Backends: GLFW: Update mouse inputs using glfwSetCursorPosCallback() (breaking) + fallback to provide it when focused but not hovered/captured + update MousePos before MouseButtons.

+ Allegro5 remove unnecessary clear.

backends/imgui_impl_allegro5.cpp

@@ -414,8 +414,6 @@ bool ImGui_ImplAllegro5_Init(ALLEGRO_DISPLAY* display)
     };
     bd->VertexDecl = al_create_vertex_decl(elems, sizeof(ImDrawVertAllegro));
 
-    io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
-
 #if ALLEGRO_HAS_CLIPBOARD
     io.SetClipboardTextFn = ImGui_ImplAllegro5_SetClipboardText;
     io.GetClipboardTextFn = ImGui_ImplAllegro5_GetClipboardText;

backends/imgui_impl_glfw.cpp

@@ -16,6 +16,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2022-01-12: *BREAKING CHANGE*: Now using glfwSetCursorPosCallback(). If you called ImGui_ImplGlfw_InitXXX() with install_callbacks = false, you MUST install glfwSetCursorPosCallback() and forward it to the backend via ImGui_ImplGlfw_CursorPosCallback().
 //  2022-01-10: Inputs: calling new io.AddKeyEvent(), io.AddKeyModsEvent() + io.SetKeyEventNativeData() API (1.87+). Support for full ImGuiKey range.
 //  2022-01-05: Inputs: Converting GLFW untranslated keycodes back to translated keycodes (in the ImGui_ImplGlfw_KeyCallback() function) in order to match the behavior of every other backend, and facilitate the use of GLFW with lettered-shortcuts API.
 //  2021-08-17: *BREAKING CHANGE*: Now using glfwSetWindowFocusCallback() to calling io.AddFocusEvent(). If you called ImGui_ImplGlfw_InitXXX() with install_callbacks = false, you MUST install glfwSetWindowFocusCallback() and forward it to the backend via ImGui_ImplGlfw_WindowFocusCallback().
@@ -90,6 +91,7 @@ struct ImGui_ImplGlfw_Data
 
     // Chain GLFW callbacks: our callbacks will call the user's previously installed callbacks, if any.
     GLFWwindowfocusfun      PrevUserCallbackWindowFocus;
+    GLFWcursorposfun        PrevUserCallbackCursorPos;
     GLFWcursorenterfun      PrevUserCallbackCursorEnter;
     GLFWmousebuttonfun      PrevUserCallbackMousebutton;
     GLFWscrollfun           PrevUserCallbackScroll;
@@ -307,16 +309,30 @@ void ImGui_ImplGlfw_WindowFocusCallback(GLFWwindow* window, int focused)
     io.AddFocusEvent(focused != 0);
 }
 
+void ImGui_ImplGlfw_CursorPosCallback(GLFWwindow* window, double x, double y)
+{
+    ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
+    if (bd->PrevUserCallbackCursorPos != NULL && window == bd->Window)
+        bd->PrevUserCallbackCursorPos(window, x, y);
+
+    ImGuiIO& io = ImGui::GetIO();
+    io.MousePos = ImVec2((float)x, (float)y);
+}
+
 void ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered)
 {
     ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
     if (bd->PrevUserCallbackCursorEnter != NULL && window == bd->Window)
         bd->PrevUserCallbackCursorEnter(window, entered);
 
