Method RenderText

KBotExt/imgui/imgui_draw.cpp:3612–3794

Note: as with every ImDrawList drawing function, this expects that the font atlas texture is bound.

// Note: as with every ImDrawList drawing function, this expects that the font atlas texture is bound.
void ImFont::RenderText(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, const ImVec4& clip_rect, const char* text_begin, const char* text_end, float wrap_width, bool cpu_fine_clip) const
{
	if (!text_end)
		text_end = text_begin + strlen(text_begin); // ImGui:: functions generally already provides a valid text_end, so this is merely to handle direct calls.

	// Align to be pixel perfect
	float x = IM_FLOOR(pos.x);
	float y = IM_FLOOR(pos.y);
	if (y > clip_rect.w)
		return;

	const float start_x = x;
	const float scale = size / FontSize;
	const float line_height = FontSize * scale;
	const bool word_wrap_enabled = (wrap_width > 0.0f);

	// Fast-forward to first visible line
	const char* s = text_begin;
	if (y + line_height < clip_rect.y)
		while (y + line_height < clip_rect.y && s < text_end)
		{
			const char* line_end = (const char*)memchr(s, '\n', text_end - s);
			if (word_wrap_enabled)
			{
				// FIXME-OPT: This is not optimal as do first do a search for \n before calling CalcWordWrapPositionA().
				// If the specs for CalcWordWrapPositionA() were reworked to optionally return on \n we could combine both.
				// However it is still better than nothing performing the fast-forward!
				s = CalcWordWrapPositionA(scale, s, line_end ? line_end : text_end, wrap_width);
				s = CalcWordWrapNextLineStartA(s, text_end);
			}
			else
			{
				s = line_end ? line_end + 1 : text_end;
			}
			y += line_height;
		}

	// For large text, scan for the last visible line in order to avoid over-reserving in the call to PrimReserve()
	// Note that very large horizontal line will still be affected by the issue (e.g. a one megabyte string buffer without a newline will likely crash atm)
	if (text_end - s > 10000 && !word_wrap_enabled)
	{
		const char* s_end = s;
		float y_end = y;
		while (y_end < clip_rect.w && s_end < text_end)
		{
			s_end = (const char*)memchr(s_end, '\n', text_end - s_end);
			s_end = s_end ? s_end + 1 : text_end;
			y_end += line_height;
		}
		text_end = s_end;
	}
	if (s == text_end)
		return;

	// Reserve vertices for remaining worse case (over-reserving is useful and easily amortized)
	const int vtx_count_max = (int)(text_end - s) * 4;
	const int idx_count_max = (int)(text_end - s) * 6;
	const int idx_expected_size = draw_list->IdxBuffer.Size + idx_count_max;