Backends: SDL2: Extend global mouse pos availability check (#3950)

backends/imgui_impl_sdl.cpp

@@ -17,6 +17,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-03-22: Rework global mouse pos availability check listing supported platforms explicitly, effectively fixing mouse access on Raspberry Pi. (#2837, #3950)
 //  2020-05-25: Misc: Report a zero display-size when window is minimized, to be consistent with other backends.
 //  2020-02-20: Inputs: Fixed mapping for ImGuiKey_KeyPadEnter (using SDL_SCANCODE_KP_ENTER instead of SDL_SCANCODE_RETURN2).
 //  2019-12-17: Inputs: On Wayland, use SDL_GetMouseState (because there is no global mouse state).
@@ -177,8 +178,14 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window)
     g_MouseCursors[ImGuiMouseCursor_Hand] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_HAND);
     g_MouseCursors[ImGuiMouseCursor_NotAllowed] = SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_NO);
 
-    // Check and store if we are on Wayland
-    g_MouseCanUseGlobalState = strncmp(SDL_GetCurrentVideoDriver(), "wayland", 7) != 0;
+    // 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)
+    const char* sdl_backend = SDL_GetCurrentVideoDriver();
+    const char* global_mouse_whitelist[] = { "windows", "cocoa", "x11", "DIVE", "VMAN" };
+    g_MouseCanUseGlobalState = false;
+    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)
+            g_MouseCanUseGlobalState = true;
 
 #ifdef _WIN32
     SDL_SysWMinfo wmInfo;
@@ -259,7 +266,7 @@ static void ImGui_ImplSDL2_UpdateMousePosAndButtons()
         {
             // SDL_GetMouseState() gives mouse position seemingly based on the last window entered/focused(?)
             // The creation of a new windows at runtime and SDL_CaptureMouse both seems to severely mess up with that, so we retrieve that position globally.
-            // Won't use this workaround when on Wayland, as there is no global mouse position.
+            // Won't use this workaround on SDL backends that have no global mouse position, like Wayland or RPI
             int wx, wy;
             SDL_GetWindowPosition(focused_window, &wx, &wy);
             SDL_GetGlobalMouseState(&mx, &my);

docs/CHANGELOG.txt

@@ -44,6 +44,8 @@ Other Changes:
 - Drags, Sliders, Inputs: Specifying a NULL format to Float functions default them to "%.3f" to be
   consistent with the compile-time default. (#3922)
 - DragScalar: Add default value for v_speed argument to match higher-level functions. (#3922) [@eliasdaler]
+- Backends: SDL: Rework global mouse pos availability check listing supported platforms explicitly,
+  effectively fixing mouse access on Raspberry Pi. (#2837, #3950) [@lethal-guitar, @hinxx]
 - Backends: DirectX9: calling IDirect3DStateBlock9::Capture() after CreateStateBlock() which appears to
   workaround/fix state restoring issues. Unknown exactly why so, but bit of a cargo-cult fix. (#3857)
 - Backends: Vulkan: Fix mapped memory Vulkan validation error when buffer sizes are not multiple of