SetKeyboardFocusHere focus broken in popups / with clipping

[benvanik]

This issue makes it difficult to auto-highlight/focus text inputs in popups that aren't at the top.

Repro in imgui_demo.cpp, change the first aquarium popup to:

            bool opened_popup = false;
            if (ImGui::Button("Select..")) {
              ImGui::OpenPopup("select");
              opened_popup = true;
            }
            ImGui::SameLine();
            ImGui::Text(selected_fish == -1 ? "<None>" : names[selected_fish]);
            if (ImGui::BeginPopup("select"))
            {
                ImGui::Separator();
                for (int i = 0; i < IM_ARRAYSIZE(names); i++)
                    if (ImGui::Selectable(names[i]))
                        selected_fish = i;
                if (opened_popup) {
                  ImGui::SetKeyboardFocusHere();
                }
                char input[32] = "Aquarium";
                ImGui::InputText("test", input, sizeof(input));
                ImGui::EndPopup();
            }

If you do this, the SetKeyboardFocusHere fails because the first time the BeginPopup runs the InputText ends up getting clipped in InputText>InputTextEx>ItemAdd>IsClippedEx. If the InputText (and SKFH) is at the top of the popup as the first item it works, but anywhere below other items and it fails.

A workaround is that on the next pass through BeginPopup it works (as the InputText is no longer clipped), however that makes the logic messier as one has to keep a counter to wait for the second pass to do the SKFH :(

[ocornut]

One right way to fix it would be to do the processing for FocusableItemRegister() prior to clipping. This would also allow to tab-past the visible widgets (would also require to alter scroll accordingly).

This ties to a larger totally missing feature, that is keyboard/controller navigation. Which would require every widget to be focusable so this probably needs to be re-engineered. If only for performances, but also because this whole SKFH is probably a bit short-sighted and we'd ideally need ways of selecting / triggering any widget given an ID.

There's also the ImGuiSetCond_Appearing condition used by functions such as which might tie into a potential better API.

I'm not really sure what to do short term, I'd prefer to tackle the larger set of focus related problems. I may go for a short-term fix of just making SetKeyboardFocusHere() set a counter to essentially make IsClippedEx() not clip, but that would only work with positive values of the 'offset=0' parameter (which is most of the case).

This is all quite smelly.

[benvanik]

Excellent points! For now I'll keep my workaround in.

[ocornut]

Better late than never.... using SetKeyboardFocusHere() on non-visible item is finally fixed by 31d033c + 8f495e5.
It was particularly trickier than meet-the-eyes but satisfied with current version.

(I'm not done with the refactor as Tabbing currently doesn't scroll, I still have a few things I don't yet know how to solve for the tabbing but we are nearly there).