Backends: SDL: Update mouse inputs using SDL_MOUSEMOTION/SDL_WINDOWEVENT_LEAVE + fallback to provide it when focused but not hovered/captured + update MousePos before MouseButtons.

backends/imgui_impl_sdl.cpp

@@ -18,6 +18,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2022-01-12: Update mouse inputs using SDL_MOUSEMOTION/SDL_WINDOWEVENT_LEAVE + fallback to provide it when focused but not hovered/captured. More standard and will allow us to pass it to future input queue API.
 //  2022-01-12: Maintain our own copy of MouseButtonsDown mask instead of using ImGui::IsAnyMouseDown() which will be obsoleted.
 //  2022-01-10: Inputs: calling new io.AddKeyEvent(), io.AddKeyModsEvent() + io.SetKeyEventNativeData() API (1.87+). Support for full ImGuiKey range.
 //  2021-08-17: Calling io.AddFocusEvent() on SDL_WINDOWEVENT_FOCUS_GAINED/SDL_WINDOWEVENT_FOCUS_LOST.
@@ -233,6 +234,11 @@ bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
 
     switch (event->type)
     {
+        case SDL_MOUSEMOTION:
+        {
+            io.MousePos = ImVec2((float)event->motion.x, (float)event->motion.y);
+            return true;
+        }
         case SDL_MOUSEWHEEL:
         {
             if (event->wheel.x > 0) io.MouseWheelH += 1;
@@ -270,6 +276,8 @@ bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
         }
         case SDL_WINDOWEVENT:
         {
+            if (event->window.event == SDL_WINDOWEVENT_LEAVE)
+                io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
             if (event->window.event == SDL_WINDOWEVENT_FOCUS_GAINED)
                 io.AddFocusEvent(true);
             else if (event->window.event == SDL_WINDOWEVENT_FOCUS_LOST)
@@ -391,61 +399,42 @@ void ImGui_ImplSDL2_Shutdown()
     IM_DELETE(bd);
 }
 
-static void ImGui_ImplSDL2_UpdateMousePosAndButtons()
+static void ImGui_ImplSDL2_UpdateMouseData()
 {
     ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
     ImGuiIO& io = ImGui::GetIO();
 
