ImGui_ImplWin32_UpdateMousePos BugFix

[1s0t]

v1.66
Back-ends: ImGui_ImplWin32_UpdateMousePos
OS: win10 pro
Compiler:VS2017

I found a bug in ImGui_ImplWin32_UpdateMousePos more specific the windows function GetActiveWindow. It fails in some cases to get the window without any error codes so i re coded it using GetGUIThreadInfo instead and that managed to return the active window handle. I have no experience with github so i cant push this so i am giving the fix here.

// ImGui v1.66
static void ImGui_ImplWin32_UpdateMousePos()
{
   ImGuiIO& io = ImGui::GetIO();

   // Set OS mouse position if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
   if (io.WantSetMousePos)
   {
       POINT pos = { (int)io.MousePos.x, (int)io.MousePos.y };
       ::ClientToScreen(g_hWnd, &pos);
       ::SetCursorPos(pos.x, pos.y);
   }

   // Set mouse position
   io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
   POINT pos;
   
   // Getting active window handle from the window threads processID # Bacause ::GetActiveWindow() fails in some cases.
   GUITHREADINFO guiThreadInfo; guiThreadInfo.cbSize = sizeof(GUITHREADINFO);
   GetGUIThreadInfo(GetWindowThreadProcessId(g_hWnd, 0), &guiThreadInfo);

   if (guiThreadInfo.hwndActive == g_hWnd && ::GetCursorPos(&pos))
       if (::ScreenToClient(g_hWnd, &pos))
           io.MousePos = ImVec2((float)pos.x, (float)pos.y);
}

[ocornut]

Could you explain/justify in greater in which situation ::GetActiveWindow() may fails.

(Linking this to #1951.)

[1s0t]

I am hooking into an app and when the app loads the 3d Environment GetActiveWindow fails. I am not sure whats happening but GetActiveWindow fails and GetForegroundWindow is not a good solution. I read somewhere that you do it like this because you wanna be able to drag outside of the clientarea. And that's cool and if that wasnt the case i think putting it back to being handled inside the WndProc would be the best way. But doing it like im doing it here i think is the best solution to this problem. I dont think that checking witch window the mouse is in is that good as Nukem9 does here #1951 Because if theres an overlay then that could possibly trigger on that window instead.

[Epicccccccccc]

thank you this was troubling me for a while

[ghost]

I can confirm this issue when hooking into the Unity Editor as well as my Unity game. Your bugfix allows mouse input to get through as intended.

[ocornut]

@skillessgamer Today I have pushed a change to use GetForegroundWindow(), howver your last post mention:

I am hooking into an app and when the app loads the 3d Environment GetActiveWindow fails. I am not sure whats happening but GetActiveWindow fails and GetForegroundWindow is not a good solution.

Could you clarify why GetForegroundWindow is not a good solution?

[1s0t]

@ocornut GetForegroundWindow() will return the topmost window if i am not mistaken. That will be an issue if you have a overlay of some sort. My solution will get the active window from the executable ImGui runs.