Backends: GLFW: enable ImGuiBackendFlags_HasMouseHoveredViewport supp…

…ort with GLFW 3.3.x. (#7316)

backends/imgui_impl_glfw.cpp

@@ -581,7 +581,7 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
 #ifndef __EMSCRIPTEN__
     io.BackendFlags |= ImGuiBackendFlags_PlatformHasViewports;    // We can create multi-viewports on the Platform side (optional)
 #endif
-#if GLFW_HAS_MOUSE_PASSTHROUGH || (GLFW_HAS_WINDOW_HOVERED && defined(_WIN32))
+#if GLFW_HAS_MOUSE_PASSTHROUGH || GLFW_HAS_WINDOW_HOVERED
     io.BackendFlags |= ImGuiBackendFlags_HasMouseHoveredViewport; // We can call io.AddMouseViewportEvent() with correct data (optional)
 #endif
 
@@ -748,20 +748,21 @@ static void ImGui_ImplGlfw_UpdateMouseData()
 
         // (Optional) When using multiple viewports: call io.AddMouseViewportEvent() with the viewport the OS mouse cursor is hovering.
         // If ImGuiBackendFlags_HasMouseHoveredViewport is not set by the backend, Dear imGui will ignore this field and infer the information using its flawed heuristic.
-        // - [X] GLFW >= 3.3 backend ON WINDOWS ONLY does correctly ignore viewports with the _NoInputs flag.
+        // - [X] GLFW >= 3.3 backend ON WINDOWS ONLY does correctly ignore viewports with the _NoInputs flag (since we implement hit via our WndProc hook)
+        //       On other platforms we rely on the library fallbacking to its own search when reporting a viewport with _NoInputs flag.
         // - [!] GLFW <= 3.2 backend CANNOT correctly ignore viewports with the _NoInputs flag, and CANNOT reported Hovered Viewport because of mouse capture.
         //       Some backend are not able to handle that correctly. If a backend report an hovered viewport that has the _NoInputs flag (e.g. when dragging a window
         //       for docking, the viewport has the _NoInputs flag in order to allow us to find the viewport under), then Dear ImGui is forced to ignore the value reported
         //       by the backend, and use its flawed heuristic to guess the viewport behind.
         // - [X] GLFW backend correctly reports this regardless of another viewport behind focused and dragged from (we need this to find a useful drag and drop target).
         // FIXME: This is currently only correct on Win32. See what we do below with the WM_NCHITTEST, missing an equivalent for other systems.
         // See https://github.com/glfw/glfw/issues/1236 if you want to help in making this a GLFW feature.
-#if GLFW_HAS_MOUSE_PASSTHROUGH || (GLFW_HAS_WINDOW_HOVERED && defined(_WIN32))
-        const bool window_no_input = (viewport->Flags & ImGuiViewportFlags_NoInputs) != 0;
 #if GLFW_HAS_MOUSE_PASSTHROUGH
+        const bool window_no_input = (viewport->Flags & ImGuiViewportFlags_NoInputs) != 0;
         glfwSetWindowAttrib(window, GLFW_MOUSE_PASSTHROUGH, window_no_input);
 #endif
-        if (glfwGetWindowAttrib(window, GLFW_HOVERED) && !window_no_input)
+#if GLFW_HAS_MOUSE_PASSTHROUGH || GLFW_HAS_WINDOW_HOVERED
+        if (glfwGetWindowAttrib(window, GLFW_HOVERED))
             mouse_viewport_id = viewport->ID;
 #else
         // We cannot use bd->MouseWindow maintained from CursorEnter/Leave callbacks, because it is locked to the window capturing mouse.

docs/CHANGELOG.txt

@@ -35,6 +35,22 @@ HOW TO UPDATE?
   and API updates have been a little more frequent lately. They are documented below and in imgui.cpp and should not affect all users.
 - Please report any issue!
 
+-----------------------------------------------------------------------
+ VERSION 1.90.4 (In Progress)
+-----------------------------------------------------------------------
+
+Breaking changes:
+
+Other changes:
+
+Docking+Viewports Branch:
+
+- Backends: GLFW: enable ImGuiBackendFlags_HasMouseHoveredViewport support with GLFW 3.3.x,
+  as required specs for it was relaxed in 1.87. This enable better viewport hovering detection
+  without GLFW 3.4's GLFW_MOUSE_PASSTHROUGH, with less reliance on dear imgui's own heuristic
+  of platform windows order. (#7316)
+
+
 -----------------------------------------------------------------------
  VERSION 1.90.3 (Released 2024-02-14)
 -----------------------------------------------------------------------