ImGui InputText with right aligned text (when text wider than widget)

InputTextRightAligned.cpp

bool InputTextRightAligned(const char* label, const char* text, size_t length, ImGuiInputTextFlags flags, ImGuiInputTextCallback pCallback, void* pUserData)
{
	const ImGuiContext& g = *ImGui::GetCurrentContext();
	const ImGuiStyle& style = ImGui::GetStyle();
	ImGuiWindow& window = *ImGui::GetCurrentWindow();
	ImGuiID id = window.GetID(label);

	bool active = g.ActiveId == id;

	ImVec2 labelSize = ImGui::CalcTextSize(label, nullptr, true);
	ImVec2 frameSize = ImGui::CalcItemSize(ImVec2(0, 0), CalcItemWidth(), labelSize.y + style.FramePadding.y * 2.0f);
	ImRect frame(window.DC.CursorPos, window.DC.CursorPos + frameSize);
	ImVec2 textPos = frame.Min + style.FramePadding; // left aligned

	// right align text
	ImVec2 textSize = ImGui::CalcTextSize(text);
	textPos.x = std::min(frame.Max.x - style.FramePadding.x - textSize.x, textPos.x);

	bool modified = ImGui::InputText(label, text, length, flags, pCallback, pUserData);

	// overdraw text with right aligned text when widget not active
	if(!active)
	{
		ImDrawList& drawList = *ImGui::GetWindowDrawList();
		ImVec4 clipRect(frame.Min.x, frame.Min.y, frame.Max.x, frame.Max.y);
		drawList.AddRectFilled(frame.Min, frame.Max, ImColor(style.Colors[ImGuiCol_FrameBg]));
		drawList.AddText(nullptr, 0.0f, textPos, ImColor(ImGui::GetStyle().Colors[ImGuiCol_Text]), text, nullptr, 0.0f, &clipRect);
	}

	// fix cursor position and scrolling when the widget becomes active
	if(!active && ImGui::IsItemActive())
	{
		ImGuiInputTextState* state = ImGui::GetInputTextState(id);
		if(state)
		{
			const ImGuiIO& io = ImGui::GetIO();
			float cursorOffsetX = io.MousePos.x - textPos.x;

			int cursor = 0;
			int length = strlen(text);
			while(cursor < length)
			{
				if(ImGui::CalcTextSize(text, text + cursor + 1).x > cursorOffsetX)
					break;

				cursor++;
			}

			state->Stb.cursor = cursor;
			state->Stb.select_start = cursor;
			state->Stb.select_end = cursor;

			state->ScrollX = std::max(frame.Min.x + style.FramePadding.x - textPos.x, 0.0f);
		}
	}

	return modified;
}