Backends: SDL: Fix more dragging issues. SDL_CaptureMouse() is essentially broken. (#5012, #5082)

master got c5f6721 which is combining f337378 and this commit.

backends/imgui_impl_sdl.cpp

@@ -21,6 +21,7 @@
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
 //  2022-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
+//  2022-03-22: Inputs: Fix mouse position issues when dragging outside of boundaries. SDL_CaptureMouse() erroneously still gives out LEAVE events when hovering OS decorations.
 //  2022-02-04: Added SDL_Renderer* parameter to ImGui_ImplSDL2_InitForSDLRenderer(), so we can use SDL_GetRendererOutputSize() instead of SDL_GL_GetDrawableSize() when bound to a SDL_Renderer.
 //  2022-01-26: Inputs: replaced short-lived io.AddKeyModsEvent() (added two weeks ago)with io.AddKeyEvent() using ImGuiKey_ModXXX flags. Sorry for the confusion.
 //  2021-01-20: Inputs: calling new io.AddKeyAnalogEvent() for gamepad support, instead of writing directly to io.NavInputs[].
@@ -669,9 +670,10 @@ 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;
 
-    if (bd->PendingMouseLeaveFrame && bd->PendingMouseLeaveFrame == ImGui::GetFrameCount())
+    if (bd->PendingMouseLeaveFrame && bd->PendingMouseLeaveFrame >= ImGui::GetFrameCount() && bd->MouseButtonsDown == 0)
     {
         bd->MouseWindowID = 0;
+        bd->PendingMouseLeaveFrame = 0;
         io.AddMousePosEvent(-FLT_MAX, -FLT_MAX);
     }