Version/Branch of Dear ImGui:

Version 1.91.9, Branch: docking

Back-ends:

imgui_impl_dx11 + imgui_impl_win32

Compiler, OS:

MSVC

Full config/build information:

Dear ImGui 1.91.9 WIP (19184)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 4, sizeof(ImDrawVert): 20
define: __cplusplus=199711
define: IMGUI_DISABLE_OBSOLETE_FUNCTIONS
define: _WIN32
define: _WIN64
define: _MSC_VER=1940
define: _MSVC_LANG=202002
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK
--------------------------------
io.BackendPlatformName: imgui_impl_win32
io.BackendRendererName: imgui_impl_dx11
io.ConfigFlags: 0x0000C481
 NavEnableKeyboard
 DockingEnable
 ViewportsEnable
 DpiEnableScaleViewports
 DpiEnableScaleFonts
io.ConfigViewportsNoAutoMerge
io.ConfigViewportsNoDefaultParent
io.ConfigDockingWithShift
io.ConfigNavCaptureKeyboard
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x00001C0E
 HasMouseCursors
 HasSetMousePos
 PlatformHasViewports
 HasMouseHoveredViewport
 RendererHasVtxOffset
 RendererHasViewports
--------------------------------
io.Fonts: 11 fonts, Flags: 0x00000000, TexSize: 1024,1024
io.DisplaySize: 1795.00,1161.00
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:

I've been seeing some desync issues happening on occasion, and they may or may not all be related to each other.

One of the cases is when working with ImGui over RDP, when switching back one user reported that the mouse showed the hover over controls that were about 20px below where the mouse was (once the window was moved it was correct again).

And another user commented that our hovering app bar was not above the windows taskbar as it usually is, but right over it (and no amount of dragging fixed that).

I believe (perhaps both) these are related to the fact that the monitor layout is different and changes (in several ways). ImGui already handled the WM_DISPLAYCHANGE message, so this confused me. However, something else I saw when switching from and to RDP is that after connecting, Windows goes wild reordering windows (and the task bar) for a few more seconds, thus even though ImGui received the WM_DISPLAYCHANGE shortly after connecting, there may still be additional messages needed.

Indeed, I also saw that resizing the windows task bar did not update ImGui's internal metrics of monitor work sizes real-time as it should, so I added some debugging to see the messages being dispatched.

I'm not sure if it is the correct message, but I also added WM_GETMINMAXINFO to:

    case WM_DISPLAYCHANGE:
    case WM_GETMINMAXINFO:
        bd->WantUpdateMonitors = true;
        return 0;

And this at least solved how ImGui responds to taskbar changes.

I'm not an experienced windows programmer, and if anyone else can see an issue with this, perhaps there is a better message, but I believe this will address that shortfall.

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

No response