Child window (auto-fit) scrollbar appearing when it should not

[Devyre]

Hello,

I have been using ImGui (docking) for an editor of my game engine and updated to 1.90 for the content auto-fit of child windows.

It seems to work great but I noticed an issue where a scrollbar appeared in both child window and main window, when the child is supposed to grow within the main window.

I made sure to pass ImGuiChildFlags_AutoResizeY.
I actually stepped through it all and narrowed down the reason why the scrollbar appeared.

While debugging I noticed that window->Size/SizeFull were always 2 pixels lower than the content size.
It seems that child windows use the CalcWindowAutoFitSize function, which makes use of style.DisplaySafeAreaPadding.
I assume this style variable is only meant to be applied when it is a real window and not a child window.

Once I set style.DisplaySafeAreaPadding to 0 the scrollbar of the child disappeared.

The specific line of code causing this problem:

imgui/imgui.cpp

Line 5792 in bce4db0

ImVec2 size_auto_fit = ImClamp(size_desired, size_min, ImMax(size_min, avail_size - style.DisplaySafeAreaPadding * 2.0f));

[ocornut]

Thank you, I confirmed this and pushed a fix f37f6f6

Repro was:

ImGui::Begin("Bug #7063");
ImGui::BeginChild("blah", ImVec2(0, 0), ImGuiChildFlags_AutoResizeY);
for (int n = 0; n < 1000; n++)
    ImGui::Text("...");
ImGui::EndChild();
ImGui::End();