+    ImGuiIO& io = ImGui::GetIO();
     if (entered)
         bd->MouseWindow = window;
     if (!entered && bd->MouseWindow == window)
+    {
         bd->MouseWindow = NULL;
+        io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
+    }
 }
 
 void ImGui_ImplGlfw_CharCallback(GLFWwindow* window, unsigned int c)
@@ -394,6 +410,7 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
         bd->InstalledCallbacks = true;
         bd->PrevUserCallbackWindowFocus = glfwSetWindowFocusCallback(window, ImGui_ImplGlfw_WindowFocusCallback);
         bd->PrevUserCallbackCursorEnter = glfwSetCursorEnterCallback(window, ImGui_ImplGlfw_CursorEnterCallback);
+        bd->PrevUserCallbackCursorPos = glfwSetCursorPosCallback(window, ImGui_ImplGlfw_CursorPosCallback);
         bd->PrevUserCallbackMousebutton = glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
         bd->PrevUserCallbackScroll = glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
         bd->PrevUserCallbackKey = glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
@@ -430,6 +447,7 @@ void ImGui_ImplGlfw_Shutdown()
     {
         glfwSetWindowFocusCallback(bd->Window, bd->PrevUserCallbackWindowFocus);
         glfwSetCursorEnterCallback(bd->Window, bd->PrevUserCallbackCursorEnter);
+        glfwSetCursorPosCallback(bd->Window, bd->PrevUserCallbackCursorPos);
         glfwSetMouseButtonCallback(bd->Window, bd->PrevUserCallbackMousebutton);
         glfwSetScrollCallback(bd->Window, bd->PrevUserCallbackScroll);
         glfwSetKeyCallback(bd->Window, bd->PrevUserCallbackKey);
@@ -445,40 +463,37 @@ void ImGui_ImplGlfw_Shutdown()
     IM_DELETE(bd);
 }
 
-static void ImGui_ImplGlfw_UpdateMousePosAndButtons()
+static void ImGui_ImplGlfw_UpdateMouseData()
 {
     ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
     ImGuiIO& io = ImGui::GetIO();
 
-    const ImVec2 mouse_pos_prev = io.MousePos;
-    io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
+#ifdef __EMSCRIPTEN__
+    const bool is_app_focused = true;
+#else
+    const bool is_app_focused = glfwGetWindowAttrib(bd->Window, GLFW_FOCUSED) != 0;
+#endif
+    if (is_app_focused)
+    {
+        // (Optional) Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
+        if (io.WantSetMousePos)
+            glfwSetCursorPos(bd->Window, (double)io.MousePos.x, (double)io.MousePos.y);
 
-    // Update mouse buttons
-    // (if a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame)
+        // (Optional) Fallback to provide mouse position when focused (ImGui_ImplGlfw_CursorPosCallback already provides this when hovered or captured)
+        if (is_app_focused && bd->MouseWindow == NULL)
+        {
+            double mouse_x, mouse_y;
+            glfwGetCursorPos(bd->Window, &mouse_x, &mouse_y);
+            io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);
+        }
+    }
+
+    // Update buttons
     for (int i = 0; i < IM_ARRAYSIZE(io.MouseDown); i++)
     {
         io.MouseDown[i] = bd->MouseJustPressed[i] || glfwGetMouseButton(bd->Window, i) != 0;
         bd->MouseJustPressed[i] = false;
     }
-
-#ifdef __EMSCRIPTEN__
-    const bool focused = true;
-#else
-    const bool focused = glfwGetWindowAttrib(bd->Window, GLFW_FOCUSED) != 0;
-#endif
-    GLFWwindow* mouse_window = (bd->MouseWindow == bd->Window || focused) ? bd->Window : NULL;
-
-    // Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
-    if (io.WantSetMousePos && focused)
-        glfwSetCursorPos(bd->Window, (double)mouse_pos_prev.x, (double)mouse_pos_prev.y);
-
-    // Set Dear ImGui mouse position from OS position
-    if (mouse_window != NULL)
-    {
-        double mouse_x, mouse_y;
-        glfwGetCursorPos(mouse_window, &mouse_x, &mouse_y);
-        io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);
-    }
 }
 
 static void ImGui_ImplGlfw_UpdateMouseCursor()
@@ -572,10 +587,8 @@ void ImGui_ImplGlfw_NewFrame()
     io.DeltaTime = bd->Time > 0.0 ? (float)(current_time - bd->Time) : (float)(1.0f / 60.0f);
     bd->Time = current_time;
 
