Clicking an OSX app title bar clears the focused item in the window

[Pix3lP3rf3ct]

Version/Branch of Dear ImGui:

v1.91.9 WIP Docking

Back-ends:

Custom

Compiler, OS:

Clang 16

Full config/build information:

Dear ImGui 1.91.9 WIP (19186)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=202002
define: IMGUI_DISABLE_DEFAULT_FORMAT_FUNCTIONS
define: IMGUI_DISABLE_DEFAULT_FILE_FUNCTIONS
define: IMGUI_DISABLE_FILE_FUNCTIONS
define: IMGUI_DISABLE_DEFAULT_ALLOCATORS
define: __APPLE__
define: __GNUC__=4
define: __clang_version__=16.0.0 (clang-1600.0.26.6)
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK
--------------------------------
io.BackendPlatformName: NULL
io.BackendRendererName: imgui_impl_TGCEngine
io.ConfigFlags: 0x00000081
 NavEnableKeyboard
 DockingEnable
io.ConfigViewportsNoDecoration
io.ConfigMacOSXBehaviors
io.ConfigNavCaptureKeyboard
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigWindowsMoveFromTitleBarOnly
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x00001408
 PlatformHasViewports
 RendererHasVtxOffset
 RendererHasViewports
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 1024,2048
io.DisplaySize: 2586.00,1493.00
io.DisplayFramebufferScale: 2.00,2.00
--------------------------------
style.WindowPadding: 6.00,6.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,4.00
style.FrameRounding: 2.00
style.FrameBorderSize: 1.00
style.ItemSpacing: 6.00,4.00
style.ItemInnerSpacing: 4.00,4.00

Details:

Clicking the native OSX window title bar to drag the window causes the internal focused window to be cleared. This causes the user to have to click back into the window to set the focus before triggering any shortcuts.

Screenshots/Video:

Tests tab has focus.

After clicking on the title bar you can see it has lost focus.

Callstack.

Code that clears the focus.

Commenting that line out fixes the issue. That isn't the right solution but shows there needs to be more logic around that call.

Minimal, Complete and Verifiable Example code:

[ocornut]

Hello Joe,
Could you open Debug Log->IO and report mouse events passed to the app and imgui ?
This would happen if clicking the osx title bar would report a mouse click to the event, but afaik standard backends shouldn’t do that.

[Pix3lP3rf3ct]

Hi Omar! You are right, if the app is focused we always pass mouse movement changes to the application and if you click the title bar we do pass the click event to Imgui. I'll look into our backend and see why we're doing that.

[Pix3lP3rf3ct]

I ended up having to write a function to check if the mouse position was over one of the viewports before adding the mouse button event. I still feel like this is wrong but I couldn't see anywhere this case was handled in your backend.

bool IsOverViewport( const ImVec2& mousePos )
{
	ImGuiContext& g = *ImGui::GetCurrentContext();
	for( ImGuiViewportP* viewport : g.Viewports )
	{
		if( viewport->PlatformHandle )
		{
			ImVec2 pos = viewport->WorkPos;
			ImVec2 size = viewport->WorkSize;
			if( mousePos.x >= pos.x && mousePos.x < pos.x + size.x && 
				mousePos.y >= pos.y && mousePos.y < pos.y + size.y )
			{
				return true;
			}
		}
	}

	return false;
}

then

	if( down && !IsOverViewport( ImGui::GetMousePos() ) )
		break;

	io.AddMouseButtonEvent( 0, down );