Backends: SDL2, SDL3: don't attempt to call SDL_CaptureMouse() on drivers where we don't call SDL_GetGlobalMouseState(). (#8561)

backends/imgui_impl_sdl2.cpp

@@ -21,6 +21,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-04-09: Don't attempt to call SDL_CaptureMouse() on drivers where we don't call SDL_GetGlobalMouseState(). (#8561)
 //  2025-03-21: Fill gamepad inputs and set ImGuiBackendFlags_HasGamepad regardless of ImGuiConfigFlags_NavEnableGamepad being set.
 //  2025-03-10: When dealing with OEM keys, use scancodes instead of translated keycodes to choose ImGuiKey values. (#7136, #7201, #7206, #7306, #7670, #7672, #8468)
 //  2025-02-26: Only start SDL_CaptureMouse() when mouse is being dragged, to mitigate issues with e.g.Linux debuggers not claiming capture back. (#6410, #3650)
@@ -142,6 +143,7 @@ struct ImGui_ImplSDL2_Data
     SDL_Cursor*             MouseLastCursor;
     int                     MouseLastLeaveFrame;
     bool                    MouseCanUseGlobalState;
+    bool                    MouseCanUseCapture;
 
     // Gamepad handling
     ImVector<SDL_GameController*> Gamepads;
@@ -474,17 +476,6 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window, SDL_Renderer* renderer, void
     IMGUI_CHECKVERSION();
     IM_ASSERT(io.BackendPlatformUserData == nullptr && "Already initialized a platform backend!");
 
-    // Check and store if we are on a SDL backend that supports global mouse position
-    // ("wayland" and "rpi" don't support it, but we chose to use a white-list instead of a black-list)
-    bool mouse_can_use_global_state = false;
-#if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
-    const char* sdl_backend = SDL_GetCurrentVideoDriver();
-    const char* global_mouse_whitelist[] = { "windows", "cocoa", "x11", "DIVE", "VMAN" };
-    for (int n = 0; n < IM_ARRAYSIZE(global_mouse_whitelist); n++)
-        if (strncmp(sdl_backend, global_mouse_whitelist[n], strlen(global_mouse_whitelist[n])) == 0)
-            mouse_can_use_global_state = true;
-#endif
-
     // Setup backend capabilities flags
     ImGui_ImplSDL2_Data* bd = IM_NEW(ImGui_ImplSDL2_Data)();
     io.BackendPlatformUserData = (void*)bd;
@@ -495,7 +486,18 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window, SDL_Renderer* renderer, void
     bd->Window = window;
     bd->WindowID = SDL_GetWindowID(window);
     bd->Renderer = renderer;
-    bd->MouseCanUseGlobalState = mouse_can_use_global_state;
+
+    // Check and store if we are on a SDL backend that supports SDL_GetGlobalMouseState() and SDL_CaptureMouse()
+    // ("wayland" and "rpi" don't support it, but we chose to use a white-list instead of a black-list)
+    bd->MouseCanUseGlobalState = false;
+    bd->MouseCanUseCapture = false;
+#if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
+    const char* sdl_backend = SDL_GetCurrentVideoDriver();
+    const char* capture_and_global_state_whitelist[] = { "windows", "cocoa", "x11", "DIVE", "VMAN" };
+    for (const char* item : capture_and_global_state_whitelist)
+        if (strncmp(sdl_backend, item, strlen(item)) == 0)
+            bd->MouseCanUseGlobalState = bd->MouseCanUseCapture = true;
+#endif
 
     ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
     platform_io.Platform_SetClipboardTextFn = ImGui_ImplSDL2_SetClipboardText;
@@ -630,12 +632,15 @@ static void ImGui_ImplSDL2_UpdateMouseData()
     // We forward mouse input when hovered or captured (via SDL_MOUSEMOTION) or when focused (below)
 #if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
     // - SDL_CaptureMouse() let the OS know e.g. that our drags can extend outside of parent boundaries (we want updated position) and shouldn't trigger other operations outside.
-    // - Debuggers under Linux tends to leave captured mouse on break, which may be very inconvenient, so to migitate the issue we wait until mouse has moved to begin capture.
-    bool want_capture = false;
-    for (int button_n = 0; button_n < ImGuiMouseButton_COUNT && !want_capture; button_n++)
-        if (ImGui::IsMouseDragging(button_n, 1.0f))
-            want_capture = true;
-    SDL_CaptureMouse(want_capture ? SDL_TRUE : SDL_FALSE);
+    // - Debuggers under Linux tends to leave captured mouse on break, which may be very inconvenient, so to mitigate the issue we wait until mouse has moved to begin capture.
+    if (bd->MouseCanUseCapture)
+    {
+        bool want_capture = false;
+        for (int button_n = 0; button_n < ImGuiMouseButton_COUNT && !want_capture; button_n++)
+            if (ImGui::IsMouseDragging(button_n, 1.0f))
+                want_capture = true;
+        SDL_CaptureMouse(want_capture ? SDL_TRUE : SDL_FALSE);
+    }
 
     SDL_Window* focused_window = SDL_GetKeyboardFocus();
     const bool is_app_focused = (bd->Window == focused_window);

backends/imgui_impl_sdl3.cpp

@@ -20,6 +20,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-04-09: Don't attempt to call SDL_CaptureMouse() on drivers where we don't call SDL_GetGlobalMouseState(). (#8561)
 //  2025-03-30: Update for SDL3 api changes: Revert SDL_GetClipboardText() memory ownership change. (#8530, #7801)
 //  2025-03-21: Fill gamepad inputs and set ImGuiBackendFlags_HasGamepad regardless of ImGuiConfigFlags_NavEnableGamepad being set.
 //  2025-03-10: When dealing with OEM keys, use scancodes instead of translated keycodes to choose ImGuiKey values. (#7136, #7201, #7206, #7306, #7670, #7672, #8468)
@@ -110,6 +111,7 @@ struct ImGui_ImplSDL3_Data
     SDL_Cursor*             MouseLastCursor;
     int                     MousePendingLeaveFrame;
     bool                    MouseCanUseGlobalState;
+    bool                    MouseCanUseCapture;
 
