Add `Visuals::weak_text_alpha` and `weak_text_color` (#7285)

* Closes https://github.com/emilk/egui/issues/7262

This also makes the default weak color slightly less weak in most cases.

crates/egui/src/style.rs

@@ -936,6 +936,17 @@ pub struct Visuals {
     /// it is disabled, non-interactive, hovered etc.
     pub override_text_color: Option<Color32>,
 
+    /// How strong "weak" text is.
+    ///
+    /// Ignored if [`Self::weak_text_color`] is set.
+    pub weak_text_alpha: f32,
+
+    /// Color of "weak" text.
+    ///
+    /// If `None`, the color is [`Self::text_color`]
+    /// multiplied by [`Self::weak_text_alpha`].
+    pub weak_text_color: Option<Color32>,
+
     /// Visual styles of widgets
     pub widgets: Widgets,
 
@@ -1043,7 +1054,8 @@ impl Visuals {
     }
 
     pub fn weak_text_color(&self) -> Color32 {
-        self.gray_out(self.text_color())
+        self.weak_text_color
+            .unwrap_or_else(|| self.text_color().gamma_multiply(self.weak_text_alpha))
     }
 
     #[inline(always)]
@@ -1363,6 +1375,8 @@ impl Visuals {
         Self {
             dark_mode: true,
             override_text_color: None,
+            weak_text_alpha: 0.6,
+            weak_text_color: None,
             widgets: Widgets::default(),
             selection: Selection::default(),
             hyperlink_color: Color32::from_rgb(90, 170, 255),
@@ -2055,6 +2069,8 @@ impl Visuals {
         let Self {
             dark_mode,
             override_text_color: _,
+            weak_text_alpha,
+            weak_text_color,
             widgets,
             selection,
             hyperlink_color,
@@ -2098,7 +2114,45 @@ impl Visuals {
             disabled_alpha,
         } = self;
 
+        fn ui_optional_color(
+            ui: &mut Ui,
+            color: &mut Option<Color32>,
+            default_value: Color32,
+            label: impl Into<WidgetText>,
+        ) -> Response {
+            let label_response = ui.label(label);
+
+            ui.horizontal(|ui| {
+                let mut set = color.is_some();
+                ui.checkbox(&mut set, "");
+                if set {
+                    let color = color.get_or_insert(default_value);
+                    ui.color_edit_button_srgba(color);
+                } else {
+                    *color = None;
+                };
+            });
+
+            ui.end_row();
+
+            label_response
+        }
+
         ui.collapsing("Background colors", |ui| {
+            Grid::new("background_colors")
+                .num_columns(2)
+                .show(ui, |ui| {
+                    fn ui_color(
+                        ui: &mut Ui,
+                        color: &mut Color32,
+                        label: impl Into<WidgetText>,
+                    ) -> Response {
+                        let label_response = ui.label(label);
+                        ui.color_edit_button_srgba(color);
+                        ui.end_row();
+                        label_response
+                    }
+
                     ui_color(ui, &mut widgets.inactive.weak_bg_fill, "Buttons");
                     ui_color(ui, window_fill, "Windows");
                     ui_color(ui, panel_fill, "Panels");
@@ -2108,16 +2162,21 @@ impl Visuals {
                     ui_color(ui, extreme_bg_color, "Extreme")
                         .on_hover_text("Background of plots and paintings");
 
-            ui_color(
+                    ui_optional_color(ui, text_edit_bg_color, *extreme_bg_color, "TextEdit")
-                ui,
-                text_edit_bg_color.get_or_insert(*extreme_bg_color),
-                "TextEdit",
-            )
                         .on_hover_text("Background of TextEdit");
                 });
+        });
 
         ui.collapsing("Text color", |ui| {
+            fn ui_text_color(ui: &mut Ui, color: &mut Color32, label: impl Into<RichText>) {
+                ui.label(label.into().color(*color));
+                ui.color_edit_button_srgba(color);
+                ui.end_row();
+            }
+
+            Grid::new("text_color").num_columns(2).show(ui, |ui| {
                 ui_text_color(ui, &mut widgets.noninteractive.fg_stroke.color, "Label");
+
                 ui_text_color(
                     ui,
                     &mut widgets.inactive.fg_stroke.color,
@@ -2131,16 +2190,32 @@ impl Visuals {
 
                 ui_text_color(ui, hyperlink_color, "hyperlink_color");
 
-            ui_color(ui, code_bg_color, RichText::new("Code background").code()).on_hover_ui(
+                ui.label(RichText::new("Code background").code())
-                |ui| {
+                    .on_hover_ui(|ui| {
                         ui.horizontal(|ui| {
                             ui.spacing_mut().item_spacing.x = 0.0;
                             ui.label("For monospaced inlined text ");
                             ui.code("like this");
                             ui.label(".");
                         });
-                },
+                    });
+                ui.color_edit_button_srgba(code_bg_color);
+                ui.end_row();
+
+                ui.label("Weak text alpha");
+                ui.add_enabled(
+                    weak_text_color.is_none(),
+                    DragValue::new(weak_text_alpha).speed(0.01).range(0.0..=1.0),
                 );
+                ui.end_row();
+
+                ui_optional_color(
+                    ui,
+                    weak_text_color,
+                    widgets.noninteractive.text_color(),
+                    "Weak text color",
+                );
+            });
         });
 
         ui.collapsing("Text cursor", |ui| {
@@ -2364,22 +2439,6 @@ fn two_drag_values(value: &mut Vec2, range: std::ops::RangeInclusive<f32>) -> im
     }
 }
 
-fn ui_color(ui: &mut Ui, color: &mut Color32, label: impl Into<WidgetText>) -> Response {
-    ui.horizontal(|ui| {
-        ui.color_edit_button_srgba(color);
-        ui.label(label);
-    })
-    .response
-}
-
-fn ui_text_color(ui: &mut Ui, color: &mut Color32, label: impl Into<RichText>) -> Response {
-    ui.horizontal(|ui| {
-        ui.color_edit_button_srgba(color);
-        ui.label(label.into().color(*color));
-    })
-    .response
-}
-
 impl HandleShape {
     pub fn ui(&mut self, ui: &mut Ui) {
         ui.horizontal(|ui| {

crates/egui_demo_app/tests/snapshots/easymarkeditor.png

@@ -1,3 +1,3 @@
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-size 179082
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crates/egui_demo_lib/tests/snapshots/demos/Input Test.png

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crates/egui_demo_lib/tests/snapshots/demos/Panels.png

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crates/egui_demo_lib/tests/snapshots/demos/Scene.png

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crates/egui_demo_lib/tests/snapshots/demos/Scrolling.png

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crates/egui_demo_lib/tests/snapshots/widget_gallery.png

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-size 153136
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tests/egui_tests/tests/snapshots/layout/button_image_shortcut.png

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-size 407795
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tests/egui_tests/tests/snapshots/visuals/button_image_shortcut.png

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tests/egui_tests/tests/snapshots/visuals/button_image_shortcut_selected.png

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