ - viewport: could apply monitor boundaries to cliprect to coarse clip things out of monitor? (#8698)
  - platform: glfw: no support for ImGuiBackendFlags_HasMouseHoveredViewport.
  - platform: sdl: no support for ImGuiBackendFlags_HasMouseHoveredViewport. maybe we could use SDL_GetMouseFocus() / SDL_WINDOW_MOUSE_FOCUS if imgui could fallback on its heuristic when NoInputs is set
  - platform: sdl: no refresh of monitor/display (SDL doesn't seem to have an event for it).

misc/freetype/imgui_freetype.cpp

@@ -346,7 +346,7 @@ static void* FreeType_Realloc(FT_Memory /*memory*/, long cur_size, long new_size
 
 bool ImGui_ImplFreeType_LoaderInit(ImFontAtlas* atlas)
 {
-    IM_ASSERT(atlas->FontLoaderData == NULL);
+    IM_ASSERT(atlas->FontLoaderData == nullptr);
     ImGui_ImplFreeType_Data* bd = IM_NEW(ImGui_ImplFreeType_Data)();
 
     // FreeType memory management: https://www.freetype.org/freetype2/docs/design/design-4.html
@@ -387,23 +387,23 @@ bool ImGui_ImplFreeType_LoaderInit(ImFontAtlas* atlas)
 void ImGui_ImplFreeType_LoaderShutdown(ImFontAtlas* atlas)
 {
     ImGui_ImplFreeType_Data* bd = (ImGui_ImplFreeType_Data*)atlas->FontLoaderData;
-    IM_ASSERT(bd != NULL);
+    IM_ASSERT(bd != nullptr);
     FT_Done_Library(bd->Library);
     IM_DELETE(bd);
-    atlas->FontLoaderData = NULL;
+    atlas->FontLoaderData = nullptr;
 }
 
 bool ImGui_ImplFreeType_FontSrcInit(ImFontAtlas* atlas, ImFontConfig* src)
 {
     ImGui_ImplFreeType_Data* bd = (ImGui_ImplFreeType_Data*)atlas->FontLoaderData;
     ImGui_ImplFreeType_FontSrcData* bd_font_data = IM_NEW(ImGui_ImplFreeType_FontSrcData);
-    IM_ASSERT(src->FontLoaderData == NULL);
+    IM_ASSERT(src->FontLoaderData == nullptr);
     src->FontLoaderData = bd_font_data;
 
     if (!bd_font_data->InitFont(bd->Library, src, (ImGuiFreeTypeLoaderFlags)atlas->FontLoaderFlags))
     {
         IM_DELETE(bd_font_data);
-        src->FontLoaderData = NULL;
+        src->FontLoaderData = nullptr;
         return false;
     }
 
@@ -415,7 +415,7 @@ void ImGui_ImplFreeType_FontSrcDestroy(ImFontAtlas* atlas, ImFontConfig* src)
     IM_UNUSED(atlas);
     ImGui_ImplFreeType_FontSrcData* bd_font_data = (ImGui_ImplFreeType_FontSrcData*)src->FontLoaderData;
     IM_DELETE(bd_font_data);
-    src->FontLoaderData = NULL;
+    src->FontLoaderData = nullptr;
 }
 
 bool ImGui_ImplFreeType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig* src, ImFontBaked* baked, void* loader_data_for_baked_src)
@@ -430,7 +430,7 @@ bool ImGui_ImplFreeType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig* src, ImF
 
     // We use one FT_Size per (source + baked) combination.
     ImGui_ImplFreeType_FontSrcBakedData* bd_baked_data = (ImGui_ImplFreeType_FontSrcBakedData*)loader_data_for_baked_src;
-    IM_ASSERT(bd_baked_data != NULL);
+    IM_ASSERT(bd_baked_data != nullptr);
     IM_PLACEMENT_NEW(bd_baked_data) ImGui_ImplFreeType_FontSrcBakedData();
 
     FT_New_Size(bd_font_data->FtFace, &bd_baked_data->FtSize);
@@ -470,7 +470,7 @@ void ImGui_ImplFreeType_FontBakedDestroy(ImFontAtlas* atlas, ImFontConfig* src,
     IM_UNUSED(baked);
     IM_UNUSED(src);
     ImGui_ImplFreeType_FontSrcBakedData* bd_baked_data = (ImGui_ImplFreeType_FontSrcBakedData*)loader_data_for_baked_src;
-    IM_ASSERT(bd_baked_data != NULL);
+    IM_ASSERT(bd_baked_data != nullptr);
     FT_Done_Size(bd_baked_data->FtSize);
     bd_baked_data->~ImGui_ImplFreeType_FontSrcBakedData(); // ~IM_PLACEMENT_DELETE()
 }
@@ -491,7 +491,7 @@ bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConfig* src
     }
 
     const FT_Glyph_Metrics* metrics = ImGui_ImplFreeType_LoadGlyph(bd_font_data, codepoint);
-    if (metrics == NULL)
+    if (metrics == nullptr)
         return false;
 
     // Render glyph into a bitmap (currently held by FreeType)