ImGui helper to draw text that will cut off and add an elipsis character

ImGuiTextWithEllipsis.cpp

	bool IsSpace(char aCharacter)
	{
		// all space characters are values 32 or less (space is 32)
		// so we can convert them to a bitmask and use a single condition
		const int mask = (1 << (' ' - 1)) | (1 << ('\f' - 1)) | (1 << ('\n' - 1)) | (1 << ('\r' - 1)) | (1 << ('\t' - 1)) | (1 << ('\v' - 1));
		return (mask & (1 << ((aCharacter && aCharacter <= 32) * (aCharacter - 1)))) != 0;
	}

	//-------------------------------------------------------------------------------------------------
	// Todo: Add support for soft-hyphens when using word boundaries?
	//-------------------------------------------------------------------------------------------------
	void TextWithEllipsis(char const* aString, float aMaxWidth, bool useWordBoundaries, float aSpacing)
	{
		char const* partStart = aString;
		char const* partEnd = aString;
		ImWchar elipsisChar = ImGui::GetFont()->EllipsisChar;
		char elipsisText[8];
		ImTextStrToUtf8(elipsisText, sizeof(elipsisText), &elipsisChar, (&elipsisChar) + 1);

		if (aSpacing < 0.0f) aSpacing = ImGui::GetStyle().ItemSpacing.x;

		float const ellipsisWidth = ImGui::CalcTextSize(elipsisText).x + aSpacing;
		float width = 0;
		bool addElipsis = false;

		while (*partStart != 0)
		{
			// Add space to next segment
			while (IsSpace(*partEnd)) partEnd++;

			if (useWordBoundaries)
			{
				// get next 'word' by looking for space after non-space
				while (*partEnd != 0 && !IsSpace(*partEnd)) ++partEnd;
			}
			else
			{
				if (*partEnd != 0) ++partEnd;
			}

			ImVec2 const wordSize = ImGui::CalcTextSize(partStart, partEnd);

			// Clearly we have space for this word so just add it
			if (wordSize.x + width + ellipsisWidth < aMaxWidth)
			{
				width += wordSize.x;
				partStart = partEnd;
			}
			// If we're just at the end of the word and we just fit then we can commit here
			else if (*partEnd == 0 && wordSize.x + width < aMaxWidth)
			{
				width += wordSize.x;
				partStart = partEnd;
			}
			// we're done so add elipsis where the current segment starts
			else
			{
				addElipsis = true;
				break;
			}
		}

		ImGui::TextUnformatted(aString, partStart);
		if (addElipsis)
		{
			ImGui::SameLine(0.0f, aSpacing);
			ImGui::TextUnformatted(elipsisText);
		}
	}