SDL3 backend: phantom window frame on viewport creation when NoDecoration is disabled #8328
Description
Version/Branch of Dear ImGui:
Version 1.91.7 Branch: docking
Back-ends:
imgui_impl_sdl3.cpp + imgui_impl_opengl3.cpp
Compiler, OS:
Windows 11 + MSVC 22
Full config/build information:
Dear ImGui 1.91.7 (19170)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=199711
define: _WIN32
define: _WIN64
define: _MSC_VER=1942
define: _MSVC_LANG=201402
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK
--------------------------------
io.BackendPlatformName: imgui_impl_sdl3
io.BackendRendererName: imgui_impl_dx11
io.ConfigFlags: 0x00000483
NavEnableKeyboard
NavEnableGamepad
DockingEnable
ViewportsEnable
io.ConfigViewportsNoAutoMerge
io.ConfigViewportsNoTaskBarIcon
io.ConfigViewportsNoDecoration
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x00001C0E
HasMouseCursors
HasSetMousePos
PlatformHasViewports
HasMouseHoveredViewport
RendererHasVtxOffset
RendererHasViewports
--------------------------------
io.Fonts: 4 fonts, Flags: 0x00000000, TexSize: 512,256
io.DisplaySize: 800.00,1000.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00
Details:
When the NoDecoration flag is disabled and a window is dragged outside the main viewport, the frame of the newly created window appears for one frame in the top-left corner of the screen.
Screenshots/Video:
Screen.Recording.2024-09-17.195208-1.mp4
Minimal, Complete and Verifiable Example code:
io.ConfigViewportsNoAutoMerge = false;
io.ConfigViewportsNoDecoration= false;