-    ImVec2 mouse_pos_prev = io.MousePos;
-    io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
-
-    // Update mouse buttons
-    int mouse_x_local, mouse_y_local;
-    Uint32 mouse_buttons = SDL_GetMouseState(&mouse_x_local, &mouse_y_local);
-    io.MouseDown[0] = bd->MousePressed[0] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0;  // 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.
-    io.MouseDown[1] = bd->MousePressed[1] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
-    io.MouseDown[2] = bd->MousePressed[2] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
-    bd->MousePressed[0] = bd->MousePressed[1] = bd->MousePressed[2] = false;
-
-    // Obtain focused and hovered window. We forward mouse input when focused or when hovered (and no other window is capturing)
+    // We forward mouse input when hovered or captured (via SDL_MOUSEMOTION) or when focused (below)
 #if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
-    SDL_Window* focused_window = SDL_GetKeyboardFocus();
-    SDL_Window* hovered_window = SDL_HAS_MOUSE_FOCUS_CLICKTHROUGH ? SDL_GetMouseFocus() : NULL; // This is better but is only reliably useful with SDL 2.0.5+ and SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH.
-    SDL_Window* mouse_window = NULL;
-    if (hovered_window && bd->Window == hovered_window)
-        mouse_window = hovered_window;
-    else if (focused_window && bd->Window == focused_window)
-        mouse_window = focused_window;
-
     // SDL_CaptureMouse() let the OS know e.g. that our imgui drag outside the SDL window boundaries shouldn't e.g. trigger other operations outside
     SDL_CaptureMouse(bd->MouseButtonsDown != 0 ? SDL_TRUE : SDL_FALSE);
+    SDL_Window* focused_window = SDL_GetKeyboardFocus();
+    const bool is_app_focused = (bd->Window == focused_window);
 #else
-    // SDL 2.0.3 and non-windowed systems: single-viewport only
-    SDL_Window* mouse_window = (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_INPUT_FOCUS) ? bd->Window : NULL;
+    const bool is_app_focused = (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_INPUT_FOCUS) != 0; // SDL 2.0.3 and non-windowed systems: single-viewport only
 #endif
-
-    if (mouse_window == NULL)
-       return;
-
-    // Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
-    if (io.WantSetMousePos)
-        SDL_WarpMouseInWindow(bd->Window, (int)mouse_pos_prev.x, (int)mouse_pos_prev.y);
-
-    // Set Dear ImGui mouse position from OS position + get buttons. (this is the common behavior)
-    if (bd->MouseCanUseGlobalState)
-    {
-        // Single-viewport mode: mouse position in client window coordinates (io.MousePos is (0,0) when the mouse is on the upper-left corner of the app window)
-        // Unlike local position obtained earlier this will be valid when straying out of bounds.
-        int mouse_x_global, mouse_y_global;
-        SDL_GetGlobalMouseState(&mouse_x_global, &mouse_y_global);
-        int window_x, window_y;
-        SDL_GetWindowPosition(mouse_window, &window_x, &window_y);
-        io.MousePos = ImVec2((float)(mouse_x_global - window_x), (float)(mouse_y_global - window_y));
-    }
-    else
+    if (is_app_focused)
     {
-        io.MousePos = ImVec2((float)mouse_x_local, (float)mouse_y_local);
+        // (Optional) Set OS mouse position from Dear ImGui if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
+        if (io.WantSetMousePos)
+            SDL_WarpMouseInWindow(bd->Window, (int)io.MousePos.x, (int)io.MousePos.y);
+
+        // (Optional) Fallback to provide mouse position when focused (SDL_MOUSEMOTION already provides this when hovered or captured)
+        if (bd->MouseCanUseGlobalState && bd->MouseButtonsDown == 0)
+        {
+            int window_x, window_y, mouse_x_global, mouse_y_global;
+            SDL_GetGlobalMouseState(&mouse_x_global, &mouse_y_global);
+            SDL_GetWindowPosition(focused_window, &window_x, &window_y);
+            io.MousePos = ImVec2((float)(mouse_x_global - window_x), (float)(mouse_y_global - window_y));
+        }
     }
+
+    // Update buttons
+    Uint32 mouse_buttons = SDL_GetMouseState(NULL, NULL);
+    io.MouseDown[0] = bd->MousePressed[0] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0;  // 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.
+    io.MouseDown[1] = bd->MousePressed[1] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
+    io.MouseDown[2] = bd->MousePressed[2] || (mouse_buttons & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
+    bd->MousePressed[0] = bd->MousePressed[1] = bd->MousePressed[2] = false;
 }
 
 static void ImGui_ImplSDL2_UpdateMouseCursor()
@@ -545,10 +534,8 @@ void ImGui_ImplSDL2_NewFrame()
     io.DeltaTime = bd->Time > 0 ? (float)((double)(current_time - bd->Time) / frequency) : (float)(1.0f / 60.0f);
     bd->Time = current_time;
 
-    // Update key modifiers
     ImGui_ImplSDL2_UpdateKeyModifiers();
-
-    ImGui_ImplSDL2_UpdateMousePosAndButtons();
+    ImGui_ImplSDL2_UpdateMouseData();
     ImGui_ImplSDL2_UpdateMouseCursor();
 
     // Update game controllers (if enabled and available)

docs/CHANGELOG.txt

@@ -99,6 +99,7 @@ Other Changes:
 - 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.
+- Backends: SDL: Update mouse position using SDL_MOUSEMOTION/SDL_WINDOWEVENT_LEAVE + fallback when focused but not hovered/captured.
 - Backends: SDL: Maintain a MouseButtonsDown mask instead of using ImGui::IsAnyMouseDown() which will be obsoleted.
 - Backends: Allegro5, GLFW, GLUT, SDL, OSX, Win32, Android: Updated to use io.AddKeyEvent() with full key range. (#2625) [@thedmd]
 - Backends: OpenGL3: Fixed a buffer overflow in imgui_impl_opengl3_loader.h init (added in 1.86). (#4468, #4830) [@dymk]