     // Gamepad handling
     ImVector<SDL_Gamepad*>      Gamepads;
@@ -461,17 +463,6 @@ static bool ImGui_ImplSDL3_Init(SDL_Window* window, SDL_Renderer* renderer, void
     IM_ASSERT(io.BackendPlatformUserData == nullptr && "Already initialized a platform backend!");
     IM_UNUSED(sdl_gl_context); // Unused in this branch
 
-    // Check and store if we are on a SDL backend that supports global mouse position
-    // ("wayland" and "rpi" don't support it, but we chose to use a white-list instead of a black-list)
-    bool mouse_can_use_global_state = false;
-#if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
-    const char* sdl_backend = SDL_GetCurrentVideoDriver();
-    const char* global_mouse_whitelist[] = { "windows", "cocoa", "x11", "DIVE", "VMAN" };
-    for (int n = 0; n < IM_ARRAYSIZE(global_mouse_whitelist); n++)
-        if (strncmp(sdl_backend, global_mouse_whitelist[n], strlen(global_mouse_whitelist[n])) == 0)
-            mouse_can_use_global_state = true;
-#endif
-
     // Setup backend capabilities flags
     ImGui_ImplSDL3_Data* bd = IM_NEW(ImGui_ImplSDL3_Data)();
     io.BackendPlatformUserData = (void*)bd;
@@ -482,7 +473,18 @@ static bool ImGui_ImplSDL3_Init(SDL_Window* window, SDL_Renderer* renderer, void
     bd->Window = window;
     bd->WindowID = SDL_GetWindowID(window);
     bd->Renderer = renderer;
-    bd->MouseCanUseGlobalState = mouse_can_use_global_state;
+
+    // Check and store if we are on a SDL backend that supports SDL_GetGlobalMouseState() and SDL_CaptureMouse()
+    // ("wayland" and "rpi" don't support it, but we chose to use a white-list instead of a black-list)
+    bd->MouseCanUseGlobalState = false;
+    bd->MouseCanUseCapture = false;
+#if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
+    const char* sdl_backend = SDL_GetCurrentVideoDriver();
+    const char* capture_and_global_state_whitelist[] = { "windows", "cocoa", "x11", "DIVE", "VMAN" };
+    for (const char* item : capture_and_global_state_whitelist)
+        if (strncmp(sdl_backend, item, strlen(item)) == 0)
+            bd->MouseCanUseGlobalState = bd->MouseCanUseCapture = true;
+#endif
 
     ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
     platform_io.Platform_SetClipboardTextFn = ImGui_ImplSDL3_SetClipboardText;
@@ -596,12 +598,15 @@ static void ImGui_ImplSDL3_UpdateMouseData()
     // We forward mouse input when hovered or captured (via SDL_EVENT_MOUSE_MOTION) or when focused (below)
 #if SDL_HAS_CAPTURE_AND_GLOBAL_MOUSE
     // - SDL_CaptureMouse() let the OS know e.g. that our drags can extend outside of parent boundaries (we want updated position) and shouldn't trigger other operations outside.
-    // - Debuggers under Linux tends to leave captured mouse on break, which may be very inconvenient, so to migitate the issue we wait until mouse has moved to begin capture.
-    bool want_capture = false;
-    for (int button_n = 0; button_n < ImGuiMouseButton_COUNT && !want_capture; button_n++)
-        if (ImGui::IsMouseDragging(button_n, 1.0f))
-            want_capture = true;
-    SDL_CaptureMouse(want_capture);
+    // - Debuggers under Linux tends to leave captured mouse on break, which may be very inconvenient, so to mitigate the issue we wait until mouse has moved to begin capture.
+    if (bd->MouseCanUseCapture)
+    {
+        bool want_capture = false;
+        for (int button_n = 0; button_n < ImGuiMouseButton_COUNT && !want_capture; button_n++)
+            if (ImGui::IsMouseDragging(button_n, 1.0f))
+                want_capture = true;
+        SDL_CaptureMouse(want_capture);
+    }
 
     SDL_Window* focused_window = SDL_GetKeyboardFocus();
     const bool is_app_focused = (bd->Window == focused_window);

docs/CHANGELOG.txt

@@ -81,6 +81,9 @@ Other changes:
 - Misc: added extra operators to ImVec4 in IMGUI_DEFINE_MATH_OPERATORS block. (#8510) [@gan74]
 - Backends: SDL2, SDL3, OSX: Fill gamepad inputs and set ImGuiBackendFlags_HasGamepad
   regardless of ImGuiConfigFlags_NavEnableGamepad being set. (#8508)
+- Backends: SDL2, SDL3: don't attempt to call SDL_CaptureMouse() on drivers where we don't
+  call SDL_GetGlobalMouseState(). This is specifically for Wayland but we currently use
+  the same white-list as SDL_GetGlobalMouseState(). (#8561) [@vs49688]
 - Backends: SDL3: Update for SDL3 api changes: revert SDL_GetClipboardText()
   memory ownership change. (#8530, #7801) [@Green-Sky]
 - Backends: SDLGPU3: Made ImGui_ImplSDLGPU3_PrepareDrawData() reuse GPU Transfer Buffers which