Revert "tweak: use format_args for efficiency"

This reverts commit 61486fae7d.

We convert the color inside the function, so we can't reference it outside the function

error[E0515]: cannot return value referencing local variable `c_u8`
   --> /home/ahann/Documents/GitHub/libcosmic/cosmic-theme/src/output/qt_output.rs:340:5
    |
340 |     format_args!("{},{},{}", c_u8.red, c_u8.green, c_u8.blue)
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^----^^^^^^
    |     |                                              |
    |     |                                              `c_u8` is borrowed here
    |     returns a value referencing data owned by the current function
    |

cosmic-theme/src/output/qt_output.rs

@@ -1,7 +1,6 @@
 use crate::Theme;
 use palette::{Mix, Srgba, blend::Compose};
 use std::{
-    fmt,
     fs::{self, File},
     io::{self, Write},
     path::Path,
@@ -325,13 +324,13 @@ contrast=4
 
 /// Formats a color in the form `r,g,b` e.g. `255,255,255`.
 /// If the color has transparency, it is mixed with bg first.
-fn to_rgb(c: Srgba, bg: Srgba) -> fmt::Arguments<'static> {
+fn to_rgb(c: Srgba, bg: Srgba) -> String {
     let c_u8: Srgba<u8> = c.over(bg).into_format();
-    format_args!("{},{},{}", c_u8.red, c_u8.green, c_u8.blue)
+    format!("{},{},{}", c_u8.red, c_u8.green, c_u8.blue)
 }
 
-fn format_ini_color_effects(color_effects: &IniColorEffects, bg: Srgba) -> fmt::Arguments<'_> {
+fn format_ini_color_effects(color_effects: &IniColorEffects, bg: Srgba) -> String {
-    format_args!(
+    format!(
         r#"Color={}
 ColorAmount={}
 ColorEffect={}
@@ -349,8 +348,8 @@ IntensityEffect={}"#,
     )
 }
 
-fn format_ini_colors(colors: &IniColors, bg: Srgba) -> fmt::Arguments<'_> {
+fn format_ini_colors(colors: &IniColors, bg: Srgba) -> String {
-    format_args!(
+    format!(
         r#"BackgroundAlternate={}
 BackgroundNormal={}
 DecorationFocus={}
@@ -379,12 +378,12 @@ ForegroundVisited={}"#,
 }
 
 /// Sets the colors for the titlebars of active and inactive windows.
-fn format_ini_wm_colors(view_colors: &IniColors, is_dark: bool) -> fmt::Arguments<'_> {
+fn format_ini_wm_colors(view_colors: &IniColors, is_dark: bool) -> String {
     let bg = view_colors.background_normal;
     let fg = view_colors.foreground_active;
     let blend = if is_dark { fg } else { bg };
 
-    format_args!(
+    format!(
         r#"activeBackground={}
 activeBlend={}
 activeForeground={}