-    // Update key modifiers
     ImGui_ImplGlfw_UpdateKeyModifiers();
-
-    ImGui_ImplGlfw_UpdateMousePosAndButtons();
+    ImGui_ImplGlfw_UpdateMouseData();
     ImGui_ImplGlfw_UpdateMouseCursor();
 
     // Update game controllers (if enabled and available)

backends/imgui_impl_glfw.h

@@ -32,8 +32,9 @@ IMGUI_IMPL_API void     ImGui_ImplGlfw_NewFrame();
 // GLFW callbacks
 // - When calling Init with 'install_callbacks=true': GLFW callbacks will be installed for you. They will call user's previously installed callbacks, if any.
 // - When calling Init with 'install_callbacks=false': GLFW callbacks won't be installed. You will need to call those function yourself from your own GLFW callbacks.
-IMGUI_IMPL_API void     ImGui_ImplGlfw_WindowFocusCallback(GLFWwindow* window, int focused);
-IMGUI_IMPL_API void     ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered);
+IMGUI_IMPL_API void     ImGui_ImplGlfw_WindowFocusCallback(GLFWwindow* window, int focused);        // Since 1.84
+IMGUI_IMPL_API void     ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered);        // Since 1.84
+IMGUI_IMPL_API void     ImGui_ImplGlfw_CursorPosCallback(GLFWwindow* window, double x, double y);   // Since 1.87
 IMGUI_IMPL_API void     ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow* window, int button, int action, int mods);
 IMGUI_IMPL_API void     ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset);
 IMGUI_IMPL_API void     ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods);

docs/CHANGELOG.txt

@@ -66,6 +66,10 @@ Breaking Changes:
      - io.AddKeyEvent() will later be turned into a trickling IO queue (for all inputs) to handle very low framerate better. (#2525, #2787, #3383)
      - io.SetKeyEventNativeData() include native keycode/scancode which will later be exposed. (#3141, #2959)
 - Renamed ImGuiKey_KeyPadEnter to ImGuiKey_KeypadEnter to align with new symbols. Kept redirection enum. (#2625)
+- Backends: GLFW: backend now uses glfwSetCursorPosCallback().
+  - If calling ImGui_ImplGlfw_InitXXX with install_callbacks=true: nothing to do. is already done for you.
+  - If calling ImGui_ImplGlfw_InitXXX with install_callbacks=false: you WILL NEED to register the GLFW callback
+    using glfwSetCursorPosCallback() and forward it to the backend function ImGui_ImplGlfw_CursorPosCallback().
 - Commented out redirecting functions/enums names that were marked obsolete in 1.69, 1.70, 1.71, 1.72 (March-July 2019)
   - ImGui::SetNextTreeNodeOpen()        -> use ImGui::SetNextItemOpen()
   - ImGui::GetContentRegionAvailWidth() -> use ImGui::GetContentRegionAvail().x
@@ -96,6 +100,7 @@ Other Changes:
 - Backends: GLFW: Pass localized keys (matching keyboard layout). Fix e.g. CTRL+A, CTRL+Z, CTRL+Y shortcuts.
   We are now converting GLFW untranslated keycodes back to translated keycodes in order to match the behavior of every
   other backend, and facilitate the use of GLFW with lettered-shortcuts API. (#456, #2625)
+- Backends: GLFW: Update mouse position using glfwSetCursorPosCallback() + fallback when focused but not hovered/captured.
 - Backends: Win32: Update mouse position using WM_MOUSEMOVE/WM_MOUSELEAVE + fallback when focused but not hovered/captured.
 - Backends: Win32: Maintain a MouseButtonsDown mask instead of using ImGui::IsAnyMouseDown() which will be obsoleted.
 - Backends: SDL: Pass localized keys (matching keyboard layout). Fix e.g. CTRL+A, CTRL+Z, CTRL+Y shortcuts.