print bad instead of value if cpu watts reading bad

replace string with `const string`

if cpu watts is greater then 10,000 start using abbreviated value ending
in `KW`

use `fmt::format_to` for output

Author: vandabbin

src/btop_draw.cpp

@@ -846,11 +846,15 @@ namespace Cpu {
 		}
 
 		if (show_watts) {
-			string cwatts = fmt::format(" {:>4.{}f}", cpu.usage_watts, cpu.usage_watts < 10.0f ? 2 : cpu.usage_watts < 100.0f ? 1 : 0);
-			string cwatts_post = "W";
-
+			const auto watts_error = cpu.usage_watts < 0.0f;
+			const auto cwatts = (watts_error) ? "  bad" : (cpu.usage_watts < 10'000.0f) 
+				? fmt::format(" {:>4.{}f}", cpu.usage_watts, cpu.usage_watts < 10.0f ? 2 : cpu.usage_watts < 100.0f ? 1 : 0)
+				: fmt::format(" {:>3.{}f}{}K", cpu.usage_watts / 10'000.0f, cpu.usage_watts < 100'000.0f ? 1 : 0, Theme::c("main_fg"));
 			max_observed_pwr = max(max_observed_pwr, cpu.usage_watts);
-			out += Theme::g("cached").at(clamp(cpu.usage_watts / max_observed_pwr * 100.0f, 0.0f, 100.0f)) + cwatts + Theme::c("main_fg") + cwatts_post; 
+			fmt::format_to(std::back_inserter(out), "{watts_color}{cwatts}{main_fg}W", 
+				"watts_color"_a = (!watts_error) ? Theme::g("cached").at(clamp(cpu.usage_watts / max_observed_pwr * 100.0f, 0.0f, 100.0f)) : "\x1b[0;91m",
+				"cwatts"_a = cwatts,
+				"main_fg"_a = Theme::c("main_fg"));
 		}
 
 			out += Theme::c("div_line") + Symbols::v_line;