BeginTabItem negative NameOffset - Why was NameOffset changed from int to short?

[0xSombra]

Commit introducing this issue: 46d7520
Issue: offset points outside of the buffer (backwards because it's casted to signed short without checks)
Code:

ImGui::SetNextWindowSize(ImVec2(400, 400), ImGuiCond_Once);
if (ImGui::Begin("NameOffset"))
{
    if (ImGui::BeginTabBar("tabbar", ImGuiTabBarFlags_TabListPopupButton))
    {
        // ... or long tab names, total characters should be > 32767
        for (auto i = 0; i != 2048; ++i)
        {
            ImGui::PushID(i);
            if (ImGui::BeginTabItem("ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
                ImGui::EndTabItem();
            ImGui::PopID();
        }
        ImGui::EndTabBar();
    }
    ImGui::End();
}

I don't know why it was changed to S16 but changing it to S32 fixes this as expected
This is how it looks like in the latest commit on master:

imgui/imgui_internal.h

Lines 1956 to 1971 in 04fd507

	struct ImGuiTabItem
	{
	ImGuiID ID;
	ImGuiTabItemFlags Flags;
	int LastFrameVisible;
	int LastFrameSelected; // This allows us to infer an ordered list of the last activated tabs with little maintenance
	float Offset; // Position relative to beginning of tab
	float Width; // Width currently displayed
	float ContentWidth; // Width of label, stored during BeginTabItem() call
	ImS16 NameOffset; // When Window==NULL, offset to name within parent ImGuiTabBar::TabsNames
	ImS16 BeginOrder; // BeginTabItem() order, used to re-order tabs after toggling ImGuiTabBarFlags_Reorderable
	ImS16 IndexDuringLayout; // Index only used during TabBarLayout()
	bool WantClose; // Marked as closed by SetTabItemClosed()
	ImGuiTabItem() { memset(this, 0, sizeof(*this)); LastFrameVisible = LastFrameSelected = -1; NameOffset = BeginOrder = IndexDuringLayout = -1; }
	};

imgui/imgui_widgets.cpp

Lines 7767 to 7769 in 04fd507

	// Append name with zero-terminator
	tab->NameOffset = (ImS16)tab_bar->TabsNames.size();
	tab_bar->TabsNames.append(label, label + strlen(label) + 1);

imgui/imgui_internal.h

Lines 2010 to 2014 in 04fd507

	const char* GetTabName(const ImGuiTabItem* tab) const
	{
	IM_ASSERT(tab->NameOffset != -1 && (int)tab->NameOffset < TabsNames.Buf.Size);
	return TabsNames.Buf.Data + tab->NameOffset;
	}

[ocornut]

We will revert and fix this but out of curiosity, what got you into using 32K worth of name data?

[0xSombra]

Was trying to test a file parser. loaded all files at once, forgot to not render them and it crashed in BeginTabItem
I wouldn't normally use this amount of tabs, but S16 is very limiting imo

[ocornut]

Pushed a fix for it now, thank you!